Revise error types and codes

Author: dhardy

src/cloudabi.rs

@@ -22,3 +22,6 @@ pub fn getrandom_inner(dest: &mut [u8]) -> Result<(), Error> {
         Err(Error::from(code))
     }
 }
+
+#[inline(always)]
+pub fn error_msg_inner(_: NonZeroU32) -> Option<&'static str> { None }

src/dragonfly_haiku.rs

@@ -7,11 +7,12 @@
 // except according to those terms.
 
 //! Implementation for DragonFly / Haiku
-use super::Error;
-use super::utils::use_init;
+use error::Error;
+use utils::use_init;
 use std::fs::File;
 use std::io::Read;
 use std::cell::RefCell;
+use std::num::NonZeroU32;
 
 thread_local!(static RNG_FILE: RefCell<Option<File>> = RefCell::new(None));
 
@@ -23,3 +24,6 @@ pub fn getrandom_inner(dest: &mut [u8]) -> Result<(), Error> {
         )
     })
 }
+
+#[inline(always)]
+pub fn error_msg_inner(_: NonZeroU32) -> Option<&'static str> { None }

src/dummy.rs

@@ -7,9 +7,13 @@
 // except according to those terms.
 
 //! A dummy implementation for unsupported targets which always returns
-//! `Err(UNAVAILABLE_ERROR)`
-use super::UNAVAILABLE_ERROR;
+//! `Err(error::UNAVAILABLE)`
+use std::num::NonZeroU32;
+use error::{Error, UNAVAILABLE};
 
-pub fn getrandom_inner(dest: &mut [u8]) -> Result<(), Error> {
-    Err(UNAVAILABLE_ERROR)
+pub fn getrandom_inner(_: &mut [u8]) -> Result<(), Error> {
+    Err(UNAVAILABLE)
 }
+
+#[inline(always)]
+pub fn error_msg_inner(_: NonZeroU32) -> Option<&'static str> { None }

src/emscripten.rs

@@ -7,11 +7,12 @@
 // except according to those terms.
 
 //! Implementation for Emscripten
-use super::Error;
+use error::Error;
 use std::fs::File;
 use std::io::Read;
 use std::cell::RefCell;
-use super::utils::use_init;
+use std::num::NonZeroU32;
+use utils::use_init;
 
 thread_local!(static RNG_FILE: RefCell<Option<File>> = RefCell::new(None));
 
@@ -29,3 +30,6 @@ pub fn getrandom_inner(dest: &mut [u8]) -> Result<(), Error> {
         })
     })
 }
+
+#[inline(always)]
+pub fn error_msg_inner(_: NonZeroU32) -> Option<&'static str> { None }

src/error.rs

@@ -12,20 +12,25 @@ use core::fmt;
 #[cfg(not(target_env = "sgx"))]
 use std::{io, error};
 
+// A randomly-chosen 16-bit prefix for our codes
+pub(crate) const CODE_PREFIX: u32 = 0x57f40000;
+const CODE_UNKNOWN: u32 = CODE_PREFIX | 0;
+const CODE_UNAVAILABLE: u32 = CODE_PREFIX | 1;
+
 /// An unknown error.
-pub const UNKNOWN_ERROR: Error = Error(unsafe {
-    NonZeroU32::new_unchecked(0x756e6b6e) // "unkn"
+pub const UNKNOWN: Error = Error(unsafe {
+    NonZeroU32::new_unchecked(CODE_UNKNOWN)
 });
 
 /// No generator is available.
-pub const UNAVAILABLE_ERROR: Error = Error(unsafe {
-    NonZeroU32::new_unchecked(0x4e416e61) // "NAna"
+pub const UNAVAILABLE: Error = Error(unsafe {
+    NonZeroU32::new_unchecked(CODE_UNAVAILABLE)
 });
 
 /// The error type.
 /// 
 /// This type is small and no-std compatible.
-#[derive(Copy, Clone, Debug, Eq, PartialEq)]
+#[derive(Copy, Clone, Eq, PartialEq)]
 pub struct Error(NonZeroU32);
 
 impl Error {
@@ -38,14 +43,34 @@ impl Error {
     pub fn code(&self) -> NonZeroU32 {
         self.0
     }
+    
+    fn msg(&self) -> Option<&'static str> {
+        if let Some(msg) = super::error_msg_inner(self.0) {
+            Some(msg)
+        } else {
+            match *self {
+                UNKNOWN => Some("getrandom: unknown error"),
+                UNAVAILABLE => Some("getrandom: unavailable"),
+                _ => None
+            }
+        }
+    }
+}
+
+impl fmt::Debug for Error {
+    fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
+        match self.msg() {
+            Some(msg) => write!(f, "Error(\"{}\")", msg),
+            None => write!(f, "Error({})", self.0.get()),
+        }
+    }
 }
 
 impl fmt::Display for Error {
     fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
-        match *self {
-            UNKNOWN_ERROR => write!(f, "Getrandom Error: unknown"),
-            UNAVAILABLE_ERROR => write!(f, "Getrandom Error: unavailable"),
-            code => write!(f, "Getrandom Error: {}", code.0.get()),
+        match self.msg() {
+            Some(msg) => write!(f, "{}", msg),
+            None => write!(f, "getrandom: unknown code {}", self.0.get()),
         }
     }
 }
@@ -63,22 +88,31 @@ impl From<io::Error> for Error {
             .and_then(|code| NonZeroU32::new(code as u32))
             .map(|code| Error(code))
             // in practice this should never happen
-            .unwrap_or(UNKNOWN_ERROR)
+            .unwrap_or(UNKNOWN)
     }
 }
 
