replace libio with core_io

* based on https://github.com/jethrogb/rust-core_io but could not get the packaging scripts to work
  and the repos is unmaintained anyway, so just copied the result
* more features and more up-to-date
* compatible with the fatfs crate

src/Cargo.lock

@@ -32,9 +32,16 @@ checksum = "4785bdd1c96b2a846b2bd7cc02e86b6b3dbf14e7e53446c4f54c92a361040822"
 
 [[package]]
 name = "compiler_builtins"
-version = "0.1.28"
+version = "0.1.32"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "439a6fab343b1dab347823537734a5cd4ae6ae2000b465ab886f64cdb723bd14"
+checksum = "7bc4ac2c824d2bfc612cba57708198547e9a26943af0632aff033e0693074d5c"
+
+[[package]]
+name = "core_io"
+version = "0.1.20200410"
+dependencies = [
+ "memchr",
+]
 
 [[package]]
 name = "cslice"
@@ -151,17 +158,10 @@ dependencies = [
  "proc-macro-nested",
 ]
 
-[[package]]
-name = "io"
-version = "0.1.0"
-dependencies = [
- "byteorder",
-]
-
 [[package]]
 name = "libasync"
 version = "0.0.0"
-source = "git+https://git.m-labs.hk/M-Labs/zc706.git#0c48dd934eb65e1cbd0124200ae2e08c7049c903"
+source = "git+https://git.m-labs.hk/M-Labs/zc706.git#40d5eb8232de1bec19e8bb81ad09351537926a06"
 dependencies = [
  "embedded-hal",
  "libcortex_a9",
@@ -173,7 +173,7 @@ dependencies = [
 [[package]]
 name = "libboard_zynq"
 version = "0.0.0"
-source = "git+https://git.m-labs.hk/M-Labs/zc706.git#0c48dd934eb65e1cbd0124200ae2e08c7049c903"
+source = "git+https://git.m-labs.hk/M-Labs/zc706.git#40d5eb8232de1bec19e8bb81ad09351537926a06"
 dependencies = [
  "bit_field",
  "embedded-hal",
@@ -189,7 +189,7 @@ dependencies = [
 [[package]]
 name = "libcortex_a9"
 version = "0.0.0"
-source = "git+https://git.m-labs.hk/M-Labs/zc706.git#0c48dd934eb65e1cbd0124200ae2e08c7049c903"
+source = "git+https://git.m-labs.hk/M-Labs/zc706.git#40d5eb8232de1bec19e8bb81ad09351537926a06"
 dependencies = [
  "bit_field",
  "libregister",
@@ -198,7 +198,7 @@ dependencies = [
 [[package]]
 name = "libregister"
 version = "0.0.0"
-source = "git+https://git.m-labs.hk/M-Labs/zc706.git#0c48dd934eb65e1cbd0124200ae2e08c7049c903"
+source = "git+https://git.m-labs.hk/M-Labs/zc706.git#40d5eb8232de1bec19e8bb81ad09351537926a06"
 dependencies = [
  "bit_field",
  "vcell",
@@ -208,7 +208,7 @@ dependencies = [
 [[package]]
 name = "libsupport_zynq"
 version = "0.0.0"
-source = "git+https://git.m-labs.hk/M-Labs/zc706.git#0c48dd934eb65e1cbd0124200ae2e08c7049c903"
+source = "git+https://git.m-labs.hk/M-Labs/zc706.git#40d5eb8232de1bec19e8bb81ad09351537926a06"
 dependencies = [
  "compiler_builtins",
  "libboard_zynq",
@@ -273,18 +273,18 @@ dependencies = [
 
 [[package]]
 name = "pin-project"
-version = "0.4.16"
+version = "0.4.19"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "81d480cb4e89522ccda96d0eed9af94180b7a5f93fb28f66e1fd7d68431663d1"
+checksum = "ba3a1acf4a3e70849f8a673497ef984f043f95d2d8252dcdf74d54e6a1e47e8a"
 dependencies = [
  "pin-project-internal",
 ]
 
 [[package]]
 name = "pin-project-internal"
-version = "0.4.16"
+version = "0.4.19"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a82996f11efccb19b685b14b5df818de31c1edcee3daa256ab5775dd98e72feb"
+checksum = "194e88048b71a3e02eb4ee36a6995fed9b8236c11a7bb9f7247a9d9835b3f265"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -299,9 +299,9 @@ checksum = "8b870d8c151b6f2fb93e84a13146138f05d02ed11c7e7c54f8826aaaf7c9f184"
 
 [[package]]
 name = "proc-macro-hack"
-version = "0.5.15"
+version = "0.5.16"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0d659fe7c6d27f25e9d80a1a094c223f5246f6a6596453e09d7229bf42750b63"
+checksum = "7e0456befd48169b9f13ef0f0ad46d492cf9d2dbb918bcf38e01eed4ce3ec5e4"
 
 [[package]]
 name = "proc-macro-nested"
@@ -311,18 +311,18 @@ checksum = "8e946095f9d3ed29ec38de908c22f95d9ac008e424c7bcae54c75a79c527c694"
 
 [[package]]
 name = "proc-macro2"
-version = "1.0.12"
+version = "1.0.18"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "8872cf6f48eee44265156c111456a700ab3483686b3f96df4cf5481c89157319"
+checksum = "beae6331a816b1f65d04c45b078fd8e6c93e8071771f41b8163255bbd8d7c8fa"
 dependencies = [
  "unicode-xid",
 ]
 
 [[package]]
 name = "quote"
-version = "1.0.5"
+version = "1.0.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "42934bc9c8ab0d3b273a16d8551c8f0fcff46be73276ca083ec2414c15c4ba5e"
+checksum = "54a21852a652ad6f610c9510194f398ff6f8692e334fd1145fed931f7fbe44ea"
 dependencies = [
  "proc-macro2",
 ]
@@ -337,10 +337,11 @@ checksum = "bd7a31eed1591dcbc95d92ad7161908e72f4677f8fabf2a32ca49b4237cbf211"
 name = "runtime"
 version = "0.1.0"
 dependencies = [
+ "byteorder",
+ "core_io",
  "cslice",
  "dyld",
  "futures",
- "io",
  "libasync",
  "libboard_zynq",
  "libcortex_a9",
@@ -364,9 +365,9 @@ dependencies = [
 
 [[package]]
 name = "syn"
-version = "1.0.21"
+version = "1.0.30"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "4696caa4048ac7ce2bcd2e484b3cef88c1004e41b8e945a277e2c25dc0b72060"
+checksum = "93a56fabc59dce20fe48b6c832cc249c713e7ed88fa28b0ee0a3bfcaae5fe4e2"
 dependencies = [
  "proc-macro2",
  "quote",

src/Cargo.toml

@@ -1,7 +1,7 @@
 [workspace]
 members = [
   "libdyld",
-  "libio",
+  "libcoreio",
   "runtime",
   "szl"
 ]
@@ -17,3 +17,6 @@ debug = true
 # turn off if you get unusable debug symbols.
 lto = true
 opt-level = 'z'  # Optimize for size.
+
+[patch.crates-io]
+core_io = { path = "./libcoreio" }

src/Makefile

@@ -9,7 +9,7 @@ all: ../build/firmware/armv7-none-eabihf/release/szl
 	mkdir -p ../build
 	python zc706.py -r ../build/pl.rs -V $(VARIANT)
 
-../build/firmware/armv7-none-eabihf/release/runtime: .cargo/* armv7-none-eabihf.json Cargo.lock Cargo.toml libdyld/* libdyld/src/* libio/* libio/src/* runtime/* runtime/src/* ../build/pl.rs
+../build/firmware/armv7-none-eabihf/release/runtime: .cargo/* armv7-none-eabihf.json Cargo.lock Cargo.toml libdyld/* libdyld/src/* libcoreio/* libcoreio/src/* libcoreio/src/io/* runtime/* runtime/src/* ../build/pl.rs
 	XBUILD_SYSROOT_PATH=`pwd`/../build/sysroot cargo xbuild --release -p runtime --target-dir ../build/firmware
 
 ../build/szl-payload.bin.lzma: ../build/firmware/armv7-none-eabihf/release/runtime

src/libcoreio/Cargo.toml

@@ -0,0 +1,14 @@
+[package]
+authors = ["M-Labs"]
+name = "core_io"
+version = "0.1.20200410"
+
+[lib]
+name = "core_io"
+
+[dependencies]
+memchr = { version = "2", default-features = false, optional = true }
+
+[features]
+alloc = []
+collections = ["alloc", "memchr"]

