diff --git a/.cargo_vcs_info.json b/.cargo_vcs_info.json
new file mode 100644
index 0000000..ff846a0
--- /dev/null
+++ b/.cargo_vcs_info.json
@@ -0,0 +1,5 @@
+{
+  "git": {
+    "sha1": "db9289a32df4ba3b1de8c383b68b342be4a8a1ba"
+  }
+}
diff --git a/Android.bp b/Android.bp
new file mode 100644
index 0000000..ade0621
--- /dev/null
+++ b/Android.bp
@@ -0,0 +1,8 @@
+// This file is generated by cargo2android.py.
+
+rust_library_host_rlib {
+    name: "liblazycell",
+    crate_name: "lazycell",
+    srcs: ["src/lib.rs"],
+    edition: "2015",
+}
diff --git a/CHANGELOG.md b/CHANGELOG.md
new file mode 100644
index 0000000..33f1a7d
--- /dev/null
+++ b/CHANGELOG.md
@@ -0,0 +1,178 @@
+<a name="v1.2.1"></a>
+## v1.2.1 (2018-12-03)
+
+
+#### Features
+
+*   Implement Clone for LazyCell and AtomicLazyCell ([30fe4a8f](https://github.com/indiv0/lazycell/commit/30fe4a8f568059b3c78ed149a810962a676cb2b2))
+
+
+
+<a name="v1.2.0"></a>
+## v1.2.0 (2018-09-19)
+
+
+#### Features
+
+*   add `LazyCell::replace` for infallible access ([a63ffb90](https://github.com/indiv0/lazycell/commit/a63ffb9040a5e0683a9bbf9d3d5ef589f2ca8b7c))
+
+
+
+<a name="v1.1.0"></a>
+## v1.1.0 (2018-09-10)
+
+
+#### Documentation
+
+*   add note regarding LazyCell::borrow_mut ([9d634d1f](https://github.com/indiv0/lazycell/commit/9d634d1fd9a21b7aa075d407bedf9fe77ba8b79f))
+*   describe mutability more consistently ([b8078029](https://github.com/indiv0/lazycell/commit/b80780294611e92efddcdd33a701b3049ab5c5eb), closes [#78](https://github.com/indiv0/lazycell/issues/78))
+
+#### Improvements
+
+*   add NONE constant for an empty AtomicLazyCell ([31aff0da](https://github.com/indiv0/lazycell/commit/31aff0dacf824841c5f38ef4acf0aa71ec4c36eb), closes [#87](https://github.com/indiv0/lazycell/issues/87))
+*   add `LazyCell::borrow_mut_with` and `LazyCell::try_borrow_mut_with` ([fdc6d268](https://github.com/indiv0/lazycell/commit/fdc6d268f0e9a6668768302f45fe2bb4aa9a7c34), closes [#79](https://github.com/indiv0/lazycell/issues/79), [#80](https://github.com/indiv0/lazycell/issues/80))
+
+
+
+<a name="v1.0.0"></a>
+## v1.0.0 (2018-06-06)
+
+
+#### Features
+
+*   Add #![no_std] ([e59f6b55](https://github.com/indiv0/lazycell/commit/e59f6b5531e310d3df26b0eb40b1431937f38096))
+
+
+
+<a name="0.6.0"></a>
+## 0.6.0 (2017-11-25)
+
+
+#### Bug Fixes
+
+*   fix soundness hole in borrow_with ([d1f46bef](https://github.com/indiv0/lazycell/commit/d1f46bef9d1397570aa9c3e87e18e0d16e6d1585))
+
+#### Features
+
+*   add Default derives ([71bc5088](https://github.com/indiv0/lazycell/commit/71bc50880cd8e20002038197c9b890f5b76ad096))
+*   add LazyCell::try_borrow_with ([bffa4028](https://github.com/indiv0/lazycell/commit/bffa402896670b5c78a9ec050d82a58ee98de6fb))
+*   add LazyCell::borrow_mut method ([fd419dea](https://github.com/indiv0/lazycell/commit/fd419dea965ff1ad3853f26f37e8d107c6ca096c))
+
+#### Breaking Changes
+
+*   add `T: Send` for `AtomicLazyCell` `Sync` impl ([668bb2fa](https://github.com/indiv0/lazycell/commit/668bb2fa974fd6707c4c7edad292c76a9017d74d), closes [#67](https://github.com/indiv0/lazycell/issues/67))
+
+#### Improvements
+
+*   add `T: Send` for `AtomicLazyCell` `Sync` impl ([668bb2fa](https://github.com/indiv0/lazycell/commit/668bb2fa974fd6707c4c7edad292c76a9017d74d), closes [#67](https://github.com/indiv0/lazycell/issues/67))
+
+
+
+<a name="v0.5.1"></a>
+## v0.5.1 (2017-03-24)
+
+
+#### Documentation
+
+*   fix missing backticks ([44bafaaf](https://github.com/indiv0/lazycell/commit/44bafaaf93a91641261f58ee38adadcd4af6458e))
+
+#### Improvements
+
+*   derive `Debug` impls ([9da0a5a2](https://github.com/indiv0/lazycell/commit/9da0a5a2ffac1fef03ef02851c2c89d26d67d225))
+
+#### Features
+
+*   Add get method for Copy types ([dc8f8209](https://github.com/indiv0/lazycell/commit/dc8f8209888b6eba6d18717eba6a22614629b997))
+
+
+
+<a name="v0.5.0"></a>
+## v0.5.0 (2016-12-08)
+
+
+#### Features
+
+*   add borrow_with to LazyCell ([a15efa35](https://github.com/indiv0/lazycell/commit/a15efa359ea5a31a66ba57fc5b25f90c87b4b0dd))
