src/lib.rs - platform/external/rust/crates/getrandom - Git at Google

 // Copyright 2019 Developers of the Rand project.
 //
 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
 // https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
 // <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.

 //! Interface to the random number generator of the operating system.
 //!
 //! # Platform sources
 //!
 //! | OS               | interface
 //! |------------------|---------------------------------------------------------
 //! | Linux, Android   | [`getrandom`][1] system call if available, otherwise [`/dev/urandom`][2] after successfully polling `/dev/random`
 //! | Windows          | [`RtlGenRandom`][3]
 //! | macOS            | [`getentropy()`][19] if available, otherwise [`/dev/random`][20] (identical to `/dev/urandom`)
 //! | iOS              | [`SecRandomCopyBytes`][4]
 //! | FreeBSD          | [`getrandom()`][21] if available, otherwise [`kern.arandom`][5]
 //! | OpenBSD          | [`getentropy`][6]
 //! | NetBSD           | [`kern.arandom`][7]
 //! | Dragonfly BSD    | [`/dev/random`][8]
 //! | Solaris, illumos | [`getrandom`][9] system call if available, otherwise [`/dev/random`][10]
 //! | Fuchsia OS       | [`cprng_draw`][11]
 //! | Redox            | [`rand:`][12]
 //! | CloudABI         | [`cloudabi_sys_random_get`][13]
 //! | Haiku            | `/dev/random` (identical to `/dev/urandom`)
 //! | L4RE, SGX, UEFI  | [RDRAND][18]
 //! | Hermit           | [RDRAND][18] as [`sys_rand`][22] is currently broken.
 //! | VxWorks          | `randABytes` after checking entropy pool initialization with `randSecure`
 //! | Web browsers     | [`Crypto.getRandomValues`][14] (see [Support for WebAssembly and asm.js][16])
 //! | Node.js          | [`crypto.randomBytes`][15] (see [Support for WebAssembly and asm.js][16])
 //! | WASI             | [`__wasi_random_get`][17]
 //!
 //! Getrandom doesn't have a blanket implementation for all Unix-like operating
 //! systems that reads from `/dev/urandom`. This ensures all supported operating
 //! systems are using the recommended interface and respect maximum buffer
 //! sizes.
 //!
 //! ## Unsupported targets
 //!
 //! By default, compiling `getrandom` for an unsupported target will result in
 //! a compilation error. If you want to build an application which uses `getrandom`
 //! for such target, you can either:
 //! - Use [`[replace]`][replace] or [`[patch]`][patch] section in your `Cargo.toml`
 //! to switch to a custom implementation with a support of your target.
 //! - Enable the `dummy` feature to have getrandom use an implementation that always
 //! fails at run-time on unsupported targets.
 //!
 //! [replace]: https://doc.rust-lang.org/cargo/reference/manifest.html#the-replace-section
 //! [patch]: https://doc.rust-lang.org/cargo/reference/manifest.html#the-patch-section
 //!
 //! ## Support for WebAssembly and asm.js
 //!
 //! Getrandom supports all of Rust's current `wasm32` targets, and it works with
 //! both Node.js and web browsers. The three Emscripten targets
 //! `asmjs-unknown-emscripten`, `wasm32-unknown-emscripten`, and
 //! `wasm32-experimental-emscripten` use Emscripten's `/dev/random` emulation.
 //! The WASI target `wasm32-wasi` uses the [`__wasi_random_get`][17] function
 //! defined by the WASI standard.
 //!
 //! Getrandom also supports `wasm32-unknown-unknown` by directly calling
 //! JavaScript methods. Rust currently has two ways to do this: [bindgen] and
 //! [stdweb]. Getrandom supports using either one by enabling the
