diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..96ef6c0
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+/target
+Cargo.lock
diff --git a/Android.bp b/Android.bp
new file mode 100644
index 0000000..bb5293f
--- /dev/null
+++ b/Android.bp
@@ -0,0 +1,45 @@
+// This file is generated by cargo2android.py --run --device --tests.
+// Do not modify this file as changes will be overridden on upgrade.
+
+
+
+rust_library {
+    name: "libprotobuf_json_mapping",
+    host_supported: true,
+    crate_name: "protobuf_json_mapping",
+    cargo_env_compat: true,
+    cargo_pkg_version: "3.2.0",
+    srcs: ["src/lib.rs"],
+    edition: "2021",
+    rustlibs: [
+        "libprotobuf",
+        "libprotobuf_support",
+        "libthiserror",
+    ],
+    apex_available: [
+        "//apex_available:platform",
+        "//apex_available:anyapex",
+    ],
+    product_available: true,
+    vendor_available: true,
+}
+
+rust_test {
+    name: "protobuf-json-mapping_test_src_lib",
+    host_supported: true,
+    crate_name: "protobuf_json_mapping",
+    cargo_env_compat: true,
+    cargo_pkg_version: "3.2.0",
+    srcs: ["src/lib.rs"],
+    test_suites: ["general-tests"],
+    auto_gen_config: true,
+    test_options: {
+        unit_test: true,
+    },
+    edition: "2021",
+    rustlibs: [
+        "libprotobuf",
+        "libprotobuf_support",
+        "libthiserror",
+    ],
+}
diff --git a/Cargo.toml b/Cargo.toml
new file mode 100644
index 0000000..965427b
--- /dev/null
+++ b/Cargo.toml
@@ -0,0 +1,39 @@
+# THIS FILE IS AUTOMATICALLY GENERATED BY CARGO
+#
+# When uploading crates to the registry Cargo will automatically
+# "normalize" Cargo.toml files for maximal compatibility
+# with all versions of Cargo and also rewrite `path` dependencies
+# to registry (e.g., crates.io) dependencies.
+#
+# If you are reading this file be aware that the original Cargo.toml
+# will likely look very different (and much more reasonable).
+# See Cargo.toml.orig for the original contents.
+
+[package]
+edition = "2021"
+name = "protobuf-json-mapping"
+version = "3.2.0"
+authors = ["Stepan Koltsov <stepan.koltsov@gmail.com>"]
+description = """
+JSON mapping for Protocol Buffers messages.
+"""
+homepage = "https://github.com/stepancheg/rust-protobuf/"
+documentation = "https://github.com/stepancheg/rust-protobuf/blob/master/README.md"
+readme = "README.md"
+license = "MIT"
+repository = "https://github.com/stepancheg/rust-protobuf/"
+
+[package.metadata.docs.rs]
+all-features = true
+
+[lib]
+bench = false
+
+[dependencies.protobuf]
+version = "=3.2.0"
+
+[dependencies.protobuf-support]
+version = "=3.2.0"
+
+[dependencies.thiserror]
+version = "1.0.30"
diff --git a/Cargo.toml.orig b/Cargo.toml.orig
new file mode 100644
index 0000000..be24813
--- /dev/null
+++ b/Cargo.toml.orig
@@ -0,0 +1,25 @@
+[package]
+
+name = "protobuf-json-mapping"
+version = "3.2.0"
+authors = ["Stepan Koltsov <stepan.koltsov@gmail.com>"]
+edition = "2021"
+license = "MIT"
+homepage = "https://github.com/stepancheg/rust-protobuf/"
+repository = "https://github.com/stepancheg/rust-protobuf/"
+documentation = "https://github.com/stepancheg/rust-protobuf/blob/master/README.md"
+description = """
+JSON mapping for Protocol Buffers messages.
+"""
+
+[lib]
+bench = false
+
+[dependencies]
+thiserror = "1.0.30"
+
+protobuf = { path = "../protobuf", version = "=3.2.0" }
+protobuf-support = { path = "../protobuf-support", version = "=3.2.0" }
+
+[package.metadata.docs.rs]
+all-features = true
diff --git a/LICENSE b/LICENSE
new file mode 100644
index 0000000..21f30fa
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,19 @@
+Copyright (c) 2019 Stepan Koltsov
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE
+OR OTHER DEALINGS IN THE SOFTWARE.
diff --git a/METADATA b/METADATA
new file mode 100644
index 0000000..248872e
--- /dev/null
+++ b/METADATA
@@ -0,0 +1,17 @@
+name: "protobuf-json-mapping"
+description:
+    "JSON printer and parser which tries to follow protobuf conventions."
+
+third_party {
+  url {
+    type: HOMEPAGE
+    value: "https://crates.io/crates/protobuf-json-mapping"
+  }
+  url {
+    type: ARCHIVE
+    value: "https://static.crates.io/crates/protobuf-json-mapping/protobuf-json-mapping-3.2.0.crate"
+  }
+  version: "3.2.0"
+  last_upgrade_date { year: 2023 month: 3 day: 22 }
+  license_type: NOTICE
+}
diff --git a/MODULE_LICENSE_MIT b/MODULE_LICENSE_MIT
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/MODULE_LICENSE_MIT
diff --git a/NOTICE b/NOTICE
new file mode 120000
index 0000000..7a694c9
--- /dev/null
+++ b/NOTICE
@@ -0,0 +1 @@
+LICENSE
\ No newline at end of file
diff --git a/OWNERS b/OWNERS
new file mode 100644
index 0000000..45dc4dd
--- /dev/null
+++ b/OWNERS
@@ -0,0 +1 @@
+include platform/prebuilts/rust:master:/OWNERS
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..b6b05a0
--- /dev/null
+++ b/README.md
@@ -0,0 +1,6 @@
+<!-- cargo-sync-readme start -->
+
+JSON printer and parser which tries to follow
+[protobuf conventions](https://developers.google.com/protocol-buffers/docs/proto3#json).
+
+<!-- cargo-sync-readme end -->
diff --git a/src/base64.rs b/src/base64.rs
new file mode 100644
index 0000000..c8461c6
--- /dev/null
+++ b/src/base64.rs
@@ -0,0 +1,227 @@
+//! Copy-pasted from the internet
+/// Available encoding character sets
+#[derive(Clone, Copy, Debug)]
+enum _CharacterSet {
+    /// The standard character set (uses `+` and `/`)
+    _Standard,
+    /// The URL safe character set (uses `-` and `_`)
+    _UrlSafe,
+}
+
+static STANDARD_CHARS: &'static [u8] = b"ABCDEFGHIJKLMNOPQRSTUVWXYZ\
+                                        abcdefghijklmnopqrstuvwxyz\
+                                        0123456789+/";
+
+static _URLSAFE_CHARS: &'static [u8] = b"ABCDEFGHIJKLMNOPQRSTUVWXYZ\
+                                       abcdefghijklmnopqrstuvwxyz\
+                                       0123456789-_";
+
+pub fn encode(input: &[u8]) -> String {
+    let bytes = STANDARD_CHARS;
+
+    let len = input.len();
+
+    // Preallocate memory.
+    let prealloc_len = (len + 2) / 3 * 4;
+    let mut out_bytes = vec![b'='; prealloc_len];
+
+    // Deal with padding bytes
+    let mod_len = len % 3;
+
+    // Use iterators to reduce branching
+    {
+        let mut s_in = input[..len - mod_len].iter().map(|&x| x as u32);
+        let mut s_out = out_bytes.iter_mut();
+
+        // Convenient shorthand
+        let enc = |val| bytes[val as usize];
+        let mut write = |val| *s_out.next().unwrap() = val;
+
+        // Iterate though blocks of 4
+        while let (Some(first), Some(second), Some(third)) = (s_in.next(), s_in.next(), s_in.next())
+        {
+            let n = first << 16 | second << 8 | third;
+
+            // This 24-bit number gets separated into four 6-bit numbers.
+            write(enc((n >> 18) & 63));
+            write(enc((n >> 12) & 63));
+            write(enc((n >> 6) & 63));
+            write(enc((n >> 0) & 63));
+        }
+
+        // Heh, would be cool if we knew this was exhaustive
+        // (the dream of bounded integer types)
+        match mod_len {
+            0 => (),
+            1 => {
+                let n = (input[len - 1] as u32) << 16;
+                write(enc((n >> 18) & 63));
+                write(enc((n >> 12) & 63));
+            }
+            2 => {
+                let n = (input[len - 2] as u32) << 16 | (input[len - 1] as u32) << 8;
+                write(enc((n >> 18) & 63));
+                write(enc((n >> 12) & 63));
+                write(enc((n >> 6) & 63));
+            }
+            _ => panic!("Algebra is broken, please alert the math police"),
+        }
+    }
+
+    // `out_bytes` vec is prepopulated with `=` symbols and then only updated
+    // with base64 chars, so this unsafe is safe.
+    unsafe { String::from_utf8_unchecked(out_bytes) }
+}
+
+/// Errors that can occur when decoding a base64 encoded string
+#[derive(Clone, Copy, Debug, thiserror::Error)]
+pub enum FromBase64Error {
+    /// The input contained a character not part of the base64 format
+    #[error("Invalid base64 byte")]
+    InvalidBase64Byte(u8, usize),
+    /// The input had an invalid length
+    #[error("Invalid base64 length")]
+    InvalidBase64Length,
+}
+
+pub fn decode(input: &str) -> Result<Vec<u8>, FromBase64Error> {
+    let mut r = Vec::with_capacity(input.len());
+    let mut buf: u32 = 0;
+    let mut modulus = 0;
+
+    let mut it = input.as_bytes().iter();
+    for byte in it.by_ref() {
+        let code = DECODE_TABLE[*byte as usize];
+        if code >= SPECIAL_CODES_START {
+            match code {
+                NEWLINE_CODE => continue,
+                EQUALS_CODE => break,
+                INVALID_CODE => {
+                    return Err(FromBase64Error::InvalidBase64Byte(
+                        *byte,
+                        (byte as *const _ as usize) - input.as_ptr() as usize,
+                    ))
+                }
+                _ => unreachable!(),
+            }
+        }
+        buf = (buf | code as u32) << 6;
+        modulus += 1;
+        if modulus == 4 {
+            modulus = 0;
+            r.push((buf >> 22) as u8);
+            r.push((buf >> 14) as u8);
+            r.push((buf >> 6) as u8);
+        }
+    }
+
+    for byte in it {
+        match *byte {
+            b'=' | b'\r' | b'\n' => continue,
+            _ => {
+                return Err(FromBase64Error::InvalidBase64Byte(
+                    *byte,
+                    (byte as *const _ as usize) - input.as_ptr() as usize,
+                ))
+            }
+        }
+    }
+
+    match modulus {
+        2 => {
+            r.push((buf >> 10) as u8);
+        }
+        3 => {
+            r.push((buf >> 16) as u8);
+            r.push((buf >> 8) as u8);
+        }
+        0 => (),
+        _ => return Err(FromBase64Error::InvalidBase64Length),
+    }
+
+    Ok(r)
+}
+
+const DECODE_TABLE: [u8; 256] = [
+    0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFD, 0xFF, 0xFF, 0xFD, 0xFF, 0xFF,
+    0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
+    0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0x3E, 0xFF, 0x3E, 0xFF, 0x3F,
+    0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x3A, 0x3B, 0x3C, 0x3D, 0xFF, 0xFF, 0xFF, 0xFE, 0xFF, 0xFF,
+    0xFF, 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E,
+    0x0F, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19, 0xFF, 0xFF, 0xFF, 0xFF, 0x3F,
+    0xFF, 0x1A, 0x1B, 0x1C, 0x1D, 0x1E, 0x1F, 0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28,
+    0x29, 0x2A, 0x2B, 0x2C, 0x2D, 0x2E, 0x2F, 0x30, 0x31, 0x32, 0x33, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
+    0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
+    0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
+    0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
+    0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
+    0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
+    0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
+    0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
+    0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
+];
+const INVALID_CODE: u8 = 0xFF;
+const EQUALS_CODE: u8 = 0xFE;
+const NEWLINE_CODE: u8 = 0xFD;
+const SPECIAL_CODES_START: u8 = NEWLINE_CODE;
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_encode_basic() {
+        assert_eq!(encode(b""), "");
+        assert_eq!(encode(b"f"), "Zg==");
+        assert_eq!(encode(b"fo"), "Zm8=");
+        assert_eq!(encode(b"foo"), "Zm9v");
+        assert_eq!(encode(b"foob"), "Zm9vYg==");
+        assert_eq!(encode(b"fooba"), "Zm9vYmE=");
+        assert_eq!(encode(b"foobar"), "Zm9vYmFy");
+    }
+
+    #[test]
+    fn test_encode_standard_safe() {
+        assert_eq!(encode(&[251, 255]), "+/8=");
+    }
+
+    #[test]
+    fn test_decode_basic() {
+        assert_eq!(decode("").unwrap(), b"");
+        assert_eq!(decode("Zg==").unwrap(), b"f");
+        assert_eq!(decode("Zm8=").unwrap(), b"fo");
+        assert_eq!(decode("Zm9v").unwrap(), b"foo");
+        assert_eq!(decode("Zm9vYg==").unwrap(), b"foob");
+        assert_eq!(decode("Zm9vYmE=").unwrap(), b"fooba");
+        assert_eq!(decode("Zm9vYmFy").unwrap(), b"foobar");
+    }
+
+    #[test]
+    fn test_decode() {
+        assert_eq!(decode("Zm9vYmFy").unwrap(), b"foobar");
+    }
+
+    #[test]
+    fn test_decode_newlines() {
+        assert_eq!(decode("Zm9v\r\nYmFy").unwrap(), b"foobar");
+        assert_eq!(decode("Zm9vYg==\r\n").unwrap(), b"foob");
+        assert_eq!(decode("Zm9v\nYmFy").unwrap(), b"foobar");
+        assert_eq!(decode("Zm9vYg==\n").unwrap(), b"foob");
+    }
+
+    #[test]
+    fn test_decode_urlsafe() {
+        assert_eq!(decode("-_8").unwrap(), decode("+/8=").unwrap());
+    }
+
+    #[test]
+    fn test_from_base64_invalid_char() {
+        assert!(decode("Zm$=").is_err());
+        assert!(decode("Zg==$").is_err());
+    }
+
+    #[test]
+    fn test_decode_invalid_padding() {
+        assert!(decode("Z===").is_err());
+    }
+}
diff --git a/src/float.rs b/src/float.rs
new file mode 100644
index 0000000..a082933
--- /dev/null
+++ b/src/float.rs
@@ -0,0 +1,3 @@
+pub const PROTOBUF_JSON_NAN: &str = "NaN";
+pub const PROTOBUF_JSON_INF: &str = "Infinity";
+pub const PROTOBUF_JSON_MINUS_INF: &str = "-Infinity";
diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 0000000..1f152c4
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1,22 @@
+//! JSON printer and parser which tries to follow
+//! [protobuf conventions](https://developers.google.com/protocol-buffers/docs/proto3#json).