+
+
+
+<a name="v0.4.0"></a>
+##  (2016-08-17)
+
+
+#### Breaking Changes
+
+* **LazyCell:**  return Err(value) on full cell ([68f3415d](https://github.com/indiv0/lazycell/commit/68f3415dd5d6a66ba047a133b7028ebe4f1c5070), breaks [#](https://github.com/indiv0/lazycell/issues/))
+
+#### Improvements
+
+* **LazyCell:**  return Err(value) on full cell ([68f3415d](https://github.com/indiv0/lazycell/commit/68f3415dd5d6a66ba047a133b7028ebe4f1c5070), breaks [#](https://github.com/indiv0/lazycell/issues/))
+
+
+
+<a name="v0.3.0"></a>
+##  (2016-08-16)
+
+
+#### Features
+
+*   add AtomicLazyCell which is thread-safe ([85afbd36](https://github.com/indiv0/lazycell/commit/85afbd36d8a148e14cc53654b39ddb523980124d))
+
+#### Improvements
+
+*   Use UnsafeCell instead of RefCell ([3347a8e9](https://github.com/indiv0/lazycell/commit/3347a8e97d2215a47e25c1e2fc953e8052ad8eb6))
+
+
+
+<a name="v0.2.1"></a>
+##  (2016-04-18)
+
+
+#### Documentation
+
+*   put types in between backticks ([607cf939](https://github.com/indiv0/lazycell/commit/607cf939b05e35001ba3070ec7a0b17b064e7be1))
+
+
+
+<a name="v0.2.0"></a>
+## v0.2.0 (2016-03-28)
+
+
+#### Features
+
+* **lazycell:**
+  *  add tests for `LazyCell` struct ([38f1313d](https://github.com/indiv0/lazycell/commit/38f1313d98542ca8c98b424edfa9ba9c3975f99e), closes [#30](https://github.com/indiv0/lazycell/issues/30))
+  *  remove unnecessary `Default` impl ([68c16d2d](https://github.com/indiv0/lazycell/commit/68c16d2df4e9d13d5298162c06edf918246fd758))
+
+#### Documentation
+
+* **CHANGELOG:**  removed unnecessary sections ([1cc0555d](https://github.com/indiv0/lazycell/commit/1cc0555d875898a01b0832ff967aed6b40e720eb))
+* **README:**  add link to documentation ([c8dc33f0](https://github.com/indiv0/lazycell/commit/c8dc33f01f2c0dc187f59ee53a2b73081053012b), closes [#13](https://github.com/indiv0/lazycell/issues/13))
+
+
+
+<a name="v0.1.0"></a>
+## v0.1.0 (2016-03-16)
+
+
+#### Features
+
+* **lib.rs:**  implement Default trait for LazyCell ([150a6304](https://github.com/indiv0/LazyCell/commit/150a6304a230ee1de8424e49c447ec1b2d6578ce))
+
+
+
+<a name="v0.0.1"></a>
+## v0.0.1 (2016-03-16)
+
+
+#### Bug Fixes
+
+* **Cargo.toml:**  loosen restrictions on Clippy version ([84dd8f96](https://github.com/indiv0/LazyCell/commit/84dd8f960000294f9dad47d776a41b98ed812981))
+
+#### Features
+
+*   add initial implementation ([4b39764a](https://github.com/indiv0/LazyCell/commit/4b39764a575bcb701dbd8047b966f72720fd18a4))
+*   add initial commit ([a80407a9](https://github.com/indiv0/LazyCell/commit/a80407a907ef7c9401f120104663172f6965521a))
+
+
+
diff --git a/Cargo.toml b/Cargo.toml
new file mode 100644
index 0000000..faecd45
--- /dev/null
+++ b/Cargo.toml
@@ -0,0 +1,30 @@
+# 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 believe there's an error in this file please file an
+# issue against the rust-lang/cargo repository. If you're
+# editing this file be aware that the upstream Cargo.toml
+# will likely look very different (and much more reasonable)
+
+[package]
+name = "lazycell"
+version = "1.2.1"
+authors = ["Alex Crichton <alex@alexcrichton.com>", "Nikita Pekin <contact@nikitapek.in>"]
+include = ["CHANGELOG.md", "Cargo.toml", "LICENSE-MIT", "LICENSE-APACHE", "README.md", "src/**/*.rs"]
+description = "A library providing a lazily filled Cell struct"
+documentation = "http://indiv0.github.io/lazycell/lazycell/"
+readme = "README.md"
+keywords = ["lazycell", "lazy", "cell", "library"]
+license = "MIT/Apache-2.0"
+repository = "https://github.com/indiv0/lazycell"
+[dependencies.clippy]
+version = "0.0"
+optional = true
+
+[features]
+nightly = []
+nightly-testing = ["clippy", "nightly"]
diff --git a/Cargo.toml.orig b/Cargo.toml.orig
new file mode 100644
index 0000000..5a4d935
--- /dev/null
+++ b/Cargo.toml.orig
@@ -0,0 +1,26 @@
+[package]
+name = "lazycell"
+version = "1.2.1"
+authors = ["Alex Crichton <alex@alexcrichton.com>",
+           "Nikita Pekin <contact@nikitapek.in>"]
+description = "A library providing a lazily filled Cell struct"
