no_std support (using enabled-by-default "std" feature)

- Changes all references to libcore features from ::std to ::core
- Feature gates anything dependent on std on the "std" feature

.travis.yml

@@ -36,6 +36,10 @@ matrix:
     # Serde implementation
     - env: EXTRA_ARGS="--features serde"
 
+    # Ensure crate compiles without default features (i.e. for no_std)
+    - env: EXTRA_ARGS="--no-default-features"
+      script: cargo build $EXTRA_ARGS
+
 before_install: set -e
 
 install:

Cargo.toml

@@ -17,12 +17,19 @@ exclude       = [
     "bench/**/*",
     "test/**/*"
 ]
-categories = ["network-programming", "data-structures"]
+categories = ["network-programming", "data-structures", "no-std"]
 
 [dependencies]
 byteorder = "1.0.0"
-iovec = "0.1"
 serde = { version = "1.0", optional = true }
 
+[dependencies.iovec]
+version = "0.1"
+optional = true
+
 [dev-dependencies]
 serde_test = "1.0"
+
+[features]
+default = ["std"]
+std = ["iovec"]

src/buf/buf.rs

@@ -1,8 +1,15 @@
-use super::{IntoBuf, Take, Reader, Iter, FromBuf, Chain};
+use super::{IntoBuf, Take, Reader, Iter, Chain};
+#[cfg(feature = "std")]
+use super::FromBuf;
+
 use byteorder::ByteOrder;
+#[cfg(feature = "std")]
 use iovec::IoVec;
 
-use std::{cmp, io, ptr};
+use core::{cmp, ptr};
+
+#[cfg(feature = "std")]
+use std::io;
 
 /// Read bytes from a buffer.
 ///
@@ -12,7 +19,7 @@ use std::{cmp, io, ptr};
 /// position. It can be thought of as an efficient `Iterator` for collections of
 /// bytes.
 ///
-/// The simplest `Buf` is a `Cursor` wrapping a `[u8]`.
+/// The simplest `Buf` is a `io::Cursor` wrapping a `[u8]`.
 ///
 /// ```
 /// use bytes::Buf;
@@ -113,6 +120,7 @@ pub trait Buf {
     /// with `dst` being a zero length slice.
     ///
     /// [`writev`]: http://man7.org/linux/man-pages/man2/readv.2.html
+    #[cfg(feature = "std")]
     fn bytes_vec<'a>(&'a self, dst: &mut [&'a IoVec]) -> usize {
         if dst.is_empty() {
             return 0;
@@ -520,6 +528,7 @@ pub trait Buf {
     ///
     /// assert_eq!(vec, &b"hello world"[..]);
     /// ```
+    #[cfg(feature = "std")]
     fn collect<B>(self) -> B
         where Self: Sized,
               B: FromBuf,
@@ -662,6 +671,7 @@ impl<'a, T: Buf + ?Sized> Buf for &'a mut T {
         (**self).bytes()
     }
 
+    #[cfg(feature = "std")]
     fn bytes_vec<'b>(&'b self, dst: &mut [&'b IoVec]) -> usize {
         (**self).bytes_vec(dst)
     }
@@ -671,6 +681,7 @@ 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()
@@ -680,6 +691,7 @@ impl<T: Buf + ?Sized> Buf for Box<T> {
         (**self).bytes()
     }
 
+    #[cfg(feature = "std")]
     fn bytes_vec<'b>(&'b self, dst: &mut [&'b IoVec]) -> usize {
         (**self).bytes_vec(dst)
     }
@@ -689,6 +701,7 @@ 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 +1,12 @@
 use super::{IntoBuf, Writer};
 use byteorder::ByteOrder;
+#[cfg(feature = "std")]
 use iovec::IoVec;
 
-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.
 ///
@@ -188,6 +192,7 @@ pub trait BufMut {
     /// with `dst` being a zero length slice.
     ///
     /// [`readv`]: http://man7.org/linux/man-pages/man2/readv.2.html
+    #[cfg(feature = "std")]
     unsafe fn bytes_vec_mut<'a>(&'a mut self, dst: &mut [&'a mut IoVec]) -> usize {
         if dst.is_empty() {
             return 0;
@@ -645,6 +650,7 @@ impl<'a, T: BufMut + ?Sized> BufMut for &'a mut T {
         (**self).bytes_mut()
     }
 