 #[cfg(not(target_env = "sgx"))]
 impl From<Error> for io::Error {
     fn from(err: Error) -> Self {
-        match err {
-            UNKNOWN_ERROR => io::Error::new(io::ErrorKind::Other,
-                "getrandom error: unknown"),
-            UNAVAILABLE_ERROR => io::Error::new(io::ErrorKind::Other,
-                "getrandom error: entropy source is unavailable"),
-            code => io::Error::from_raw_os_error(code.0.get() as i32),
+        match err.msg() {
+            Some(msg) => io::Error::new(io::ErrorKind::Other, msg),
+            None => io::Error::from_raw_os_error(err.0.get() as i32),
         }
     }
 }
 
 #[cfg(not(target_env = "sgx"))]
 impl error::Error for Error { }
+
+#[cfg(test)]
+mod tests {
+    use std::mem::size_of;
+    use super::Error;
+    
+    #[test]
+    fn test_size() {
+        assert_eq!(size_of::<Error>(), 4);
+        assert_eq!(size_of::<Result<(), Error>>(), 4);
+    }
+}

src/freebsd.rs

@@ -9,9 +9,10 @@
 //! Implementation for FreeBSD
 extern crate libc;
 
-use super::Error;
+use error::Error;
 use core::ptr;
 use std::io;
+use std::num::NonZeroU32;
 
 pub fn getrandom_inner(dest: &mut [u8]) -> Result<(), Error> {
     let mib = [libc::CTL_KERN, libc::KERN_ARND];
@@ -30,3 +31,6 @@ pub fn getrandom_inner(dest: &mut [u8]) -> Result<(), Error> {
     }
     Ok(())
 }
+
+#[inline(always)]
+pub fn error_msg_inner(_: NonZeroU32) -> Option<&'static str> { None }

src/fuchsia.rs

@@ -9,9 +9,13 @@
 //! Implementation for Fuchsia Zircon
 extern crate fuchsia_cprng;
 
-use super::Error;
+use std::num::NonZeroU32;
+use error::Error;
 
 pub fn getrandom_inner(dest: &mut [u8]) -> Result<(), Error> {
     fuchsia_cprng::cprng_draw(dest);
     Ok(())
 }
+
+#[inline(always)]
+pub fn error_msg_inner(_: NonZeroU32) -> Option<&'static str> { None }

src/lib.rs

@@ -123,8 +123,7 @@ extern crate wasm_bindgen;
     target_arch = "wasm32",
 ))]
 mod utils;
-mod error;
-pub use error::{Error, UNKNOWN_ERROR, UNAVAILABLE_ERROR};
+pub mod error;
 
 
 // System-specific implementations.
@@ -136,7 +135,7 @@ macro_rules! mod_use {
         #[$cond]
         mod $module;
         #[$cond]
-        use $module::getrandom_inner;
+        use $module::{getrandom_inner, error_msg_inner};
     }
 }
 
@@ -221,7 +220,7 @@ mod_use!(
 /// 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> {
+pub fn getrandom(dest: &mut [u8]) -> Result<(), error::Error> {
     getrandom_inner(dest)
 }
 

src/linux_android.rs

@@ -9,12 +9,13 @@
 //! Implementation for Linux / Android
 extern crate libc;
 
-use super::Error;
-use super::utils::use_init;
+use error::Error;
+use utils::use_init;
 use std::fs::File;
 use std::io;
 use std::io::Read;
 use std::cell::RefCell;
+use std::num::NonZeroU32;
 use std::sync::atomic::{AtomicBool, Ordering};
 
 static RNG_INIT: AtomicBool = AtomicBool::new(false);
@@ -80,3 +81,6 @@ fn is_getrandom_available() -> bool {
 
     AVAILABLE.load(Ordering::Relaxed)
 }
+
+#[inline(always)]
+pub fn error_msg_inner(_: NonZeroU32) -> Option<&'static str> { None }

src/macos.rs

@@ -9,8 +9,9 @@
 //! Implementation for MacOS / iOS
 extern crate libc;
 
-use super::Error;
+use error::Error;
 use std::io;
+use std::num::NonZeroU32;
 use self::libc::{c_int, size_t};
 
 enum SecRandom {}
@@ -40,3 +41,6 @@ pub fn getrandom_inner(dest: &mut [u8]) -> Result<(), Error> {
         Ok(())
     }
 }
+
+#[inline(always)]
+pub fn error_msg_inner(_: NonZeroU32) -> Option<&'static str> { None }