+
+mod base64;
+mod float;
+mod parse;
+mod print;
+mod rfc_3339;
+mod well_known_wrapper;
+
+pub use self::parse::merge_from_str;
+pub use self::parse::merge_from_str_with_options;
+pub use self::parse::parse_dyn_from_str;
+pub use self::parse::parse_dyn_from_str_with_options;
+pub use self::parse::parse_from_str;
+pub use self::parse::parse_from_str_with_options;
+pub use self::parse::ParseError;
+pub use self::parse::ParseOptions;
+pub use self::print::print_to_string;
+pub use self::print::print_to_string_with_options;
+pub use self::print::PrintError;
+pub use self::print::PrintOptions;
diff --git a/src/parse.rs b/src/parse.rs
new file mode 100644
index 0000000..e09fc57
--- /dev/null
+++ b/src/parse.rs
@@ -0,0 +1,914 @@
+use std::num::ParseFloatError;
+use std::num::ParseIntError;
+
+use protobuf::reflect::EnumDescriptor;
+use protobuf::reflect::EnumValueDescriptor;
+use protobuf::reflect::FieldDescriptor;
+use protobuf::reflect::MessageDescriptor;
+use protobuf::reflect::ReflectValueBox;
+use protobuf::reflect::RuntimeFieldType;
+use protobuf::reflect::RuntimeType;
+use protobuf::well_known_types::any::Any;
+use protobuf::well_known_types::duration::Duration;
+use protobuf::well_known_types::field_mask::FieldMask;
+use protobuf::well_known_types::struct_;
+use protobuf::well_known_types::struct_::ListValue;
+use protobuf::well_known_types::struct_::NullValue;
+use protobuf::well_known_types::struct_::Struct;
+use protobuf::well_known_types::struct_::Value;
+use protobuf::well_known_types::timestamp::Timestamp;
+use protobuf::well_known_types::wrappers::BoolValue;
+use protobuf::well_known_types::wrappers::BytesValue;
+use protobuf::well_known_types::wrappers::DoubleValue;
+use protobuf::well_known_types::wrappers::FloatValue;
+use protobuf::well_known_types::wrappers::Int32Value;
+use protobuf::well_known_types::wrappers::Int64Value;
+use protobuf::well_known_types::wrappers::StringValue;
+use protobuf::well_known_types::wrappers::UInt32Value;
+use protobuf::well_known_types::wrappers::UInt64Value;
+use protobuf::Enum;
+use protobuf::MessageDyn;
+use protobuf::MessageFull;
+use protobuf_support::lexer::json_number_lit::JsonNumberLit;
+use protobuf_support::lexer::lexer_impl::Lexer;
+use protobuf_support::lexer::lexer_impl::LexerError;
+use protobuf_support::lexer::loc::Loc;
+use protobuf_support::lexer::parser_language::ParserLanguage;
+use protobuf_support::lexer::token::Token;
+use protobuf_support::lexer::tokenizer::Tokenizer;
+use protobuf_support::lexer::tokenizer::TokenizerError;
+
+use super::base64;
+use super::float;
+use super::rfc_3339;
+use crate::base64::FromBase64Error;
+use crate::well_known_wrapper::WellKnownWrapper;
+
+#[derive(Debug, thiserror::Error)]
+enum ParseErrorWithoutLocInner {
+    #[error(transparent)]
+    TokenizerError(#[from] TokenizerError),
+    #[error("Unknown field name: `{}`", .0)]
+    UnknownFieldName(String),
+    #[error("Unknown enum variant name: `{}`", .0)]
+    UnknownEnumVariantName(String),
+    #[error(transparent)]
+    FromBase64Error(#[from] FromBase64Error),
+    #[error(transparent)]
+    IncorrectStrLit(#[from] LexerError),
+    #[error("Incorrect duration")]
+    IncorrectDuration,
+    #[error(transparent)]
+    Rfc3339(#[from] rfc_3339::Rfc3339ParseError),
+    #[error(transparent)]
+    ParseIntError(#[from] ParseIntError),
+    #[error(transparent)]
+    ParseFloatError(#[from] ParseFloatError),
+    #[error("Expecting bool")]
+    ExpectingBool,
+    #[error("Expecting string or integer")]
+    ExpectingStrOrInt,
+    #[error("Expecting number")]
+    ExpectingNumber,
+    #[error("Unexpected token")]
+    UnexpectedToken,
+    #[error("Any parsing is not implemented")]
+    AnyParsingIsNotImplemented,
+    #[error("Message not initialized")]
+    MessageNotInitialized,
+}
+
+/// JSON parse error.
+#[derive(Debug, thiserror::Error)]
+#[error(transparent)]
+struct ParseErrorWithoutLoc(ParseErrorWithoutLocInner);
+
+impl From<TokenizerError> for ParseErrorWithoutLoc {
+    fn from(e: TokenizerError) -> Self {
+        ParseErrorWithoutLoc(ParseErrorWithoutLocInner::TokenizerError(e))
+    }
+}
+
+impl From<FromBase64Error> for ParseErrorWithoutLoc {
+    fn from(e: FromBase64Error) -> Self {
+        ParseErrorWithoutLoc(ParseErrorWithoutLocInner::FromBase64Error(e))
+    }
+}
+
+impl From<ParseIntError> for ParseErrorWithoutLoc {
+    fn from(e: ParseIntError) -> Self {
+        ParseErrorWithoutLoc(ParseErrorWithoutLocInner::ParseIntError(e))
+    }
+}
+
+impl From<ParseFloatError> for ParseErrorWithoutLoc {
+    fn from(e: ParseFloatError) -> Self {
+        ParseErrorWithoutLoc(ParseErrorWithoutLocInner::ParseFloatError(e))
+    }
+}
+
+impl From<rfc_3339::Rfc3339ParseError> for ParseErrorWithoutLoc {
+    fn from(e: rfc_3339::Rfc3339ParseError) -> Self {
+        ParseErrorWithoutLoc(ParseErrorWithoutLocInner::Rfc3339(e))
+    }
+}
+
+/// JSON parse error
+#[derive(Debug, thiserror::Error)]
+#[error("{} at {}", error, loc)]
+pub struct ParseError {
+    error: ParseErrorWithoutLoc,
+    loc: Loc,
+}
+
+type ParseResultWithoutLoc<A> = Result<A, ParseErrorWithoutLoc>;
+type ParseResult<A> = Result<A, ParseError>;
+
+#[derive(Clone)]
+struct Parser<'a> {
+    tokenizer: Tokenizer<'a>,
+    parse_options: ParseOptions,
+}
+
+trait FromJsonNumber: PartialEq + Sized {
+    fn from_f64(v: f64) -> Self;
+    fn to_f64(&self) -> f64;
+    fn from_string(v: &str) -> ParseResultWithoutLoc<Self>;
+}
+
+impl FromJsonNumber for u32 {
+    fn from_f64(v: f64) -> Self {
+        v as u32
+    }
+
+    fn to_f64(&self) -> f64 {
+        *self as f64
+    }
+
+    fn from_string(v: &str) -> Result<Self, ParseErrorWithoutLoc> {
+        Ok(v.parse()?)
+    }
+}
+
+impl FromJsonNumber for u64 {
+    fn from_f64(v: f64) -> Self {
+        v as u64
+    }
+
+    fn to_f64(&self) -> f64 {
+        *self as f64
+    }
+
+    fn from_string(v: &str) -> Result<Self, ParseErrorWithoutLoc> {
+        Ok(v.parse()?)
+    }
+}
+
+impl FromJsonNumber for i32 {
+    fn from_f64(v: f64) -> Self {
+        v as i32
+    }
+
+    fn to_f64(&self) -> f64 {
+        *self as f64
+    }
+
+    fn from_string(v: &str) -> Result<Self, ParseErrorWithoutLoc> {
+        Ok(v.parse()?)
+    }
+}
+
+impl FromJsonNumber for i64 {
+    fn from_f64(v: f64) -> Self {
+        v as i64
+    }
+
+    fn to_f64(&self) -> f64 {
+        *self as f64
+    }
+
+    fn from_string(v: &str) -> Result<Self, ParseErrorWithoutLoc> {
+        Ok(v.parse()?)
+    }
+}
+
+impl FromJsonNumber for f32 {
+    fn from_f64(v: f64) -> Self {
+        v as f32
+    }
+
+    fn to_f64(&self) -> f64 {
+        *self as f64
+    }
+
+    fn from_string(v: &str) -> Result<Self, ParseErrorWithoutLoc> {
+        if v == float::PROTOBUF_JSON_INF {
+            Ok(f32::INFINITY)
+        } else if v == float::PROTOBUF_JSON_MINUS_INF {
+            Ok(f32::NEG_INFINITY)
+        } else if v == float::PROTOBUF_JSON_NAN {
+            Ok(f32::NAN)
+        } else {
+            Ok(v.parse()?)
+        }
+    }
+}
+
+impl FromJsonNumber for f64 {
+    fn from_f64(v: f64) -> Self {
+        v
+    }
+
+    fn to_f64(&self) -> f64 {
+        *self
+    }
+
+    fn from_string(v: &str) -> Result<Self, ParseErrorWithoutLoc> {
+        if v == float::PROTOBUF_JSON_INF {
+            Ok(f64::INFINITY)
+        } else if v == float::PROTOBUF_JSON_MINUS_INF {
+            Ok(f64::NEG_INFINITY)
+        } else if v == float::PROTOBUF_JSON_NAN {
+            Ok(f64::NAN)
+        } else {
+            Ok(v.parse()?)