src/libcoreio/src/io/cursor.rs

@@ -0,0 +1,896 @@
+use crate::io::prelude::*;
+
+use core::cmp;
+use crate::io::{self, Error, ErrorKind, Initializer, SeekFrom};
+
+#[cfg(feature = "collections")]
+use core::convert::TryInto;
+
+#[cfg(feature="collections")] 
+use collections::vec::Vec;
+
+#[cfg(feature = "alloc")]
+use alloc::boxed::Box;
+
+/// A `Cursor` wraps an in-memory buffer and provides it with a
+/// [`Seek`] implementation.
+///
+/// `Cursor`s are used with in-memory buffers, anything implementing
+/// `AsRef<[u8]>`, to allow them to implement [`Read`] and/or [`Write`],
+/// allowing these buffers to be used anywhere you might use a reader or writer
+/// that does actual I/O.
+///
+/// The standard library implements some I/O traits on various types which
+/// are commonly used as a buffer, like `Cursor<`[`Vec`]`<u8>>` and
+/// `Cursor<`[`&[u8]`][bytes]`>`.
+///
+/// # Examples
+///
+/// We may want to write bytes to a [`File`] in our production
+/// code, but use an in-memory buffer in our tests. We can do this with
+/// `Cursor`:
+///
+/// [`Seek`]: trait.Seek.html
+/// [`Read`]: ../../std/io/trait.Read.html
+/// [`Write`]: ../../std/io/trait.Write.html
+/// [`Vec`]: ../../std/vec/struct.Vec.html
+/// [bytes]: ../../std/primitive.slice.html
+/// [`File`]: ../fs/struct.File.html
+///
+/// ```no_run
+/// use std::io::prelude::*;
+/// use std::io::{self, SeekFrom};
+/// use std::fs::File;
+///
+/// // a library function we've written
+/// fn write_ten_bytes_at_end<W: Write + Seek>(writer: &mut W) -> io::Result<()> {
+///     writer.seek(SeekFrom::End(-10))?;
+///
+///     for i in 0..10 {
+///         writer.write(&[i])?;
+///     }
+///
+///     // all went well
+///     Ok(())
+/// }
+///
+/// # fn foo() -> io::Result<()> {
+/// // Here's some code that uses this library function.
+/// //
+/// // We might want to use a BufReader here for efficiency, but let's
+/// // keep this example focused.
+/// let mut file = File::create("foo.txt")?;
+///
+/// write_ten_bytes_at_end(&mut file)?;
+/// # Ok(())
+/// # }
+///
+/// // now let's write a test
+/// #[test]
+/// fn test_writes_bytes() {
+///     // setting up a real File is much slower than an in-memory buffer,
+///     // let's use a cursor instead
+///     use std::io::Cursor;
+///     let mut buff = Cursor::new(vec![0; 15]);
+///
+///     write_ten_bytes_at_end(&mut buff).unwrap();
+///
+///     assert_eq!(&buff.get_ref()[5..15], &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
+/// }
+/// ```
+#[derive(Clone, Debug, Default, Eq, PartialEq)]
+pub struct Cursor<T> {
+    inner: T,
+    pos: u64,
+}
+
+impl<T> Cursor<T> {
+    /// Creates a new cursor wrapping the provided underlying in-memory buffer.
+    ///
+    /// Cursor initial position is `0` even if underlying buffer (e.g., `Vec`)
+    /// is not empty. So writing to cursor starts with overwriting `Vec`
+    /// content, not with appending to it.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::io::Cursor;
+    ///
+    /// let buff = Cursor::new(Vec::new());
+    /// # fn force_inference(_: &Cursor<Vec<u8>>) {}
+    /// # force_inference(&buff);
+    /// ```
+    pub fn new(inner: T) -> Cursor<T> {
+        Cursor { pos: 0, inner }
+    }
+
+    /// Consumes this cursor, returning the underlying value.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::io::Cursor;
+    ///
+    /// let buff = Cursor::new(Vec::new());
+    /// # fn force_inference(_: &Cursor<Vec<u8>>) {}
+    /// # force_inference(&buff);
+    ///
+    /// let vec = buff.into_inner();
+    /// ```
+    pub fn into_inner(self) -> T {
+        self.inner
+    }
+
+    /// Gets a reference to the underlying value in this cursor.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::io::Cursor;
+    ///
+    /// let buff = Cursor::new(Vec::new());
+    /// # fn force_inference(_: &Cursor<Vec<u8>>) {}
+    /// # force_inference(&buff);
+    ///
+    /// let reference = buff.get_ref();
+    /// ```
+    pub fn get_ref(&self) -> &T {
+        &self.inner
+    }
+
+    /// Gets a mutable reference to the underlying value in this cursor.
+    ///
+    /// Care should be taken to avoid modifying the internal I/O state of the
+    /// underlying value as it may corrupt this cursor's position.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::io::Cursor;
+    ///
+    /// let mut buff = Cursor::new(Vec::new());
+    /// # fn force_inference(_: &Cursor<Vec<u8>>) {}
+    /// # force_inference(&buff);
+    ///
+    /// let reference = buff.get_mut();
+    /// ```
+    pub fn get_mut(&mut self) -> &mut T {
+        &mut self.inner
+    }
+
+    /// Returns the current position of this cursor.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::io::Cursor;
+    /// use std::io::prelude::*;
+    /// use std::io::SeekFrom;
+    ///
+    /// let mut buff = Cursor::new(vec![1, 2, 3, 4, 5]);
+    ///
+    /// assert_eq!(buff.position(), 0);
+    ///
+    /// buff.seek(SeekFrom::Current(2)).unwrap();
+    /// assert_eq!(buff.position(), 2);
+    ///
+    /// buff.seek(SeekFrom::Current(-1)).unwrap();
+    /// assert_eq!(buff.position(), 1);
+    /// ```
+    pub fn position(&self) -> u64 {
+        self.pos
+    }
+
+    /// Sets the position of this cursor.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::io::Cursor;
+    ///
+    /// let mut buff = Cursor::new(vec![1, 2, 3, 4, 5]);
+    ///
+    /// assert_eq!(buff.position(), 0);
+    ///
+    /// buff.set_position(2);
+    /// assert_eq!(buff.position(), 2);
+    ///
+    /// buff.set_position(4);
+    /// assert_eq!(buff.position(), 4);
+    /// ```
+    pub fn set_position(&mut self, pos: u64) {
+        self.pos = pos;
+    }
+}
+
+impl<T> io::Seek for Cursor<T>
+where
+    T: AsRef<[u8]>,
+{
+    fn seek(&mut self, style: SeekFrom) -> io::Result<u64> {
+        let (base_pos, offset) = match style {
+            SeekFrom::Start(n) => {
+                self.pos = n;
+                return Ok(n);
+            }
+            SeekFrom::End(n) => (self.inner.as_ref().len() as u64, n),
+            SeekFrom::Current(n) => (self.pos, n),
+        };
+        let new_pos = if offset >= 0 {
+            base_pos.checked_add(offset as u64)
+        } else {
+            base_pos.checked_sub((offset.wrapping_neg()) as u64)
+        };
+        match new_pos {
+            Some(n) => {
+                self.pos = n;
+                Ok(self.pos)
+            }
+            None => Err(Error::new(
+                ErrorKind::InvalidInput,
+                "invalid seek to a negative or overflowing position",
+            )),
+        }
+    }
+
+    fn stream_len(&mut self) -> io::Result<u64> {
+        Ok(self.inner.as_ref().len() as u64)
+    }
+
+    fn stream_position(&mut self) -> io::Result<u64> {
+        Ok(self.pos)
+    }
+}
+
+impl<T> Read for Cursor<T>
+where
+    T: AsRef<[u8]>,
+{
+    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
+        let n = Read::read(&mut self.get_ref().as_ref(), buf)?;
+        self.pos += n as u64;
+        Ok(n)
+    }
+
+    fn read_exact(&mut self, buf: &mut [u8]) -> io::Result<()> {
+        let n = buf.len();
+        Read::read_exact(&mut self.get_ref().as_ref(), buf)?;
+        self.pos += n as u64;
+        Ok(())
+    }
+
+    #[inline]
+    unsafe fn initializer(&self) -> Initializer {
+        Initializer::nop()
+    }
+}
+
+#[cfg(feature = "collections")]
+impl<T> BufRead for Cursor<T>
+where
+    T: AsRef<[u8]>,
+{
+    fn fill_buf(&mut self) -> io::Result<&[u8]> {
+        let amt = cmp::min(self.pos, self.inner.as_ref().len() as u64);
+        Ok(&self.inner.as_ref()[(amt as usize)..])
+    }
+    fn consume(&mut self, amt: usize) {
+        self.pos += amt as u64;
+    }
+}
+
+// Non-resizing write implementation
+#[inline]
+fn slice_write(pos_mut: &mut u64, slice: &mut [u8], buf: &[u8]) -> io::Result<usize> {
+    let pos = cmp::min(*pos_mut, slice.len() as u64);
+    let amt = (&mut slice[(pos as usize)..]).write(buf)?;
+    *pos_mut += amt as u64;
+    Ok(amt)
+}
+
+// Resizing write implementation
+#[cfg(feature = "collections")]
+fn vec_write(pos_mut: &mut u64, vec: &mut Vec<u8>, buf: &[u8]) -> io::Result<usize> {
+    let pos: usize = (*pos_mut).try_into().map_err(|_| {
+        Error::new(
+            ErrorKind::InvalidInput,
+            "cursor position exceeds maximum possible vector length",
+        )
+    })?;
+    // Make sure the internal buffer is as least as big as where we
+    // currently are
+    let len = vec.len();
+    if len < pos {
+        // use `resize` so that the zero filling is as efficient as possible
+        vec.resize(pos, 0);
+    }
+    // Figure out what bytes will be used to overwrite what's currently
+    // there (left), and what will be appended on the end (right)
+    {
+        let space = vec.len() - pos;
+        let (left, right) = buf.split_at(cmp::min(space, buf.len()));
+        vec[pos..pos + left.len()].copy_from_slice(left);
+        vec.extend_from_slice(right);
+    }
+
+    // Bump us forward
+    *pos_mut = (pos + buf.len()) as u64;
+    Ok(buf.len())
+}
+
+impl Write for Cursor<&mut [u8]> {
+    #[inline]
+    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
+        slice_write(&mut self.pos, self.inner, buf)
+    }
+
+    #[inline]
+    fn flush(&mut self) -> io::Result<()> {
+        Ok(())
+    }
+}
+
+#[cfg(feature = "collections")]
+impl Write for Cursor<&mut Vec<u8>> {
+    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
+        vec_write(&mut self.pos, self.inner, buf)
+    }
+
+    #[inline]
+    fn flush(&mut self) -> io::Result<()> {
+        Ok(())
+    }
+}
+
+#[cfg(feature = "collections")]
+impl Write for Cursor<Vec<u8>> {
+    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
+        vec_write(&mut self.pos, &mut self.inner, buf)
+    }
+
+    #[inline]
+    fn flush(&mut self) -> io::Result<()> {
+        Ok(())
+    }
+}
+
+#[cfg(feature = "alloc")]
+impl Write for Cursor<Box<[u8]>> {
+    #[inline]
+    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
+        slice_write(&mut self.pos, &mut self.inner, buf)
