Export std::io instead of always using thin reimplementation

This allows most implementers of `BinRead` to use std features
on the reader instead of restricting them to the subset of
features exposed by the no_std reimplementation. This also
appears to have been the original intent of the `binread::io`
module, per the module-level comment.

This is a breaking change because `iter_bytes` is called `bytes`
in std and consumes the reader, so this has been changed in the
binread implementation to conform to that API.

This commit also fixes the earlier binread implementations not
handling errors as std does; this is now fixed (by copying
from std).

(Hopefully rust-lang/rust#48331 will be addressed someday and then
this code can disappear entirely.)

binread/src/io/error.rs

@@ -16,7 +16,7 @@ enum Repr {
 }
 
 #[non_exhaustive]
-#[derive(Debug)]
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
 pub enum ErrorKind {
     NotFound,
     PermissionDenied,
@@ -44,4 +44,10 @@ impl Error {
             repr: Repr::Simple(kind)
         }
     }
+
+    pub fn kind(&self) -> ErrorKind {
+        match self.repr {
+            Repr::Simple(kind) => kind,
+        }
+    }
 }

binread/src/io/mod.rs

@@ -1,91 +1,14 @@
 //! A swappable version of [std::io](std::io) that works in `no_std + alloc` environments.
 //! If the feature flag `std` is enabled (as it is by default), this will just re-export types from `std::io`.
+
 pub mod prelude;
 pub mod cursor;
 pub mod error;
 
-#[cfg(feature = "std")]
-pub use std::io::{Error, ErrorKind};
-
-#[cfg(not(feature = "std"))]
-pub use error::{Error, ErrorKind};
-
-#[cfg(feature = "std")]
-pub use std::io::Result;
-
 #[cfg(not(feature = "std"))]
-pub type Result<T> = core::result::Result<T, Error>;
-
-/// A simplified version of [std::io::Read](std::io::Read) for use in no_std environments
-pub trait Read {
-    fn read(&mut self, buf: &mut [u8]) -> Result<usize>;
-
-    fn read_exact(&mut self, buf: &mut [u8]) -> Result<()> {
-        if let Ok(n) = self.read(buf) {
-            if n == buf.len() {
-                return Ok(())
-            }
-        }
-
-        Err(Error::new(ErrorKind::UnexpectedEof, "Out of bytes in reader"))
-    }
-
-    fn iter_bytes(&mut self) -> Bytes<'_, Self>
-        where Self: Sized,
-    {
-        Bytes {
-            inner: self
-        }
-    }
-}
-
-pub struct Bytes<'a, R: Read> {
-    inner: &'a mut R
-}
-
-impl<'a, R: Read> Iterator for Bytes<'a, R> {
-    type Item = Result<u8>;
-
-    fn next(&mut self) -> Option<Self::Item> {
-        let mut byte = [0u8];
-        Some(
-            self.inner.read_exact(&mut byte)
-                .map(|_| byte[0])
-        )
-    }
-}
-
-#[cfg(feature = "std")]
-pub use std::io::SeekFrom;
-
+mod no_std;
 #[cfg(not(feature = "std"))]
-#[derive(Debug, Clone, Copy)]
-pub enum SeekFrom {
-    Start(u64),
-    End(i64),
-    Current(i64),
-}
-
-pub trait Seek {
-    fn seek(&mut self, pos: SeekFrom) -> Result<u64>;
-}
+pub use no_std::*;
 
 #[cfg(feature = "std")]
-impl<R: std::io::Read> Read for R {
-    fn read(&mut self, buf: &mut [u8]) -> Result<usize> {
-        self.read(buf)
-    }
-}
-
-#[cfg(feature = "std")]
-impl<S: std::io::Seek> Seek for S {
-    fn seek(&mut self, pos: SeekFrom) -> Result<u64> {
-        self.seek(pos)
-    }
-}
-
-#[cfg(feature = "std")]
-pub use std::io::Cursor;
-
-#[cfg(not(feature = "std"))]
-pub use cursor::Cursor;
+pub use std::io::{Bytes, Cursor, Error, ErrorKind, Read, Result, Seek, SeekFrom};

binread/src/io/no_std.rs

@@ -0,0 +1,92 @@
+pub use super::{cursor::Cursor, error::{Error, ErrorKind}};
+
+pub type Result<T> = core::result::Result<T, Error>;
+
+/// A simplified version of [std::io::Read](std::io::Read) for use in no_std environments
+pub trait Read {
+    fn read(&mut self, buf: &mut [u8]) -> Result<usize>;
+
+    fn read_exact(&mut self, mut buf: &mut [u8]) -> Result<()> {
+        while !buf.is_empty() {
+            match self.read(buf) {
+                Ok(0) => break,
+                Ok(n) => {
+                    let tmp = buf;
+                    buf = &mut tmp[n..];
+                }
+                Err(ref e) if e.kind() == ErrorKind::Interrupted => {}
+                Err(e) => return Err(e),
+            }
+        }
+        if !buf.is_empty() {
+            Err(Error::new(ErrorKind::UnexpectedEof, "failed to fill whole buffer"))
+        } else {
+            Ok(())
+        }
+    }
+
+    fn bytes(self) -> Bytes<Self>
+    where
+        Self: Sized,
+    {
+        Bytes { inner: self }
+    }
+
+    fn by_ref(&mut self) -> &mut Self
+    where
+        Self: Sized,
+    {
+        self
+    }
+}
+
+impl<R: Read + ?Sized> Read for &mut R {
+    #[inline]
+    fn read(&mut self, buf: &mut [u8]) -> Result<usize> {
+        (**self).read(buf)
+    }
+
+    #[inline]
+    fn read_exact(&mut self, buf: &mut [u8]) -> Result<()> {
+        (**self).read_exact(buf)
+    }
+}
+
+#[derive(Debug)]
+pub struct Bytes<R: Read> {
+    inner: R
+}
+
+impl<R: Read> Iterator for Bytes<R> {
+    type Item = Result<u8>;
+
+    fn next(&mut self) -> Option<Result<u8>> {
+        let mut byte = 0;
+        loop {
+            return match self.inner.read(core::slice::from_mut(&mut byte)) {
+                Ok(0) => None,
+                Ok(..) => Some(Ok(byte)),
+                Err(ref e) if e.kind() == ErrorKind::Interrupted => continue,
+                Err(e) => Some(Err(e)),
+            };
+        }
+    }
+}
+
+#[derive(Debug, Clone, Copy)]
+pub enum SeekFrom {
+    Start(u64),
+    End(i64),
+    Current(i64),
+}
+
+pub trait Seek {
+    fn seek(&mut self, pos: SeekFrom) -> Result<u64>;
+}
+
+impl<S: Seek + ?Sized> Seek for &mut S {
+    #[inline]
+    fn seek(&mut self, pos: SeekFrom) -> Result<u64> {
+        (**self).seek(pos)
+    }
+}