+        }
+    }
+}
+
+impl<'a> Parser<'a> {
+    fn read_bool(&mut self) -> ParseResultWithoutLoc<bool> {
+        if self.tokenizer.next_ident_if_eq("true")? {
+            Ok(true)
+        } else if self.tokenizer.next_ident_if_eq("false")? {
+            Ok(false)
+        } else {
+            Err(ParseErrorWithoutLoc(
+                ParseErrorWithoutLocInner::ExpectingBool,
+            ))
+        }
+    }
+
+    fn parse_bool(&self, s: &str) -> ParseResultWithoutLoc<bool> {
+        if s == "true" {
+            Ok(true)
+        } else if s == "false" {
+            Ok(false)
+        } else {
+            Err(ParseErrorWithoutLoc(
+                ParseErrorWithoutLocInner::ExpectingBool,
+            ))
+        }
+    }
+
+    fn read_json_number_opt(&mut self) -> ParseResultWithoutLoc<Option<JsonNumberLit>> {
+        Ok(self.tokenizer.next_token_if_map(|t| match t {
+            Token::JsonNumber(v) => Some(v.clone()),
+            _ => None,
+        })?)
+    }
+
+    fn read_number<V: FromJsonNumber>(&mut self) -> ParseResultWithoutLoc<V> {
+        if let Some(v) = self.read_json_number_opt()? {
+            V::from_string(&v.0)
+        } else if self.tokenizer.lookahead_is_str_lit()? {
+            let v = self.read_string()?;
+            self.parse_number(&v)
+        } else {
+            Err(ParseErrorWithoutLoc(
+                ParseErrorWithoutLocInner::ExpectingNumber,
+            ))
+        }
+    }
+
+    fn parse_number<V: FromJsonNumber>(&self, s: &str) -> ParseResultWithoutLoc<V> {
+        V::from_string(s)
+    }
+
+    fn merge_wrapper<W>(&mut self, w: &mut W) -> ParseResultWithoutLoc<()>
+    where
+        W: WellKnownWrapper,
+        W::Underlying: FromJsonNumber,
+    {
+        *w.get_mut() = self.read_number()?;
+        Ok(())
+    }
+
+    fn merge_bool_value(&mut self, w: &mut BoolValue) -> ParseResultWithoutLoc<()> {
+        w.value = self.read_bool()?;
+        Ok(())
+    }
+
+    fn merge_string_value(&mut self, w: &mut StringValue) -> ParseResultWithoutLoc<()> {
+        w.value = self.read_string()?;
+        Ok(())
+    }
+
+    fn merge_bytes_value(&mut self, w: &mut BytesValue) -> ParseResultWithoutLoc<()> {
+        w.value = self.read_bytes()?;
+        Ok(())
+    }
+
+    fn read_u32(&mut self) -> ParseResultWithoutLoc<u32> {
+        self.read_number()
+    }
+
+    fn read_u64(&mut self) -> ParseResultWithoutLoc<u64> {
+        self.read_number()
+    }
+
+    fn read_i32(&mut self) -> ParseResultWithoutLoc<i32> {
+        self.read_number()
+    }
+
+    fn read_i64(&mut self) -> ParseResultWithoutLoc<i64> {
+        self.read_number()
+    }
+
+    fn read_f32(&mut self) -> ParseResultWithoutLoc<f32> {
+        self.read_number()
+    }
+
+    fn read_f64(&mut self) -> ParseResultWithoutLoc<f64> {
+        self.read_number()
+    }
+
+    fn read_string(&mut self) -> ParseResultWithoutLoc<String> {
+        let str_lit = self.tokenizer.next_str_lit()?;
+
+        let mut lexer = Lexer::new(&str_lit.escaped, ParserLanguage::Json);
+        let mut r = String::new();
+        while !lexer.eof() {
+            r.push(
+                lexer
+                    .next_json_char_value()
+                    .map_err(ParseErrorWithoutLocInner::IncorrectStrLit)
+                    .map_err(ParseErrorWithoutLoc)?,
+            );
+        }
+        Ok(r)
+    }
+
+    fn read_bytes(&mut self) -> ParseResultWithoutLoc<Vec<u8>> {
+        let s = self.read_string()?;
+        self.parse_bytes(&s)
+    }
+
+    fn parse_bytes(&self, s: &str) -> ParseResultWithoutLoc<Vec<u8>> {
+        Ok(base64::decode(s)?)
+    }
+
+    fn read_enum(&mut self, descriptor: &EnumDescriptor) -> ParseResultWithoutLoc<i32> {
+        if descriptor.is::<NullValue>() {
+            return Ok(self.read_wk_null_value()?.value());
+        }
+
+        if self.tokenizer.lookahead_is_str_lit()? {
+            let name = self.read_string()?;
+            Ok(self.parse_enum(name, descriptor)?.value())
+        } else if self.tokenizer.lookahead_is_json_number()? {
+            self.read_i32()
+        } else {
+            Err(ParseErrorWithoutLoc(
+                ParseErrorWithoutLocInner::ExpectingStrOrInt,
+            ))
+        }
+    }
+
+    fn parse_enum(
+        &self,
+        name: String,
+        descriptor: &EnumDescriptor,
+    ) -> ParseResultWithoutLoc<EnumValueDescriptor> {
+        match descriptor.value_by_name(&name) {
+            Some(v) => Ok(v),
+            None => Err(ParseErrorWithoutLoc(
+                ParseErrorWithoutLocInner::UnknownEnumVariantName(name),
+            )),
+        }
+    }
+
+    fn read_wk_null_value(&mut self) -> ParseResultWithoutLoc<NullValue> {
+        self.tokenizer.next_ident_expect_eq("null")?;
+        Ok(NullValue::NULL_VALUE)
+    }
+
+    fn read_message(
+        &mut self,
+        descriptor: &MessageDescriptor,
+    ) -> ParseResultWithoutLoc<Box<dyn MessageDyn>> {
+        let mut m = descriptor.new_instance();
+        self.merge_inner(&mut *m)?;
+        Ok(m)
+    }
+
+    fn read_value(&mut self, t: &RuntimeType) -> ParseResultWithoutLoc<ReflectValueBox> {
+        match t {
+            RuntimeType::I32 => self.read_i32().map(ReflectValueBox::from),
+            RuntimeType::I64 => self.read_i64().map(ReflectValueBox::from),
+            RuntimeType::U32 => self.read_u32().map(ReflectValueBox::from),
+            RuntimeType::U64 => self.read_u64().map(ReflectValueBox::from),
+            RuntimeType::F32 => self.read_f32().map(ReflectValueBox::from),
+            RuntimeType::F64 => self.read_f64().map(ReflectValueBox::from),
+            RuntimeType::Bool => self.read_bool().map(ReflectValueBox::from),
+            RuntimeType::String => self.read_string().map(ReflectValueBox::from),
+            RuntimeType::VecU8 => self.read_bytes().map(ReflectValueBox::from),
+            RuntimeType::Enum(e) => self
+                .read_enum(&e)
+                .map(|v| ReflectValueBox::Enum(e.clone(), v)),
+            RuntimeType::Message(m) => self.read_message(&m).map(ReflectValueBox::from),
+        }
+    }
+
+    fn merge_singular_field(
+        &mut self,
+        message: &mut dyn MessageDyn,
+        field: &FieldDescriptor,
+        t: &RuntimeType,
+    ) -> ParseResultWithoutLoc<()> {
+        field.set_singular_field(message, self.read_value(t)?);
+        Ok(())
+    }
+
+    fn read_list<C>(&mut self, mut read_item: C) -> ParseResultWithoutLoc<()>
+    where
+        C: for<'b> FnMut(&'b mut Self) -> ParseResultWithoutLoc<()>,
+    {
+        if self.tokenizer.next_ident_if_eq("null")? {
+            return Ok(());
+        }
+
+        // TODO: better error reporting on wrong field type
+        self.tokenizer.next_symbol_expect_eq('[', "list")?;
+        let mut first = true;
+        while !self.tokenizer.next_symbol_if_eq(']')? {
+            if !first {
+                self.tokenizer.next_symbol_expect_eq(',', "list")?;
+            }
+            first = false;
+
+            read_item(self)?;
+        }
+
+        Ok(())
+    }
+
+    fn merge_repeated_field(
+        &mut self,
+        message: &mut dyn MessageDyn,
+        field: &FieldDescriptor,
+        t: &RuntimeType,
+    ) -> ParseResultWithoutLoc<()> {
+        let mut repeated = field.mut_repeated(message);
+        repeated.clear();
+
+        self.read_list(|s| {
+            repeated.push(s.read_value(t)?);
+            Ok(())
+        })
+    }
+
+    fn merge_wk_list_value(&mut self, list: &mut ListValue) -> ParseResultWithoutLoc<()> {
+        list.values.clear();
+
+        self.read_list(|s| {
+            list.values.push(s.read_wk_value()?);
+            Ok(())
+        })
+    }
+
+    fn read_map<K, Fk, Fi>(
+        &mut self,
+        mut parse_key: Fk,
+        mut read_value_and_insert: Fi,
+    ) -> ParseResultWithoutLoc<()>
+    where
+        Fk: for<'b> FnMut(&Self, String) -> ParseResultWithoutLoc<K>,
+        Fi: for<'b> FnMut(&mut Self, K) -> ParseResultWithoutLoc<()>,
+    {
+        if self.tokenizer.next_ident_if_eq("null")? {
+            return Ok(());
+        }
+
+        self.tokenizer.next_symbol_expect_eq('{', "map")?;
+        let mut first = true;
+        while !self.tokenizer.next_symbol_if_eq('}')? {
+            if !first {
+                self.tokenizer.next_symbol_expect_eq(',', "map")?;
+            }
+            first = false;
+
+            let key_string = self.read_string()?;
+            let k = parse_key(self, key_string)?;
+
+            self.tokenizer.next_symbol_expect_eq(':', "map")?;
+            read_value_and_insert(self, k)?;
+        }
+
+        Ok(())
+    }
+
+    fn parse_key(&self, key: String, t: &RuntimeType) -> ParseResultWithoutLoc<ReflectValueBox> {
+        match t {
+            RuntimeType::I32 => self.parse_number::<i32>(&key).map(ReflectValueBox::I32),
+            RuntimeType::I64 => self.parse_number::<i64>(&key).map(ReflectValueBox::I64),
+            RuntimeType::U32 => self.parse_number::<u32>(&key).map(ReflectValueBox::U32),
+            RuntimeType::U64 => self.parse_number::<u64>(&key).map(ReflectValueBox::U64),
+            RuntimeType::Bool => self.parse_bool(&key).map(ReflectValueBox::Bool),
+            RuntimeType::String => Ok(ReflectValueBox::String(key)),
+            t @ RuntimeType::F32
+            | t @ RuntimeType::F64
+            | t @ RuntimeType::VecU8
+            | t @ RuntimeType::Enum(..) => panic!("{} cannot be a map key", t),
+            RuntimeType::Message(_) => panic!("message cannot be a map key"),
+        }
+    }
+
+    fn merge_map_field(
+        &mut self,
+        message: &mut dyn MessageDyn,
+        field: &FieldDescriptor,
+        kt: &RuntimeType,
+        vt: &RuntimeType,
+    ) -> ParseResultWithoutLoc<()> {
+        let mut map = field.mut_map(message);
+        map.clear();
+
+        self.read_map(
+            |ss, s| ss.parse_key(s, kt),
+            |s, k| {
+                let v = s.read_value(vt)?;
+                map.insert(k, v);
+                Ok(())
+            },
+        )
+    }
+
+    fn merge_wk_struct(&mut self, struct_value: &mut Struct) -> ParseResultWithoutLoc<()> {
+        struct_value.fields.clear();
+
+        self.read_map(
+            |_, s| Ok(s),
+            |s, k| {
+                let v = s.read_wk_value()?;
+                struct_value.fields.insert(k, v);
+                Ok(())
+            },
+        )
+    }
+
+    fn skip_json_value(&mut self) -> ParseResultWithoutLoc<()> {
+        if self
+            .tokenizer
+            .next_ident_if_in(&["true", "false", "null"])?