+    }
+
+    #[inline]
+    fn flush(&mut self) -> io::Result<()> {
+        Ok(())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::io::prelude::*;
+    use crate::io::{Cursor, IoSlice, IoSliceMut, SeekFrom};
+
+    #[test]
+    fn test_vec_writer() {
+        let mut writer = Vec::new();
+        assert_eq!(writer.write(&[0]).unwrap(), 1);
+        assert_eq!(writer.write(&[1, 2, 3]).unwrap(), 3);
+        assert_eq!(writer.write(&[4, 5, 6, 7]).unwrap(), 4);
+        assert_eq!(
+            writer
+                .write_vectored(&[IoSlice::new(&[]), IoSlice::new(&[8, 9]), IoSlice::new(&[10])],)
+                .unwrap(),
+            3
+        );
+        let b: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
+        assert_eq!(writer, b);
+    }
+
+    #[test]
+    fn test_mem_writer() {
+        let mut writer = Cursor::new(Vec::new());
+        assert_eq!(writer.write(&[0]).unwrap(), 1);
+        assert_eq!(writer.write(&[1, 2, 3]).unwrap(), 3);
+        assert_eq!(writer.write(&[4, 5, 6, 7]).unwrap(), 4);
+        assert_eq!(
+            writer
+                .write_vectored(&[IoSlice::new(&[]), IoSlice::new(&[8, 9]), IoSlice::new(&[10])],)
+                .unwrap(),
+            3
+        );
+        let b: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
+        assert_eq!(&writer.get_ref()[..], b);
+    }
+
+    #[test]
+    fn test_mem_mut_writer() {
+        let mut vec = Vec::new();
+        let mut writer = Cursor::new(&mut vec);
+        assert_eq!(writer.write(&[0]).unwrap(), 1);
+        assert_eq!(writer.write(&[1, 2, 3]).unwrap(), 3);
+        assert_eq!(writer.write(&[4, 5, 6, 7]).unwrap(), 4);
+        assert_eq!(
+            writer
+                .write_vectored(&[IoSlice::new(&[]), IoSlice::new(&[8, 9]), IoSlice::new(&[10])],)
+                .unwrap(),
+            3
+        );
+        let b: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
+        assert_eq!(&writer.get_ref()[..], b);
+    }
+
+    #[test]
+    fn test_box_slice_writer() {
+        let mut writer = Cursor::new(vec![0u8; 9].into_boxed_slice());
+        assert_eq!(writer.position(), 0);
+        assert_eq!(writer.write(&[0]).unwrap(), 1);
+        assert_eq!(writer.position(), 1);
+        assert_eq!(writer.write(&[1, 2, 3]).unwrap(), 3);
+        assert_eq!(writer.write(&[4, 5, 6, 7]).unwrap(), 4);
+        assert_eq!(writer.position(), 8);
+        assert_eq!(writer.write(&[]).unwrap(), 0);
+        assert_eq!(writer.position(), 8);
+
+        assert_eq!(writer.write(&[8, 9]).unwrap(), 1);
+        assert_eq!(writer.write(&[10]).unwrap(), 0);
+        let b: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7, 8];
+        assert_eq!(&**writer.get_ref(), b);
+    }
+
+    #[test]
+    fn test_box_slice_writer_vectored() {
+        let mut writer = Cursor::new(vec![0u8; 9].into_boxed_slice());
+        assert_eq!(writer.position(), 0);
+        assert_eq!(writer.write_vectored(&[IoSlice::new(&[0])]).unwrap(), 1);
+        assert_eq!(writer.position(), 1);
+        assert_eq!(
+            writer
+                .write_vectored(&[IoSlice::new(&[1, 2, 3]), IoSlice::new(&[4, 5, 6, 7]),])
+                .unwrap(),
+            7,
+        );
+        assert_eq!(writer.position(), 8);
+        assert_eq!(writer.write_vectored(&[]).unwrap(), 0);
+        assert_eq!(writer.position(), 8);
+
+        assert_eq!(writer.write_vectored(&[IoSlice::new(&[8, 9])]).unwrap(), 1);
+        assert_eq!(writer.write_vectored(&[IoSlice::new(&[10])]).unwrap(), 0);
+        let b: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7, 8];
+        assert_eq!(&**writer.get_ref(), b);
+    }
+
+    #[test]
+    fn test_buf_writer() {
+        let mut buf = [0 as u8; 9];
+        {
+            let mut writer = Cursor::new(&mut buf[..]);
+            assert_eq!(writer.position(), 0);
+            assert_eq!(writer.write(&[0]).unwrap(), 1);
+            assert_eq!(writer.position(), 1);
+            assert_eq!(writer.write(&[1, 2, 3]).unwrap(), 3);
+            assert_eq!(writer.write(&[4, 5, 6, 7]).unwrap(), 4);
+            assert_eq!(writer.position(), 8);
+            assert_eq!(writer.write(&[]).unwrap(), 0);
+            assert_eq!(writer.position(), 8);
+
+            assert_eq!(writer.write(&[8, 9]).unwrap(), 1);
+            assert_eq!(writer.write(&[10]).unwrap(), 0);
+        }
+        let b: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7, 8];
+        assert_eq!(buf, b);
+    }
+
+    #[test]
+    fn test_buf_writer_vectored() {
+        let mut buf = [0 as u8; 9];
+        {
+            let mut writer = Cursor::new(&mut buf[..]);
+            assert_eq!(writer.position(), 0);
+            assert_eq!(writer.write_vectored(&[IoSlice::new(&[0])]).unwrap(), 1);
+            assert_eq!(writer.position(), 1);
+            assert_eq!(
+                writer
+                    .write_vectored(&[IoSlice::new(&[1, 2, 3]), IoSlice::new(&[4, 5, 6, 7])],)
+                    .unwrap(),
+                7,
+            );
+            assert_eq!(writer.position(), 8);
+            assert_eq!(writer.write_vectored(&[]).unwrap(), 0);
+            assert_eq!(writer.position(), 8);
+
+            assert_eq!(writer.write_vectored(&[IoSlice::new(&[8, 9])]).unwrap(), 1);
+            assert_eq!(writer.write_vectored(&[IoSlice::new(&[10])]).unwrap(), 0);
+        }
+        let b: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7, 8];
+        assert_eq!(buf, b);
+    }
+
+    #[test]
+    fn test_buf_writer_seek() {
+        let mut buf = [0 as u8; 8];
+        {
+            let mut writer = Cursor::new(&mut buf[..]);
+            assert_eq!(writer.position(), 0);
+            assert_eq!(writer.write(&[1]).unwrap(), 1);
+            assert_eq!(writer.position(), 1);
+
+            assert_eq!(writer.seek(SeekFrom::Start(2)).unwrap(), 2);
+            assert_eq!(writer.position(), 2);
+            assert_eq!(writer.write(&[2]).unwrap(), 1);
+            assert_eq!(writer.position(), 3);
+
+            assert_eq!(writer.seek(SeekFrom::Current(-2)).unwrap(), 1);
+            assert_eq!(writer.position(), 1);
+            assert_eq!(writer.write(&[3]).unwrap(), 1);
+            assert_eq!(writer.position(), 2);
+
+            assert_eq!(writer.seek(SeekFrom::End(-1)).unwrap(), 7);
+            assert_eq!(writer.position(), 7);
+            assert_eq!(writer.write(&[4]).unwrap(), 1);
+            assert_eq!(writer.position(), 8);
+        }
+        let b: &[_] = &[1, 3, 2, 0, 0, 0, 0, 4];
+        assert_eq!(buf, b);
+    }
+
+    #[test]
+    fn test_buf_writer_error() {
+        let mut buf = [0 as u8; 2];
+        let mut writer = Cursor::new(&mut buf[..]);
+        assert_eq!(writer.write(&[0]).unwrap(), 1);
+        assert_eq!(writer.write(&[0, 0]).unwrap(), 1);
+        assert_eq!(writer.write(&[0, 0]).unwrap(), 0);
+    }
+
+    #[test]
+    fn test_mem_reader() {
+        let mut reader = Cursor::new(vec![0, 1, 2, 3, 4, 5, 6, 7]);
+        let mut buf = [];
+        assert_eq!(reader.read(&mut buf).unwrap(), 0);
+        assert_eq!(reader.position(), 0);
+        let mut buf = [0];
+        assert_eq!(reader.read(&mut buf).unwrap(), 1);
+        assert_eq!(reader.position(), 1);
+        let b: &[_] = &[0];
+        assert_eq!(buf, b);
+        let mut buf = [0; 4];
+        assert_eq!(reader.read(&mut buf).unwrap(), 4);
+        assert_eq!(reader.position(), 5);
+        let b: &[_] = &[1, 2, 3, 4];
+        assert_eq!(buf, b);
+        assert_eq!(reader.read(&mut buf).unwrap(), 3);
+        let b: &[_] = &[5, 6, 7];
+        assert_eq!(&buf[..3], b);
+        assert_eq!(reader.read(&mut buf).unwrap(), 0);
+    }
+
+    #[test]
+    fn test_mem_reader_vectored() {
+        let mut reader = Cursor::new(vec![0, 1, 2, 3, 4, 5, 6, 7]);
+        let mut buf = [];
+        assert_eq!(reader.read_vectored(&mut [IoSliceMut::new(&mut buf)]).unwrap(), 0);
+        assert_eq!(reader.position(), 0);
+        let mut buf = [0];
+        assert_eq!(
+            reader
+                .read_vectored(&mut [IoSliceMut::new(&mut []), IoSliceMut::new(&mut buf),])
+                .unwrap(),
+            1,
+        );
+        assert_eq!(reader.position(), 1);
+        let b: &[_] = &[0];
+        assert_eq!(buf, b);
+        let mut buf1 = [0; 4];
+        let mut buf2 = [0; 4];
+        assert_eq!(
+            reader
+                .read_vectored(&mut [IoSliceMut::new(&mut buf1), IoSliceMut::new(&mut buf2),])
+                .unwrap(),
+            7,
+        );
+        let b1: &[_] = &[1, 2, 3, 4];
+        let b2: &[_] = &[5, 6, 7];
+        assert_eq!(buf1, b1);
+        assert_eq!(&buf2[..3], b2);
+        assert_eq!(reader.read(&mut buf).unwrap(), 0);
+    }
+
+    #[test]
+    fn test_boxed_slice_reader() {
+        let mut reader = Cursor::new(vec![0, 1, 2, 3, 4, 5, 6, 7].into_boxed_slice());
+        let mut buf = [];
+        assert_eq!(reader.read(&mut buf).unwrap(), 0);
+        assert_eq!(reader.position(), 0);
+        let mut buf = [0];
+        assert_eq!(reader.read(&mut buf).unwrap(), 1);
+        assert_eq!(reader.position(), 1);
+        let b: &[_] = &[0];
+        assert_eq!(buf, b);
+        let mut buf = [0; 4];
+        assert_eq!(reader.read(&mut buf).unwrap(), 4);
+        assert_eq!(reader.position(), 5);
+        let b: &[_] = &[1, 2, 3, 4];
+        assert_eq!(buf, b);
+        assert_eq!(reader.read(&mut buf).unwrap(), 3);
+        let b: &[_] = &[5, 6, 7];
+        assert_eq!(&buf[..3], b);
+        assert_eq!(reader.read(&mut buf).unwrap(), 0);
+    }
+
+    #[test]
+    fn test_boxed_slice_reader_vectored() {
+        let mut reader = Cursor::new(vec![0, 1, 2, 3, 4, 5, 6, 7].into_boxed_slice());
+        let mut buf = [];
+        assert_eq!(reader.read_vectored(&mut [IoSliceMut::new(&mut buf)]).unwrap(), 0);
+        assert_eq!(reader.position(), 0);
+        let mut buf = [0];
+        assert_eq!(
+            reader
+                .read_vectored(&mut [IoSliceMut::new(&mut []), IoSliceMut::new(&mut buf),])