+repository = "https://github.com/indiv0/lazycell"
+documentation = "http://indiv0.github.io/lazycell/lazycell/"
+readme = "README.md"
+keywords = ["lazycell", "lazy", "cell", "library"]
+license = "MIT/Apache-2.0"
+include = [
+    "CHANGELOG.md",
+    "Cargo.toml",
+    "LICENSE-MIT",
+    "LICENSE-APACHE",
+    "README.md",
+    "src/**/*.rs",
+]
+
+[dependencies]
+clippy = { version = "0.0", optional = true }
+
+[features]
+nightly = []
+nightly-testing = ["clippy", "nightly"]
diff --git a/LICENSE b/LICENSE
new file mode 120000
index 0000000..6b579aa
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1 @@
+LICENSE-APACHE
\ No newline at end of file
diff --git a/LICENSE-APACHE b/LICENSE-APACHE
new file mode 100644
index 0000000..16fe87b
--- /dev/null
+++ b/LICENSE-APACHE
@@ -0,0 +1,201 @@
+                              Apache License
+                        Version 2.0, January 2004
+                     http://www.apache.org/licenses/
+
+TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+
+1. Definitions.
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+   "License" shall mean the terms and conditions for use, reproduction,
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+5. Submission of Contributions. Unless You explicitly state otherwise,
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+6. Trademarks. This License does not grant permission to use the trade
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diff --git a/LICENSE-MIT b/LICENSE-MIT
new file mode 100644
index 0000000..b4cbb4b
--- /dev/null
+++ b/LICENSE-MIT
@@ -0,0 +1,26 @@
+Original work Copyright (c) 2014 The Rust Project Developers
+Modified work Copyright (c) 2016-2018 Nikita Pekin and lazycell contributors
+
+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,
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+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
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+TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
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+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..6cd979d
--- /dev/null
+++ b/METADATA
@@ -0,0 +1,19 @@
+name: "lazycell"
+description: "Rust library providing a lazily filled Cell."
+third_party {
+  url {
+    type: HOMEPAGE
+    value: "https://crates.io/crates/lazycell"
+  }
+  url {
+    type: GIT
+    value: "https://github.com/indiv0/lazycell"
+  }
+  version: "1.2.1"
+  license_type: NOTICE
+  last_upgrade_date {
+    year: 2020
+    month: 3
+    day: 31
+  }
+}
diff --git a/MODULE_LICENSE_APACHE2 b/MODULE_LICENSE_APACHE2
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/MODULE_LICENSE_APACHE2
diff --git a/OWNERS b/OWNERS
new file mode 100644
index 0000000..46fc303
--- /dev/null
+++ b/OWNERS
@@ -0,0 +1 @@
+include platform/prebuilts/rust:/OWNERS
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..4e1dd99
--- /dev/null
+++ b/README.md
@@ -0,0 +1,72 @@
+# lazycell
+
+<table>
+    <tr>
+        <td><strong>Linux</strong></td>
+        <td><a href="https://travis-ci.org/indiv0/lazycell" title="Travis Build Status"><img src="https://travis-ci.org/indiv0/lazycell.svg?branch=master" alt="travis-badge"></img></a></td>
+    </tr>
+    <tr>
+        <td colspan="2">
+            <a href="https://indiv0.github.io/lazycell/lazycell" title="API Docs"><img src="https://img.shields.io/badge/API-docs-blue.svg" alt="api-docs-badge"></img></a>
+            <a href="https://crates.io/crates/lazycell" title="Crates.io"><img src="https://img.shields.io/crates/v/lazycell.svg" alt="crates-io"></img></a>
+            <a href="#license" title="License: MIT/Apache-2.0"><img src="https://img.shields.io/crates/l/lazycell.svg" alt="license-badge"></img></a>
+            <a href="https://coveralls.io/github/indiv0/lazycell?branch=master" title="Coverage Status"><img src="https://coveralls.io/repos/github/indiv0/lazycell/badge.svg?branch=master" alt="coveralls-badge"></img></a>
+        </td>
+    </tr>
+</table>
+
+Rust library providing a lazily filled Cell.