+            .is_some()
+        {
+        } else if self.tokenizer.lookahead_is_str_lit()? {
+            self.tokenizer.next_str_lit()?;
+        } else if self.tokenizer.lookahead_is_json_number()? {
+            self.read_json_number_opt()?;
+        } else if self.tokenizer.lookahead_is_symbol('[')? {
+            self.read_list(|s| s.skip_json_value())?;
+        } else if self.tokenizer.lookahead_is_symbol('{')? {
+            self.read_map(|_, _| Ok(()), |s, ()| s.skip_json_value())?;
+        } else {
+            return Err(ParseErrorWithoutLoc(
+                ParseErrorWithoutLocInner::UnexpectedToken,
+            ));
+        }
+        Ok(())
+    }
+
+    fn merge_field(
+        &mut self,
+        message: &mut dyn MessageDyn,
+        field: &FieldDescriptor,
+    ) -> ParseResultWithoutLoc<()> {
+        match field.runtime_field_type() {
+            RuntimeFieldType::Singular(t) => self.merge_singular_field(message, field, &t),
+            RuntimeFieldType::Repeated(t) => self.merge_repeated_field(message, field, &t),
+            RuntimeFieldType::Map(kt, vt) => self.merge_map_field(message, field, &kt, &vt),
+        }
+    }
+
+    fn merge_inner(&mut self, message: &mut dyn MessageDyn) -> ParseResultWithoutLoc<()> {
+        if let Some(duration) = message.downcast_mut() {
+            return self.merge_wk_duration(duration);
+        }
+
+        if let Some(timestamp) = message.downcast_mut() {
+            return self.merge_wk_timestamp(timestamp);
+        }
+
+        if let Some(field_mask) = message.downcast_mut() {
+            return self.merge_wk_field_mask(field_mask);
+        }
+
+        if let Some(value) = message.downcast_mut() {
+            return self.merge_wk_value(value);
+        }
+
+        if let Some(value) = message.downcast_mut() {
+            return self.merge_wk_any(value);
+        }
+
+        if let Some(value) = message.downcast_mut::<DoubleValue>() {
+            return self.merge_wrapper(value);
+        }
+
+        if let Some(value) = message.downcast_mut::<FloatValue>() {
+            return self.merge_wrapper(value);
+        }
+
+        if let Some(value) = message.downcast_mut::<Int64Value>() {
+            return self.merge_wrapper(value);
+        }
+
+        if let Some(value) = message.downcast_mut::<UInt64Value>() {
+            return self.merge_wrapper(value);
+        }
+
+        if let Some(value) = message.downcast_mut::<Int32Value>() {
+            return self.merge_wrapper(value);
+        }
+
+        if let Some(value) = message.downcast_mut::<UInt32Value>() {
+            return self.merge_wrapper(value);
+        }
+
+        if let Some(value) = message.downcast_mut::<BoolValue>() {
+            return self.merge_bool_value(value);
+        }
+
+        if let Some(value) = message.downcast_mut::<StringValue>() {
+            return self.merge_string_value(value);
+        }
+
+        if let Some(value) = message.downcast_mut::<BytesValue>() {
+            return self.merge_bytes_value(value);
+        }
+
+        if let Some(value) = message.downcast_mut::<ListValue>() {
+            return self.merge_wk_list_value(value);
+        }
+
+        if let Some(value) = message.downcast_mut::<Struct>() {
+            return self.merge_wk_struct(value);
+        }
+
+        let descriptor = message.descriptor_dyn();
+
+        self.tokenizer.next_symbol_expect_eq('{', "object")?;
+        let mut first = true;
+        while !self.tokenizer.next_symbol_if_eq('}')? {
+            if !first {
+                self.tokenizer.next_symbol_expect_eq(',', "object")?;
+            }
+            first = false;
+
+            let field_name = self.read_string()?;
+            // Proto3 JSON parsers are required to accept both
+            // the converted `lowerCamelCase` name and the proto field name.
+            match descriptor.field_by_name_or_json_name(&field_name) {
+                Some(field) => {
+                    self.tokenizer.next_symbol_expect_eq(':', "object")?;
+                    self.merge_field(message, &field)?;
+                }
+                None if self.parse_options.ignore_unknown_fields => {
+                    self.tokenizer.next_symbol_expect_eq(':', "object")?;
+                    self.skip_json_value()?;
+                }
+                None => {
+                    return Err(ParseErrorWithoutLoc(
+                        ParseErrorWithoutLocInner::UnknownFieldName(field_name),
+                    ))
+                }
+            };
+        }
+        Ok(())
+    }
+
+    fn merge_wk_duration(&mut self, duration: &mut Duration) -> ParseResultWithoutLoc<()> {
+        let s = self.read_string()?;
+        let mut lexer = Lexer::new(&s, ParserLanguage::Json);
+
+        fn next_dec(lexer: &mut Lexer) -> ParseResultWithoutLoc<(u64, u32)> {
+            let s = lexer.take_while(|c| c >= '0' && c <= '9');
+
+            if s.len() == 0 {
+                Ok((0, 0))
+            } else {
+                match s.parse() {
+                    Ok(n) => Ok((n, s.len() as u32)),
+                    Err(_) => Err(ParseErrorWithoutLoc(
+                        ParseErrorWithoutLocInner::IncorrectDuration,
+                    )),
+                }
+            }
+        }
+
+        let minus = lexer.next_char_if_eq('-');
+        let seconds = match next_dec(&mut lexer)? {
+            (_, 0) => {
+                return Err(ParseErrorWithoutLoc(
+                    ParseErrorWithoutLocInner::IncorrectDuration,
+                ))
+            }
+            (s, _) => s,
+        };
+        let nanos = if lexer.next_char_if_eq('.') {
+            let (mut a, mut b) = next_dec(&mut lexer)?;
+            if b > 9 {
+                return Err(ParseErrorWithoutLoc(
+                    ParseErrorWithoutLocInner::IncorrectDuration,
+                ));
+            }
+            while b != 9 {
+                b += 1;
+                a *= 10;
+            }
+
+            if a > 999_999_999 {
+                return Err(ParseErrorWithoutLoc(
+                    ParseErrorWithoutLocInner::IncorrectDuration,
+                ));
+            }
+
+            a
+        } else {
+            0
+        };
+
+        // The suffix "s" is required
+        if !lexer.next_char_if_eq('s') {
+            return Err(ParseErrorWithoutLoc(
+                ParseErrorWithoutLocInner::IncorrectDuration,
+            ));
+        }
+
+        if !lexer.eof() {
+            return Err(ParseErrorWithoutLoc(
+                ParseErrorWithoutLocInner::IncorrectDuration,
+            ));
+        }
+
+        if minus {
+            duration.seconds = -(seconds as i64);
+            duration.nanos = -(nanos as i32);
+        } else {
+            duration.seconds = seconds as i64;
+            duration.nanos = nanos as i32;
+        }
+        Ok(())
+    }
+
+    fn merge_wk_timestamp(&mut self, timestamp: &mut Timestamp) -> ParseResultWithoutLoc<()> {
+        let s = self.read_string()?;
+        let (seconds, nanos) = rfc_3339::TmUtc::parse_rfc_3339(&s)?;
+        timestamp.seconds = seconds;
+        timestamp.nanos = nanos as i32;
+        Ok(())
+    }
+
+    fn merge_wk_field_mask(&mut self, field_mask: &mut FieldMask) -> ParseResultWithoutLoc<()> {
+        let s = self.read_string()?;
+        if !s.is_empty() {
+            field_mask.paths = s.split(',').map(|s| s.to_owned()).collect();
+        }
+        Ok(())
+    }
+
+    fn read_wk_list_value(&mut self) -> ParseResultWithoutLoc<ListValue> {
+        let mut r = ListValue::new();
+        self.merge_wk_list_value(&mut r)?;
+        Ok(r)
+    }
+
+    fn read_wk_struct(&mut self) -> ParseResultWithoutLoc<Struct> {
+        let mut r = Struct::new();
+        self.merge_wk_struct(&mut r)?;
+        Ok(r)
+    }
+
+    fn merge_wk_value(&mut self, value: &mut Value) -> ParseResultWithoutLoc<()> {
+        if self.tokenizer.lookahead_is_ident("null")? {
+            value.kind = Some(struct_::value::Kind::NullValue(
+                self.read_wk_null_value()?.into(),
+            ));
+        } else if self.tokenizer.lookahead_is_ident("true")?
+            || self.tokenizer.lookahead_is_ident("false")?
+        {
+            value.kind = Some(struct_::value::Kind::BoolValue(self.read_bool()?));
+        } else if self.tokenizer.lookahead_is_json_number()? {
+            value.kind = Some(struct_::value::Kind::NumberValue(self.read_f64()?));
+        } else if self.tokenizer.lookahead_is_str_lit()? {
+            value.kind = Some(struct_::value::Kind::StringValue(self.read_string()?));
+        } else if self.tokenizer.lookahead_is_symbol('[')? {
+            value.kind = Some(struct_::value::Kind::ListValue(self.read_wk_list_value()?));
+        } else if self.tokenizer.lookahead_is_symbol('{')? {
+            value.kind = Some(struct_::value::Kind::StructValue(self.read_wk_struct()?));
+        } else {
+            return Err(ParseErrorWithoutLoc(
+                ParseErrorWithoutLocInner::UnexpectedToken,
+            ));
+        }
+        Ok(())
+    }
+
+    fn merge_wk_any(&mut self, _value: &mut Any) -> ParseResultWithoutLoc<()> {
+        Err(ParseErrorWithoutLoc(
+            ParseErrorWithoutLocInner::AnyParsingIsNotImplemented,
+        ))
+    }
+
+    fn read_wk_value(&mut self) -> ParseResultWithoutLoc<Value> {
+        let mut v = Value::new();
+        self.merge_wk_value(&mut v)?;
+        Ok(v)
+    }
+
+    fn merge(&mut self, message: &mut dyn MessageDyn) -> ParseResult<()> {
+        match self.merge_inner(message) {
+            Ok(()) => Ok(()),
+            Err(error) => Err(ParseError {
+                error,
+                loc: self.tokenizer.loc(),
+            }),
+        }
+    }
+}
+
+/// JSON parse options.
+///
+/// # Examples
+///
+/// ```
+/// let parse_options = protobuf_json_mapping::ParseOptions {
+///     ignore_unknown_fields: true,
+///     ..Default::default()
+/// };
+/// ```
+#[derive(Default, Debug, Clone)]
+pub struct ParseOptions {
+    /// Ignore unknown fields when parsing.
+    ///
+    /// When `true` fields with unknown names are ignored.
+    /// When `false` parser returns an error on unknown field.
+    pub ignore_unknown_fields: bool,
+    /// Prevent initializing `ParseOptions` enumerating all field.
+    pub _future_options: (),
+}
+
+/// Merge JSON into provided message
+pub fn merge_from_str_with_options(
+    message: &mut dyn MessageDyn,
+    json: &str,
+    parse_options: &ParseOptions,
+) -> ParseResult<()> {
+    let mut parser = Parser {
+        tokenizer: Tokenizer::new(json, ParserLanguage::Json),
+        parse_options: parse_options.clone(),
+    };
+    parser.merge(message)
+}
+
+/// Merge JSON into provided message
+pub fn merge_from_str(message: &mut dyn MessageDyn, json: &str) -> ParseResult<()> {
+    merge_from_str_with_options(message, json, &ParseOptions::default())
+}
+
+/// Parse JSON to protobuf message.
+pub fn parse_dyn_from_str_with_options(
+    d: &MessageDescriptor,
+    json: &str,
+    parse_options: &ParseOptions,
+) -> ParseResult<Box<dyn MessageDyn>> {
+    let mut m = d.new_instance();
+    merge_from_str_with_options(&mut *m, json, parse_options)?;
+    if let Err(_) = m.check_initialized_dyn() {
+        return Err(ParseError {
+            error: ParseErrorWithoutLoc(ParseErrorWithoutLocInner::MessageNotInitialized),
+            loc: Loc::start(),
+        });
+    }
+    Ok(m)
+}
+
+/// Parse JSON to protobuf message.
+pub fn parse_dyn_from_str(d: &MessageDescriptor, json: &str) -> ParseResult<Box<dyn MessageDyn>> {
+    parse_dyn_from_str_with_options(d, json, &ParseOptions::default())
+}
+
+/// Parse JSON to protobuf message.
+pub fn parse_from_str_with_options<M: MessageFull>(
+    json: &str,
+    parse_options: &ParseOptions,
+) -> ParseResult<M> {
+    let m = parse_dyn_from_str_with_options(&M::descriptor(), json, parse_options)?;
+    Ok(*m.downcast_box().unwrap())
+}
+
+/// Parse JSON to protobuf message.