 //! `wasm-bindgen` or `stdweb` crate features. Note that if both features are
 //! enabled, `wasm-bindgen` will be used. If neither feature is enabled, calls
 //! to `getrandom` will always fail at runtime.
 //!
 //! [bindgen]: https://github.com/rust-lang/rust-bindgen
 //! [stdweb]: https://github.com/koute/stdweb
 //!
 //! ## Early boot
 //!
 //! It is possible that early in the boot process the OS hasn't had enough time
 //! yet to collect entropy to securely seed its RNG, especially on virtual
 //! machines.
 //!
 //! Some operating systems always block the thread until the RNG is securely
 //! seeded. This can take anywhere from a few seconds to more than a minute.
 //! Others make a best effort to use a seed from before the shutdown and don't
 //! document much.
 //!
 //! A few, Linux, NetBSD and Solaris, offer a choice between blocking and
 //! getting an error; in these cases we always choose to block.
 //!
 //! On Linux (when the `getrandom` system call is not available) and on NetBSD
 //! reading from `/dev/urandom` never blocks, even when the OS hasn't collected
 //! enough entropy yet. To avoid returning low-entropy bytes, we first read from
 //! `/dev/random` and only switch to `/dev/urandom` once this has succeeded.
 //!
 //! # Error handling
 //!
 //! We always choose failure over returning insecure "random" bytes. In general,
 //! on supported platforms, failure is highly unlikely, though not impossible.
 //! If an error does occur, then it is likely that it will occur on every call to
 //! `getrandom`, hence after the first successful call one can be reasonably
 //! confident that no errors will occur.
 //!
 //! On unsupported platforms, `getrandom` always fails. See the [`Error`] type
 //! for more information on what data is returned on failure.
 //!
 //! [1]: http://man7.org/linux/man-pages/man2/getrandom.2.html
 //! [2]: http://man7.org/linux/man-pages/man4/urandom.4.html
 //! [3]: https://docs.microsoft.com/en-us/windows/desktop/api/ntsecapi/nf-ntsecapi-rtlgenrandom
 //! [4]: https://developer.apple.com/documentation/security/1399291-secrandomcopybytes?language=objc
 //! [5]: https://www.freebsd.org/cgi/man.cgi?query=random&sektion=4
 //! [6]: https://man.openbsd.org/getentropy.2
 //! [7]: https://netbsd.gw.com/cgi-bin/man-cgi?sysctl+7+NetBSD-8.0
 //! [8]: https://leaf.dragonflybsd.org/cgi/web-man?command=random&section=4
 //! [9]: https://docs.oracle.com/cd/E88353_01/html/E37841/getrandom-2.html
 //! [10]: https://docs.oracle.com/cd/E86824_01/html/E54777/random-7d.html
 //! [11]: https://fuchsia.dev/fuchsia-src/zircon/syscalls/cprng_draw
 //! [12]: https://github.com/redox-os/randd/blob/master/src/main.rs
 //! [13]: https://github.com/nuxinl/cloudabi#random_get
 //! [14]: https://www.w3.org/TR/WebCryptoAPI/#Crypto-method-getRandomValues
 //! [15]: https://nodejs.org/api/crypto.html#crypto_crypto_randombytes_size_callback
 //! [16]: #support-for-webassembly-and-asmjs
 //! [17]: https://github.com/WebAssembly/WASI/blob/master/design/WASI-core.md#__wasi_random_get
 //! [18]: https://software.intel.com/en-us/articles/intel-digital-random-number-generator-drng-software-implementation-guide
 //! [19]: https://www.unix.com/man-page/mojave/2/getentropy/
 //! [20]: https://www.unix.com/man-page/mojave/4/random/
 //! [21]: https://www.freebsd.org/cgi/man.cgi?query=getrandom&manpath=FreeBSD+12.0-stable
 //! [22]: https://github.com/hermitcore/libhermit-rs/blob/09c38b0371cee6f56a541400ba453e319e43db53/src/syscalls/random.rs#L21

