Unify getentropy-based implementations (#418)

Signed-off-by: Joe Richey <joerichey@google.com>

src/openbsd.rs → src/getentropy.rs

@@ -1,12 +1,17 @@
-//! Implementation for OpenBSD
+//! Implementation using libc::getentropy
+//!
+//! Available since:
+//!   - macOS 10.12
+//!   - OpenBSD 5.6
+//!   - Emscripten 2.0.5
+//!   - vita newlib since Dec 2021
 use crate::{util_libc::last_os_error, Error};
 use core::mem::MaybeUninit;
 
 pub fn getrandom_inner(dest: &mut [MaybeUninit<u8>]) -> Result<(), Error> {
-    // getentropy(2) was added in OpenBSD 5.6, so we can use it unconditionally.
     for chunk in dest.chunks_mut(256) {
         let ret = unsafe { libc::getentropy(chunk.as_mut_ptr() as *mut libc::c_void, chunk.len()) };
-        if ret == -1 {
+        if ret != 0 {
             return Err(last_os_error());
         }
     }

src/lib.rs

@@ -26,8 +26,8 @@
 //! | Web Browser and Node.js | `wasm*‑*‑unknown` | [`Crypto.getRandomValues`] if available, then [`crypto.randomFillSync`] if on Node.js, see [WebAssembly support]
 //! | SOLID             | `*-kmc-solid_*`    | `SOLID_RNG_SampleRandomBytes`
 //! | Nintendo 3DS      | `armv6k-nintendo-3ds` | [`getrandom`][1]
-//! | PS Vita           | `armv7-sony-vita-newlibeabihf` | [`getentropy`][13]
-//! | QNX Neutrino      | `*‑nto-qnx*`          | [`/dev/urandom`][14] (identical to `/dev/random`)
+//! | PS Vita           | `*-vita-*`         | [`getentropy`][13]
+//! | QNX Neutrino      | `*‑nto-qnx*`       | [`/dev/urandom`][14] (identical to `/dev/random`)
 //! | AIX               | `*-ibm-aix`        | [`/dev/urandom`][15]
 //!
 //! There is no blanket implementation on `unix` targets that reads from
@@ -237,6 +237,14 @@ cfg_if! {
     if #[cfg(any(target_os = "haiku", target_os = "redox", target_os = "nto", target_os = "aix"))] {
         mod util_libc;
         #[path = "use_file.rs"] mod imp;
+    } else if #[cfg(any(
+        target_os = "macos",
+        target_os = "openbsd",
+        target_os = "vita",
+        target_os = "emscripten",
+    ))] {
+        mod util_libc;
+        #[path = "getentropy.rs"] mod imp;
     } else if #[cfg(any(
         target_os = "dragonfly",
         target_os = "freebsd",
@@ -305,12 +313,6 @@ cfg_if! {
         #[path = "fuchsia.rs"] mod imp;
     } else if #[cfg(any(target_os = "ios", target_os = "visionos", target_os = "watchos", target_os = "tvos"))] {
         #[path = "apple-other.rs"] mod imp;
-    } else if #[cfg(target_os = "macos")] {
-        mod util_libc;
-        #[path = "macos.rs"] mod imp;
-    } else if #[cfg(target_os = "openbsd")] {
-        mod util_libc;
-        #[path = "openbsd.rs"] mod imp;
     } else if #[cfg(all(target_arch = "wasm32", target_os = "wasi"))] {
         #[path = "wasi.rs"] mod imp;
     } else if #[cfg(target_os = "hermit")] {
@@ -324,12 +326,6 @@ cfg_if! {
         #[path = "espidf.rs"] mod imp;
     } else if #[cfg(windows)] {
         #[path = "windows.rs"] mod imp;
-    } else if #[cfg(target_os = "vita")] {
-        mod util_libc;
-        #[path = "vita.rs"] mod imp;
-    } else if #[cfg(target_os = "emscripten")] {
-        mod util_libc;
-        #[path = "emscripten.rs"] mod imp;
     } else if #[cfg(all(target_arch = "x86_64", target_env = "sgx"))] {
         mod lazy;
         #[path = "rdrand.rs"] mod imp;