+pub fn parse_from_str<M: MessageFull>(json: &str) -> ParseResult<M> {
+    parse_from_str_with_options(json, &ParseOptions::default())
+}
diff --git a/src/print.rs b/src/print.rs
new file mode 100644
index 0000000..eef44ca
--- /dev/null
+++ b/src/print.rs
@@ -0,0 +1,586 @@
+use std::fmt;
+use std::fmt::Write as fmt_Write;
+
+use protobuf::reflect::EnumDescriptor;
+use protobuf::reflect::EnumValueDescriptor;
+use protobuf::reflect::MessageRef;
+use protobuf::reflect::ReflectFieldRef;
+use protobuf::reflect::ReflectMapRef;
+use protobuf::reflect::ReflectRepeatedRef;
+use protobuf::reflect::ReflectValueRef;
+use protobuf::reflect::RuntimeFieldType;
+use protobuf::reflect::RuntimeType;
+use protobuf::well_known_types::any::Any;
+use protobuf::well_known_types::duration::Duration;
+use protobuf::well_known_types::field_mask::FieldMask;
+use protobuf::well_known_types::struct_::value;
+use protobuf::well_known_types::struct_::ListValue;
+use protobuf::well_known_types::struct_::NullValue;
+use protobuf::well_known_types::struct_::Struct;
+use protobuf::well_known_types::struct_::Value;
+use protobuf::well_known_types::timestamp::Timestamp;
+use protobuf::well_known_types::wrappers::BoolValue;
+use protobuf::well_known_types::wrappers::BytesValue;
+use protobuf::well_known_types::wrappers::DoubleValue;
+use protobuf::well_known_types::wrappers::FloatValue;
+use protobuf::well_known_types::wrappers::Int32Value;
+use protobuf::well_known_types::wrappers::Int64Value;
+use protobuf::well_known_types::wrappers::StringValue;
+use protobuf::well_known_types::wrappers::UInt32Value;
+use protobuf::well_known_types::wrappers::UInt64Value;
+use protobuf::MessageDyn;
+
+use crate::base64;
+use crate::float;
+use crate::rfc_3339::TmUtc;
+use crate::well_known_wrapper::WellKnownWrapper;
+
+#[derive(Debug, thiserror::Error)]
+enum PrintErrorInner {
+    #[error(transparent)]
+    Fmt(fmt::Error),
+    #[error("JSON printing of Any is not implemented")]
+    AnyPrintingIsNotImplemented,
+    #[error("Negative nanoseconds in timestamp")]
+    TimestampNegativeNanos,
+    #[error("Unknown struct value kind")]
+    UnknownStructValueKind,
+}
+
+/// Print to JSON error.
+#[derive(Debug, thiserror::Error)]
+#[error(transparent)]
+pub struct PrintError(PrintErrorInner);
+
+impl From<fmt::Error> for PrintError {
+    fn from(e: fmt::Error) -> Self {
+        PrintError(PrintErrorInner::Fmt(e))
+    }
+}
+
+pub type PrintResult<T> = Result<T, PrintError>;
+
+struct Printer {
+    buf: String,
+    print_options: PrintOptions,
+}
+
+trait PrintableToJson {
+    fn print_to_json(&self, w: &mut Printer) -> PrintResult<()>;
+}
+
+trait JsonFloat: fmt::Display + fmt::Debug + PrintableToJson {
+    fn is_nan(&self) -> bool;
+    fn is_pos_infinity(&self) -> bool;
+    fn is_neg_infinity(&self) -> bool;
+
+    fn print_to_json_impl(&self, w: &mut String) -> PrintResult<()> {
+        Ok(if self.is_nan() {
+            write!(w, "\"{}\"", float::PROTOBUF_JSON_NAN)?
+        } else if self.is_pos_infinity() {
+            write!(w, "\"{}\"", float::PROTOBUF_JSON_INF)?
+        } else if self.is_neg_infinity() {
+            write!(w, "\"{}\"", float::PROTOBUF_JSON_MINUS_INF)?
+        } else {
+            write!(w, "{:?}", self)?
+        })
+    }
+}
+
+impl JsonFloat for f32 {
+    fn is_nan(&self) -> bool {
+        f32::is_nan(*self)
+    }
+
+    fn is_pos_infinity(&self) -> bool {
+        f32::is_infinite(*self) && self > &0.0
+    }
+
+    fn is_neg_infinity(&self) -> bool {
+        f32::is_infinite(*self) && self < &0.0
+    }
+}
+
+impl PrintableToJson for f32 {
+    fn print_to_json(&self, w: &mut Printer) -> PrintResult<()> {
+        Ok(self.print_to_json_impl(&mut w.buf)?)
+    }
+}
+
+impl JsonFloat for f64 {
+    fn is_nan(&self) -> bool {
+        f64::is_nan(*self)
+    }
+
+    fn is_pos_infinity(&self) -> bool {
+        f64::is_infinite(*self) && self > &0.0
+    }
+
+    fn is_neg_infinity(&self) -> bool {
+        f64::is_infinite(*self) && self < &0.0
+    }
+}
+
+impl PrintableToJson for f64 {
+    fn print_to_json(&self, w: &mut Printer) -> PrintResult<()> {
+        self.print_to_json_impl(&mut w.buf)
+    }
+}
+
+impl PrintableToJson for u64 {
+    fn print_to_json(&self, w: &mut Printer) -> PrintResult<()> {
+        // 64-bit integers are quoted by default
+        Ok(write!(w.buf, "\"{}\"", self)?)
+    }
+}
+
+impl PrintableToJson for i64 {
+    fn print_to_json(&self, w: &mut Printer) -> PrintResult<()> {
+        // 64-bit integers are quoted by default
+        Ok(write!(w.buf, "\"{}\"", self)?)
+    }
+}
+
+impl PrintableToJson for u32 {
+    fn print_to_json(&self, w: &mut Printer) -> PrintResult<()> {
+        Ok(write!(w.buf, "{}", self)?)
+    }
+}
+
+impl PrintableToJson for i32 {
+    fn print_to_json(&self, w: &mut Printer) -> PrintResult<()> {
+        Ok(write!(w.buf, "{}", self)?)
+    }
+}
+
+impl PrintableToJson for bool {
+    fn print_to_json(&self, w: &mut Printer) -> PrintResult<()> {
+        Ok(write!(w.buf, "{}", self)?)
+    }
+}
+
+impl PrintableToJson for str {
+    fn print_to_json(&self, w: &mut Printer) -> PrintResult<()> {
+        write!(w.buf, "\"")?;
+        for c in self.chars() {
+            match c {
+                '"' => write!(w.buf, "\\\""),
+                '\\' => write!(w.buf, "\\\\"),
+                '\n' => write!(w.buf, "\\n"),
+                '\r' => write!(w.buf, "\\r"),
+                '\t' => write!(w.buf, "\\t"),
+                c if c.is_control() => write!(w.buf, "\\u{:04x}", c as u32),
+                c => write!(w.buf, "{}", c),
+            }?;
+        }
+        write!(w.buf, "\"")?;
+        Ok(())
+    }
+}
+
+impl PrintableToJson for String {
+    fn print_to_json(&self, w: &mut Printer) -> PrintResult<()> {
+        self.as_str().print_to_json(w)
+    }
+}
+
+impl PrintableToJson for [u8] {
+    fn print_to_json(&self, w: &mut Printer) -> PrintResult<()> {
+        let encoded = base64::encode(self);
+        encoded.print_to_json(w)
+    }
+}
+
+impl PrintableToJson for Vec<u8> {
+    fn print_to_json(&self, w: &mut Printer) -> PrintResult<()> {
+        self.as_slice().print_to_json(w)
+    }
+}
+
+impl<'a> PrintableToJson for ReflectValueRef<'a> {
+    fn print_to_json(&self, w: &mut Printer) -> PrintResult<()> {
+        match self {
+            ReflectValueRef::U32(v) => w.print_printable(v),
+            ReflectValueRef::U64(v) => w.print_printable(v),
+            ReflectValueRef::I32(v) => w.print_printable(v),
+            ReflectValueRef::I64(v) => w.print_printable(v),
+            ReflectValueRef::F32(v) => w.print_printable(v),
+            ReflectValueRef::F64(v) => w.print_printable(v),
+            ReflectValueRef::Bool(v) => w.print_printable(v),
+            ReflectValueRef::String(v) => w.print_printable::<str>(v),
+            ReflectValueRef::Bytes(v) => w.print_printable::<[u8]>(v),
+            ReflectValueRef::Enum(d, v) => w.print_enum(d, *v),
+            ReflectValueRef::Message(v) => w.print_message(v),
+        }
+    }
+}
+
+impl PrintableToJson for Duration {
+    fn print_to_json(&self, w: &mut Printer) -> PrintResult<()> {
+        let sign = if self.seconds >= 0 { "" } else { "-" };
+        Ok(write!(
+            w.buf,
+            "\"{}{}.{:09}s\"",
+            sign,
+            self.seconds.abs(),
+            self.nanos.abs()
+        )?)
+    }
+}
+
+impl PrintableToJson for Timestamp {
+    fn print_to_json(&self, w: &mut Printer) -> PrintResult<()> {
+        if self.nanos < 0 {
+            return Err(PrintError(PrintErrorInner::TimestampNegativeNanos));
+        }
+        let tm_utc = TmUtc::from_protobuf_timestamp(self.seconds, self.nanos as u32);
+        w.print_printable(&tm_utc.to_string())
+    }
+}
+
+impl PrintableToJson for FieldMask {
+    fn print_to_json(&self, w: &mut Printer) -> PrintResult<()> {
+        w.print_printable(&self.paths.join(","))
+    }
+}
+
+impl PrintableToJson for Any {
+    fn print_to_json(&self, _w: &mut Printer) -> PrintResult<()> {
+        Err(PrintError(PrintErrorInner::AnyPrintingIsNotImplemented))
+    }
+}
+
+impl PrintableToJson for Value {
+    fn print_to_json(&self, w: &mut Printer) -> PrintResult<()> {
+        match self.kind {
+            // None should not be possible here, but it's better to print null than crash
+            None => w.print_json_null(),
+            Some(value::Kind::NullValue(null_value)) => {
+                match null_value.enum_value() {
+                    Ok(value) => w.print_wk_null_value(&value),
+                    Err(n) => {
+                        // Practically not possible, but it is safer this way.
+                        w.print_printable(&n)
+                    }
+                }
+            }
+            Some(value::Kind::BoolValue(b)) => w.print_printable(&b),
+            Some(value::Kind::NumberValue(n)) => w.print_printable(&n),
+            Some(value::Kind::StringValue(ref s)) => w.print_printable::<String>(&s),
+            Some(value::Kind::StructValue(ref s)) => w.print_printable(&s),
+            Some(value::Kind::ListValue(ref l)) => w.print_printable(&l),
+            Some(_) => Err(PrintError(PrintErrorInner::UnknownStructValueKind)),
+        }
+    }
+}
+
+impl PrintableToJson for ListValue {
+    fn print_to_json(&self, w: &mut Printer) -> PrintResult<()> {
+        w.print_list(&self.values)
+    }
+}
+
+impl PrintableToJson for Struct {
+    fn print_to_json(&self, w: &mut Printer) -> PrintResult<()> {
+        w.print_object(&self.fields)
+    }
+}
+
+impl<'a, P: PrintableToJson> PrintableToJson for &'a P {
+    fn print_to_json(&self, w: &mut Printer) -> PrintResult<()> {
+        (*self).print_to_json(w)
+    }
+}
+
+trait ObjectKey {
+    fn print_object_key(&self, w: &mut Printer) -> PrintResult<()>;
+}
+
+impl<'a> ObjectKey for ReflectValueRef<'a> {
+    fn print_object_key(&self, w: &mut Printer) -> PrintResult<()> {
+        match self {
+            ReflectValueRef::String(v) => return w.print_printable::<str>(v),
+            ReflectValueRef::Bytes(v) => return w.print_printable::<[u8]>(v),
+            // do not quote, because printable is quoted
+            ReflectValueRef::U64(v) => return w.print_printable(v),
+            ReflectValueRef::I64(v) => return w.print_printable(v),
+            ReflectValueRef::Enum(d, v) if !w.print_options.enum_values_int => {
+                return w.print_enum(d, *v)
+            }
+            _ => {}
+        }
+
+        write!(w.buf, "\"")?;
+
+        match self {
+            ReflectValueRef::U32(v) => w.print_printable(v),
+            ReflectValueRef::I32(v) => w.print_printable(v),
+            ReflectValueRef::Bool(v) => w.print_printable(v),
+            ReflectValueRef::Enum(d, v) if w.print_options.enum_values_int => w.print_enum(d, *v),
+            ReflectValueRef::Enum(..)