+                .unwrap(),
+            1,
+        );
+        assert_eq!(reader.position(), 1);
+        let b: &[_] = &[0];
+        assert_eq!(buf, b);
+        let mut buf1 = [0; 4];
+        let mut buf2 = [0; 4];
+        assert_eq!(
+            reader
+                .read_vectored(&mut [IoSliceMut::new(&mut buf1), IoSliceMut::new(&mut buf2)],)
+                .unwrap(),
+            7,
+        );
+        let b1: &[_] = &[1, 2, 3, 4];
+        let b2: &[_] = &[5, 6, 7];
+        assert_eq!(buf1, b1);
+        assert_eq!(&buf2[..3], b2);
+        assert_eq!(reader.read(&mut buf).unwrap(), 0);
+    }
+
+    #[test]
+    fn read_to_end() {
+        let mut reader = Cursor::new(vec![0, 1, 2, 3, 4, 5, 6, 7]);
+        let mut v = Vec::new();
+        reader.read_to_end(&mut v).unwrap();
+        assert_eq!(v, [0, 1, 2, 3, 4, 5, 6, 7]);
+    }
+
+    #[test]
+    fn test_slice_reader() {
+        let in_buf = vec![0, 1, 2, 3, 4, 5, 6, 7];
+        let reader = &mut &in_buf[..];
+        let mut buf = [];
+        assert_eq!(reader.read(&mut buf).unwrap(), 0);
+        let mut buf = [0];
+        assert_eq!(reader.read(&mut buf).unwrap(), 1);
+        assert_eq!(reader.len(), 7);
+        let b: &[_] = &[0];
+        assert_eq!(&buf[..], b);
+        let mut buf = [0; 4];
+        assert_eq!(reader.read(&mut buf).unwrap(), 4);
+        assert_eq!(reader.len(), 3);
+        let b: &[_] = &[1, 2, 3, 4];
+        assert_eq!(&buf[..], b);
+        assert_eq!(reader.read(&mut buf).unwrap(), 3);
+        let b: &[_] = &[5, 6, 7];
+        assert_eq!(&buf[..3], b);
+        assert_eq!(reader.read(&mut buf).unwrap(), 0);
+    }
+
+    #[test]
+    fn test_slice_reader_vectored() {
+        let in_buf = vec![0, 1, 2, 3, 4, 5, 6, 7];
+        let reader = &mut &in_buf[..];
+        let mut buf = [];
+        assert_eq!(reader.read_vectored(&mut [IoSliceMut::new(&mut buf)]).unwrap(), 0);
+        let mut buf = [0];
+        assert_eq!(
+            reader
+                .read_vectored(&mut [IoSliceMut::new(&mut []), IoSliceMut::new(&mut buf),])
+                .unwrap(),
+            1,
+        );
+        assert_eq!(reader.len(), 7);
+        let b: &[_] = &[0];
+        assert_eq!(buf, b);
+        let mut buf1 = [0; 4];
+        let mut buf2 = [0; 4];
+        assert_eq!(
+            reader
+                .read_vectored(&mut [IoSliceMut::new(&mut buf1), IoSliceMut::new(&mut buf2)],)
+                .unwrap(),
+            7,
+        );
+        let b1: &[_] = &[1, 2, 3, 4];
+        let b2: &[_] = &[5, 6, 7];
+        assert_eq!(buf1, b1);
+        assert_eq!(&buf2[..3], b2);
+        assert_eq!(reader.read(&mut buf).unwrap(), 0);
+    }
+
+    #[test]
+    fn test_read_exact() {
+        let in_buf = vec![0, 1, 2, 3, 4, 5, 6, 7];
+        let reader = &mut &in_buf[..];
+        let mut buf = [];
+        assert!(reader.read_exact(&mut buf).is_ok());
+        let mut buf = [8];
+        assert!(reader.read_exact(&mut buf).is_ok());
+        assert_eq!(buf[0], 0);
+        assert_eq!(reader.len(), 7);
+        let mut buf = [0, 0, 0, 0, 0, 0, 0];
+        assert!(reader.read_exact(&mut buf).is_ok());
+        assert_eq!(buf, [1, 2, 3, 4, 5, 6, 7]);
+        assert_eq!(reader.len(), 0);
+        let mut buf = [0];
+        assert!(reader.read_exact(&mut buf).is_err());
+    }
+
+    #[test]
+    fn test_buf_reader() {
+        let in_buf = vec![0, 1, 2, 3, 4, 5, 6, 7];
+        let mut reader = Cursor::new(&in_buf[..]);
+        let mut buf = [];
+        assert_eq!(reader.read(&mut buf).unwrap(), 0);
+        assert_eq!(reader.position(), 0);
+        let mut buf = [0];
+        assert_eq!(reader.read(&mut buf).unwrap(), 1);
+        assert_eq!(reader.position(), 1);
+        let b: &[_] = &[0];
+        assert_eq!(buf, b);
+        let mut buf = [0; 4];
+        assert_eq!(reader.read(&mut buf).unwrap(), 4);
+        assert_eq!(reader.position(), 5);
+        let b: &[_] = &[1, 2, 3, 4];
+        assert_eq!(buf, b);
+        assert_eq!(reader.read(&mut buf).unwrap(), 3);
+        let b: &[_] = &[5, 6, 7];
+        assert_eq!(&buf[..3], b);
+        assert_eq!(reader.read(&mut buf).unwrap(), 0);
+    }
+
+    #[test]
+    fn seek_past_end() {
+        let buf = [0xff];
+        let mut r = Cursor::new(&buf[..]);
+        assert_eq!(r.seek(SeekFrom::Start(10)).unwrap(), 10);
+        assert_eq!(r.read(&mut [0]).unwrap(), 0);
+
+        let mut r = Cursor::new(vec![10]);
+        assert_eq!(r.seek(SeekFrom::Start(10)).unwrap(), 10);
+        assert_eq!(r.read(&mut [0]).unwrap(), 0);
+
+        let mut buf = [0];
+        let mut r = Cursor::new(&mut buf[..]);
+        assert_eq!(r.seek(SeekFrom::Start(10)).unwrap(), 10);
+        assert_eq!(r.write(&[3]).unwrap(), 0);
+
+        let mut r = Cursor::new(vec![10].into_boxed_slice());
+        assert_eq!(r.seek(SeekFrom::Start(10)).unwrap(), 10);
+        assert_eq!(r.write(&[3]).unwrap(), 0);
+    }
+
+    #[test]
+    fn seek_past_i64() {
+        let buf = [0xff];
+        let mut r = Cursor::new(&buf[..]);
+        assert_eq!(r.seek(SeekFrom::Start(6)).unwrap(), 6);
+        assert_eq!(r.seek(SeekFrom::Current(0x7ffffffffffffff0)).unwrap(), 0x7ffffffffffffff6);
+        assert_eq!(r.seek(SeekFrom::Current(0x10)).unwrap(), 0x8000000000000006);
+        assert_eq!(r.seek(SeekFrom::Current(0)).unwrap(), 0x8000000000000006);
+        assert!(r.seek(SeekFrom::Current(0x7ffffffffffffffd)).is_err());
+        assert_eq!(r.seek(SeekFrom::Current(-0x8000000000000000)).unwrap(), 6);
+
+        let mut r = Cursor::new(vec![10]);
+        assert_eq!(r.seek(SeekFrom::Start(6)).unwrap(), 6);
+        assert_eq!(r.seek(SeekFrom::Current(0x7ffffffffffffff0)).unwrap(), 0x7ffffffffffffff6);
+        assert_eq!(r.seek(SeekFrom::Current(0x10)).unwrap(), 0x8000000000000006);
+        assert_eq!(r.seek(SeekFrom::Current(0)).unwrap(), 0x8000000000000006);
+        assert!(r.seek(SeekFrom::Current(0x7ffffffffffffffd)).is_err());
+        assert_eq!(r.seek(SeekFrom::Current(-0x8000000000000000)).unwrap(), 6);
+
+        let mut buf = [0];
+        let mut r = Cursor::new(&mut buf[..]);
+        assert_eq!(r.seek(SeekFrom::Start(6)).unwrap(), 6);
+        assert_eq!(r.seek(SeekFrom::Current(0x7ffffffffffffff0)).unwrap(), 0x7ffffffffffffff6);
+        assert_eq!(r.seek(SeekFrom::Current(0x10)).unwrap(), 0x8000000000000006);
+        assert_eq!(r.seek(SeekFrom::Current(0)).unwrap(), 0x8000000000000006);
+        assert!(r.seek(SeekFrom::Current(0x7ffffffffffffffd)).is_err());
+        assert_eq!(r.seek(SeekFrom::Current(-0x8000000000000000)).unwrap(), 6);
+
+        let mut r = Cursor::new(vec![10].into_boxed_slice());
+        assert_eq!(r.seek(SeekFrom::Start(6)).unwrap(), 6);
+        assert_eq!(r.seek(SeekFrom::Current(0x7ffffffffffffff0)).unwrap(), 0x7ffffffffffffff6);
+        assert_eq!(r.seek(SeekFrom::Current(0x10)).unwrap(), 0x8000000000000006);
+        assert_eq!(r.seek(SeekFrom::Current(0)).unwrap(), 0x8000000000000006);
+        assert!(r.seek(SeekFrom::Current(0x7ffffffffffffffd)).is_err());
+        assert_eq!(r.seek(SeekFrom::Current(-0x8000000000000000)).unwrap(), 6);
+    }
+
+    #[test]
+    fn seek_before_0() {
+        let buf = [0xff];
+        let mut r = Cursor::new(&buf[..]);
+        assert!(r.seek(SeekFrom::End(-2)).is_err());
+
+        let mut r = Cursor::new(vec![10]);
+        assert!(r.seek(SeekFrom::End(-2)).is_err());
+
+        let mut buf = [0];
+        let mut r = Cursor::new(&mut buf[..]);
+        assert!(r.seek(SeekFrom::End(-2)).is_err());
+
+        let mut r = Cursor::new(vec![10].into_boxed_slice());
+        assert!(r.seek(SeekFrom::End(-2)).is_err());
+    }
+
+    #[test]
+    fn test_seekable_mem_writer() {
+        let mut writer = Cursor::new(Vec::<u8>::new());
+        assert_eq!(writer.position(), 0);
+        assert_eq!(writer.write(&[0]).unwrap(), 1);
+        assert_eq!(writer.position(), 1);
+        assert_eq!(writer.write(&[1, 2, 3]).unwrap(), 3);
+        assert_eq!(writer.write(&[4, 5, 6, 7]).unwrap(), 4);
+        assert_eq!(writer.position(), 8);
+        let b: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7];
+        assert_eq!(&writer.get_ref()[..], b);
+
+        assert_eq!(writer.seek(SeekFrom::Start(0)).unwrap(), 0);
+        assert_eq!(writer.position(), 0);
+        assert_eq!(writer.write(&[3, 4]).unwrap(), 2);
+        let b: &[_] = &[3, 4, 2, 3, 4, 5, 6, 7];
+        assert_eq!(&writer.get_ref()[..], b);
+
+        assert_eq!(writer.seek(SeekFrom::Current(1)).unwrap(), 3);
+        assert_eq!(writer.write(&[0, 1]).unwrap(), 2);
+        let b: &[_] = &[3, 4, 2, 0, 1, 5, 6, 7];
+        assert_eq!(&writer.get_ref()[..], b);
+
+        assert_eq!(writer.seek(SeekFrom::End(-1)).unwrap(), 7);
+        assert_eq!(writer.write(&[1, 2]).unwrap(), 2);
+        let b: &[_] = &[3, 4, 2, 0, 1, 5, 6, 1, 2];
+        assert_eq!(&writer.get_ref()[..], b);
+
+        assert_eq!(writer.seek(SeekFrom::End(1)).unwrap(), 10);
+        assert_eq!(writer.write(&[1]).unwrap(), 1);
+        let b: &[_] = &[3, 4, 2, 0, 1, 5, 6, 1, 2, 0, 1];
+        assert_eq!(&writer.get_ref()[..], b);
+    }
+
+    #[test]
+    fn vec_seek_past_end() {
+        let mut r = Cursor::new(Vec::new());
+        assert_eq!(r.seek(SeekFrom::Start(10)).unwrap(), 10);
+        assert_eq!(r.write(&[3]).unwrap(), 1);
+    }
+
+    #[test]
+    fn vec_seek_before_0() {
+        let mut r = Cursor::new(Vec::new());
+        assert!(r.seek(SeekFrom::End(-2)).is_err());
+    }
+
+    #[test]
+    #[cfg(target_pointer_width = "32")]
+    fn vec_seek_and_write_past_usize_max() {
+        let mut c = Cursor::new(Vec::new());
+        c.set_position(<usize>::max_value() as u64 + 1);
+        assert!(c.write_all(&[1, 2, 3]).is_err());
+    }
+
+    #[test]
+    fn test_partial_eq() {
+        assert_eq!(Cursor::new(Vec::<u8>::new()), Cursor::new(Vec::<u8>::new()));
+    }
+
+    #[test]
+    fn test_eq() {
+        struct AssertEq<T: Eq>(pub T);
+
+        let _: AssertEq<Cursor<Vec<u8>>> = AssertEq(Cursor::new(Vec::new()));
+    }
+}