+
+# Table of Contents
+
+* [Usage](#usage)
+* [Contributing](#contributing)
+* [Credits](#credits)
+* [License](#license)
+
+## Usage
+
+Add the following to your `Cargo.toml`:
+
+```toml
+[dependencies]
+lazycell = "1.2"
+```
+
+And in your `lib.rs` or `main.rs`:
+
+```rust
+extern crate lazycell;
+```
+
+See the [API docs][api-docs] for information on using the crate in your library.
+
+## Contributing
+
+Contributions are always welcome!
+If you have an idea for something to add (code, documentation, tests, examples,
+etc.) feel free to give it a shot.
+
+Please read [CONTRIBUTING.md][contributing] before you start contributing.
+
+## Credits
+
+The LazyCell library is based originally on work by The Rust Project Developers
+for the project [crates.io][crates-io-repo].
+
+The list of contributors to this project can be found at
+[CONTRIBUTORS.md][contributors].
+
+## License
+
+LazyCell is distributed under the terms of both the MIT license and the Apache
+License (Version 2.0).
+
+See [LICENSE-APACHE][license-apache], and [LICENSE-MIT][license-mit] for details.
+
+[api-docs]: https://indiv0.github.io/lazycell/lazycell
+[contributing]: https://github.com/indiv0/lazycell/blob/master/CONTRIBUTING.md "Contribution Guide"
+[contributors]: https://github.com/indiv0/lazycell/blob/master/CONTRIBUTORS.md "List of Contributors"
+[crates-io-repo]: https://github.com/rust-lang/crates.io "rust-lang/crates.io: Source code for crates.io"
+[license-apache]: https://github.com/indiv0/lazycell/blob/master/LICENSE-APACHE "Apache-2.0 License"
+[license-mit]: https://github.com/indiv0/lazycell/blob/master/LICENSE-MIT "MIT License"
diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 0000000..f7f8488
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1,649 @@
+// Original work Copyright (c) 2014 The Rust Project Developers
+// Modified work Copyright (c) 2016-2018 Nikita Pekin and the lazycell contributors
+// See the README.md file at the top-level directory of this distribution.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![cfg_attr(not(test), no_std)]
+
+#![deny(missing_docs)]
+#![cfg_attr(feature = "nightly", feature(plugin))]
+#![cfg_attr(feature = "clippy", plugin(clippy))]
+
+//! This crate provides a `LazyCell` struct which acts as a lazily filled
+//! `Cell`.
+//!
+//! With a `RefCell`, the inner contents cannot be borrowed for the lifetime of
+//! the entire object, but only of the borrows returned. A `LazyCell` is a
+//! variation on `RefCell` which allows borrows to be tied to the lifetime of
+//! the outer object.
+//!
+//! # Example
+//!
+//! The following example shows a quick example of the basic functionality of
+//! `LazyCell`.
+//!
+//! ```
+//! use lazycell::LazyCell;
+//!
+//! let lazycell = LazyCell::new();
+//!
+//! assert_eq!(lazycell.borrow(), None);
+//! assert!(!lazycell.filled());
+//! lazycell.fill(1).ok();
+//! assert!(lazycell.filled());
+//! assert_eq!(lazycell.borrow(), Some(&1));
+//! assert_eq!(lazycell.into_inner(), Some(1));
+//! ```
+//!
+//! `AtomicLazyCell` is a variant that uses an atomic variable to manage
+//! coordination in a thread-safe fashion. The limitation of an `AtomicLazyCell`
+//! is that after it is initialized, it can't be modified.
+
+
+#[cfg(not(test))]
+#[macro_use]
+extern crate core as std;
+
+use std::cell::UnsafeCell;
+use std::mem;
+use std::sync::atomic::{AtomicUsize, Ordering};
+
+/// A lazily filled `Cell`, with mutable contents.
+///
+/// A `LazyCell` is completely frozen once filled, **unless** you have `&mut`
+/// access to it, in which case `LazyCell::borrow_mut` may be used to mutate the
+/// contents.
+#[derive(Debug, Default)]
+pub struct LazyCell<T> {
+    inner: UnsafeCell<Option<T>>,
+}
+
+impl<T> LazyCell<T> {
+    /// Creates a new, empty, `LazyCell`.
+    pub fn new() -> LazyCell<T> {
+        LazyCell { inner: UnsafeCell::new(None) }
+    }
+
+    /// Put a value into this cell.
+    ///
+    /// This function will return `Err(value)` is the cell is already full.
+    pub fn fill(&self, value: T) -> Result<(), T> {
+        let slot = unsafe { &mut *self.inner.get() };
+        if slot.is_some() {
+            return Err(value);
+        }
+        *slot = Some(value);
+
+        Ok(())
+    }
+
+    /// Put a value into this cell.