+            | ReflectValueRef::U64(_)
+            | ReflectValueRef::I64(_)
+            | ReflectValueRef::String(_)
+            | ReflectValueRef::Bytes(_) => unreachable!(),
+            ReflectValueRef::F32(_) | ReflectValueRef::F64(_) | ReflectValueRef::Message(_) => {
+                panic!("cannot be object key")
+            }
+        }?;
+
+        write!(w.buf, "\"")?;
+
+        Ok(())
+    }
+}
+
+impl ObjectKey for String {
+    fn print_object_key(&self, w: &mut Printer) -> PrintResult<()> {
+        w.print_printable(self)
+    }
+}
+
+impl<'a, O: ObjectKey> ObjectKey for &'a O {
+    fn print_object_key(&self, w: &mut Printer) -> PrintResult<()> {
+        (*self).print_object_key(w)
+    }
+}
+
+impl Printer {
+    fn print_comma_but_first(&mut self, first: &mut bool) -> fmt::Result {
+        if *first {
+            *first = false;
+            Ok(())
+        } else {
+            write!(self.buf, ", ")
+        }
+    }
+
+    fn print_json_null(&mut self) -> PrintResult<()> {
+        Ok(write!(self.buf, "null")?)
+    }
+
+    fn print_printable<F: PrintableToJson + ?Sized>(&mut self, f: &F) -> PrintResult<()> {
+        f.print_to_json(self)
+    }
+
+    fn print_list<I>(&mut self, items: I) -> PrintResult<()>
+    where
+        I: IntoIterator,
+        I::Item: PrintableToJson,
+    {
+        write!(self.buf, "[")?;
+        for (i, item) in items.into_iter().enumerate() {
+            if i != 0 {
+                write!(self.buf, ", ")?;
+            }
+            self.print_printable(&item)?;
+        }
+        write!(self.buf, "]")?;
+        Ok(())
+    }
+
+    fn print_repeated(&mut self, repeated: &ReflectRepeatedRef) -> PrintResult<()> {
+        self.print_list(repeated)
+    }
+
+    fn print_object<I, K, V>(&mut self, items: I) -> PrintResult<()>
+    where
+        I: IntoIterator<Item = (K, V)>,
+        K: ObjectKey,
+        V: PrintableToJson,
+    {
+        write!(self.buf, "{{")?;
+        for (i, (k, v)) in items.into_iter().enumerate() {
+            if i != 0 {
+                write!(self.buf, ", ")?;
+            }
+            k.print_object_key(self)?;
+            write!(self.buf, ": ")?;
+            self.print_printable(&v)?;
+        }
+        write!(self.buf, "}}")?;
+        Ok(())
+    }
+
+    fn print_map(&mut self, map: &ReflectMapRef) -> PrintResult<()> {
+        self.print_object(map.into_iter())
+    }
+
+    fn print_enum_known(&mut self, value: &EnumValueDescriptor) -> PrintResult<()> {
+        if let Some(null_value) = value.cast() {
+            self.print_wk_null_value(&null_value)
+        } else {
+            if self.print_options.enum_values_int {
+                self.print_printable(&value.value())
+            } else {
+                Ok(write!(self.buf, "\"{}\"", value.name())?)
+            }
+        }
+    }
+
+    fn print_enum(&mut self, descriptor: &EnumDescriptor, v: i32) -> PrintResult<()> {
+        if self.print_options.enum_values_int {
+            self.print_printable(&v)
+        } else {
+            match descriptor.value_by_number(v) {
+                Some(value) => self.print_enum_known(&value),
+                None => self.print_printable(&v),
+            }
+        }
+    }
+
+    fn print_message(&mut self, message: &MessageRef) -> PrintResult<()> {
+        if let Some(duration) = message.downcast_ref::<Duration>() {
+            self.print_printable(duration)
+        } else if let Some(timestamp) = message.downcast_ref::<Timestamp>() {
+            self.print_printable(timestamp)
+        } else if let Some(field_mask) = message.downcast_ref::<FieldMask>() {
+            self.print_printable(field_mask)
+        } else if let Some(any) = message.downcast_ref::<Any>() {
+            self.print_printable(any)
+        } else if let Some(value) = message.downcast_ref::<Value>() {
+            self.print_printable(value)
+        } else if let Some(value) = message.downcast_ref::<DoubleValue>() {
+            self.print_wrapper(value)
+        } else if let Some(value) = message.downcast_ref::<FloatValue>() {
+            self.print_wrapper(value)
+        } else if let Some(value) = message.downcast_ref::<Int64Value>() {
+            self.print_wrapper(value)
+        } else if let Some(value) = message.downcast_ref::<UInt64Value>() {
+            self.print_wrapper(value)
+        } else if let Some(value) = message.downcast_ref::<Int32Value>() {
+            self.print_wrapper(value)
+        } else if let Some(value) = message.downcast_ref::<UInt32Value>() {
+            self.print_wrapper(value)
+        } else if let Some(value) = message.downcast_ref::<BoolValue>() {
+            self.print_wrapper(value)
+        } else if let Some(value) = message.downcast_ref::<StringValue>() {
+            self.print_wrapper(value)
+        } else if let Some(value) = message.downcast_ref::<BytesValue>() {
+            self.print_wrapper(value)
+        } else if let Some(value) = message.downcast_ref::<ListValue>() {
+            self.print_printable(value)
+        } else if let Some(value) = message.downcast_ref::<Struct>() {
+            self.print_printable(value)
+        } else {
+            self.print_regular_message(message)
+        }
+    }
+
+    fn print_regular_message(&mut self, message: &MessageRef) -> Result<(), PrintError> {
+        let descriptor = message.descriptor_dyn();
+
+        write!(self.buf, "{{")?;
+        let mut first = true;
+        for field in descriptor.fields() {
+            let json_field_name = if self.print_options.proto_field_name {
+                field.name()
+            } else {
+                field.json_name()
+            };
+
+            let field_type = field.runtime_field_type();
+
+            match field.get_reflect(&**message) {
+                ReflectFieldRef::Optional(v) => match v.value() {
+                    None => {
+                        if self.print_options.always_output_default_values {
+                            let is_message = match field_type {
+                                RuntimeFieldType::Singular(s) => match s {
+                                    RuntimeType::Message(_) => true,
+                                    _ => false,
+                                },
+                                _ => unreachable!(),
+                            };
+
+                            let is_oneof = field.proto().has_oneof_index();
+
+                            if !is_message && !is_oneof {
+                                let v = field.get_singular_field_or_default(&**message);
+                                self.print_comma_but_first(&mut first)?;
+                                write!(self.buf, "\"{}\": ", json_field_name)?;
+                                self.print_printable(&v)?;
+                            }
+                        }
+                    }
+                    Some(v) => {
+                        self.print_comma_but_first(&mut first)?;
+                        write!(self.buf, "\"{}\": ", json_field_name)?;
+                        self.print_printable(&v)?;
+                    }
+                },
+                ReflectFieldRef::Repeated(v) => {
+                    if !v.is_empty() || self.print_options.always_output_default_values {
+                        self.print_comma_but_first(&mut first)?;
+                        write!(self.buf, "\"{}\": ", json_field_name)?;
+                        self.print_repeated(&v)?;
+                    }
+                }
+                ReflectFieldRef::Map(v) => {
+                    if !v.is_empty() || self.print_options.always_output_default_values {
+                        self.print_comma_but_first(&mut first)?;
+                        write!(self.buf, "\"{}\": ", json_field_name)?;
+                        self.print_map(&v)?;
+                    }
+                }
+            }
+        }
+        write!(self.buf, "}}")?;
+        Ok(())
+    }
+
+    fn print_wk_null_value(&mut self, _null_value: &NullValue) -> PrintResult<()> {
+        self.print_json_null()
+    }
+
+    fn print_wrapper<W>(&mut self, value: &W) -> PrintResult<()>
+    where
+        W: WellKnownWrapper,
+        W::Underlying: PrintableToJson,
+    {
+        self.print_printable(value.get_ref())
+    }
+}
+
+/// Options for printing JSON to string
+///
+/// # Examples
+///
+/// ```
+/// let print_options = protobuf_json_mapping::PrintOptions {
+///     enum_values_int: true,
+///     ..Default::default()
+/// };
+/// ```
+#[derive(Default, Debug, Clone)]
+pub struct PrintOptions {
+    /// Use ints instead of strings for enums.
+    ///
+    /// Note both string or int can be parsed.
+    pub enum_values_int: bool,
+    /// Use protobuf field names instead of `lowerCamelCase` which is used by default.
+    /// Note both names are supported when JSON is parsed.
+    pub proto_field_name: bool,
+    /// Output field default values.
+    pub always_output_default_values: bool,
+    /// Prevent initializing `PrintOptions` enumerating all field.
+    pub _future_options: (),
+}
+
+/// Serialize message to JSON according to protobuf specification.
+pub fn print_to_string_with_options(
+    message: &dyn MessageDyn,
+    print_options: &PrintOptions,
+) -> PrintResult<String> {
+    let mut printer = Printer {
+        buf: String::new(),
+        print_options: print_options.clone(),
+    };
+    printer.print_message(&MessageRef::from(message))?;
+    Ok(printer.buf)
+}
+
+/// Serialize message to JSON according to protobuf specification.
+pub fn print_to_string(message: &dyn MessageDyn) -> PrintResult<String> {
+    print_to_string_with_options(message, &PrintOptions::default())
+}
diff --git a/src/rfc_3339.rs b/src/rfc_3339.rs
new file mode 100644
index 0000000..ef04bcf
--- /dev/null
+++ b/src/rfc_3339.rs
@@ -0,0 +1,585 @@
+use std::fmt;
+use std::time::Duration;
+
+// Number of seconds in a day is a constant.
+// We do not support leap seconds here.
+const SECONDS_IN_DAY: u64 = 86400;
+
+// Gregorian calendar has 400 years cycles, this is a procedure
+// for computing if a year is a leap year.
+fn is_leap_year(year: i64) -> bool {
+    if year % 4 != 0 {
+        false
+    } else if year % 100 != 0 {
+        true
+    } else if year % 400 != 0 {
+        false
+    } else {
+        true
+    }
+}
+
+fn days_in_year(year: i64) -> u32 {
+    if is_leap_year(year) {
+        366
+    } else {
+        365
+    }
+}
+
+// Number of leap years among 400 consecutive years.
+const CYCLE_LEAP_YEARS: u32 = 400 / 4 - 400 / 100 + 400 / 400;
+// Number of days in 400 years cycle.
+const CYCLE_DAYS: u32 = 400 * 365 + CYCLE_LEAP_YEARS;
+// Number of seconds in 400 years cycle.
+const CYCLE_SECONDS: u64 = CYCLE_DAYS as u64 * SECONDS_IN_DAY;
+
+// Number of seconds between 1 Jan 1970 and 1 Jan 2000.
+// Check with:
+// `TZ=UTC gdate --rfc-3339=seconds --date @946684800`
+const YEARS_1970_2000_SECONDS: u64 = 946684800;
+// Number of seconds between 1 Jan 1600 and 1 Jan 1970.
+const YEARS_1600_1970_SECONDS: u64 = CYCLE_SECONDS - YEARS_1970_2000_SECONDS;
+
+// For each year in the cycle, number of leap years before in the cycle.