 #![doc(
     html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk.png",
     html_favicon_url = "https://www.rust-lang.org/favicon.ico",
     html_root_url = "https://rust-random.github.io/rand/"
 )]
 #![no_std]
 #![cfg_attr(feature = "stdweb", recursion_limit = "128")]
 #![warn(rust_2018_idioms, unused_lifetimes, missing_docs)]

 #[macro_use]
 extern crate cfg_if;

 cfg_if! {
     if #[cfg(feature = "log")] {
         #[allow(unused)]
         #[macro_use]
         extern crate log;
     } else {
         #[allow(unused)]
         macro_rules! error {
             ($($x:tt)*) => {};
         }
         #[allow(unused)]
         macro_rules! warn {
             ($($x:tt)*) => {};
         }
         #[allow(unused)]
         macro_rules! info {
             ($($x:tt)*) => {};
         }
     }
 }

 mod error;
 pub use crate::error::Error;

 #[allow(dead_code)]
 mod util;

 #[cfg(target_os = "vxworks")]
 #[allow(dead_code)]
 mod util_libc;

 cfg_if! {
     // Unlike the other Unix, Fuchsia and iOS don't use the libc to make any calls.
     if #[cfg(any(target_os = "android", target_os = "dragonfly", target_os = "emscripten",
                  target_os = "freebsd", target_os = "haiku",     target_os = "illumos",
                  target_os = "linux",   target_os = "macos",     target_os = "netbsd",
                  target_os = "openbsd", target_os = "redox",     target_os = "solaris"))] {
         #[allow(dead_code)]
         mod util_libc;
         // Keep std-only trait definitions for backwards compatibility
         mod error_impls;
     } else if #[cfg(feature = "std")] {
         mod error_impls;
     }
 }

 // These targets read from a file as a fallback method.
 #[cfg(any(
     target_os = "android",
     target_os = "linux",
     target_os = "macos",
     target_os = "solaris",
     target_os = "illumos",
 ))]
 mod use_file;

 // System-specific implementations.
 //
 // These should all provide getrandom_inner with the same signature as getrandom.
 cfg_if! {
     if #[cfg(target_os = "android")] {
         #[path = "linux_android.rs"] mod imp;
     } else if #[cfg(target_os = "cloudabi")] {
         #[path = "cloudabi.rs"] mod imp;
     } else if #[cfg(target_os = "dragonfly")] {
         #[path = "use_file.rs"] mod imp;
     } else if #[cfg(target_os = "emscripten")] {
         #[path = "use_file.rs"] mod imp;
     } else if #[cfg(target_os = "freebsd")] {
         #[path = "bsd_arandom.rs"] mod imp;
     } else if #[cfg(target_os = "fuchsia")] {
         #[path = "fuchsia.rs"] mod imp;
     } else if #[cfg(target_os = "haiku")] {
         #[path = "use_file.rs"] mod imp;
     } else if #[cfg(target_os = "illumos")] {
         #[path = "solaris_illumos.rs"] mod imp;
     } else if #[cfg(target_os = "ios")] {
         #[path = "ios.rs"] mod imp;
     } else if #[cfg(target_os = "linux")] {
         #[path = "linux_android.rs"] mod imp;
     } else if #[cfg(target_os = "macos")] {
         #[path = "macos.rs"] mod imp;
     } else if #[cfg(target_os = "netbsd")] {
         #[path = "bsd_arandom.rs"] mod imp;
     } else if #[cfg(target_os = "openbsd")] {
         #[path = "openbsd.rs"] mod imp;
     } else if #[cfg(target_os = "redox")] {
         #[path = "use_file.rs"] mod imp;
     } else if #[cfg(target_os = "solaris")] {
         #[path = "solaris_illumos.rs"] mod imp;
     } else if #[cfg(target_os = "wasi")] {
         #[path = "wasi.rs"] mod imp;
     } else if #[cfg(target_os = "vxworks")] {
         #[path = "vxworks.rs"] mod imp;
     } else if #[cfg(all(windows, getrandom_uwp))] {
         #[path = "windows_uwp.rs"] mod imp;
     } else if #[cfg(windows)] {
         #[path = "windows.rs"] mod imp;
     } else if #[cfg(all(target_arch = "x86_64", any(
                   target_os = "hermit",
                   target_os = "l4re",
                   target_os = "uefi",
                   target_env = "sgx",
               )))] {
         #[path = "rdrand.rs"] mod imp;
     } else if #[cfg(all(target_arch = "wasm32", target_os = "unknown"))] {
         cfg_if! {
             if #[cfg(feature = "wasm-bindgen")] {
                 #[path = "wasm32_bindgen.rs"] mod imp;
             } else if #[cfg(feature = "stdweb")] {
                 #[path = "wasm32_stdweb.rs"] mod imp;
             } else {
                 // Always have an implementation for wasm32-unknown-unknown.
                 // See https://github.com/rust-random/getrandom/issues/87
                 #[path = "dummy.rs"] mod imp;
             }
         }
     } else if #[cfg(feature = "dummy")] {
         #[path = "dummy.rs"] mod imp;
     } else {
         compile_error!("\
             target is not supported, for more information see: \
             https://docs.rs/getrandom/#unsupported-targets\
         ");
     }
 }

