alloc support (for no_std environments)

Gates all allocator-dependent features on the 'alloc' cargo feature,
allowing use in no_std environments which have a heap and defined
allocator, but not full support for 'std'.

Author: tarcieri

.travis.yml

@@ -37,6 +37,10 @@ matrix:
     - env: EXTRA_ARGS="--no-default-features"
       script: cargo build $EXTRA_ARGS
 
+    # `alloc` crate-based implementation
+    - env: EXTRA_ARGS="--no-default-features --features=alloc --lib --tests"
+      rust: nightly # TODO: test 'alloc' on stable rust when it is fully stabilized
+
     # Serde implementation
     - env: EXTRA_ARGS="--features serde"
 

Cargo.toml

@@ -38,5 +38,6 @@ serde_test = "1.0"
 
 [features]
 default = ["std"]
+alloc = []
 i128 = ["byteorder/i128"]
-std = ["iovec"]
+std = ["alloc", "iovec"]

src/buf/buf.rs

@@ -2,7 +2,7 @@ use super::{IntoBuf, Take, Reader, Iter, FromBuf, Chain};
 use byteorder::{BigEndian, ByteOrder, LittleEndian};
 #[cfg(feature = "iovec")]
 use iovec::IoVec;
-#[cfg(feature = "std")]
+#[cfg(feature = "alloc")]
 use prelude::*;
 
 use core::{cmp, ptr};
@@ -1077,7 +1077,7 @@ impl<'a, T: Buf + ?Sized> Buf for &'a mut T {
     }
 }
 
-#[cfg(feature = "std")]
+#[cfg(feature = "alloc")]
 impl<T: Buf + ?Sized> Buf for Box<T> {
     fn remaining(&self) -> usize {
         (**self).remaining()

src/buf/buf_mut.rs

@@ -2,7 +2,7 @@ use super::{IntoBuf, Writer};
 use byteorder::{LittleEndian, ByteOrder, BigEndian};
 #[cfg(feature = "iovec")]
 use iovec::IoVec;
-#[cfg(feature = "std")]
+#[cfg(feature = "alloc")]
 use prelude::*;
 
 use core::{cmp, ptr, usize};
@@ -1088,7 +1088,7 @@ impl<'a, T: BufMut + ?Sized> BufMut for &'a mut T {
     }
 }
 
-#[cfg(feature = "std")]
+#[cfg(feature = "alloc")]
 impl<T: BufMut + ?Sized> BufMut for Box<T> {
     fn remaining_mut(&self) -> usize {
         (**self).remaining_mut()
@@ -1098,6 +1098,7 @@ impl<T: BufMut + ?Sized> BufMut for Box<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)
     }
@@ -1136,7 +1137,7 @@ impl<T: AsMut<[u8]> + AsRef<[u8]>> BufMut for io::Cursor<T> {
     }
 }
 
-#[cfg(feature = "std")]
+#[cfg(feature = "alloc")]
 impl BufMut for Vec<u8> {
     #[inline]
     fn remaining_mut(&self) -> usize {

src/buf/from_buf.rs

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

src/buf/mod.rs

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

src/buf/vec_deque.rs

@@ -1,3 +1,6 @@
+#[cfg(all(feature = "alloc", not(feature = "std")))]
+use alloc::collections::vec_deque::VecDeque;
+#[cfg(feature = "std")]
 use std::collections::VecDeque;
 
 use super::Buf;

src/bytes.rs

@@ -1,14 +1,19 @@
-use {IntoBuf, Buf, BufMut};
+use {BufMut};
+#[cfg(feature = "std")]
+use {Buf, IntoBuf};
+#[cfg(feature = "std")]
 use buf::Iter;
 use debug;
 use prelude::*;
 
-use std::{cmp, fmt, mem, hash, ops, slice, ptr, usize};
-use std::borrow::{Borrow, BorrowMut};
+use core::{cmp, fmt, mem, hash, ops, slice, ptr, usize};
+use core::borrow::{Borrow, BorrowMut};
+use core::sync::atomic::{self, AtomicUsize, AtomicPtr};
+use core::sync::atomic::Ordering::{Relaxed, Acquire, Release, AcqRel};
+use core::iter::{FromIterator, Iterator};
+
+#[cfg(feature = "std")]
 use std::io::Cursor;
-use std::sync::atomic::{self, AtomicUsize, AtomicPtr};
-use std::sync::atomic::Ordering::{Relaxed, Acquire, Release, AcqRel};
-use std::iter::{FromIterator, Iterator};
 
 /// A reference counted contiguous slice of memory.
 ///
@@ -835,6 +840,7 @@ impl Bytes {
     }
 }
 
+#[cfg(feature = "std")]
 impl IntoBuf for Bytes {
     type Buf = Cursor<Self>;
 
@@ -843,6 +849,7 @@ impl IntoBuf for Bytes {
     }
 }
 
+#[cfg(feature = "std")]
 impl<'a> IntoBuf for &'a Bytes {
     type Buf = Cursor<Self>;
 
@@ -986,6 +993,7 @@ impl Borrow<[u8]> for Bytes {
     }
 }
 
+#[cfg(feature = "std")]
 impl IntoIterator for Bytes {
     type Item = u8;
     type IntoIter = Iter<Cursor<Bytes>>;
@@ -995,6 +1003,7 @@ impl IntoIterator for Bytes {
     }
 }
 
+#[cfg(feature = "std")]
 impl<'a> IntoIterator for &'a Bytes {
     type Item = u8;
     type IntoIter = Iter<Cursor<&'a Bytes>>;
@@ -1563,6 +1572,7 @@ impl BufMut for BytesMut {
     }
 }
 