+#[cfg_attr(rustfmt, rustfmt_skip)]
+static YEAR_DELTAS: [u8; 401] = [
+    0,  1,  1,  1,  1,  2,  2,  2,  2,  3,  3,  3,  3,  4,  4,  4,  4,  5,  5,  5,
+    5,  6,  6,  6,  6,  7,  7,  7,  7,  8,  8,  8,  8,  9,  9,  9,  9, 10, 10, 10,
+    10, 11, 11, 11, 11, 12, 12, 12, 12, 13, 13, 13, 13, 14, 14, 14, 14, 15, 15, 15,
+    15, 16, 16, 16, 16, 17, 17, 17, 17, 18, 18, 18, 18, 19, 19, 19, 19, 20, 20, 20,
+    20, 21, 21, 21, 21, 22, 22, 22, 22, 23, 23, 23, 23, 24, 24, 24, 24, 25, 25, 25, // 100
+    25, 25, 25, 25, 25, 26, 26, 26, 26, 27, 27, 27, 27, 28, 28, 28, 28, 29, 29, 29,
+    29, 30, 30, 30, 30, 31, 31, 31, 31, 32, 32, 32, 32, 33, 33, 33, 33, 34, 34, 34,
+    34, 35, 35, 35, 35, 36, 36, 36, 36, 37, 37, 37, 37, 38, 38, 38, 38, 39, 39, 39,
+    39, 40, 40, 40, 40, 41, 41, 41, 41, 42, 42, 42, 42, 43, 43, 43, 43, 44, 44, 44,
+    44, 45, 45, 45, 45, 46, 46, 46, 46, 47, 47, 47, 47, 48, 48, 48, 48, 49, 49, 49, // 200
+    49, 49, 49, 49, 49, 50, 50, 50, 50, 51, 51, 51, 51, 52, 52, 52, 52, 53, 53, 53,
+    53, 54, 54, 54, 54, 55, 55, 55, 55, 56, 56, 56, 56, 57, 57, 57, 57, 58, 58, 58,
+    58, 59, 59, 59, 59, 60, 60, 60, 60, 61, 61, 61, 61, 62, 62, 62, 62, 63, 63, 63,
+    63, 64, 64, 64, 64, 65, 65, 65, 65, 66, 66, 66, 66, 67, 67, 67, 67, 68, 68, 68,
+    68, 69, 69, 69, 69, 70, 70, 70, 70, 71, 71, 71, 71, 72, 72, 72, 72, 73, 73, 73, // 300
+    73, 73, 73, 73, 73, 74, 74, 74, 74, 75, 75, 75, 75, 76, 76, 76, 76, 77, 77, 77,
+    77, 78, 78, 78, 78, 79, 79, 79, 79, 80, 80, 80, 80, 81, 81, 81, 81, 82, 82, 82,
+    82, 83, 83, 83, 83, 84, 84, 84, 84, 85, 85, 85, 85, 86, 86, 86, 86, 87, 87, 87,
+    87, 88, 88, 88, 88, 89, 89, 89, 89, 90, 90, 90, 90, 91, 91, 91, 91, 92, 92, 92,
+    92, 93, 93, 93, 93, 94, 94, 94, 94, 95, 95, 95, 95, 96, 96, 96, 96, 97, 97, 97, 97,
+];
+
+/// UTC time
+pub struct TmUtc {
+    /// Year
+    year: i64,
+    /// 1..=12
+    month: u32,
+    /// 1-based day of month
+    day: u32,
+    /// 0..=23
+    hour: u32,
+    /// 0..=59
+    minute: u32,
+    /// 0..=59; no leap seconds
+    second: u32,
+    /// 0..=999_999_999
+    nanos: u32,
+}
+
+#[derive(Debug, thiserror::Error)]
+pub enum Rfc3339ParseError {
+    #[error("Unexpected EOF")]
+    UnexpectedEof,
+    #[error("Trailing characters")]
+    TrailngCharacters,
+    #[error("Expecting digits")]
+    ExpectingDigits,
+    #[error("Expecting character: {:?}", .0)]
+    ExpectingChar(char),
+    #[error("Expecting timezone")]
+    ExpectingTimezone,
+    #[error("No digits after dot")]
+    NoDigitsAfterDot,
+    #[error("Date-time field is out of range")]
+    DateTimeFieldOutOfRange,
+    #[error("Expecting date-time separator")]
+    ExpectingDateTimeSeparator,
+}
+
+pub type Rfc3339ParseResult<A> = Result<A, Rfc3339ParseError>;
+
+impl TmUtc {
+    fn day_of_cycle_to_year_day_of_year(day_of_cycle: u32) -> (i64, u32) {
+        debug_assert!(day_of_cycle < CYCLE_DAYS);
+
+        let mut year_mod_400 = (day_of_cycle / 365) as i64;
+        let mut day_or_year = (day_of_cycle % 365) as u32;
+
+        let delta = YEAR_DELTAS[year_mod_400 as usize] as u32;
+        if day_or_year < delta {
+            year_mod_400 -= 1;
+            day_or_year += 365 - YEAR_DELTAS[year_mod_400 as usize] as u32;
+        } else {
+            day_or_year -= delta;
+        }
+
+        (year_mod_400, day_or_year)
+    }
+
+    fn year_day_of_year_to_day_of_cycle(year_mod_400: u32, day_of_year: u32) -> u32 {
+        debug_assert!(year_mod_400 < 400);
+        debug_assert!(day_of_year < days_in_year(year_mod_400 as i64));
+
+        year_mod_400 * 365 + YEAR_DELTAS[year_mod_400 as usize] as u32 + day_of_year
+    }
+
+    // Convert seconds of the day of hour, minute and second
+    fn second_of_day_to_h_m_s(seconds: u32) -> (u32, u32, u32) {
+        debug_assert!(seconds < 86400);
+
+        let hour = seconds / 3600;
+        let minute = seconds % 3600 / 60;
+        let second = seconds % 60;
+
+        (hour, minute, second)
+    }
+
+    fn h_m_s_to_second_of_day(hour: u32, minute: u32, second: u32) -> u32 {
+        debug_assert!(hour < 24);
+        debug_assert!(minute < 60);
+        debug_assert!(second < 60);
+
+        hour * 3600 + minute * 60 + second
+    }
+
+    fn days_in_months(year: i64) -> &'static [u32] {
+        if is_leap_year(year) {
+            &[31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]
+        } else {
+            &[31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]
+        }
+    }
+
+    // Convert day of year (0-based) to month and day
+    fn day_of_year_to_month_day(year: i64, day_of_year: u32) -> (u32, u32) {
+        debug_assert!(day_of_year < days_in_year(year));
+
+        let days_in_months = TmUtc::days_in_months(year);
+
+        let mut rem_days = day_of_year;
+        let mut month = 1;
+        while rem_days >= days_in_months[month - 1] {
+            rem_days -= days_in_months[month - 1];
+            month += 1;
+        }
+
+        debug_assert!(rem_days + 1 <= days_in_months[month - 1]);
+
+        (month as u32, rem_days + 1)
+    }
+
+    fn month_day_to_day_of_year(year: i64, month: u32, day: u32) -> u32 {
+        debug_assert!(month >= 1);
+        debug_assert!(month <= 12);
+
+        debug_assert!(day >= 1);
+
+        let days_in_months = TmUtc::days_in_months(year);
+
+        // TODO: replace loop with precomputed table
+        let mut day_of_year = 0;
+        for next_month in 1..month {
+            day_of_year += days_in_months[next_month as usize - 1];
+        }
+
+        debug_assert!(day <= days_in_months[month as usize - 1]);
+
+        day_of_year + day - 1
+    }
+
+    // Construct from duration added to cycle start year
+    fn from_cycle_start_add_duration(mut cycle_start: i64, add: Duration) -> TmUtc {
+        debug_assert!(cycle_start % 400 == 0);
+
+        // Split duration to days and duration within day
+
+        let days = add.as_secs() / SECONDS_IN_DAY;
+        let duration_of_day = add - Duration::from_secs(days * SECONDS_IN_DAY);
+
+        let cycles = days / CYCLE_DAYS as u64;
+        cycle_start += cycles as i64 * 400;
+        let day_of_cycle = days % CYCLE_DAYS as u64;
+
+        let (year_mod_400, day_of_year) =
+            TmUtc::day_of_cycle_to_year_day_of_year(day_of_cycle as u32);
+
+        let (year,) = (cycle_start + year_mod_400,);
+        let (month, day) = TmUtc::day_of_year_to_month_day(year, day_of_year);
+        let (hour, minute, second) =
+            TmUtc::second_of_day_to_h_m_s(duration_of_day.as_secs() as u32);
+
+        TmUtc {
+            year,
+            month,
+            day,
+            hour,
+            minute,
+            second,
+            nanos: duration_of_day.subsec_nanos(),
+        }
+    }
+
+    // Protobuf timestamp: seconds from epoch, and nanos 0..=999_999_999 counting forward.
+    pub fn from_protobuf_timestamp(seconds: i64, nanos: u32) -> TmUtc {
+        assert!(nanos <= 999_999_999);
+
+        let (mut year, mut seconds) = if seconds >= 0 {
+            (1970, seconds as u64)
+        } else {
+            let minus_seconds = if seconds == i64::MIN {
+                i64::MIN as u64
+            } else {
+                -seconds as u64
+            };
+
+            let cycles = (minus_seconds + CYCLE_SECONDS) / CYCLE_SECONDS;
+
+            (
+                1970 - 400 * cycles as i64,
+                cycles * CYCLE_SECONDS - minus_seconds,
+            )
+        };
+
+        year -= 370;
+        seconds += YEARS_1600_1970_SECONDS;
+
+        TmUtc::from_cycle_start_add_duration(year, Duration::new(seconds, nanos))
+    }
+
+    pub fn to_protobuf_timestamp(&self) -> (i64, u32) {
+        assert!(self.year >= 0);
+        assert!(self.year <= 9999);
+
+        let year_mod_400 = ((self.year % 400 + 400) % 400) as u32;
+        let cycle_start = self.year - year_mod_400 as i64;
+
+        let day_of_year = TmUtc::month_day_to_day_of_year(self.year, self.month, self.day);
+        let day_of_cycle = TmUtc::year_day_of_year_to_day_of_cycle(year_mod_400, day_of_year);
+        let second_of_day = TmUtc::h_m_s_to_second_of_day(self.hour, self.minute, self.second);
+
+        let second_of_cycle = day_of_cycle as u64 * SECONDS_IN_DAY + second_of_day as u64;
+
+        let epoch_seconds = (cycle_start - 1600) / 400 * CYCLE_SECONDS as i64
+            - YEARS_1600_1970_SECONDS as i64
+            + second_of_cycle as i64;
+
+        (epoch_seconds, self.nanos)
+    }
+
+    pub fn parse_rfc_3339(s: &str) -> Rfc3339ParseResult<(i64, u32)> {
+        struct Parser<'a> {
+            s: &'a [u8],
+            pos: usize,
+        }
+
+        impl<'a> Parser<'a> {
+            fn next_number(&mut self, len: usize) -> Rfc3339ParseResult<u32> {
+                let end_pos = self.pos + len;
+                if end_pos > self.s.len() {
+                    return Err(Rfc3339ParseError::UnexpectedEof);
+                }
+                let mut r = 0;
+                for i in 0..len {
+                    let c = self.s[self.pos + i];
+                    if c >= b'0' && c <= b'9' {
+                        r = r * 10 + (c - b'0') as u32;
+                    } else {
+                        return Err(Rfc3339ParseError::ExpectingDigits);
+                    }
+                }
+                self.pos += len;
+                Ok(r)
+            }
+
+            fn lookahead_char(&self) -> Rfc3339ParseResult<u8> {
+                if self.pos == self.s.len() {
+                    return Err(Rfc3339ParseError::UnexpectedEof);
+                }
+                Ok(self.s[self.pos])
+            }
+
+            fn next_char(&mut self, expect: u8) -> Rfc3339ParseResult<()> {
+                assert!(expect < 0x80);
+                let c = self.lookahead_char()?;
+                if c != expect {
+                    return Err(Rfc3339ParseError::ExpectingChar(expect as char));
+                }
+                self.pos += 1;
+                Ok(())
+            }
+        }
+
+        let mut parser = Parser {
+            s: s.as_bytes(),
+            pos: 0,
+        };
+
+        let year = parser.next_number(4)? as i64;
+        parser.next_char(b'-')?;
+        let month = parser.next_number(2)?;
+        parser.next_char(b'-')?;
+        let day = parser.next_number(2)?;
+
+        if month < 1 || month > 12 {
+            return Err(Rfc3339ParseError::DateTimeFieldOutOfRange);
+        }
+
+        if day < 1 || day > TmUtc::days_in_months(year as i64)[month as usize - 1] {
+            return Err(Rfc3339ParseError::DateTimeFieldOutOfRange);
+        }
+
+        match parser.lookahead_char()? {
+            b'T' | b't' | b' ' => parser.pos += 1,
+            _ => return Err(Rfc3339ParseError::ExpectingDateTimeSeparator),
+        }
+
+        let hour = parser.next_number(2)?;
+        parser.next_char(b':')?;
+        let minute = parser.next_number(2)?;
+        parser.next_char(b':')?;
+        let second = parser.next_number(2)?;
+
+        if hour > 23 || minute > 59 || second > 60 {
+            return Err(Rfc3339ParseError::DateTimeFieldOutOfRange);
+        }
+
+        // round down leap second
+        let second = if second == 60 { 59 } else { second };
+
+        let nanos = if parser.lookahead_char()? == b'.' {
+            parser.pos += 1;
+            let mut digits = 0;
+            let mut nanos = 0;
+            while parser.lookahead_char()? >= b'0' && parser.lookahead_char()? <= b'9' {
+                let digit = (parser.lookahead_char()? - b'0') as u32;
+                parser.pos += 1;
+                if digits == 9 {
+                    continue;
+                }
+                digits += 1;
+                nanos = nanos * 10 + digit;
+            }
+
+            if digits == 0 {
+                return Err(Rfc3339ParseError::NoDigitsAfterDot);
+            }
+
+            for _ in digits..9 {
+                nanos *= 10;
+            }
+            nanos
+        } else {
+            0
+        };
+
+        let offset_seconds = if parser.lookahead_char()? == b'Z' || parser.lookahead_char()? == b'z'
+        {
+            parser.pos += 1;
+            0
+        } else {
+            let sign = if parser.lookahead_char()? == b'+' {
+                1
+            } else if parser.lookahead_char()? == b'-' {
+                -1
+            } else {
+                return Err(Rfc3339ParseError::ExpectingTimezone);
+            };
+
+            parser.pos += 1;
+
+            let hour_offset = parser.next_number(2)?;
+            parser.next_char(b':')?;
+            let minute_offset = parser.next_number(2)?;
+
+            (hour_offset * 3600 + 60 * minute_offset) as i64 * sign
+        };
+
+        if parser.pos != parser.s.len() {
+            return Err(Rfc3339ParseError::TrailngCharacters);
+        }
+
+        let (seconds, nanos) = TmUtc {
+            year,
+            month,
+            day,
+            hour,
+            minute,
+            second,
+            nanos,
+        }
+        .to_protobuf_timestamp();
+
+        Ok((seconds - offset_seconds, nanos))
+    }
+}
+
+impl fmt::Display for TmUtc {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        if self.year > 9999 {
+            write!(f, "+{}", self.year)?;
+        } else if self.year < 0 {
+            write!(f, "{:05}", self.year)?;
+        } else {
+            write!(f, "{:04}", self.year)?;
+        }
+        write!(
+            f,
+            "-{:02}-{:02}T{:02}:{:02}:{:02}",
+            self.month, self.day, self.hour, self.minute, self.second
+        )?;
+
+        // if precision is not specified, print nanoseconds
+        let subsec_digits = f.precision().unwrap_or(9);
+        if subsec_digits != 0 {
+            let mut subsec_digits = subsec_digits;
+
+            let width = if subsec_digits > 9 { 9 } else { subsec_digits };
+
+            // "Truncated" nanonseconds.