src/libcoreio/src/io/error.rs

@@ -0,0 +1,551 @@
+#[cfg(feature="alloc")] use alloc::boxed::Box;
+#[cfg(not(feature="alloc"))] use ::FakeBox as Box;
+use core::convert::Into;
+use core::fmt;
+use core::marker::{Send, Sync};
+use core::option::Option::{self, Some, None};
+use core::result;
+#[cfg(feature="collections")] use collections::string::String;
+#[cfg(not(feature="collections"))] use ::ErrorString as String;
+use core::convert::From;
+
+/// A specialized [`Result`](../result/enum.Result.html) type for I/O
+/// operations.
+///
+/// This type is broadly used across [`std::io`] for any operation which may
+/// produce an error.
+///
+/// This typedef is generally used to avoid writing out [`io::Error`] directly and
+/// is otherwise a direct mapping to [`Result`].
+///
+/// While usual Rust style is to import types directly, aliases of [`Result`]
+/// often are not, to make it easier to distinguish between them. [`Result`] is
+/// generally assumed to be [`std::result::Result`][`Result`], and so users of this alias
+/// will generally use `io::Result` instead of shadowing the prelude's import
+/// of [`std::result::Result`][`Result`].
+///
+/// [`std::io`]: ../io/index.html
+/// [`io::Error`]: ../io/struct.Error.html
+/// [`Result`]: ../result/enum.Result.html
+///
+/// # Examples
+///
+/// A convenience function that bubbles an `io::Result` to its caller:
+///
+/// ```
+/// use std::io;
+///
+/// fn get_string() -> io::Result<String> {
+///     let mut buffer = String::new();
+///
+///     io::stdin().read_line(&mut buffer)?;
+///
+///     Ok(buffer)
+/// }
+/// ```
+pub type Result<T> = result::Result<T, Error>;
+
+/// The error type for I/O operations of the [`Read`], [`Write`], [`Seek`], and
+/// associated traits.
+///
+/// Errors mostly originate from the underlying OS, but custom instances of
+/// `Error` can be created with crafted error messages and a particular value of
+/// [`ErrorKind`].
+///
+/// [`Read`]: ../io/trait.Read.html
+/// [`Write`]: ../io/trait.Write.html
+/// [`Seek`]: ../io/trait.Seek.html
+/// [`ErrorKind`]: enum.ErrorKind.html
+pub struct Error {
+    repr: Repr,
+}
+
+impl fmt::Debug for Error {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        fmt::Debug::fmt(&self.repr, f)
+    }
+}
+
+enum Repr {
+    Os(i32),
+    Simple(ErrorKind),
+    #[cfg(feature="alloc")]
+    Custom(Box<Custom>),
+    #[cfg(not(feature="alloc"))]
+    Custom(Custom),
+}
+
+#[derive(Debug)]
+struct Custom {
+    kind: ErrorKind,
+    error: String,
+}
+
+/// A list specifying general categories of I/O error.
+///
+/// This list is intended to grow over time and it is not recommended to
+/// exhaustively match against it.
+///
+/// It is used with the [`io::Error`] type.
+///
+/// [`io::Error`]: struct.Error.html
+#[derive(Clone, Copy, Debug, Eq, Hash, Ord, PartialEq, PartialOrd)]
+#[allow(deprecated)]
+#[non_exhaustive]
+pub enum ErrorKind {
+    /// An entity was not found, often a file.
+    NotFound,
+    /// The operation lacked the necessary privileges to complete.
+    PermissionDenied,
+    /// The connection was refused by the remote server.
+    ConnectionRefused,
+    /// The connection was reset by the remote server.
+    ConnectionReset,
+    /// The connection was aborted (terminated) by the remote server.
+    ConnectionAborted,
+    /// The network operation failed because it was not connected yet.
+    NotConnected,
+    /// A socket address could not be bound because the address is already in
+    /// use elsewhere.
+    AddrInUse,
+    /// A nonexistent interface was requested or the requested address was not
+    /// local.
+    AddrNotAvailable,
+    /// The operation failed because a pipe was closed.
+    BrokenPipe,
+    /// An entity already exists, often a file.
+    AlreadyExists,
+    /// The operation needs to block to complete, but the blocking operation was
+    /// requested to not occur.
+    WouldBlock,
+    /// A parameter was incorrect.
+    InvalidInput,
+    /// Data not valid for the operation were encountered.
+    ///
+    /// Unlike [`InvalidInput`], this typically means that the operation
+    /// parameters were valid, however the error was caused by malformed
+    /// input data.
+    ///
+    /// For example, a function that reads a file into a string will error with
+    /// `InvalidData` if the file's contents are not valid UTF-8.
+    ///
+    /// [`InvalidInput`]: #variant.InvalidInput
+    InvalidData,
+    /// The I/O operation's timeout expired, causing it to be canceled.
+    TimedOut,
+    /// An error returned when an operation could not be completed because a
+    /// call to [`write`] returned [`Ok(0)`].
+    ///
+    /// This typically means that an operation could only succeed if it wrote a
+    /// particular number of bytes but only a smaller number of bytes could be
+    /// written.
+    ///
+    /// [`write`]: ../../std/io/trait.Write.html#tymethod.write
+    /// [`Ok(0)`]: ../../std/io/type.Result.html
+    WriteZero,
+    /// This operation was interrupted.
+    ///
+    /// Interrupted operations can typically be retried.
+    Interrupted,
+    /// Any I/O error not part of this list.
+    Other,
+
+    /// An error returned when an operation could not be completed because an
+    /// "end of file" was reached prematurely.
+    ///
+    /// This typically means that an operation could only succeed if it read a
+    /// particular number of bytes but only a smaller number of bytes could be
+    /// read.
+    UnexpectedEof,
+}
+
+impl ErrorKind {
+    pub(crate) fn as_str(&self) -> &'static str {
+        match *self {
+            ErrorKind::NotFound => "entity not found",
+            ErrorKind::PermissionDenied => "permission denied",
+            ErrorKind::ConnectionRefused => "connection refused",
+            ErrorKind::ConnectionReset => "connection reset",
+            ErrorKind::ConnectionAborted => "connection aborted",
+            ErrorKind::NotConnected => "not connected",
+            ErrorKind::AddrInUse => "address in use",
+            ErrorKind::AddrNotAvailable => "address not available",
+            ErrorKind::BrokenPipe => "broken pipe",
+            ErrorKind::AlreadyExists => "entity already exists",
+            ErrorKind::WouldBlock => "operation would block",
+            ErrorKind::InvalidInput => "invalid input parameter",
+            ErrorKind::InvalidData => "invalid data",
+            ErrorKind::TimedOut => "timed out",
+            ErrorKind::WriteZero => "write zero",
+            ErrorKind::Interrupted => "operation interrupted",
+            ErrorKind::Other => "other os error",
+            ErrorKind::UnexpectedEof => "unexpected end of file",
+        }
+    }
+}
+
+/// Intended for use for errors not exposed to the user, where allocating onto
+/// the heap (for normal construction via Error::new) is too costly.
+impl From<ErrorKind> for Error {
+    /// Converts an [`ErrorKind`] into an [`Error`].
+    ///
+    /// This conversion allocates a new error with a simple representation of error kind.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::io::{Error, ErrorKind};
+    ///
+    /// let not_found = ErrorKind::NotFound;
+    /// let error = Error::from(not_found);
+    /// assert_eq!("entity not found", format!("{}", error));
+    /// ```
+    ///
+    /// [`ErrorKind`]: ../../std/io/enum.ErrorKind.html
+    /// [`Error`]: ../../std/io/struct.Error.html
+    #[inline]
+    fn from(kind: ErrorKind) -> Error {
+        Error { repr: Repr::Simple(kind) }
+    }
+}
+
+impl Error {
+    /// Creates a new I/O error from a known kind of error as well as an
+    /// arbitrary error payload.
+    ///
+    /// This function is used to generically create I/O errors which do not
+    /// originate from the OS itself. The `error` argument is an arbitrary
+    /// payload which will be contained in this `Error`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::io::{Error, ErrorKind};
+    ///
+    /// // errors can be created from strings
+    /// let custom_error = Error::new(ErrorKind::Other, "oh no!");
+    ///
+    /// // errors can also be created from other errors
+    /// let custom_error2 = Error::new(ErrorKind::Interrupted, custom_error);
+    /// ```
+    pub fn new<E>(kind: ErrorKind, error: E) -> Error
+    where
+        E: Into<String>,
+    {
+        Self::_new(kind, error.into())
+    }
+
+    fn _new(kind: ErrorKind, error: String) -> Error {
+        Error { repr: Repr::Custom(Box::new(Custom { kind, error })) }
+    }
+
+    /// Creates a new instance of an `Error` from a particular OS error code.
+    ///
+    /// # Examples
+    ///
+    /// On Linux:
+    ///
+    /// ```
+    /// # if cfg!(target_os = "linux") {
+    /// use std::io;
+    ///
+    /// let error = io::Error::from_raw_os_error(22);
+    /// assert_eq!(error.kind(), io::ErrorKind::InvalidInput);
+    /// # }
+    /// ```
+    ///
+    /// On Windows:
+    ///
+    /// ```
+    /// # if cfg!(windows) {
+    /// use std::io;
+    ///
+    /// let error = io::Error::from_raw_os_error(10022);
+    /// assert_eq!(error.kind(), io::ErrorKind::InvalidInput);
+    /// # }
+    /// ```
+    pub fn from_raw_os_error(code: i32) -> Error {
+        Error { repr: Repr::Os(code) }
+    }
+
+    /// Returns the OS error that this error represents (if any).
+    ///
+    /// If this `Error` was constructed via `last_os_error` or
+    /// `from_raw_os_error`, then this function will return `Some`, otherwise
+    /// it will return `None`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::io::{Error, ErrorKind};
+    ///
+    /// fn print_os_error(err: &Error) {
+    ///     if let Some(raw_os_err) = err.raw_os_error() {
+    ///         println!("raw OS error: {:?}", raw_os_err);
+    ///     } else {
+    ///         println!("Not an OS error");
+    ///     }
+    /// }
+    ///
+    /// fn main() {
+    ///     // Will print "raw OS error: ...".
+    ///     print_os_error(&Error::last_os_error());
+    ///     // Will print "Not an OS error".
+    ///     print_os_error(&Error::new(ErrorKind::Other, "oh no!"));
+    /// }
+    /// ```
+    pub fn raw_os_error(&self) -> Option<i32> {
+        match self.repr {
+            Repr::Os(i) => Some(i),
+            Repr::Custom(..) => None,
+            Repr::Simple(..) => None,
+        }
+    }
+
+    /// Returns a reference to the inner error wrapped by this error (if any).
+    ///
+    /// If this `Error` was constructed via `new` then this function will
+    /// return `Some`, otherwise it will return `None`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::io::{Error, ErrorKind};
+    ///
+    /// fn print_error(err: &Error) {
+    ///     if let Some(inner_err) = err.get_ref() {
+    ///         println!("Inner error: {:?}", inner_err);
+    ///     } else {
+    ///         println!("No inner error");
+    ///     }
+    /// }
+    ///
+    /// fn main() {
+    ///     // Will print "No inner error".
+    ///     print_error(&Error::last_os_error());
+    ///     // Will print "Inner error: ...".
+    ///     print_error(&Error::new(ErrorKind::Other, "oh no!"));
+    /// }
+    /// ```
+    pub fn get_ref(&self) -> Option<&String> {
+        match self.repr {
+            Repr::Os(..) => None,
+            Repr::Simple(..) => None,
+            Repr::Custom(ref c) => Some(&c.error),
+        }
+    }
+
+    /// Returns a mutable reference to the inner error wrapped by this error
+    /// (if any).
+    ///
+    /// If this `Error` was constructed via `new` then this function will
+    /// return `Some`, otherwise it will return `None`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::io::{Error, ErrorKind};
+    /// use std::{error, fmt};
+    /// use std::fmt::Display;
+    ///
+    /// #[derive(Debug)]
+    /// struct MyError {
+    ///     v: String,
+    /// }
+    ///
+    /// impl MyError {
+    ///     fn new() -> MyError {
+    ///         MyError {
+    ///             v: "oh no!".to_string()
+    ///         }
+    ///     }
+    ///
+    ///     fn change_message(&mut self, new_message: &str) {
+    ///         self.v = new_message.to_string();
+    ///     }
+    /// }
+    ///
+    /// impl error::Error for MyError {}
+    ///
+    /// impl Display for MyError {
+    ///     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+    ///         write!(f, "MyError: {}", &self.v)
+    ///     }
+    /// }
+    ///
+    /// fn change_error(mut err: Error) -> Error {
+    ///     if let Some(inner_err) = err.get_mut() {
+    ///         inner_err.downcast_mut::<MyError>().unwrap().change_message("I've been changed!");
+    ///     }
+    ///     err
+    /// }
+    ///
+    /// fn print_error(err: &Error) {
+    ///     if let Some(inner_err) = err.get_ref() {
+    ///         println!("Inner error: {}", inner_err);
+    ///     } else {
+    ///         println!("No inner error");
+    ///     }
+    /// }
+    ///
+    /// fn main() {
+    ///     // Will print "No inner error".
+    ///     print_error(&change_error(Error::last_os_error()));
+    ///     // Will print "Inner error: ...".
+    ///     print_error(&change_error(Error::new(ErrorKind::Other, MyError::new())));
+    /// }
+    /// ```
+    pub fn get_mut(&mut self) -> Option<&mut String> {
+        match self.repr {
+            Repr::Os(..) => None,
+            Repr::Simple(..) => None,
+            Repr::Custom(ref mut c) => Some(&mut c.error),
+        }
+    }
+
+    /// Consumes the `Error`, returning its inner error (if any).
+    ///
+    /// If this `Error` was constructed via `new` then this function will
+    /// return `Some`, otherwise it will return `None`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::io::{Error, ErrorKind};
+    ///
+    /// fn print_error(err: Error) {
+    ///     if let Some(inner_err) = err.into_inner() {
+    ///         println!("Inner error: {}", inner_err);
+    ///     } else {
+    ///         println!("No inner error");
+    ///     }
+    /// }
+    ///
+    /// fn main() {
+    ///     // Will print "No inner error".
+    ///     print_error(Error::last_os_error());
+    ///     // Will print "Inner error: ...".
+    ///     print_error(Error::new(ErrorKind::Other, "oh no!"));
+    /// }
+    /// ```
+    pub fn into_inner(self) -> Option<String> {
+        match self.repr {
+            Repr::Os(..) => None,
+            Repr::Simple(..) => None,
+            Repr::Custom(c) => Some(c.error),
+        }
+    }
+
+    /// Returns the corresponding `ErrorKind` for this error.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::io::{Error, ErrorKind};
+    ///
+    /// fn print_error(err: Error) {
+    ///     println!("{:?}", err.kind());
+    /// }
+    ///
+    /// fn main() {
+    ///     // Will print "No inner error".
+    ///     print_error(Error::last_os_error());
+    ///     // Will print "Inner error: ...".
+    ///     print_error(Error::new(ErrorKind::AddrInUse, "oh no!"));
+    /// }
+    /// ```
+    pub fn kind(&self) -> ErrorKind {
+        match self.repr {
+            Repr::Os(_code) => ErrorKind::Other,
+            Repr::Custom(ref c) => c.kind,
+            Repr::Simple(kind) => kind,
+        }
+    }
+}
+
+impl fmt::Debug for Repr {
+    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match *self {
+            Repr::Os(code) => fmt
+                .debug_struct("Os")
+                .field("code", &code)
+                .finish(),
+            Repr::Custom(ref c) => fmt::Debug::fmt(&c, fmt),
+            Repr::Simple(kind) => fmt.debug_tuple("Kind").field(&kind).finish(),
+        }
+    }
+}
+
+impl fmt::Display for Error {
+    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self.repr {
+            Repr::Os(code) => {
+                write!(fmt, "os error {}", code)
+            }
+            Repr::Custom(ref c) => c.error.fmt(fmt),
+            Repr::Simple(kind) => write!(fmt, "{}", kind.as_str()),
+        }
+    }
+}
+
+fn _assert_error_is_sync_send() {
+    fn _is_sync_send<T: Sync + Send>() {}
+    _is_sync_send::<Error>();
+}
+
+#[cfg(test)]
+mod test {
+    use super::{Custom, Error, ErrorKind, Repr};
+    use crate::error;
+    use crate::fmt;
+    use crate::sys::decode_error_kind;
+    use crate::sys::os::error_string;
+
+    #[test]
+    fn test_debug_error() {
+        let code = 6;
+        let msg = error_string(code);
+        let kind = decode_error_kind(code);
+        let err = Error {
+            repr: Repr::Custom(box Custom {
+                kind: ErrorKind::InvalidInput,
+                error: box Error { repr: super::Repr::Os(code) },
+            }),
+        };
+        let expected = format!(
+            "Custom {{ \
+             kind: InvalidInput, \
+             error: Os {{ \
+             code: {:?}, \
+             kind: {:?}, \
+             message: {:?} \
+             }} \
+             }}",
+            code, kind, msg
+        );
+        assert_eq!(format!("{:?}", err), expected);
+    }
+
+    #[test]
+    fn test_downcasting() {
+        #[derive(Debug)]
+        struct TestError;
+
+        impl fmt::Display for TestError {
+            fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+                f.write_str("asdf")
+            }
+        }
+
+        impl error::Error for TestError {}
+
+        // we have to call all of these UFCS style right now since method
+        // resolution won't implicitly drop the Send+Sync bounds
+        let mut err = Error::new(ErrorKind::Other, TestError);
+        assert!(err.get_ref().unwrap().is::<TestError>());
+        assert_eq!("asdf", err.get_ref().unwrap().to_string());
+        assert!(err.get_mut().unwrap().is::<TestError>());
+        let extracted = err.into_inner().unwrap();
+        extracted.downcast::<TestError>().unwrap();
+    }
+}