+#[cfg(feature = "std")]
 impl IntoBuf for BytesMut {
     type Buf = Cursor<Self>;
 
@@ -1571,6 +1581,7 @@ impl IntoBuf for BytesMut {
     }
 }
 
+#[cfg(feature = "std")]
 impl<'a> IntoBuf for &'a BytesMut {
     type Buf = Cursor<&'a BytesMut>;
 
@@ -1736,6 +1747,7 @@ impl Clone for BytesMut {
     }
 }
 
+#[cfg(feature = "std")]
 impl IntoIterator for BytesMut {
     type Item = u8;
     type IntoIter = Iter<Cursor<BytesMut>>;
@@ -1745,6 +1757,7 @@ impl IntoIterator for BytesMut {
     }
 }
 
+#[cfg(feature = "std")]
 impl<'a> IntoIterator for &'a BytesMut {
     type Item = u8;
     type IntoIter = Iter<Cursor<&'a BytesMut>>;

src/debug.rs

@@ -1,4 +1,4 @@
-use std::fmt;
+use core::fmt;
 
 /// Alternative implementation of `fmt::Debug` for byte slice.
 ///

src/lib.rs

@@ -71,7 +71,10 @@
 #![deny(warnings, missing_docs, missing_debug_implementations)]
 #![doc(html_root_url = "https://docs.rs/bytes/0.4.12")]
 #![no_std]
+#![cfg_attr(feature = "alloc", feature(alloc))]
 
+#[cfg(feature = "alloc")]
+extern crate alloc;
 extern crate byteorder;
 #[cfg(feature = "iovec")]
 extern crate iovec;
@@ -92,13 +95,12 @@ pub use buf::{
     Take,
 };
 
-#[cfg(feature = "std")]
+#[cfg(feature = "alloc")]
 mod bytes;
-#[cfg(feature = "std")]
 mod debug;
-#[cfg(feature = "std")]
-pub use bytes::{Bytes, BytesMut};
 mod prelude;
+#[cfg(feature = "alloc")]
+pub use bytes::{Bytes, BytesMut};
 
 #[deprecated]
 pub use byteorder::{ByteOrder, BigEndian, LittleEndian};

src/prelude.rs

@@ -1,5 +1,15 @@
 //! Crate-local import prelude, primarily intended as a facade for accessing
 //! heap-allocated data structures.
 
+#[cfg(all(feature = "alloc", not(feature = "std")))]
+mod alloc_prelude {
+    pub use alloc::boxed::Box;
+    pub use alloc::string::String;
+    pub use alloc::vec::Vec;
+}
+
+#[cfg(all(feature = "alloc", not(feature = "std")))]
+pub use self::alloc_prelude::*;
+
 #[cfg(feature = "std")]
 pub use std::prelude::v1::*;

tests/test_buf.rs

@@ -1,12 +1,17 @@
 extern crate bytes;
 extern crate byteorder;
+#[cfg(feature = "iovec")]
 extern crate iovec;
 
+#[cfg(feature = "std")]
 use bytes::Buf;
+#[cfg(feature = "iovec")]
 use iovec::IoVec;
+#[cfg(feature = "std")]
 use std::io::Cursor;
 
 #[test]
+#[cfg(feature = "std")]
 fn test_fresh_cursor_vec() {
     let mut buf = Cursor::new(b"hello".to_vec());
 
@@ -25,12 +30,14 @@ fn test_fresh_cursor_vec() {
 }
 
 #[test]
+#[cfg(feature = "std")]
 fn test_get_u8() {
     let mut buf = Cursor::new(b"\x21zomg");
     assert_eq!(0x21, buf.get_u8());
 }
 
 #[test]
+#[cfg(feature = "std")]
 fn test_get_u16() {
     let buf = b"\x21\x54zomg";
     assert_eq!(0x2154, Cursor::new(buf).get_u16_be());
@@ -39,12 +46,14 @@ fn test_get_u16() {
 
 #[test]
 #[should_panic]
+#[cfg(feature = "std")]
 fn test_get_u16_buffer_underflow() {
     let mut buf = Cursor::new(b"\x21");
     buf.get_u16_be();
 }
 
 #[test]
+#[cfg(all(feature = "iovec", feature = "std"))]
 fn test_bufs_vec() {
     let buf = Cursor::new(b"hello world");
 

tests/test_buf_mut.rs

@@ -1,13 +1,20 @@
 extern crate bytes;
 extern crate byteorder;
+#[cfg(feature = "iovec")]
 extern crate iovec;
 
-use bytes::{BufMut, BytesMut};
+use bytes::BufMut;
+#[cfg(feature = "std")]
+use bytes::BytesMut;
+#[cfg(feature = "iovec")]
 use iovec::IoVec;
+#[cfg(feature = "std")]
 use std::usize;
+#[cfg(feature = "std")]
 use std::fmt::Write;
 
 #[test]
+#[cfg(feature = "std")]
 fn test_vec_as_mut_buf() {
     let mut buf = Vec::with_capacity(64);
 
@@ -61,6 +68,7 @@ fn test_vec_advance_mut() {
 }
 
 #[test]
+#[cfg(feature = "std")]
 fn test_clone() {
     let mut buf = BytesMut::with_capacity(100);
     buf.write_str("this is a test").unwrap();
@@ -71,6 +79,7 @@ fn test_clone() {
 }
 
 #[test]
+#[cfg(feature = "iovec")]
 fn test_bufs_vec_mut() {
     use std::mem;