+    ///
+    /// Note that this function is infallible but requires `&mut self`. By
+    /// requiring `&mut self` we're guaranteed that no active borrows to this
+    /// cell can exist so we can always fill in the value. This may not always
+    /// be usable, however, as `&mut self` may not be possible to borrow.
+    ///
+    /// # Return value
+    ///
+    /// This function returns the previous value, if any.
+    pub fn replace(&mut self, value: T) -> Option<T> {
+        mem::replace(unsafe { &mut *self.inner.get() }, Some(value))
+    }
+
+    /// Test whether this cell has been previously filled.
+    pub fn filled(&self) -> bool {
+        self.borrow().is_some()
+    }
+
+    /// Borrows the contents of this lazy cell for the duration of the cell
+    /// itself.
+    ///
+    /// This function will return `Some` if the cell has been previously
+    /// initialized, and `None` if it has not yet been initialized.
+    pub fn borrow(&self) -> Option<&T> {
+        unsafe { &*self.inner.get() }.as_ref()
+    }
+
+    /// Borrows the contents of this lazy cell mutably for the duration of the cell
+    /// itself.
+    ///
+    /// This function will return `Some` if the cell has been previously
+    /// initialized, and `None` if it has not yet been initialized.
+    pub fn borrow_mut(&mut self) -> Option<&mut T> {
+        unsafe { &mut *self.inner.get() }.as_mut()
+    }
+
+    /// Borrows the contents of this lazy cell for the duration of the cell
+    /// itself.
+    ///
+    /// If the cell has not yet been filled, the cell is first filled using the
+    /// function provided.
+    ///
+    /// # Panics
+    ///
+    /// Panics if the cell becomes filled as a side effect of `f`.
+    pub fn borrow_with<F: FnOnce() -> T>(&self, f: F) -> &T {
+        if let Some(value) = self.borrow() {
+            return value;
+        }
+        let value = f();
+        if self.fill(value).is_err() {
+            panic!("borrow_with: cell was filled by closure")
+        }
+        self.borrow().unwrap()
+    }
+
+    /// Borrows the contents of this `LazyCell` mutably for the duration of the
+    /// cell itself.
+    ///
+    /// If the cell has not yet been filled, the cell is first filled using the
+    /// function provided.
+    ///
+    /// # Panics
+    ///
+    /// Panics if the cell becomes filled as a side effect of `f`.
+    pub fn borrow_mut_with<F: FnOnce() -> T>(&mut self, f: F) -> &mut T {
+        if !self.filled() {
+            let value = f();
+            if self.fill(value).is_err() {
+                panic!("borrow_mut_with: cell was filled by closure")
+            }
+        }
+
+        self.borrow_mut().unwrap()
+    }
+
+    /// Same as `borrow_with`, but allows the initializing function to fail.
+    ///
+    /// # Panics
+    ///
+    /// Panics if the cell becomes filled as a side effect of `f`.
+    pub fn try_borrow_with<E, F>(&self, f: F) -> Result<&T, E>
+        where F: FnOnce() -> Result<T, E>
+    {
+        if let Some(value) = self.borrow() {
+            return Ok(value);
+        }
+        let value = f()?;
+        if self.fill(value).is_err() {
+            panic!("try_borrow_with: cell was filled by closure")
+        }
+        Ok(self.borrow().unwrap())
+    }
+
+    /// Same as `borrow_mut_with`, but allows the initializing function to fail.
+    ///
+    /// # Panics
+    ///
+    /// Panics if the cell becomes filled as a side effect of `f`.
+    pub fn try_borrow_mut_with<E, F>(&mut self, f: F) -> Result<&mut T, E>
+        where F: FnOnce() -> Result<T, E>
+    {
+        if self.filled() {
+            return Ok(self.borrow_mut().unwrap());
+        }
+        let value = f()?;
+        if self.fill(value).is_err() {
+            panic!("try_borrow_mut_with: cell was filled by closure")
+        }
+        Ok(self.borrow_mut().unwrap())
+    }
+
+    /// Consumes this `LazyCell`, returning the underlying value.
+    pub fn into_inner(self) -> Option<T> {
+        // Rust 1.25 changed UnsafeCell::into_inner() from unsafe to safe
+        // function. This unsafe can be removed when supporting Rust older than
+        // 1.25 is not needed.
+        #[allow(unused_unsafe)]
+        unsafe { self.inner.into_inner() }
+    }
+}
+
+impl<T: Copy> LazyCell<T> {
+    /// Returns a copy of the contents of the lazy cell.
+    ///
+    /// This function will return `Some` if the cell has been previously initialized,
+    /// and `None` if it has not yet been initialized.
+    pub fn get(&self) -> Option<T> {
+        unsafe { *self.inner.get() }
+    }
+}
+
+impl <T: Clone> Clone for LazyCell<T> {
+    /// Create a clone of this `LazyCell`
+    ///
+    /// If self has not been initialized, returns an uninitialized `LazyCell`
+    /// otherwise returns a `LazyCell` already initialized with a clone of the
+    /// contents of self.