binread/src/strings.rs

@@ -27,7 +27,7 @@ impl BinRead for Vec<NonZeroU8> {
     fn read_options<R: Read + Seek>(reader: &mut R, _: &ReadOptions, _: Self::Args) -> BinResult<Self>
     {
         reader
-            .iter_bytes()
+            .bytes()
             .take_while(|x| !matches!(x, Ok(0)))
             .map(|x| Ok(x.map(|byte| unsafe { NonZeroU8::new_unchecked(byte) })?))
             .collect()

binread/tests/io/mod.rs

@@ -0,0 +1,2 @@
+#[cfg(not(feature = "std"))]
+mod no_std;

binread/tests/io/no_std.rs

@@ -0,0 +1,87 @@
+use binread::io::{Cursor, Error, ErrorKind, Read, Result};
+
+#[derive(Debug)]
+struct MalfunctioningEddie<'data> {
+    error: Option<Error>,
+    data: Cursor<&'data [u8]>,
+}
+
+impl <'data> MalfunctioningEddie<'data> {
+    fn new(data: &'data[u8]) -> Self {
+        Self {
+            error: None,
+            data: Cursor::new(data),
+        }
+    }
+
+    fn nice_to_meet_you(&mut self) {
+        self.error = Some(Error::new(ErrorKind::BrokenPipe, ""));
+    }
+
+    fn what_a_surprise(&mut self) {
+        self.error = Some(Error::new(ErrorKind::Interrupted, ""));
+    }
+}
+
+impl Read for MalfunctioningEddie<'_> {
+    fn read(&mut self, buf: &mut [u8]) -> Result<usize> {
+        if let Some(error) = self.error.take() {
+            Err(error)
+        } else {
+            self.data.read(buf)
+        }
+    }
+}
+
+#[test]
+fn bytes() {
+    let mut cursor = MalfunctioningEddie::new(b"\0\x01\x02\x03\x04\x05");
+    {
+        let mut bytes = cursor.by_ref().bytes();
+        assert!(matches!(bytes.next(), Some(Ok(0))));
+        assert!(matches!(bytes.next(), Some(Ok(1))));
+    }
+
+    // Interrupted error should cause a retry
+    cursor.what_a_surprise();
+    {
+        let mut bytes = cursor.by_ref().bytes();
+        assert!(matches!(bytes.next(), Some(Ok(2))));
+    }
+
+    // Reads through Bytes should have advanced the underlying stream
+    let mut raw_read_data = [0u8; 2];
+    assert_eq!(cursor.read(&mut raw_read_data).unwrap(), 2);
+    assert_eq!(raw_read_data, [3, 4]);
+
+    // Errors other than Interrupted should be returned
+    cursor.nice_to_meet_you();
+    let mut bytes = cursor.bytes();
+    assert_eq!(bytes.next().unwrap().unwrap_err().kind(), ErrorKind::BrokenPipe);
+}
+
+#[test]
+fn read_exact() {
+    let mut cursor = MalfunctioningEddie::new(b"\0\x01\x02\x03\x04\x05");
+
+    let mut raw_read_data = [0u8; 2];
+    cursor.read_exact(&mut raw_read_data).unwrap();
+    assert_eq!(raw_read_data, [0, 1]);
+
+    // Interrupted error should cause a retry
+    cursor.what_a_surprise();
+    cursor.read_exact(&mut raw_read_data).unwrap();
+    assert_eq!(raw_read_data, [2, 3]);
+
+    // Errors other than Interrupted should be returned
+    cursor.nice_to_meet_you();
+    assert_eq!(cursor.read_exact(&mut raw_read_data).unwrap_err().kind(), ErrorKind::BrokenPipe);
+
+    // Read through a mutable reference should work as if it were directly on
+    // the cursor
+    cursor.by_ref().read_exact(&mut raw_read_data).unwrap();
+    assert_eq!(raw_read_data, [4, 5]);
+
+    // EOF reads should not succeed
+    assert_eq!(cursor.read_exact(&mut raw_read_data).unwrap_err().kind(), ErrorKind::UnexpectedEof);
+}

binread/tests/lib.rs

@@ -0,0 +1 @@
+mod io;