"allocator" and "nightly" features (for no_std environments)

This commit gates all allocator-dependent features on an "allocator" feature.

It also adds a "nightly" feature which enables using the "allocator" feature in
no_std environments. This requires using #[feature(alloc)] which requires
nightly.

The "allocator" feature is automatically enabled when either the "std" or
"nightly" features are enabled.

Travis CI is configured to check that builds succeed with both the "nightly"
feature along with "std" and "nightly" in combination. To avoid the problem
of nightly changes breaking the build, these combinations are specifically
flagged as allowed failures in the Travis CI configuration.

.travis.yml

@@ -40,6 +40,25 @@ matrix:
     - env: EXTRA_ARGS="--no-default-features"
       script: cargo build $EXTRA_ARGS
 
+    # Ensure crate compiles with "nightly" feature (i.e. for allocation w\ no_std)
+    - env: EXTRA_ARGS="--no-default-features --features nightly"
+      script: cargo build $EXTRA_ARGS
+      rust: nightly
+
+    # Ensure crate compiles with both "std" and "nightly" features
+    - env: EXTRA_ARGS="--no-default-features --features std,nightly"
+      script: cargo build $EXTRA_ARGS
+      rust: nightly
+
+  # Allow "nightly" feature to fail (so we aren't blocked on upstream nightly changes)
+  allow_failures:
+    - env: EXTRA_ARGS="--no-default-features --features nightly"
+      script: cargo build $EXTRA_ARGS
+      rust: nightly
+    - env: EXTRA_ARGS="--no-default-features --features std,nightly"
+      script: cargo build $EXTRA_ARGS
+      rust: nightly
+
 before_install: set -e
 
 install:

Cargo.toml

@@ -9,7 +9,6 @@ documentation = "https://carllerche.github.io/bytes/bytes"
 homepage      = "https://github.com/carllerche/bytes"
 repository    = "https://github.com/carllerche/bytes"
 readme        = "README.md"
-categories    = ["no-std"]
 keywords      = ["buffers", "zero-copy", "io"]
 exclude       = [
     ".gitignore",
@@ -18,7 +17,7 @@ exclude       = [
     "bench/**/*",
     "test/**/*"
 ]
-categories = ["network-programming", "data-structures"]
+categories = ["network-programming", "data-structures", "no-std"]
 
 [dependencies]
 byteorder = "1.0.0"
@@ -32,5 +31,7 @@ optional = true
 serde_test = "1.0"
 
 [features]
+allocator = []
 default = ["std"]
-std = ["iovec"]
+nightly = ["allocator"]
+std = ["allocator", "iovec"]

src/buf/buf.rs

@@ -1,5 +1,5 @@
 use super::{IntoBuf, Take, Reader, Iter, Chain};
-#[cfg(feature = "std")]
+#[cfg(feature = "allocator")]
 use super::FromBuf;
 
 use byteorder::ByteOrder;
@@ -11,6 +11,9 @@ use core::{cmp, ptr};
 #[cfg(feature = "std")]
 use std::io;
 
+#[allow(unused_imports)]
+use prelude::*;
+
 /// Read bytes from a buffer.
 ///
 /// A buffer stores bytes in memory such that read operations are infallible.
@@ -528,7 +531,7 @@ pub trait Buf {
     ///
     /// assert_eq!(vec, &b"hello world"[..]);
     /// ```
-    #[cfg(feature = "std")]
+    #[cfg(feature = "allocator")]
     fn collect<B>(self) -> B
         where Self: Sized,
               B: FromBuf,
@@ -681,7 +684,7 @@ impl<'a, T: Buf + ?Sized> Buf for &'a mut T {
     }
 }
 
-#[cfg(feature = "std")]
+#[cfg(feature = "allocator")]
 impl<T: Buf + ?Sized> Buf for Box<T> {
     fn remaining(&self) -> usize {
         (**self).remaining()

src/buf/buf_mut.rs

@@ -1,5 +1,6 @@
 use super::{IntoBuf, Writer};
 use byteorder::ByteOrder;
+
 #[cfg(feature = "std")]
 use iovec::IoVec;
 
@@ -8,6 +9,9 @@ use core::{cmp, ptr, usize};
 #[cfg(feature = "std")]
 use std::io;
 
+#[allow(unused_imports)]
+use prelude::*;
+
 /// A trait for values that provide sequential write access to bytes.
 ///
 /// Write bytes to a buffer
@@ -660,7 +664,7 @@ impl<'a, T: BufMut + ?Sized> BufMut for &'a mut T {
     }
 }
 
-#[cfg(feature = "std")]
+#[cfg(feature = "allocator")]
 impl<T: BufMut + ?Sized> BufMut for Box<T> {
     fn remaining_mut(&self) -> usize {
         (**self).remaining_mut()
@@ -709,7 +713,7 @@ impl<T: AsMut<[u8]> + AsRef<[u8]>> BufMut for io::Cursor<T> {
     }
 }
 