 /// Fill `dest` with random bytes from the system's preferred random number
 /// source.
 ///
 /// This function returns an error on any failure, including partial reads. We
 /// make no guarantees regarding the contents of `dest` on error. If `dest` is
 /// empty, `getrandom` immediately returns success, making no calls to the
 /// underlying operating system.
 ///
 /// Blocking is possible, at least during early boot; see module documentation.
 ///
 /// In general, `getrandom` will be fast enough for interactive usage, though
 /// significantly slower than a user-space CSPRNG; for the latter consider
 /// [`rand::thread_rng`](https://docs.rs/rand/*/rand/fn.thread_rng.html).
 pub fn getrandom(dest: &mut [u8]) -> Result<(), error::Error> {
     if dest.is_empty() {
         return Ok(());
     }
     imp::getrandom_inner(dest)
 }
	// Copyright 2019 Developers of the Rand project.
	//
	// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
	// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
	// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
	// option. This file may not be copied, modified, or distributed
	// except according to those terms.

	//! Interface to the random number generator of the operating system.
	//!
	//! # Platform sources
	//!
	//! \| OS \| interface
	//! \|------------------\|---------------------------------------------------------
	//! \| Linux, Android \| [`getrandom`][1] system call if available, otherwise [`/dev/urandom`][2] after successfully polling `/dev/random`
	//! \| Windows \| [`RtlGenRandom`][3]
	//! \| macOS \| [`getentropy()`][19] if available, otherwise [`/dev/random`][20] (identical to `/dev/urandom`)
	//! \| iOS \| [`SecRandomCopyBytes`][4]
	//! \| FreeBSD \| [`getrandom()`][21] if available, otherwise [`kern.arandom`][5]
	//! \| OpenBSD \| [`getentropy`][6]
	//! \| NetBSD \| [`kern.arandom`][7]
	//! \| Dragonfly BSD \| [`/dev/random`][8]
	//! \| Solaris, illumos \| [`getrandom`][9] system call if available, otherwise [`/dev/random`][10]
	//! \| Fuchsia OS \| [`cprng_draw`][11]
	//! \| Redox \| [`rand:`][12]
	//! \| CloudABI \| [`cloudabi_sys_random_get`][13]
	//! \| Haiku \| `/dev/random` (identical to `/dev/urandom`)
	//! \| L4RE, SGX, UEFI \| [RDRAND][18]
	//! \| Hermit \| [RDRAND][18] as [`sys_rand`][22] is currently broken.
	//! \| VxWorks \| `randABytes` after checking entropy pool initialization with `randSecure`
	//! \| Web browsers \| [`Crypto.getRandomValues`][14] (see [Support for WebAssembly and asm.js][16])
	//! \| Node.js \| [`crypto.randomBytes`][15] (see [Support for WebAssembly and asm.js][16])
	//! \| WASI \| [`__wasi_random_get`][17]
	//!
	//! Getrandom doesn't have a blanket implementation for all Unix-like operating
	//! systems that reads from `/dev/urandom`. This ensures all supported operating
	//! systems are using the recommended interface and respect maximum buffer
	//! sizes.
	//!
	//! ## Unsupported targets
	//!
	//! By default, compiling `getrandom` for an unsupported target will result in
	//! a compilation error. If you want to build an application which uses `getrandom`
	//! for such target, you can either:
	//! - Use [`[replace]`][replace] or [`[patch]`][patch] section in your `Cargo.toml`
	//! to switch to a custom implementation with a support of your target.
	//! - Enable the `dummy` feature to have getrandom use an implementation that always
	//! fails at run-time on unsupported targets.
	//!
	//! [replace]: https://doc.rust-lang.org/cargo/reference/manifest.html#the-replace-section
	//! [patch]: https://doc.rust-lang.org/cargo/reference/manifest.html#the-patch-section
	//!
	//! ## Support for WebAssembly and asm.js
	//!
	//! Getrandom supports all of Rust's current `wasm32` targets, and it works with
	//! both Node.js and web browsers. The three Emscripten targets
	//! `asmjs-unknown-emscripten`, `wasm32-unknown-emscripten`, and
