no_std support (with default-enabled "std" cargo feature)

Feature gates anything dependent on `std` on the eponymous cargo
feature, and changes references to libcore features from `std` to `core`

Author: tarcieri

.travis.yml

@@ -33,6 +33,10 @@ matrix:
     - env: RUST_TEST_THREADS=1 TARGET=powerpc-unknown-linux-gnu
     - env: RUST_TEST_THREADS=1 TARGET=powerpc64-unknown-linux-gnu
 
+    # Ensure crate compiles without default features (i.e. for no_std)
+    - env: EXTRA_ARGS="--no-default-features"
+      script: cargo build $EXTRA_ARGS
+
     # Serde implementation
     - env: EXTRA_ARGS="--features serde"
 

Cargo.toml

@@ -22,19 +22,21 @@ exclude       = [
     "bench/**/*",
     "test/**/*"
 ]
-categories = ["network-programming", "data-structures"]
+categories = ["network-programming", "data-structures", "no-std"]
 
 [package.metadata.docs.rs]
 features = ["i128"]
 
 [dependencies]
 byteorder = "1.1.0"
-iovec = "0.1"
+iovec = { version = "0.1", optional = true }
 serde = { version = "1.0", optional = true }
 either = { version = "1.5", default-features = false, optional = true }
 
 [dev-dependencies]
 serde_test = "1.0"
 
 [features]
+default = ["std"]
 i128 = ["byteorder/i128"]
+std = ["iovec"]

src/buf/buf.rs

@@ -1,8 +1,13 @@
 use super::{IntoBuf, Take, Reader, Iter, FromBuf, Chain};
 use byteorder::{BigEndian, ByteOrder, LittleEndian};
+#[cfg(feature = "iovec")]
 use iovec::IoVec;
+#[cfg(feature = "std")]
+use prelude::*;
 
-use std::{cmp, io, ptr};
+use core::{cmp, ptr};
+#[cfg(feature = "std")]
+use std::io;
 
 macro_rules! buf_get_impl {
     ($this:ident, $size:expr, $conv:path) => ({
@@ -146,6 +151,7 @@ pub trait Buf {
     /// with `dst` being a zero length slice.
     ///
     /// [`writev`]: http://man7.org/linux/man-pages/man2/readv.2.html
+    #[cfg(feature = "iovec")]
     fn bytes_vec<'a>(&'a self, dst: &mut [&'a IoVec]) -> usize {
         if dst.is_empty() {
             return 0;
@@ -1061,6 +1067,7 @@ impl<'a, T: Buf + ?Sized> Buf for &'a mut T {
         (**self).bytes()
     }
 
+    #[cfg(feature = "iovec")]
     fn bytes_vec<'b>(&'b self, dst: &mut [&'b IoVec]) -> usize {
         (**self).bytes_vec(dst)
     }
@@ -1070,6 +1077,7 @@ impl<'a, T: Buf + ?Sized> Buf for &'a mut T {
     }
 }
 
+#[cfg(feature = "std")]
 impl<T: Buf + ?Sized> Buf for Box<T> {
     fn remaining(&self) -> usize {
         (**self).remaining()
@@ -1079,6 +1087,7 @@ impl<T: Buf + ?Sized> Buf for Box<T> {
         (**self).bytes()
     }
 
+    #[cfg(feature = "iovec")]
     fn bytes_vec<'b>(&'b self, dst: &mut [&'b IoVec]) -> usize {
         (**self).bytes_vec(dst)
     }
@@ -1088,6 +1097,7 @@ impl<T: Buf + ?Sized> Buf for Box<T> {
     }
 }
 
+#[cfg(feature = "std")]
 impl<T: AsRef<[u8]>> Buf for io::Cursor<T> {
     fn remaining(&self) -> usize {
         let len = self.get_ref().as_ref().len();

src/buf/buf_mut.rs

@@ -1,8 +1,13 @@
 use super::{IntoBuf, Writer};
 use byteorder::{LittleEndian, ByteOrder, BigEndian};
+#[cfg(feature = "iovec")]
 use iovec::IoVec;
+#[cfg(feature = "std")]
+use prelude::*;
 
-use std::{cmp, io, ptr, usize};
+use core::{cmp, ptr, usize};
+#[cfg(feature = "std")]
+use std::io;
 