+    fn clone(&self) -> LazyCell<T> {
+        LazyCell { inner: UnsafeCell::new(self.borrow().map(Clone::clone) ) }
+    }
+}
+
+// Tracks the AtomicLazyCell inner state
+const NONE: usize = 0;
+const LOCK: usize = 1;
+const SOME: usize = 2;
+
+/// A lazily filled and thread-safe `Cell`, with frozen contents.
+#[derive(Debug, Default)]
+pub struct AtomicLazyCell<T> {
+    inner: UnsafeCell<Option<T>>,
+    state: AtomicUsize,
+}
+
+impl<T> AtomicLazyCell<T> {
+    /// An empty `AtomicLazyCell`.
+    pub const NONE: Self = Self {
+        inner: UnsafeCell::new(None),
+        state: AtomicUsize::new(NONE),
+    };
+
+    /// Creates a new, empty, `AtomicLazyCell`.
+    pub fn new() -> AtomicLazyCell<T> {
+        Self::NONE
+    }
+
+    /// Put a value into this cell.
+    ///
+    /// This function will return `Err(value)` is the cell is already full.
+    pub fn fill(&self, t: T) -> Result<(), T> {
+        if NONE != self.state.compare_and_swap(NONE, LOCK, Ordering::Acquire) {
+            return Err(t);
+        }
+
+        unsafe { *self.inner.get() = Some(t) };
+
+        if LOCK != self.state.compare_and_swap(LOCK, SOME, Ordering::Release) {
+            panic!("unable to release lock");
+        }
+
+        Ok(())
+    }
+
+    /// Put a value into this cell.
+    ///
+    /// Note that this function is infallible but requires `&mut self`. By
+    /// requiring `&mut self` we're guaranteed that no active borrows to this
+    /// cell can exist so we can always fill in the value. This may not always
+    /// be usable, however, as `&mut self` may not be possible to borrow.
+    ///
+    /// # Return value
+    ///
+    /// This function returns the previous value, if any.
+    pub fn replace(&mut self, value: T) -> Option<T> {
+        match mem::replace(self.state.get_mut(), SOME) {
+            NONE | SOME => {}
+            _ => panic!("cell in inconsistent state"),
+        }
+        mem::replace(unsafe { &mut *self.inner.get() }, Some(value))
+    }
+
+    /// Test whether this cell has been previously filled.
+    pub fn filled(&self) -> bool {
+        self.state.load(Ordering::Acquire) == SOME
+    }
+
+    /// Borrows the contents of this lazy cell for the duration of the cell
+    /// itself.
+    ///
+    /// This function will return `Some` if the cell has been previously
+    /// initialized, and `None` if it has not yet been initialized.
+    pub fn borrow(&self) -> Option<&T> {
+        match self.state.load(Ordering::Acquire) {
+            SOME => unsafe { &*self.inner.get() }.as_ref(),
+            _ => None,
+        }
+    }
+
+    /// Consumes this `LazyCell`, returning the underlying value.
+    pub fn into_inner(self) -> Option<T> {
+        // Rust 1.25 changed UnsafeCell::into_inner() from unsafe to safe
+        // function. This unsafe can be removed when supporting Rust older than
+        // 1.25 is not needed.
+        #[allow(unused_unsafe)]
+        unsafe { self.inner.into_inner() }
+    }
+}
+
+impl<T: Copy> AtomicLazyCell<T> {
+    /// Returns a copy of the contents of the lazy cell.
+    ///
+    /// This function will return `Some` if the cell has been previously initialized,
+    /// and `None` if it has not yet been initialized.
+    pub fn get(&self) -> Option<T> {
+        match self.state.load(Ordering::Acquire) {
+            SOME => unsafe { *self.inner.get() },
+            _ => None,
+        }
+    }
+}
+
+impl<T: Clone> Clone for AtomicLazyCell<T> {
+    /// Create a clone of this `AtomicLazyCell`
+    ///
+    /// If self has not been initialized, returns an uninitialized `AtomicLazyCell`
+    /// otherwise returns an `AtomicLazyCell` already initialized with a clone of the
+    /// contents of self.
