1 files changed, 73 insertions, 0 deletions
diff --git a/getrandom/src/use_file.rs b/getrandom/src/use_file.rs
new file mode 100644
index 0000000..d3adaf2
--- /dev/null
+++ b/getrandom/src/use_file.rs
@@ -0,0 +1,73 @@
+// 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.
+
+//! Implementations that just need to read from a file
+use crate::util_libc::{last_os_error, open_readonly, sys_fill_exact, LazyFd};
+use crate::Error;
+
+#[cfg(target_os = "redox")]
+const FILE_PATH: &str = "rand:\0";
+#[cfg(any(
+    target_os = "dragonfly",
+    target_os = "emscripten",
+    target_os = "haiku",
+    target_os = "macos",
+    target_os = "solaris",
+    target_os = "illumos"
+))]
+const FILE_PATH: &str = "/dev/random\0";
+
+pub fn getrandom_inner(dest: &mut [u8]) -> Result<(), Error> {
+    static FD: LazyFd = LazyFd::new();
+    let fd = FD.init(init_file).ok_or_else(last_os_error)?;
+    let read = |buf: &mut [u8]| unsafe { libc::read(fd, buf.as_mut_ptr() as *mut _, buf.len()) };
+
+    if cfg!(target_os = "emscripten") {
+        // `Crypto.getRandomValues` documents `dest` should be at most 65536 bytes.
+        for chunk in dest.chunks_mut(65536) {
+            sys_fill_exact(chunk, read)?;
+        }
+    } else {
+        sys_fill_exact(dest, read)?;
+    }
+    Ok(())
+}
+
+cfg_if! {
+    if #[cfg(any(target_os = "android", target_os = "linux"))] {
+        fn init_file() -> Option<libc::c_int> {
+            // Poll /dev/random to make sure it is ok to read from /dev/urandom.
+            let mut pfd = libc::pollfd {
+                fd: unsafe { open_readonly("/dev/random\0")? },
+                events: libc::POLLIN,
+                revents: 0,
+            };
+
+            let ret = loop {
+                // A negative timeout means an infinite timeout.
+                let res = unsafe { libc::poll(&mut pfd, 1, -1) };
+                if res == 1 {
+                    break unsafe { open_readonly("/dev/urandom\0") };
+                } else if res < 0 {
+                    let e = last_os_error().raw_os_error();
+                    if e == Some(libc::EINTR) || e == Some(libc::EAGAIN) {
+                        continue;
+                    }
+                }
+                // We either hard failed, or poll() returned the wrong pfd.
+                break None;
+            };
+            unsafe { libc::close(pfd.fd) };
+            ret
+        }
+    } else {
+        fn init_file() -> Option<libc::c_int> {
+            unsafe { open_readonly(FILE_PATH) }
+        }
+    }
+}