+            let mut subsec = self.nanos;
+
+            // Performs 8 iterations when precision=1,
+            // but that's probably not a issue compared to other computations.
+            for _ in width..9 {
+                subsec /= 10;
+            }
+
+            write!(f, ".{:0width$}", subsec, width = width as usize)?;
+
+            // Adding more than 9 digits is meaningless,
+            // but if user requests it, we should print zeros.
+            for _ in 9..subsec_digits {
+                write!(f, "0")?;
+                subsec_digits -= 1;
+            }
+        }
+
+        write!(f, "Z")
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn test_fmt() {
+        fn test_impl(expected: &str, secs: i64, nanos: u32, subsec_digits: u32) {
+            let tm_utc = TmUtc::from_protobuf_timestamp(secs, nanos);
+
+            assert_eq!(
+                expected,
+                format!("{:.prec$}", tm_utc, prec = subsec_digits as usize)
+            );
+        }
+
+        // Tests can be validated with with GNU date:
+        // `TZ=UTC gdate --date @1535585179 --iso-8601=seconds`
+
+        test_impl("1970-01-01T00:00:00Z", 0, 0, 0);
+        test_impl("2018-08-29T23:26:19Z", 1535585179, 0, 0);
+        test_impl("2018-08-29T23:26:19.123Z", 1535585179, 123456789, 3);
+        test_impl("1646-04-01T03:45:44Z", -10216613656, 0, 0);
+        test_impl("1970-01-01T00:00:00.000000001000Z", 0, 1, 12);
+        test_impl("5138-11-16T09:46:40Z", 100000000000, 0, 0);
+        test_impl("+33658-09-27T01:46:41Z", 1000000000001, 0, 0);
+        // Leading zero
+        test_impl("0000-12-31T00:00:00Z", -62135683200, 0, 0);
+        // Minus zero
+        test_impl("-0003-10-30T14:13:20Z", -62235683200, 0, 0);
+        // More than 4 digits
+        // Largest value GNU date can handle
+        test_impl("+2147485547-12-31T23:59:59Z", 67768036191676799, 0, 0);
+        // Negative dates
+        test_impl("1969-12-31T23:59:59Z", -1, 0, 0);
+        test_impl("1969-12-31T23:59:00Z", -60, 0, 0);
+        test_impl("1969-12-31T23:59:58.900Z", -2, 900_000_000, 3);
+        test_impl("1966-10-31T14:13:20Z", -100000000, 0, 0);
+        test_impl("-29719-04-05T22:13:19Z", -1000000000001, 0, 0);
+        // Smallest value GNU date can handle
+        test_impl("-2147481748-01-01T00:00:00Z", -67768040609740800, 0, 0);
+    }
+
+    #[test]
+    fn test_parse_fmt() {
+        fn test_impl(s: &str, width: usize) {
+            let (seconds, nanos) = TmUtc::parse_rfc_3339(s).unwrap();
+            let formatted = format!(
+                "{:.width$}",
+                TmUtc::from_protobuf_timestamp(seconds, nanos),
+                width = width
+            );
+            assert_eq!(formatted, s);
+        }
+
+        test_impl("1970-01-01T00:00:00Z", 0);
+        test_impl("1970-01-01T00:00:00.000Z", 3);
+        test_impl("1970-01-01T00:00:00.000000000Z", 9);
+        test_impl("1970-01-02T00:00:00Z", 0);
+        test_impl("1970-03-01T00:00:00Z", 0);
+        test_impl("1974-01-01T00:00:00Z", 0);
+        test_impl("2018-01-01T00:00:00Z", 0);
+        test_impl("2018-09-02T05:49:10.123456789Z", 9);
+        test_impl("0001-01-01T00:00:00.000000000Z", 9);
+        test_impl("9999-12-31T23:59:59.999999999Z", 9);
+    }
+
+    #[test]
+    fn test_parse_alt() {
+        fn test_impl(alt: &str, parse: &str) {
+            let reference = TmUtc::parse_rfc_3339(alt).unwrap();
+            let parsed = TmUtc::parse_rfc_3339(parse).unwrap();
+            assert_eq!(reference, parsed, "{} - {}", alt, parse);
+        }
+
+        // alternative spelling
+        test_impl("1970-01-01 00:00:00Z", "1970-01-01T00:00:00Z");
+        test_impl("1970-01-01 00:00:00Z", "1970-01-01t00:00:00Z");
+        test_impl("1970-01-01 00:00:00Z", "1970-01-01 00:00:00z");
+        // leap second is rounded down
+        test_impl("2016-12-31 23:59:59Z", "2016-12-31 23:59:60Z");
+        // TZ offset
+        test_impl("1970-01-01 00:00:00Z", "1970-01-01T03:00:00+03:00");
+        test_impl("1970-01-01 00:00:00Z", "1969-12-31 22:15:00-01:45");
+    }
+
+    #[test]
+    fn test_parse_incorrect_inputs() {
+        fn test_impl(s: &str) {
+            assert!(TmUtc::parse_rfc_3339(s).is_err(), "{}", s);
+        }
+
+        test_impl("1970-01-01T00:00:61Z");
+        test_impl("1970-01-01T00:60:61Z");
+        test_impl("1970-01-01T24:00:61Z");
+        test_impl("1970-01-01T00:00:00.Z");
+        test_impl("1970-01-32T00:00:00Z");
+        test_impl("1970-02-29T00:00:00Z");
+        test_impl("1980-02-30T00:00:00Z");
+        test_impl("1980-13-01T00:00:00Z");
+        test_impl("1970-01-01T00:00:00");
+        test_impl("1970-01-01T00:00Z");
+    }
+
+    #[test]
+    fn test_fmt_max_duration() {
+        // Simply check that there are no integer overflows.
+        // I didn't check that resulting strings are correct.
+        assert_eq!(
+            "-292277022657-01-27T08:29:52.000000000Z",
+            format!("{}", TmUtc::from_protobuf_timestamp(i64::MIN, 0))
+        );
+        assert_eq!(
+            "+292277026596-12-04T15:30:07.999999999Z",
+            format!("{}", TmUtc::from_protobuf_timestamp(i64::MAX, 999_999_999))
+        );
+    }
+}
diff --git a/src/well_known_wrapper.rs b/src/well_known_wrapper.rs
new file mode 100644
index 0000000..071630c
--- /dev/null
+++ b/src/well_known_wrapper.rs
@@ -0,0 +1,128 @@
+//! Trait for well-known wrapper types
+
+use protobuf::well_known_types::wrappers::BoolValue;
+use protobuf::well_known_types::wrappers::BytesValue;
+use protobuf::well_known_types::wrappers::DoubleValue;
+use protobuf::well_known_types::wrappers::FloatValue;
+use protobuf::well_known_types::wrappers::Int32Value;
+use protobuf::well_known_types::wrappers::Int64Value;
+use protobuf::well_known_types::wrappers::StringValue;
+use protobuf::well_known_types::wrappers::UInt32Value;
+use protobuf::well_known_types::wrappers::UInt64Value;
+
+/// Well-known wrapper types have single field.
+/// This trait operations return pointers to that field.
+pub(crate) trait WellKnownWrapper {
+    type Underlying;
+
+    fn get_ref(&self) -> &Self::Underlying;
+    fn get_mut(&mut self) -> &mut Self::Underlying;
+}
+
+impl WellKnownWrapper for DoubleValue {
+    type Underlying = f64;
+
+    fn get_ref(&self) -> &f64 {
+        &self.value
+    }
+
+    fn get_mut(&mut self) -> &mut f64 {
+        &mut self.value
+    }
+}
+
+impl WellKnownWrapper for FloatValue {
+    type Underlying = f32;
+
+    fn get_ref(&self) -> &f32 {
+        &self.value
+    }
+
+    fn get_mut(&mut self) -> &mut f32 {
+        &mut self.value
+    }
+}
+
+impl WellKnownWrapper for Int64Value {
+    type Underlying = i64;
+
+    fn get_ref(&self) -> &i64 {
+        &self.value
+    }
+
+    fn get_mut(&mut self) -> &mut i64 {
+        &mut self.value
+    }
+}
+
+impl WellKnownWrapper for UInt64Value {
+    type Underlying = u64;
+
+    fn get_ref(&self) -> &u64 {
+        &self.value
+    }
+
+    fn get_mut(&mut self) -> &mut u64 {
+        &mut self.value
+    }
+}
+
+impl WellKnownWrapper for Int32Value {
+    type Underlying = i32;
+
+    fn get_ref(&self) -> &i32 {
+        &self.value
+    }
+
+    fn get_mut(&mut self) -> &mut i32 {
+        &mut self.value
+    }
+}
+
+impl WellKnownWrapper for UInt32Value {
+    type Underlying = u32;
+
+    fn get_ref(&self) -> &u32 {
+        &self.value
+    }
+
+    fn get_mut(&mut self) -> &mut u32 {
+        &mut self.value
+    }
+}
+
+impl WellKnownWrapper for BoolValue {
+    type Underlying = bool;
+
+    fn get_ref(&self) -> &bool {
+        &self.value
+    }
+
+    fn get_mut(&mut self) -> &mut bool {
+        &mut self.value
+    }
+}
+
+impl WellKnownWrapper for StringValue {
+    type Underlying = String;
+
+    fn get_ref(&self) -> &String {
+        &self.value
+    }
+
+    fn get_mut(&mut self) -> &mut String {
+        &mut self.value
+    }
+}
+
+impl WellKnownWrapper for BytesValue {
+    type Underlying = Vec<u8>;
+
+    fn get_ref(&self) -> &Vec<u8> {
+        &self.value
+    }
+
+    fn get_mut(&mut self) -> &mut Vec<u8> {
+        &mut self.value
+    }
+}