	//! `wasm32-experimental-emscripten` use Emscripten's `/dev/random` emulation.
	//! The WASI target `wasm32-wasi` uses the [`__wasi_random_get`][17] function
	//! defined by the WASI standard.
	//!
	//! Getrandom also supports `wasm32-unknown-unknown` by directly calling
	//! JavaScript methods. Rust currently has two ways to do this: [bindgen] and
	//! [stdweb]. Getrandom supports using either one by enabling the
	//! `wasm-bindgen` or `stdweb` crate features. Note that if both features are
	//! enabled, `wasm-bindgen` will be used. If neither feature is enabled, calls
	//! to `getrandom` will always fail at runtime.
	//!
	//! [bindgen]: https://github.com/rust-lang/rust-bindgen
	//! [stdweb]: https://github.com/koute/stdweb
	//!
	//! ## Early boot
	//!
	//! It is possible that early in the boot process the OS hasn't had enough time
	//! yet to collect entropy to securely seed its RNG, especially on virtual
	//! machines.
	//!
	//! Some operating systems always block the thread until the RNG is securely
	//! seeded. This can take anywhere from a few seconds to more than a minute.
	//! Others make a best effort to use a seed from before the shutdown and don't
	//! document much.
	//!
	//! A few, Linux, NetBSD and Solaris, offer a choice between blocking and
	//! getting an error; in these cases we always choose to block.
	//!
	//! On Linux (when the `getrandom` system call is not available) and on NetBSD
	//! reading from `/dev/urandom` never blocks, even when the OS hasn't collected
	//! enough entropy yet. To avoid returning low-entropy bytes, we first read from
	//! `/dev/random` and only switch to `/dev/urandom` once this has succeeded.
	//!
	//! # Error handling
	//!
	//! We always choose failure over returning insecure "random" bytes. In general,
	//! on supported platforms, failure is highly unlikely, though not impossible.
	//! If an error does occur, then it is likely that it will occur on every call to
	//! `getrandom`, hence after the first successful call one can be reasonably
	//! confident that no errors will occur.
	//!
	//! On unsupported platforms, `getrandom` always fails. See the [`Error`] type
	//! for more information on what data is returned on failure.
	//!
	//! [1]: http://man7.org/linux/man-pages/man2/getrandom.2.html
	//! [2]: http://man7.org/linux/man-pages/man4/urandom.4.html
	//! [3]: https://docs.microsoft.com/en-us/windows/desktop/api/ntsecapi/nf-ntsecapi-rtlgenrandom
	//! [4]: https://developer.apple.com/documentation/security/1399291-secrandomcopybytes?language=objc
	//! [5]: https://www.freebsd.org/cgi/man.cgi?query=random&sektion=4
	//! [6]: https://man.openbsd.org/getentropy.2
	//! [7]: https://netbsd.gw.com/cgi-bin/man-cgi?sysctl+7+NetBSD-8.0
	//! [8]: https://leaf.dragonflybsd.org/cgi/web-man?command=random&section=4
	//! [9]: https://docs.oracle.com/cd/E88353_01/html/E37841/getrandom-2.html
	//! [10]: https://docs.oracle.com/cd/E86824_01/html/E54777/random-7d.html
	//! [11]: https://fuchsia.dev/fuchsia-src/zircon/syscalls/cprng_draw
	//! [12]: https://github.com/redox-os/randd/blob/master/src/main.rs
	//! [13]: https://github.com/nuxinl/cloudabi#random_get
	//! [14]: https://www.w3.org/TR/WebCryptoAPI/#Crypto-method-getRandomValues
	//! [15]: https://nodejs.org/api/crypto.html#crypto_crypto_randombytes_size_callback
	//! [16]: #support-for-webassembly-and-asmjs
	//! [17]: https://github.com/WebAssembly/WASI/blob/master/design/WASI-core.md#__wasi_random_get
	//! [18]: https://software.intel.com/en-us/articles/intel-digital-random-number-generator-drng-software-implementation-guide
	//! [19]: https://www.unix.com/man-page/mojave/2/getentropy/
	//! [20]: https://www.unix.com/man-page/mojave/4/random/
	//! [21]: https://www.freebsd.org/cgi/man.cgi?query=getrandom&manpath=FreeBSD+12.0-stable
	//! [22]: https://github.com/hermitcore/libhermit-rs/blob/09c38b0371cee6f56a541400ba453e319e43db53/src/syscalls/random.rs#L21

