[parity-bytes] add no-std support

.travis.yml

@@ -18,6 +18,8 @@ script:
   - cargo check --all --tests
   - cargo build --all
   - cargo test --all --exclude uint --exclude fixed-hash
+  - if [ "$TRAVIS_RUST_VERSION" == "nightly" ]; then cd parity-bytes/ && cargo build --no-default-features && cd ..;
+    fi
   - cd fixed-hash/ && cargo test --all-features && cd ..
   - cd uint/ && cargo test --features=std,quickcheck --release && cd ..
   - cd plain_hasher/ && cargo test --no-default-features && cd ..

parity-bytes/Cargo.toml

@@ -7,3 +7,8 @@ description = "byte utilities for Parity"
 license = "GPL-3.0"
 
 [dependencies]
+
+
+[features]
+default = ["std"]
+std = []

parity-bytes/README.md

@@ -0,0 +1,11 @@
+## `no_std` support
+
+This crate has a feature, `std`, that is enabled by default. To use this crate
+in a `no_std` context, add the following to your `Cargo.toml` (still requires allocator though):
+
+```toml
+[dependencies]
+parity-bytes = { version = "0.1", default-features = false }
+```
+
+Until allocator api is stabilized, this type of use is limited to nightly Rust.

parity-bytes/src/lib.rs

@@ -19,9 +19,30 @@
 //! Includes a pretty-printer for bytes, in the form of `ToPretty` and `PrettySlice`
 //! as
 
-use std::fmt;
-use std::cmp::min;
-use std::ops::{Deref, DerefMut};
+#![cfg_attr(not(feature = "std"), no_std)]
+#![cfg_attr(not(feature = "std"), feature(alloc))]
+
+#[cfg(not(feature = "std"))]
+#[macro_use]
+extern crate alloc;
+
+#[cfg(feature = "std")]
+extern crate core;
+
+use core::{
+	cmp::min,
+	fmt,
+	ops::{Deref, DerefMut},
+};
+
+#[cfg(not(feature = "std"))]
+use alloc::vec::Vec;
+
+#[cfg(feature = "std")]
+use std::vec::Vec;
+
+#[cfg(not(feature = "std"))]
+use alloc::string::String;
 
 /// Slice pretty print helper
 pub struct PrettySlice<'a> (&'a [u8]);