src/libcoreio/src/io/impls.rs

@@ -0,0 +1,378 @@
+use core::cmp;
+use core::fmt;
+use crate::io::{
+    self, Error, ErrorKind, Initializer, Read, Seek, SeekFrom, Write,
+};
+#[cfg(feature = "collections")] use crate::io::BufRead;
+use core::mem;
+
+#[cfg(feature="collections")] 
+use collections::{
+    vec::Vec,
+    string::String,
+};
+#[cfg(feature = "alloc")]
+use alloc::boxed::Box;
+
+// =============================================================================
+// Forwarding implementations
+
+impl<R: Read + ?Sized> Read for &mut R {
+    #[inline]
+    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
+        (**self).read(buf)
+    }
+
+    #[inline]
+    unsafe fn initializer(&self) -> Initializer {
+        (**self).initializer()
+    }
+
+    #[cfg(feature="collections")]
+    #[inline]
+    fn read_to_end(&mut self, buf: &mut Vec<u8>) -> io::Result<usize> {
+        (**self).read_to_end(buf)
+    }
+
+    #[cfg(feature="collections")]
+    #[inline]
+    fn read_to_string(&mut self, buf: &mut String) -> io::Result<usize> {
+        (**self).read_to_string(buf)
+    }
+
+    #[inline]
+    fn read_exact(&mut self, buf: &mut [u8]) -> io::Result<()> {
+        (**self).read_exact(buf)
+    }
+}
+impl<W: Write + ?Sized> Write for &mut W {
+    #[inline]
+    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
+        (**self).write(buf)
+    }
+
+    #[inline]
+    fn flush(&mut self) -> io::Result<()> {
+        (**self).flush()
+    }
+
+    #[inline]
+    fn write_all(&mut self, buf: &[u8]) -> io::Result<()> {
+        (**self).write_all(buf)
+    }
+
+    #[inline]
+    fn write_fmt(&mut self, fmt: fmt::Arguments<'_>) -> io::Result<()> {
+        (**self).write_fmt(fmt)
+    }
+}
+impl<S: Seek + ?Sized> Seek for &mut S {
+    #[inline]
+    fn seek(&mut self, pos: SeekFrom) -> io::Result<u64> {
+        (**self).seek(pos)
+    }
+}
+#[cfg(feature = "collections")]
+impl<B: BufRead + ?Sized> BufRead for &mut B {
+    #[inline]
+    fn fill_buf(&mut self) -> io::Result<&[u8]> {
+        (**self).fill_buf()
+    }
+
+    #[inline]
+    fn consume(&mut self, amt: usize) {
+        (**self).consume(amt)
+    }
+
+    #[cfg(feature="collections")]
+    #[inline]
+    fn read_until(&mut self, byte: u8, buf: &mut Vec<u8>) -> io::Result<usize> {
+        (**self).read_until(byte, buf)
+    }
+
+    #[cfg(feature="collections")]
+    #[inline]
+    fn read_line(&mut self, buf: &mut String) -> io::Result<usize> {
+        (**self).read_line(buf)
+    }
+}
+
+#[cfg(feature="alloc")]
+#[cfg(feature="collections")]
+impl<R: Read + ?Sized> Read for Box<R> {
+    #[inline]
+    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
+        (**self).read(buf)
+    }
+
+    #[cfg(feature="collections")]
+    #[inline]
+    fn read_to_end(&mut self, buf: &mut Vec<u8>) -> io::Result<usize> {
+        (**self).read_to_end(buf)
+    }
+
+    #[cfg(feature="collections")]
+    #[inline]
+    fn read_to_string(&mut self, buf: &mut String) -> io::Result<usize> {
+        (**self).read_to_string(buf)
+    }
+
+    #[inline]
+    fn read_exact(&mut self, buf: &mut [u8]) -> io::Result<()> {
+        (**self).read_exact(buf)
+    }
+}
+#[cfg(feature="alloc")]
+#[cfg(feature="collections")]
+impl<W: Write + ?Sized> Write for Box<W> {
+    #[inline]
+    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
+        (**self).write(buf)
+    }
+
+    #[inline]
+    fn flush(&mut self) -> io::Result<()> {
+        (**self).flush()
+    }
+
+    #[inline]
+    fn write_all(&mut self, buf: &[u8]) -> io::Result<()> {
+        (**self).write_all(buf)
+    }
+
+    #[inline]
+    fn write_fmt(&mut self, fmt: fmt::Arguments<'_>) -> io::Result<()> {
+        (**self).write_fmt(fmt)
+    }
+}
+#[cfg(feature="collections")]
+impl<S: Seek + ?Sized> Seek for Box<S> {
+    #[inline]
+    fn seek(&mut self, pos: SeekFrom) -> io::Result<u64> {
+        (**self).seek(pos)
+    }
+}
+#[cfg(feature="collections")]
+impl<B: BufRead + ?Sized> BufRead for Box<B> {
+    #[inline]
+    fn fill_buf(&mut self) -> io::Result<&[u8]> {
+        (**self).fill_buf()
+    }
+
+    #[inline]
+    fn consume(&mut self, amt: usize) {
+        (**self).consume(amt)
+    }
+
+    #[inline]
+    fn read_until(&mut self, byte: u8, buf: &mut Vec<u8>) -> io::Result<usize> {
+        (**self).read_until(byte, buf)
+    }
+
+    #[inline]
+    fn read_line(&mut self, buf: &mut String) -> io::Result<usize> {
+        (**self).read_line(buf)
+    }
+}
+
+// Used by panicking::default_hook
+#[cfg(test)]
+/// This impl is only used by printing logic, so any error returned is always
+/// of kind `Other`, and should be ignored.
+#[cfg(feature="collections")]
+impl Write for Box<dyn (::realstd::io::Write) + Send> {
+    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
+        (**self).write(buf).map_err(|_| ErrorKind::Other.into())
+    }
+
+    fn flush(&mut self) -> io::Result<()> {
+        (**self).flush().map_err(|_| ErrorKind::Other.into())
+    }
+}
+
+// =============================================================================
+// In-memory buffer implementations
+
+/// Read is implemented for `&[u8]` by copying from the slice.
+///
+/// Note that reading updates the slice to point to the yet unread part.
+/// The slice will be empty when EOF is reached.
+impl Read for &[u8] {
+    #[inline]
+    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
+        let amt = cmp::min(buf.len(), self.len());
+        let (a, b) = self.split_at(amt);
+
+        // First check if the amount of bytes we want to read is small:
+        // `copy_from_slice` will generally expand to a call to `memcpy`, and
+        // for a single byte the overhead is significant.
+        if amt == 1 {
+            buf[0] = a[0];
+        } else {
+            buf[..amt].copy_from_slice(a);
+        }
+
+        *self = b;
+        Ok(amt)
+    }
+
+    #[inline]
+    unsafe fn initializer(&self) -> Initializer {
+        Initializer::nop()
+    }
+
+    #[inline]
+    fn read_exact(&mut self, buf: &mut [u8]) -> io::Result<()> {
+        if buf.len() > self.len() {
+            return Err(Error::new(ErrorKind::UnexpectedEof, "failed to fill whole buffer"));
+        }
+        let (a, b) = self.split_at(buf.len());
+
+        // First check if the amount of bytes we want to read is small:
+        // `copy_from_slice` will generally expand to a call to `memcpy`, and
+        // for a single byte the overhead is significant.
+        if buf.len() == 1 {
+            buf[0] = a[0];
+        } else {
+            buf.copy_from_slice(a);
+        }
+
+        *self = b;
+        Ok(())
+    }
+
+    #[cfg(feature="collections")]
+    #[inline]
+    fn read_to_end(&mut self, buf: &mut Vec<u8>) -> io::Result<usize> {
+        buf.extend_from_slice(*self);
+        let len = self.len();
+        *self = &self[len..];
+        Ok(len)
+    }
+}
+
+#[cfg(feature="collections")]
+impl BufRead for &[u8] {
+    #[inline]
+    fn fill_buf(&mut self) -> io::Result<&[u8]> {
+        Ok(*self)
+    }
+
+    #[inline]
+    fn consume(&mut self, amt: usize) {
+        *self = &self[amt..];
+    }
+}
+
+/// Write is implemented for `&mut [u8]` by copying into the slice, overwriting
+/// its data.
+///
+/// Note that writing updates the slice to point to the yet unwritten part.
+/// The slice will be empty when it has been completely overwritten.
+impl Write for &mut [u8] {
+    #[inline]
+    fn write(&mut self, data: &[u8]) -> io::Result<usize> {
+        let amt = cmp::min(data.len(), self.len());
+        let (a, b) = mem::replace(self, &mut []).split_at_mut(amt);
+        a.copy_from_slice(&data[..amt]);
+        *self = b;
+        Ok(amt)
+    }
+
+    #[inline]
+    fn write_all(&mut self, data: &[u8]) -> io::Result<()> {
+        if self.write(data)? == data.len() {
+            Ok(())
+        } else {
+            Err(Error::new(ErrorKind::WriteZero, "failed to write whole buffer"))
+        }
+    }
+
+    #[inline]
+    fn flush(&mut self) -> io::Result<()> {
+        Ok(())
+    }
+}
+
+/// Write is implemented for `Vec<u8>` by appending to the vector.
+/// The vector will grow as needed.
+#[cfg(feature="collections")]
+impl Write for Vec<u8> {
+    #[inline]
+    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
+        self.extend_from_slice(buf);
+        Ok(buf.len())
+    }
+
+    #[inline]
+    fn write_all(&mut self, buf: &[u8]) -> io::Result<()> {
+        self.extend_from_slice(buf);
+        Ok(())
+    }
+
+    #[inline]
+    fn flush(&mut self) -> io::Result<()> {
+        Ok(())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::io::prelude::*;
+
+    #[bench]
+    fn bench_read_slice(b: &mut test::Bencher) {
+        let buf = [5; 1024];
+        let mut dst = [0; 128];
+
+        b.iter(|| {
+            let mut rd = &buf[..];
+            for _ in 0..8 {
+                let _ = rd.read(&mut dst);
+                test::black_box(&dst);
+            }
+        })
+    }
+
+    #[bench]
+    fn bench_write_slice(b: &mut test::Bencher) {
+        let mut buf = [0; 1024];
+        let src = [5; 128];
+
+        b.iter(|| {
+            let mut wr = &mut buf[..];
+            for _ in 0..8 {
+                let _ = wr.write_all(&src);
+                test::black_box(&wr);
+            }
+        })
+    }
+
+    #[bench]
+    fn bench_read_vec(b: &mut test::Bencher) {
+        let buf = vec![5; 1024];
+        let mut dst = [0; 128];
+
+        b.iter(|| {
+            let mut rd = &buf[..];
+            for _ in 0..8 {
+                let _ = rd.read(&mut dst);
+                test::black_box(&dst);
+            }
+        })
+    }
+
+    #[bench]
+    fn bench_write_vec(b: &mut test::Bencher) {
+        let mut buf = Vec::with_capacity(1024);
+        let src = [5; 128];
+
+        b.iter(|| {
+            let mut wr = &mut buf[..];
+            for _ in 0..8 {
+                let _ = wr.write_all(&src);
+                test::black_box(&wr);
+            }
+        })
+    }
+}

src/libcoreio/src/io/prelude.rs

@@ -0,0 +1,13 @@
+//! The I/O Prelude
+//!
+//! The purpose of this module is to alleviate imports of many common I/O traits
+//! by adding a glob import to the top of I/O heavy modules:
+//!
+//! ```
+//! # #![allow(unused_imports)]
+//! use std::io::prelude::*;
+//! ```
+
+
+pub use super::{Read, Seek, Write};
+#[cfg(feature = "collections")] pub use super::BufRead;

