getrandom 0.1.4

A small cross-platform library for retrieving random data from system source
Documentation 
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// Copyright 2018 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.

//! Implementation for MacOS / iOS
extern crate std;

use crate::Error;
use core::num::NonZeroU32;
use std::io;

// TODO: Make extern once extern_types feature is stabilized. See:
//   https://github.com/rust-lang/rust/issues/43467
#[repr(C)]
struct SecRandom([u8; 0]);

#[link(name = "Security", kind = "framework")]
extern "C" {
    static kSecRandomDefault: *const SecRandom;

    fn SecRandomCopyBytes(rnd: *const SecRandom, count: usize, bytes: *mut u8) -> i32;
}

pub fn getrandom_inner(dest: &mut [u8]) -> Result<(), Error> {
    let ret = unsafe { SecRandomCopyBytes(kSecRandomDefault, dest.len(), dest.as_mut_ptr()) };
    if ret == -1 {
        error!("SecRandomCopyBytes call failed");
        Err(io::Error::last_os_error().into())
    } else {
        Ok(())
    }
}

#[inline(always)]
pub fn error_msg_inner(_: NonZeroU32) -> Option<&'static str> {
    None
}