 /// A trait for values that provide sequential write access to bytes.
 ///
@@ -189,6 +194,7 @@ pub trait BufMut {
     /// with `dst` being a zero length slice.
     ///
     /// [`readv`]: http://man7.org/linux/man-pages/man2/readv.2.html
+    #[cfg(feature = "iovec")]
     unsafe fn bytes_vec_mut<'a>(&'a mut self, dst: &mut [&'a mut IoVec]) -> usize {
         if dst.is_empty() {
             return 0;
@@ -1072,6 +1078,7 @@ impl<'a, T: BufMut + ?Sized> BufMut for &'a mut T {
         (**self).bytes_mut()
     }
 
+    #[cfg(feature = "iovec")]
     unsafe fn bytes_vec_mut<'b>(&'b mut self, dst: &mut [&'b mut IoVec]) -> usize {
         (**self).bytes_vec_mut(dst)
     }
@@ -1081,6 +1088,7 @@ impl<'a, T: BufMut + ?Sized> BufMut for &'a mut T {
     }
 }
 
+#[cfg(feature = "std")]
 impl<T: BufMut + ?Sized> BufMut for Box<T> {
     fn remaining_mut(&self) -> usize {
         (**self).remaining_mut()
@@ -1099,6 +1107,7 @@ impl<T: BufMut + ?Sized> BufMut for Box<T> {
     }
 }
 
+#[cfg(feature = "std")]
 impl<T: AsMut<[u8]> + AsRef<[u8]>> BufMut for io::Cursor<T> {
     fn remaining_mut(&self) -> usize {
         use Buf;
@@ -1127,6 +1136,7 @@ impl<T: AsMut<[u8]> + AsRef<[u8]>> BufMut for io::Cursor<T> {
     }
 }
 
+#[cfg(feature = "std")]
 impl BufMut for Vec<u8> {
     #[inline]
     fn remaining_mut(&self) -> usize {
@@ -1148,7 +1158,7 @@ impl BufMut for Vec<u8> {
 
     #[inline]
     unsafe fn bytes_mut(&mut self) -> &mut [u8] {
-        use std::slice;
+        use core::slice;
 
         if self.capacity() == self.len() {
             self.reserve(64); // Grow the vec

src/buf/chain.rs

@@ -1,4 +1,5 @@
 use {Buf, BufMut};
+#[cfg(feature = "iovec")]
 use iovec::IoVec;
 
 /// A `Chain` sequences two buffers.
@@ -177,6 +178,7 @@ impl<T, U> Buf for Chain<T, U>
         self.b.advance(cnt);
     }
 
+    #[cfg(feature = "iovec")]
     fn bytes_vec<'a>(&'a self, dst: &mut [&'a IoVec]) -> usize {
         let mut n = self.a.bytes_vec(dst);
         n += self.b.bytes_vec(&mut dst[n..]);
@@ -218,6 +220,7 @@ impl<T, U> BufMut for Chain<T, U>
         self.b.advance_mut(cnt);
     }
 
+    #[cfg(feature = "iovec")]
     unsafe fn bytes_vec_mut<'a>(&'a mut self, dst: &mut [&'a mut IoVec]) -> usize {
         let mut n = self.a.bytes_vec_mut(dst);
         n += self.b.bytes_vec_mut(&mut dst[n..]);

src/buf/from_buf.rs

@@ -1,4 +1,8 @@
-use {Buf, BufMut, IntoBuf, Bytes, BytesMut};
+use {IntoBuf};
+#[cfg(feature = "std")]
+use prelude::*;
+#[cfg(feature = "std")]
+use {Buf, BufMut, Bytes, BytesMut};
 
 /// Conversion from a [`Buf`]
 ///
@@ -86,6 +90,7 @@ pub trait FromBuf {
     fn from_buf<T>(buf: T) -> Self where T: IntoBuf;
 }
 
+#[cfg(feature = "std")]
 impl FromBuf for Vec<u8> {
     fn from_buf<T>(buf: T) -> Self
         where T: IntoBuf
@@ -97,6 +102,7 @@ impl FromBuf for Vec<u8> {
     }
 }
 
+#[cfg(feature = "std")]
 impl FromBuf for Bytes {
     fn from_buf<T>(buf: T) -> Self
         where T: IntoBuf
@@ -105,6 +111,7 @@ impl FromBuf for Bytes {
     }
 }
 