+    fn clone(&self) -> AtomicLazyCell<T> {
+        self.borrow().map_or(
+            Self::NONE,
+            |v| AtomicLazyCell {
+                inner: UnsafeCell::new(Some(v.clone())),
+                state: AtomicUsize::new(SOME),
+            }
+        )
+    }
+}
+
+unsafe impl<T: Sync + Send> Sync for AtomicLazyCell<T> {}
+
+unsafe impl<T: Send> Send for AtomicLazyCell<T> {}
+
+#[cfg(test)]
+mod tests {
+    use super::{AtomicLazyCell, LazyCell};
+
+    #[test]
+    fn test_borrow_from_empty() {
+        let lazycell: LazyCell<usize> = LazyCell::new();
+
+        let value = lazycell.borrow();
+        assert_eq!(value, None);
+
+        let value = lazycell.get();
+        assert_eq!(value, None);
+    }
+
+    #[test]
+    fn test_fill_and_borrow() {
+        let lazycell = LazyCell::new();
+
+        assert!(!lazycell.filled());
+        lazycell.fill(1).unwrap();
+        assert!(lazycell.filled());
+
+        let value = lazycell.borrow();
+        assert_eq!(value, Some(&1));
+
+        let value = lazycell.get();
+        assert_eq!(value, Some(1));
+    }
+
+    #[test]
+    fn test_borrow_mut() {
+        let mut lazycell = LazyCell::new();
+        assert!(lazycell.borrow_mut().is_none());
+
+        lazycell.fill(1).unwrap();
+        assert_eq!(lazycell.borrow_mut(), Some(&mut 1));
+
+        *lazycell.borrow_mut().unwrap() = 2;
+        assert_eq!(lazycell.borrow_mut(), Some(&mut 2));
+
+        // official way to reset the cell
+        lazycell = LazyCell::new();
+        assert!(lazycell.borrow_mut().is_none());
+    }
+
+    #[test]
+    fn test_already_filled_error() {
+        let lazycell = LazyCell::new();
+
+        lazycell.fill(1).unwrap();
+        assert_eq!(lazycell.fill(1), Err(1));
+    }
+
+    #[test]
+    fn test_borrow_with() {
+        let lazycell = LazyCell::new();
+
+        let value = lazycell.borrow_with(|| 1);
+        assert_eq!(&1, value);
+    }
+
+    #[test]
+    fn test_borrow_with_already_filled() {
+        let lazycell = LazyCell::new();
+        lazycell.fill(1).unwrap();
+
+        let value = lazycell.borrow_with(|| 1);
+        assert_eq!(&1, value);
+    }
+
+    #[test]
+    fn test_borrow_with_not_called_when_filled() {
+        let lazycell = LazyCell::new();
+
+        lazycell.fill(1).unwrap();
+
+        let value = lazycell.borrow_with(|| 2);
+        assert_eq!(&1, value);
+    }
+
+    #[test]
+    #[should_panic]
+    fn test_borrow_with_sound_with_reentrancy() {
+        // Kudos to dbaupp for discovering this issue
+        // https://www.reddit.com/r/rust/comments/5vs9rt/lazycell_a_rust_library_providing_a_lazilyfilled/de527xm/
+        let lazycell: LazyCell<Box<i32>> = LazyCell::new();
+
+        let mut reference: Option<&i32> = None;
+
+        lazycell.borrow_with(|| {
+            let _ = lazycell.fill(Box::new(1));
+            reference = lazycell.borrow().map(|r| &**r);
+            Box::new(2)
+        });
+    }
+
+    #[test]
+    fn test_borrow_mut_with() {
+        let mut lazycell = LazyCell::new();
+
+        {
+            let value = lazycell.borrow_mut_with(|| 1);
+            assert_eq!(&mut 1, value);
+            *value = 2;
+        }
+        assert_eq!(&2, lazycell.borrow().unwrap());
+    }
+
+    #[test]
+    fn test_borrow_mut_with_already_filled() {
+        let mut lazycell = LazyCell::new();
+        lazycell.fill(1).unwrap();
+
+        let value = lazycell.borrow_mut_with(|| 1);
+        assert_eq!(&1, value);
+    }
+
+    #[test]
+    fn test_borrow_mut_with_not_called_when_filled() {
+        let mut lazycell = LazyCell::new();
+
+        lazycell.fill(1).unwrap();
+
+        let value = lazycell.borrow_mut_with(|| 2);
+        assert_eq!(&1, value);
+    }
+
+    #[test]
+    fn test_try_borrow_with_ok() {
+        let lazycell = LazyCell::new();
+        let result = lazycell.try_borrow_with::<(), _>(|| Ok(1));
+        assert_eq!(result, Ok(&1));
+    }
+
+    #[test]
+    fn test_try_borrow_with_err() {
+        let lazycell = LazyCell::<()>::new();
+        let result = lazycell.try_borrow_with(|| Err(1));
+        assert_eq!(result, Err(1));
+    }
+
+    #[test]
+    fn test_try_borrow_with_already_filled() {
+        let lazycell = LazyCell::new();
+        lazycell.fill(1).unwrap();
+        let result = lazycell.try_borrow_with::<(), _>(|| unreachable!());
+        assert_eq!(result, Ok(&1));
+    }
+
+    #[test]
+    #[should_panic]
+    fn test_try_borrow_with_sound_with_reentrancy() {