src/libcoreio/src/io/util.rs

@@ -0,0 +1,269 @@
+#![allow(missing_copy_implementations)]
+
+use core::fmt;
+use core::mem;
+use crate::io::{self, ErrorKind, Initializer, Read, Write};
+#[cfg(feature = "collections")] use crate::io::BufRead;
+
+/// Copies the entire contents of a reader into a writer.
+///
+/// This function will continuously read data from `reader` and then
+/// write it into `writer` in a streaming fashion until `reader`
+/// returns EOF.
+///
+/// On success, the total number of bytes that were copied from
+/// `reader` to `writer` is returned.
+///
+/// If you’re wanting to copy the contents of one file to another and you’re
+/// working with filesystem paths, see the [`fs::copy`] function.
+///
+/// [`fs::copy`]: ../fs/fn.copy.html
+///
+/// # Errors
+///
+/// This function will return an error immediately if any call to `read` or
+/// `write` returns an error. All instances of `ErrorKind::Interrupted` are
+/// handled by this function and the underlying operation is retried.
+///
+/// # Examples
+///
+/// ```
+/// use std::io;
+///
+/// fn main() -> io::Result<()> {
+///     let mut reader: &[u8] = b"hello";
+///     let mut writer: Vec<u8> = vec![];
+///
+///     io::copy(&mut reader, &mut writer)?;
+///
+///     assert_eq!(&b"hello"[..], &writer[..]);
+///     Ok(())
+/// }
+/// ```
+pub fn copy<R: ?Sized, W: ?Sized>(reader: &mut R, writer: &mut W) -> io::Result<u64>
+where
+    R: Read,
+    W: Write,
+{
+    let mut buf = unsafe {
+        #[allow(deprecated)]
+        let mut buf: [u8; super::DEFAULT_BUF_SIZE] = mem::uninitialized();
+        reader.initializer().initialize(&mut buf);
+        buf
+    };
+
+    let mut written = 0;
+    loop {
+        let len = match reader.read(&mut buf) {
+            Ok(0) => return Ok(written),
+            Ok(len) => len,
+            Err(ref e) if e.kind() == ErrorKind::Interrupted => continue,
+            Err(e) => return Err(e),
+        };
+        writer.write_all(&buf[..len])?;
+        written += len as u64;
+    }
+}
+
+/// A reader which is always at EOF.
+///
+/// This struct is generally created by calling [`empty`]. Please see
+/// the documentation of [`empty()`][`empty`] for more details.
+///
+/// [`empty`]: fn.empty.html
+pub struct Empty {
+    _priv: (),
+}
+
+/// Constructs a new handle to an empty reader.
+///
+/// All reads from the returned reader will return [`Ok`]`(0)`.
+///
+/// [`Ok`]: ../result/enum.Result.html#variant.Ok
+///
+/// # Examples
+///
+/// A slightly sad example of not reading anything into a buffer:
+///
+/// ```
+/// use std::io::{self, Read};
+///
+/// let mut buffer = String::new();
+/// io::empty().read_to_string(&mut buffer).unwrap();
+/// assert!(buffer.is_empty());
+/// ```
+pub fn empty() -> Empty {
+    Empty { _priv: () }
+}
+
+impl Read for Empty {
+    #[inline]
+    fn read(&mut self, _buf: &mut [u8]) -> io::Result<usize> {
+        Ok(0)
+    }
+
+    #[inline]
+    unsafe fn initializer(&self) -> Initializer {
+        Initializer::nop()
+    }
+}
+
+#[cfg(feature="collections")]
+impl BufRead for Empty {
+    #[inline]
+    fn fill_buf(&mut self) -> io::Result<&[u8]> {
+        Ok(&[])
+    }
+    #[inline]
+    fn consume(&mut self, _n: usize) {}
+}
+
+impl fmt::Debug for Empty {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.pad("Empty { .. }")
+    }
+}
+
+/// A reader which yields one byte over and over and over and over and over and...
+///
+/// This struct is generally created by calling [`repeat`][repeat]. Please
+/// see the documentation of `repeat()` for more details.
+///
+/// [repeat]: fn.repeat.html
+pub struct Repeat {
+    byte: u8,
+}
+
+/// Creates an instance of a reader that infinitely repeats one byte.
+///
+/// All reads from this reader will succeed by filling the specified buffer with
+/// the given byte.
+///
+/// # Examples
+///
+/// ```
+/// use std::io::{self, Read};
+///
+/// let mut buffer = [0; 3];
+/// io::repeat(0b101).read_exact(&mut buffer).unwrap();
+/// assert_eq!(buffer, [0b101, 0b101, 0b101]);
+/// ```
+pub fn repeat(byte: u8) -> Repeat {
+    Repeat { byte }
+}
+
+impl Read for Repeat {
+    #[inline]
+    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
+        for slot in &mut *buf {
+            *slot = self.byte;
+        }
+        Ok(buf.len())
+    }
+
+    #[inline]
+    unsafe fn initializer(&self) -> Initializer {
+        Initializer::nop()
+    }
+}
+
+impl fmt::Debug for Repeat {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.pad("Repeat { .. }")
+    }
+}
+
+/// A writer which will move data into the void.
+///
+/// This struct is generally created by calling [`sink`][sink]. Please
+/// see the documentation of `sink()` for more details.
+///
+/// [sink]: fn.sink.html
+pub struct Sink {
+    _priv: (),
+}
+
+/// Creates an instance of a writer which will successfully consume all data.
+///
+/// All calls to `write` on the returned instance will return `Ok(buf.len())`
+/// and the contents of the buffer will not be inspected.
+///
+/// # Examples
+///
+/// ```rust
+/// use std::io::{self, Write};
+///
+/// let buffer = vec![1, 2, 3, 5, 8];
+/// let num_bytes = io::sink().write(&buffer).unwrap();
+/// assert_eq!(num_bytes, 5);
+/// ```
+pub fn sink() -> Sink {
+    Sink { _priv: () }
+}
+
+impl Write for Sink {
+    #[inline]
+    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
+        Ok(buf.len())
+    }
+
+    #[inline]
+    fn flush(&mut self) -> io::Result<()> {
+        Ok(())
+    }
+}
+
+impl fmt::Debug for Sink {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.pad("Sink { .. }")
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::io::prelude::*;
+    use crate::io::{copy, empty, repeat, sink};
+
+    #[test]
+    fn copy_copies() {
+        let mut r = repeat(0).take(4);
+        let mut w = sink();
+        assert_eq!(copy(&mut r, &mut w).unwrap(), 4);
+
+        let mut r = repeat(0).take(1 << 17);
+        assert_eq!(copy(&mut r as &mut dyn Read, &mut w as &mut dyn Write).unwrap(), 1 << 17);
+    }
+
+    #[test]
+    fn sink_sinks() {
+        let mut s = sink();
+        assert_eq!(s.write(&[]).unwrap(), 0);
+        assert_eq!(s.write(&[0]).unwrap(), 1);
+        assert_eq!(s.write(&[0; 1024]).unwrap(), 1024);
+        assert_eq!(s.by_ref().write(&[0; 1024]).unwrap(), 1024);
+    }
+
+    #[test]
+    fn empty_reads() {
+        let mut e = empty();
+        assert_eq!(e.read(&mut []).unwrap(), 0);
+        assert_eq!(e.read(&mut [0]).unwrap(), 0);
+        assert_eq!(e.read(&mut [0; 1024]).unwrap(), 0);
+        assert_eq!(e.by_ref().read(&mut [0; 1024]).unwrap(), 0);
+    }
+
+    #[test]
+    fn repeat_repeats() {
+        let mut r = repeat(4);
+        let mut b = [0; 1024];
+        assert_eq!(r.read(&mut b).unwrap(), 1024);
+        assert!(b.iter().all(|b| *b == 4));
+    }
+
+    #[test]
+    fn take_some_bytes() {
+        assert_eq!(repeat(4).take(100).bytes().count(), 100);
+        assert_eq!(repeat(4).take(100).bytes().next().unwrap().unwrap(), 4);
+        assert_eq!(repeat(1).take(10).chain(repeat(2).take(10)).bytes().count(), 20);
+    }
+}

src/libcoreio/src/lib.rs

@@ -0,0 +1,51 @@
+//! <p id="core_io-show-docblock"></p>
+//! This is just a listing of the functionality available in this crate. See
+//! the [std documentation](https://doc.rust-lang.org/nightly/std/io/index.html)
+//! for a full description of the functionality.
+#![allow(stable_features,unused_features)]
+#![feature(question_mark,const_fn,copy_from_slice,try_from,str_internals,align_offset,slice_internals)]
+#![cfg_attr(any(feature="alloc",feature="collections"),feature(alloc))]
+#![cfg_attr(pattern_guards,feature(bind_by_move_pattern_guards,nll))]
+#![cfg_attr(non_exhaustive,feature(non_exhaustive))]
+#![cfg_attr(unicode,feature(str_char))]
+#![cfg_attr(unicode,feature(unicode))]
+#![no_std]
+
+#[cfg_attr(feature="collections",macro_use)]
+#[cfg_attr(feature="collections",allow(unused_imports))]
+#[cfg(feature="collections")] extern crate alloc as collections;
+#[cfg(feature="alloc")] extern crate alloc;
+#[cfg(rustc_unicode)]
+extern crate rustc_unicode;
+#[cfg(std_unicode)]
+extern crate std_unicode;
+
+#[cfg(not(feature="collections"))]
+pub type ErrorString = &'static str;
+
+// Provide Box::new wrapper
+#[cfg(not(feature="alloc"))]
+struct FakeBox<T>(core::marker::PhantomData<T>);
+#[cfg(not(feature="alloc"))]
+impl<T> FakeBox<T> {
+	fn new(val: T) -> T {
+		val
+	}
+}
+
+// Needed for older compilers, to ignore vec!/format! macros in tests
+#[cfg(not(feature="collections"))]
+#[allow(unused)]
+macro_rules! vec (
+	( $ elem : expr ; $ n : expr ) => { () };
+	( $ ( $ x : expr ) , * ) => { () };
+	( $ ( $ x : expr , ) * ) => { () };
+);
+#[cfg(not(feature="collections"))]
+#[allow(unused)]
+macro_rules! format {
+	( $ ( $ arg : tt ) * ) => { () };
+}
+
+mod io;
+pub use io::*;

src/libio/Cargo.toml

@@ -1,13 +0,0 @@
-[package]
-authors = ["M-Labs"]
-name = "io"
-version = "0.1.0"
-
-[lib]
-name = "io"
-
-[dependencies]
-byteorder = { version = "1.3", default-features = false }
-
-[features]
-alloc = []

src/libio/src/cursor.rs

@@ -1,86 +0,0 @@
-use {Read, Write};
-
-#[derive(Debug, Clone)]
-pub struct Cursor<T> {
-    inner: T,
-    pos:   usize
-}
-
-impl<T> Cursor<T> {
-    #[inline]
-    pub fn new(inner: T) -> Cursor<T> {
-        Cursor { inner, pos: 0 }
-    }
-
-    #[inline]
-    pub fn into_inner(self) -> T {
-        self.inner
-    }
-
-    #[inline]
-    pub fn get_ref(&self) -> &T {
-        &self.inner
-    }
-
-    #[inline]
-    pub fn get_mut(&mut self) -> &mut T {
-        &mut self.inner
-    }
-
-    #[inline]
-    pub fn position(&self) -> usize {
-        self.pos
-    }
-
-    #[inline]
-    pub fn set_position(&mut self, pos: usize) {
-        self.pos = pos
-    }
-}
-
-impl<T: AsRef<[u8]>> Read for Cursor<T> {
-    type ReadError = !;
-
-    fn read(&mut self, buf: &mut [u8]) -> Result<usize, Self::ReadError> {
-        let data = &self.inner.as_ref()[self.pos..];
-        let len = buf.len().min(data.len());
-        buf[..len].copy_from_slice(&data[..len]);
-        self.pos += len;
-        Ok(len)
-    }
-}
-
-impl<'a> Write for Cursor<&'a mut [u8]> {
-    type WriteError = !;
-    type FlushError = !;
-
-    fn write(&mut self, buf: &[u8]) -> Result<usize, Self::WriteError> {
-        let data = &mut self.inner[self.pos..];
-        let len  = buf.len().min(data.len());
-        data[..len].copy_from_slice(&buf[..len]);
-        self.pos += len;
-        Ok(len)
-    }
-
-    #[inline]
-    fn flush(&mut self) -> Result<(), Self::FlushError> {
-        Ok(())
-    }
-}
-
-#[cfg(feature = "alloc")]
-impl Write for Cursor<&mut ::alloc::vec::Vec<u8>> {
-    type WriteError = !;
-    type FlushError = !;
-
-    #[inline]
-    fn write(&mut self, buf: &[u8]) -> Result<usize, Self::WriteError> {
-        self.inner.extend_from_slice(buf);
-        Ok(buf.len())
-    }
-
-    #[inline]
-    fn flush(&mut self) -> Result<(), Self::FlushError> {
-        Ok(())
-    }
-}