+    #[cfg(feature = "std")]
     unsafe fn bytes_vec_mut<'b>(&'b mut self, dst: &mut [&'b mut IoVec]) -> usize {
         (**self).bytes_vec_mut(dst)
     }
@@ -654,6 +660,7 @@ 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()
@@ -663,6 +670,7 @@ impl<T: BufMut + ?Sized> BufMut for Box<T> {
         (**self).bytes_mut()
     }
 
+    #[cfg(feature = "std")]
     unsafe fn bytes_vec_mut<'b>(&'b mut self, dst: &mut [&'b mut IoVec]) -> usize {
         (**self).bytes_vec_mut(dst)
     }
@@ -672,6 +680,7 @@ 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;
@@ -700,6 +709,7 @@ 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 {
@@ -721,7 +731,7 @@ 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 = "std")]
 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 = "std")]
     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 = "std")]
     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/into_buf.rs

@@ -1,5 +1,6 @@
 use super::{Buf};
 
+#[cfg(feature = "std")]
 use std::io;
 
 /// Conversion into a `Buf`
@@ -55,6 +56,7 @@ impl<T: Buf> IntoBuf for T {
     }
 }
 
+#[cfg(feature = "std")]
 impl<'a> IntoBuf for &'a [u8] {
     type Buf = io::Cursor<&'a [u8]>;
 
@@ -63,6 +65,7 @@ impl<'a> IntoBuf for &'a [u8] {
     }
 }
 
+#[cfg(feature = "std")]
 impl<'a> IntoBuf for &'a str {
     type Buf = io::Cursor<&'a [u8]>;
 
@@ -71,6 +74,7 @@ impl<'a> IntoBuf for &'a str {
     }
 }
 
+#[cfg(feature = "std")]
 impl IntoBuf for Vec<u8> {
     type Buf = io::Cursor<Vec<u8>>;
 
@@ -79,6 +83,7 @@ impl IntoBuf for Vec<u8> {
     }
 }
 
+#[cfg(feature = "std")]
 impl<'a> IntoBuf for &'a Vec<u8> {
     type Buf = io::Cursor<&'a [u8]>;
 
@@ -89,6 +94,7 @@ 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]>;
 
@@ -97,6 +103,7 @@ impl<'a> IntoBuf for &'a &'static [u8] {
     }
 }
 
+#[cfg(feature = "std")]
 impl<'a> IntoBuf for &'a &'static str {
     type Buf = io::Cursor<&'static [u8]>;
 
@@ -105,6 +112,7 @@ impl<'a> IntoBuf for &'a &'static str {
     }
 }
 
+#[cfg(feature = "std")]
 impl IntoBuf for String {
     type Buf = io::Cursor<Vec<u8>>;
 
@@ -113,6 +121,7 @@ impl IntoBuf for String {
     }
 }
 
+#[cfg(feature = "std")]
 impl<'a> IntoBuf for &'a String {
     type Buf = io::Cursor<&'a [u8]>;
 

src/buf/mod.rs

@@ -18,6 +18,7 @@
 
 mod buf;
 mod buf_mut;
+#[cfg(feature = "std")]
 mod from_buf;
 mod chain;
 mod into_buf;
@@ -28,6 +29,7 @@ mod writer;
 
 pub use self::buf::Buf;
 pub use self::buf_mut::BufMut;
+#[cfg(feature = "std")]
 pub use self::from_buf::FromBuf;
 pub use self::chain::Chain;
 pub use self::into_buf::IntoBuf;

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());

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.
 ///

src/buf/writer.rs

@@ -1,5 +1,6 @@
 use BufMut;
 
+#[cfg(feature = "std")]
 use std::{cmp, io};
 
 /// A `BufMut` adapter which implements `io::Write` for the inner value.
@@ -74,6 +75,7 @@ impl<B: BufMut> Writer<B> {
     }
 }
 
+#[cfg(feature = "std")]
 impl<B: BufMut + Sized> io::Write for Writer<B> {
     fn write(&mut self, src: &[u8]) -> io::Result<usize> {
         let n = cmp::min(self.buf.remaining_mut(), src.len());