-#[cfg(feature = "std")]
+#[cfg(feature = "allocator")]
 impl BufMut for Vec<u8> {
     #[inline]
     fn remaining_mut(&self) -> usize {

src/buf/from_buf.rs

@@ -1,5 +1,8 @@
 use {Buf, BufMut, IntoBuf, Bytes, BytesMut};
 
+#[allow(unused_imports)]
+use prelude::*;
+
 /// Conversion from a [`Buf`]
 ///
 /// Implementing `FromBuf` for a type defines how it is created from a buffer.

src/buf/mod.rs

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

src/bytes.rs

@@ -1,4 +1,7 @@
-use {IntoBuf, Buf, BufMut};
+#[cfg(feature = "std")]
+use {IntoBuf, Buf};
+use BufMut;
+#[cfg(feature = "std")]
 use buf::Iter;
 use debug;
 
@@ -11,6 +14,9 @@ use core::iter::{FromIterator, Iterator};
 #[cfg(feature = "std")]
 use std::io;
 
+#[allow(unused_imports)]
+use prelude::*;
+
 /// A reference counted contiguous slice of memory.
 ///
 /// `Bytes` is an efficient container for storing and operating on contiguous
@@ -751,6 +757,7 @@ impl Bytes {
     }
 }
 
+#[cfg(feature = "std")]
 impl IntoBuf for Bytes {
     type Buf = io::Cursor<Self>;
 
@@ -759,6 +766,7 @@ impl IntoBuf for Bytes {
     }
 }
 
+#[cfg(feature = "std")]
 impl<'a> IntoBuf for &'a Bytes {
     type Buf = io::Cursor<Self>;
 
@@ -889,6 +897,7 @@ impl Borrow<[u8]> for Bytes {
     }
 }
 
+#[cfg(feature = "std")]
 impl IntoIterator for Bytes {
     type Item = u8;
     type IntoIter = Iter<io::Cursor<Bytes>>;
@@ -898,6 +907,7 @@ impl IntoIterator for Bytes {
     }
 }
 
+#[cfg(feature = "std")]
 impl<'a> IntoIterator for &'a Bytes {
     type Item = u8;
     type IntoIter = Iter<io::Cursor<&'a Bytes>>;
@@ -1373,6 +1383,7 @@ impl BufMut for BytesMut {
     }
 }
 
+#[cfg(feature = "std")]
 impl IntoBuf for BytesMut {
     type Buf = io::Cursor<Self>;
 
@@ -1381,6 +1392,7 @@ impl IntoBuf for BytesMut {
     }
 }
 
+#[cfg(feature = "std")]
 impl<'a> IntoBuf for &'a BytesMut {
     type Buf = io::Cursor<&'a BytesMut>;
 
@@ -1540,6 +1552,7 @@ impl Clone for BytesMut {
     }
 }
 
+#[cfg(feature = "std")]
 impl IntoIterator for BytesMut {
     type Item = u8;
     type IntoIter = Iter<io::Cursor<BytesMut>>;
@@ -1549,6 +1562,7 @@ impl IntoIterator for BytesMut {
     }
 }
 
+#[cfg(feature = "std")]
 impl<'a> IntoIterator for &'a BytesMut {
     type Item = u8;
     type IntoIter = Iter<io::Cursor<&'a BytesMut>>;

src/lib.rs

@@ -71,9 +71,12 @@
 #![deny(warnings, missing_docs, missing_debug_implementations)]
 #![doc(html_root_url = "https://docs.rs/bytes/0.4")]
 #![cfg_attr(not(feature = "std"), no_std)]
+#![cfg_attr(feature = "nightly", feature(alloc))]
 
 extern crate byteorder;
 
+#[cfg(feature = "nightly")]
+extern crate alloc;
 #[cfg(feature = "std")]
 extern crate core;
 #[cfg(feature = "std")]
@@ -93,12 +96,12 @@ pub use buf::{
     Take,
 };
 
-#[cfg(feature = "std")]
+#[cfg(feature = "allocator")]
 mod bytes;
-#[cfg(feature = "std")]
+#[cfg(feature = "allocator")]
 mod debug;
 
-#[cfg(feature = "std")]
+#[cfg(feature = "allocator")]
 pub use bytes::{Bytes, BytesMut};
 
 pub use byteorder::{ByteOrder, BigEndian, LittleEndian};
@@ -107,3 +110,15 @@ pub use byteorder::{ByteOrder, BigEndian, LittleEndian};
 #[cfg(feature = "serde")]
 #[doc(hidden)]
 pub mod serde;
+
+/// Custom (internal-only) prelude for this module
+mod prelude {
+    #[cfg(feature = "nightly")]
+    pub use alloc::boxed::Box;
+
+    #[cfg(feature = "nightly")]
+    pub use alloc::string::String;
+
+    #[cfg(feature = "nightly")]
+    pub use alloc::vec::Vec;
+}