	#![doc(
	html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk.png",
	html_favicon_url = "https://www.rust-lang.org/favicon.ico",
	html_root_url = "https://rust-random.github.io/rand/"
	)]
	#![no_std]
	#![cfg_attr(feature = "stdweb", recursion_limit = "128")]
	#![warn(rust_2018_idioms, unused_lifetimes, missing_docs)]

	#[macro_use]
	extern crate cfg_if;

	cfg_if! {
	if #[cfg(feature = "log")] {
	#[allow(unused)]
	#[macro_use]
	extern crate log;
	} else {
	#[allow(unused)]
	macro_rules! error {
	($($x:tt)*) => {};
	}
	#[allow(unused)]
	macro_rules! warn {
	($($x:tt)*) => {};
	}
	#[allow(unused)]
	macro_rules! info {
	($($x:tt)*) => {};
	}
	}
	}

	mod error;
	pub use crate::error::Error;

	#[allow(dead_code)]
	mod util;

	#[cfg(target_os = "vxworks")]
	#[allow(dead_code)]
	mod util_libc;

	cfg_if! {
	// Unlike the other Unix, Fuchsia and iOS don't use the libc to make any calls.
	if #[cfg(any(target_os = "android", target_os = "dragonfly", target_os = "emscripten",
	target_os = "freebsd", target_os = "haiku", target_os = "illumos",
	target_os = "linux", target_os = "macos", target_os = "netbsd",
	target_os = "openbsd", target_os = "redox", target_os = "solaris"))] {
	#[allow(dead_code)]
	mod util_libc;
	// Keep std-only trait definitions for backwards compatibility
	mod error_impls;
	} else if #[cfg(feature = "std")] {
	mod error_impls;
	}
	}

	// These targets read from a file as a fallback method.
	#[cfg(any(
	target_os = "android",
	target_os = "linux",
	target_os = "macos",
	target_os = "solaris",
	target_os = "illumos",
	))]
	mod use_file;