+#[cfg(feature = "std")]
 impl FromBuf for BytesMut {
     fn from_buf<T>(buf: T) -> Self
         where T: IntoBuf

src/buf/into_buf.rs

@@ -1,5 +1,8 @@
 use super::{Buf};
+#[cfg(feature = "std")]
+use prelude::*;
 
+#[cfg(feature = "std")]
 use std::io;
 
 /// Conversion into a `Buf`
@@ -55,6 +58,7 @@ impl<T: Buf> IntoBuf for T {
     }
 }
 
+#[cfg(feature = "std")]
 impl<'a> IntoBuf for &'a [u8] {
     type Buf = io::Cursor<&'a [u8]>;
 
@@ -63,6 +67,7 @@ impl<'a> IntoBuf for &'a [u8] {
     }
 }
 
+#[cfg(feature = "std")]
 impl<'a> IntoBuf for &'a mut [u8] {
     type Buf = io::Cursor<&'a mut [u8]>;
 
@@ -71,6 +76,7 @@ impl<'a> IntoBuf for &'a mut [u8] {
     }
 }
 
+#[cfg(feature = "std")]
 impl<'a> IntoBuf for &'a str {
     type Buf = io::Cursor<&'a [u8]>;
 
@@ -79,6 +85,7 @@ impl<'a> IntoBuf for &'a str {
     }
 }
 
+#[cfg(feature = "std")]
 impl IntoBuf for Vec<u8> {
     type Buf = io::Cursor<Vec<u8>>;
 
@@ -87,6 +94,7 @@ impl IntoBuf for Vec<u8> {
     }
 }
 
+#[cfg(feature = "std")]
 impl<'a> IntoBuf for &'a Vec<u8> {
     type Buf = io::Cursor<&'a [u8]>;
 
@@ -97,6 +105,7 @@ impl<'a> IntoBuf for &'a Vec<u8> {
 
 // Kind of annoying... but this impl is required to allow passing `&'static
 // [u8]` where for<'a> &'a T: IntoBuf is required.
+#[cfg(feature = "std")]
 impl<'a> IntoBuf for &'a &'static [u8] {
     type Buf = io::Cursor<&'static [u8]>;
 
@@ -105,6 +114,7 @@ impl<'a> IntoBuf for &'a &'static [u8] {
     }
 }
 
+#[cfg(feature = "std")]
 impl<'a> IntoBuf for &'a &'static str {
     type Buf = io::Cursor<&'static [u8]>;
 
@@ -113,6 +123,7 @@ impl<'a> IntoBuf for &'a &'static str {
     }
 }
 
+#[cfg(feature = "std")]
 impl IntoBuf for String {
     type Buf = io::Cursor<Vec<u8>>;
 
@@ -121,6 +132,7 @@ impl IntoBuf for String {
     }
 }
 
+#[cfg(feature = "std")]
 impl<'a> IntoBuf for &'a String {
     type Buf = io::Cursor<&'a [u8]>;
 

src/buf/mod.rs

@@ -24,6 +24,7 @@ mod into_buf;
 mod iter;
 mod reader;
 mod take;
+#[cfg(feature = "std")]
 mod vec_deque;
 mod writer;
 

src/buf/reader.rs

@@ -1,5 +1,6 @@
 use {Buf};
 
+#[cfg(feature = "std")]
 use std::{cmp, io};
 
 /// A `Buf` adapter which implements `io::Read` for the inner value.
@@ -78,6 +79,7 @@ impl<B: Buf> Reader<B> {
     }
 }
 
+#[cfg(feature = "std")]
 impl<B: Buf + Sized> io::Read for Reader<B> {
     fn read(&mut self, dst: &mut [u8]) -> io::Result<usize> {
         let len = cmp::min(self.buf.remaining(), dst.len());
@@ -87,6 +89,7 @@ impl<B: Buf + Sized> io::Read for Reader<B> {
     }
 }
 
+#[cfg(feature = "std")]
 impl<B: Buf + Sized> io::BufRead for Reader<B> {
     fn fill_buf(&mut self) -> io::Result<&[u8]> {
         Ok(self.buf.bytes())

src/buf/take.rs

@@ -1,6 +1,6 @@
 use {Buf};
 
-use std::cmp;
+use core::cmp;
 
 /// A `Buf` adapter which limits the bytes read from an underlying buffer.
 ///