src/libio/src/lib.rs

@@ -1,137 +0,0 @@
-#![no_std]
-#![feature(never_type)]
-
-#[cfg(feature = "alloc")]
-extern crate alloc;
-extern crate byteorder;
-
-mod cursor;
-mod proto;
-
-pub use cursor::Cursor;
-pub use proto::{ProtoRead, ProtoWrite};
-#[cfg(feature = "alloc")]
-pub use proto::ReadStringError;
-
-#[derive(Debug, Clone, PartialEq)]
-pub enum Error<T> {
-    UnexpectedEnd,
-    Other(T)
-}
-
-impl<T> From<T> for Error<T> {
-    fn from(value: T) -> Error<T> {
-        Error::Other(value)
-    }
-}
-
-pub trait Read {
-    type ReadError;
-
-    /// Pull some bytes from this source into the specified buffer, returning
-    /// how many bytes were read.
-    fn read(&mut self, buf: &mut [u8]) -> Result<usize, Self::ReadError>;
-
-    /// Read the exact number of bytes required to fill `buf`.
-    fn read_exact(&mut self, mut buf: &mut [u8]) -> Result<(), Error<Self::ReadError>> {
-        while !buf.is_empty() {
-            let read_bytes = self.read(buf)?;
-            if read_bytes == 0 {
-                return Err(Error::UnexpectedEnd)
-            }
-
-            buf = &mut { buf }[read_bytes..];
-        }
-
-        Ok(())
-    }
-}
-
-impl<'a, T: Read> Read for &'a mut T {
-    type ReadError = T::ReadError;
-
-    fn read(&mut self, buf: &mut [u8]) -> Result<usize, Self::ReadError> {
-        T::read(self, buf)
-    }
-}
-
-pub trait Write {
-    type WriteError;
-    type FlushError;
-
-    /// Write a buffer into this object, returning how many bytes were written.
-    fn write(&mut self, buf: &[u8]) -> Result<usize, Self::WriteError>;
-
-    /// Flush this output stream, ensuring that all intermediately buffered contents
-    /// reach their destination.
-    fn flush(&mut self) -> Result<(), Self::FlushError>;
-
-    /// Attempts to write an entire buffer into `self`.
-    fn write_all(&mut self, mut buf: &[u8]) -> Result<(), Error<Self::WriteError>> {
-        while buf.len() > 0 {
-            let written_bytes = self.write(buf)?;
-            if written_bytes == 0 {
-                return Err(Error::UnexpectedEnd)
-            }
-
-            buf = &buf[written_bytes..];
-        }
-
-        Ok(())
-    }
-
-    /// Hints the writer how much bytes will be written after call to this function.
-    ///
-    /// At least `min` bytes should be written after the call to this function and
-    /// if `max` is `Some(x)` than at most `x` bytes should be written.
-    fn size_hint(&mut self, _min: usize, _max: Option<usize>) {}
-}
-
-impl<'a, T: Write> Write for &'a mut T {
-    type WriteError = T::WriteError;
-    type FlushError = T::FlushError;
-
-    fn write(&mut self, buf: &[u8]) -> Result<usize, Self::WriteError> {
-        T::write(self, buf)
-    }
-
-    fn flush(&mut self) -> Result<(), Self::FlushError> {
-        T::flush(self)
-    }
-
-    fn size_hint(&mut self, min: usize, max: Option<usize>) {
-        T::size_hint(self, min, max)
-    }
-}
-
-impl<'a> Write for &'a mut [u8] {
-    type WriteError = !;
-    type FlushError = !;
-
-    fn write(&mut self, buf: &[u8]) -> Result<usize, Self::WriteError> {
-        let len = buf.len().min(self.len());
-        self[..len].copy_from_slice(&buf[..len]);
-        Ok(len)
-    }
-
-    #[inline]
-    fn flush(&mut self) -> Result<(), Self::FlushError> {
-        Ok(())
-    }
-}
-
-#[cfg(feature = "alloc")]
-impl<'a> Write for alloc::vec::Vec<u8> {
-    type WriteError = !;
-    type FlushError = !;
-
-    fn write(&mut self, buf: &[u8]) -> Result<usize, Self::WriteError> {
-        self.extend_from_slice(buf);
-        Ok(buf.len())
-    }
-
-    #[inline]
-    fn flush(&mut self) -> Result<(), Self::FlushError> {
-        Ok(())
-    }
-}

src/runtime/Cargo.toml

@@ -14,6 +14,8 @@ num-traits = { version = "0.2", default-features = false }
 num-derive = "0.3"
 cslice = "0.3"
 log = "0.4"
+core_io = { version = "0.1", features = ["alloc", "collections"] }
+byteorder = { version = "1.3", default-features = false }
 void = { version = "1", default-features = false }
 futures = { version = "0.3", default-features = false, features = ["async-await"] }
 libboard_zynq = { git = "https://git.m-labs.hk/M-Labs/zc706.git" }
@@ -21,4 +23,3 @@ libsupport_zynq = { git = "https://git.m-labs.hk/M-Labs/zc706.git" }
 libcortex_a9 = { git = "https://git.m-labs.hk/M-Labs/zc706.git" }
 libasync = { git = "https://git.m-labs.hk/M-Labs/zc706.git" }
 dyld = { path = "../libdyld" }
-io = { path = "../libio", features = ["alloc"] }

src/runtime/src/comms.rs

@@ -21,7 +21,7 @@ use libsupport_zynq::alloc::{vec, vec::Vec};
 use libasync::{smoltcp::{Sockets, TcpStream}, task};
 use alloc::sync::Arc;
 
-use crate::proto::*;
+use crate::proto_async::*;
 use crate::kernel;
 use crate::moninj;
 

src/runtime/src/kernel.rs

@@ -7,7 +7,6 @@ use libcortex_a9::{mutex::Mutex, sync_channel::{self, sync_channel}};
 use libsupport_zynq::boot::Core1;
 
 use dyld;
-use io;
 use crate::rpc;
 use crate::rtio;
 
@@ -68,22 +67,16 @@ static mut KERNEL_CHANNEL_1TO0: *mut () = ptr::null_mut();
 extern fn rpc_send(service: u32, tag: &CSlice<u8>, data: *const *const ()) {
     let core1_rx: &mut sync_channel::Receiver<Message> = unsafe { mem::transmute(KERNEL_CHANNEL_0TO1) };
     let core1_tx: &mut sync_channel::Sender<Message> = unsafe { mem::transmute(KERNEL_CHANNEL_1TO0) };
-    let mut buffer = Arc::new(Vec::<u8>::new());
+    let mut buffer = Vec::<u8>::new();
-    {
+    rpc::send_args(&mut buffer, service, tag.as_ref(), data).expect("RPC encoding failed");
-        let mut writer = io::Cursor::new(Arc::get_mut(&mut buffer).unwrap());
+    core1_tx.send(Message::RpcSend { is_async: false, data: Arc::new(buffer) })
-        rpc::send_args(&mut writer, service, tag.as_ref(), data).expect("RPC encoding failed");
-    }
-    core1_tx.send(Message::RpcSend { is_async: false, data: buffer })
 }
 
 extern fn rpc_send_async(service: u32, tag: &CSlice<u8>, data: *const *const ()) {
     let core1_tx: &mut sync_channel::Sender<Message> = unsafe { mem::transmute(KERNEL_CHANNEL_1TO0) };
-    let mut buffer = Arc::new(Vec::<u8>::new());
+    let mut buffer = Vec::<u8>::new();
-    {
+    rpc::send_args(&mut buffer, service, tag.as_ref(), data).expect("RPC encoding failed");
-        let mut writer = io::Cursor::new(Arc::get_mut(&mut buffer).unwrap());
+    core1_tx.send(Message::RpcSend { is_async: true, data: Arc::new(buffer) })
-        rpc::send_args(&mut writer, service, tag.as_ref(), data).expect("RPC encoding failed");
-    }
-    core1_tx.send(Message::RpcSend { is_async: true, data: buffer })
 }
 
 extern fn rpc_recv(slot: *mut ()) -> usize {

src/runtime/src/main.rs

@@ -10,7 +10,8 @@ use log::info;
 use libboard_zynq::{timer::GlobalTimer, logger, devc};
 use libsupport_zynq::ram;
 
-mod proto;
+mod proto_core_io;
+mod proto_async;
 mod comms;
 mod rpc;
 #[path = "../../../build/pl.rs"]

src/runtime/src/moninj.rs

@@ -10,7 +10,7 @@ use num_derive::{FromPrimitive, ToPrimitive};
 use num_traits::{FromPrimitive, ToPrimitive};
 use futures::{pin_mut, select_biased, FutureExt};
 
-use crate::proto::*;
+use crate::proto_async::*;
 use crate::pl::csr;
 
 

src/runtime/src/proto_core_io.rs

@@ -1,13 +1,10 @@
-#[cfg(feature = "alloc")]
 use core::str::Utf8Error;
 use byteorder::{ByteOrder, NetworkEndian};
-#[cfg(feature = "alloc")]
 use alloc::vec;
 use alloc::string::String;
 
-use ::{Read, Write, Error as IoError};
+use core_io::{Read, Write, Error as IoError};
 
-#[cfg(feature = "alloc")]
 #[derive(Debug, Clone, PartialEq)]
 pub enum ReadStringError<T> {
     Utf8(Utf8Error),
@@ -52,7 +49,6 @@ pub trait ProtoRead {
         Ok(self.read_u8()? != 0)
     }
 
-    #[cfg(feature = "alloc")]
     #[inline]
     fn read_bytes(&mut self) -> Result<::alloc::vec::Vec<u8>, Self::ReadError> {
         let length = self.read_u32()?;
@@ -61,7 +57,6 @@ pub trait ProtoRead {
         Ok(value)
     }
 
-    #[cfg(feature = "alloc")]
     #[inline]
     fn read_string(&mut self) -> Result<::alloc::string::String, ReadStringError<Self::ReadError>> {
         let bytes = self.read_bytes().map_err(ReadStringError::Other)?;
@@ -146,7 +141,7 @@ pub trait ProtoWrite {
 }
 
 impl<T> ProtoRead for T where T: Read + ?Sized {
-    type ReadError = IoError<T::ReadError>;
+    type ReadError = IoError;
 
     fn read_exact(&mut self, buf: &mut [u8]) -> Result<(), Self::ReadError> {
         T::read_exact(self, buf)
@@ -154,7 +149,7 @@ impl<T> ProtoRead for T where T: Read + ?Sized {
 }
 
 impl<T> ProtoWrite for T where T: Write + ?Sized {
-    type WriteError = IoError<T::WriteError>;
+    type WriteError = IoError;
 
     fn write_all(&mut self, buf: &[u8]) -> Result<(), Self::WriteError> {
         T::write_all(self, buf)

src/runtime/src/rpc.rs

@@ -1,14 +1,16 @@
 use core::str;
 use cslice::{CSlice, CMutSlice};
 
-use io::{ProtoRead, Read, Write, ProtoWrite, Error};
+use core_io::{Read, Write, Error};
+
+use crate::proto_core_io::{ProtoRead, ProtoWrite};
 use self::tag::{Tag, TagIterator, split_tag};
 
 unsafe fn recv_value<R, E>(reader: &mut R, tag: Tag, data: &mut *mut (),
                            alloc: &dyn Fn(usize) -> Result<*mut (), E>)
                           -> Result<(), E>
     where R: Read + ?Sized,
-          E: From<Error<R::ReadError>>
+          E: From<Error>
 {
     macro_rules! consume_value {
         ($ty:ty, |$ptr:ident| $map:expr) => ({
@@ -79,7 +81,7 @@ pub fn recv_return<R, E>(reader: &mut R, tag_bytes: &[u8], data: *mut (),
                          alloc: &dyn Fn(usize) -> Result<*mut (), E>)
                         -> Result<(), E>
     where R: Read + ?Sized,
-          E: From<Error<R::ReadError>>
+          E: From<Error>
 {
     let mut it = TagIterator::new(tag_bytes);
     #[cfg(feature = "log")]
@@ -93,7 +95,7 @@ pub fn recv_return<R, E>(reader: &mut R, tag_bytes: &[u8], data: *mut (),
 }
 
 unsafe fn send_value<W>(writer: &mut W, tag: Tag, data: &mut *const ())
-                       -> Result<(), Error<W::WriteError>>
+                       -> Result<(), Error>
     where W: Write + ?Sized
 {
     macro_rules! consume_value {
@@ -170,7 +172,7 @@ unsafe fn send_value<W>(writer: &mut W, tag: Tag, data: &mut *const ())
 }
 
 pub fn send_args<W>(writer: &mut W, service: u32, tag_bytes: &[u8], data: *const *const ())
-                   -> Result<(), Error<W::WriteError>>
+                   -> Result<(), Error>
     where W: Write + ?Sized
 {
     let (arg_tags_bytes, return_tag_bytes) = split_tag(tag_bytes);