	// System-specific implementations.
	//
	// These should all provide getrandom_inner with the same signature as getrandom.
	cfg_if! {
	if #[cfg(target_os = "android")] {
	#[path = "linux_android.rs"] mod imp;
	} else if #[cfg(target_os = "cloudabi")] {
	#[path = "cloudabi.rs"] mod imp;
	} else if #[cfg(target_os = "dragonfly")] {
	#[path = "use_file.rs"] mod imp;
	} else if #[cfg(target_os = "emscripten")] {
	#[path = "use_file.rs"] mod imp;
	} else if #[cfg(target_os = "freebsd")] {
	#[path = "bsd_arandom.rs"] mod imp;
	} else if #[cfg(target_os = "fuchsia")] {
	#[path = "fuchsia.rs"] mod imp;
	} else if #[cfg(target_os = "haiku")] {
	#[path = "use_file.rs"] mod imp;
	} else if #[cfg(target_os = "illumos")] {
	#[path = "solaris_illumos.rs"] mod imp;
	} else if #[cfg(target_os = "ios")] {
	#[path = "ios.rs"] mod imp;
	} else if #[cfg(target_os = "linux")] {
	#[path = "linux_android.rs"] mod imp;
	} else if #[cfg(target_os = "macos")] {
	#[path = "macos.rs"] mod imp;
	} else if #[cfg(target_os = "netbsd")] {
	#[path = "bsd_arandom.rs"] mod imp;
	} else if #[cfg(target_os = "openbsd")] {
	#[path = "openbsd.rs"] mod imp;
	} else if #[cfg(target_os = "redox")] {
	#[path = "use_file.rs"] mod imp;
	} else if #[cfg(target_os = "solaris")] {
	#[path = "solaris_illumos.rs"] mod imp;
	} else if #[cfg(target_os = "wasi")] {
	#[path = "wasi.rs"] mod imp;
	} else if #[cfg(target_os = "vxworks")] {
	#[path = "vxworks.rs"] mod imp;
	} else if #[cfg(all(windows, getrandom_uwp))] {
	#[path = "windows_uwp.rs"] mod imp;
	} else if #[cfg(windows)] {
	#[path = "windows.rs"] mod imp;
	} else if #[cfg(all(target_arch = "x86_64", any(
	target_os = "hermit",
	target_os = "l4re",
	target_os = "uefi",
	target_env = "sgx",
	)))] {
	#[path = "rdrand.rs"] mod imp;
	} else if #[cfg(all(target_arch = "wasm32", target_os = "unknown"))] {
	cfg_if! {
	if #[cfg(feature = "wasm-bindgen")] {
	#[path = "wasm32_bindgen.rs"] mod imp;
	} else if #[cfg(feature = "stdweb")] {
	#[path = "wasm32_stdweb.rs"] mod imp;
	} else {
	// Always have an implementation for wasm32-unknown-unknown.
	// See https://github.com/rust-random/getrandom/issues/87
	#[path = "dummy.rs"] mod imp;
	}
	}
	} else if #[cfg(feature = "dummy")] {
	#[path = "dummy.rs"] mod imp;
	} else {
	compile_error!("\
	target is not supported, for more information see: \
	https://docs.rs/getrandom/#unsupported-targets\
	");
	}
	}

	/// Fill `dest` with random bytes from the system's preferred random number
	/// source.
	///
	/// This function returns an error on any failure, including partial reads. We
	/// make no guarantees regarding the contents of `dest` on error. If `dest` is
	/// empty, `getrandom` immediately returns success, making no calls to the
	/// underlying operating system.
	///
	/// Blocking is possible, at least during early boot; see module documentation.
	///
	/// In general, `getrandom` will be fast enough for interactive usage, though
	/// significantly slower than a user-space CSPRNG; for the latter consider
	/// [`rand::thread_rng`](https://docs.rs/rand/*/rand/fn.thread_rng.html).
	pub fn getrandom(dest: &mut [u8]) -> Result<(), error::Error> {
	if dest.is_empty() {
	return Ok(());
	}
	imp::getrandom_inner(dest)
	}