+        let lazycell: LazyCell<Box<i32>> = LazyCell::new();
+
+        let mut reference: Option<&i32> = None;
+
+        let _ = lazycell.try_borrow_with::<(), _>(|| {
+            let _ = lazycell.fill(Box::new(1));
+            reference = lazycell.borrow().map(|r| &**r);
+            Ok(Box::new(2))
+        });
+    }
+
+    #[test]
+    fn test_try_borrow_mut_with_ok() {
+        let mut lazycell = LazyCell::new();
+        {
+            let result = lazycell.try_borrow_mut_with::<(), _>(|| Ok(1));
+            assert_eq!(result, Ok(&mut 1));
+            *result.unwrap() = 2;
+        }
+        assert_eq!(&mut 2, lazycell.borrow().unwrap());
+    }
+
+    #[test]
+    fn test_try_borrow_mut_with_err() {
+        let mut lazycell = LazyCell::<()>::new();
+        let result = lazycell.try_borrow_mut_with(|| Err(1));
+        assert_eq!(result, Err(1));
+    }
+
+    #[test]
+    fn test_try_borrow_mut_with_already_filled() {
+        let mut lazycell = LazyCell::new();
+        lazycell.fill(1).unwrap();
+        let result = lazycell.try_borrow_mut_with::<(), _>(|| unreachable!());
+        assert_eq!(result, Ok(&mut 1));
+    }
+
+    #[test]
+    fn test_into_inner() {
+        let lazycell = LazyCell::new();
+
+        lazycell.fill(1).unwrap();
+        let value = lazycell.into_inner();
+        assert_eq!(value, Some(1));
+    }
+
+    #[test]
+    fn test_atomic_borrow_from_empty() {
+        let lazycell: AtomicLazyCell<usize> = AtomicLazyCell::new();
+
+        let value = lazycell.borrow();
+        assert_eq!(value, None);
+
+        let value = lazycell.get();
+        assert_eq!(value, None);
+    }
+
+    #[test]
+    fn test_atomic_fill_and_borrow() {
+        let lazycell = AtomicLazyCell::new();
+
+        assert!(!lazycell.filled());
+        lazycell.fill(1).unwrap();
+        assert!(lazycell.filled());
+
+        let value = lazycell.borrow();
+        assert_eq!(value, Some(&1));
+
+        let value = lazycell.get();
+        assert_eq!(value, Some(1));
+    }
+
+    #[test]
+    fn test_atomic_already_filled_panic() {
+        let lazycell = AtomicLazyCell::new();
+
+        lazycell.fill(1).unwrap();
+        assert_eq!(1, lazycell.fill(1).unwrap_err());
+    }
+
+    #[test]
+    fn test_atomic_into_inner() {
+        let lazycell = AtomicLazyCell::new();
+
+        lazycell.fill(1).unwrap();
+        let value = lazycell.into_inner();
+        assert_eq!(value, Some(1));
+    }
+
+    #[test]
+    fn normal_replace() {
+        let mut cell = LazyCell::new();
+        assert_eq!(cell.fill(1), Ok(()));
+        assert_eq!(cell.replace(2), Some(1));
+        assert_eq!(cell.replace(3), Some(2));
+        assert_eq!(cell.borrow(), Some(&3));
+
+        let mut cell = LazyCell::new();
+        assert_eq!(cell.replace(2), None);
+    }
+
+    #[test]
+    fn atomic_replace() {
+        let mut cell = AtomicLazyCell::new();
+        assert_eq!(cell.fill(1), Ok(()));
+        assert_eq!(cell.replace(2), Some(1));
+        assert_eq!(cell.replace(3), Some(2));
+        assert_eq!(cell.borrow(), Some(&3));
+    }
+
+    #[test]
+    fn clone() {
+        let mut cell = LazyCell::new();
+        let clone1 = cell.clone();
+        assert_eq!(clone1.borrow(), None);
+        assert_eq!(cell.fill(1), Ok(()));
+        let mut clone2 = cell.clone();
+        assert_eq!(clone1.borrow(), None);
+        assert_eq!(clone2.borrow(), Some(&1));
+        assert_eq!(cell.replace(2), Some(1));
+        assert_eq!(clone1.borrow(), None);
+        assert_eq!(clone2.borrow(), Some(&1));
+        assert_eq!(clone1.fill(3), Ok(()));
+        assert_eq!(clone2.replace(4), Some(1));
+        assert_eq!(clone1.borrow(), Some(&3));
+        assert_eq!(clone2.borrow(), Some(&4));
+        assert_eq!(cell.borrow(), Some(&2));
+    }
+
+    #[test]
+    fn clone_atomic() {
+        let mut cell = AtomicLazyCell::new();
+        let clone1 = cell.clone();
+        assert_eq!(clone1.borrow(), None);
+        assert_eq!(cell.fill(1), Ok(()));
+        let mut clone2 = cell.clone();
+        assert_eq!(clone1.borrow(), None);
+        assert_eq!(clone2.borrow(), Some(&1));
+        assert_eq!(cell.replace(2), Some(1));
+        assert_eq!(clone1.borrow(), None);
+        assert_eq!(clone2.borrow(), Some(&1));
+        assert_eq!(clone1.fill(3), Ok(()));
+        assert_eq!(clone2.replace(4), Some(1));
+        assert_eq!(clone1.borrow(), Some(&3));
+        assert_eq!(clone2.borrow(), Some(&4));
+        assert_eq!(cell.borrow(), Some(&2));
+    }
+}