primitive-types: add no_std support for serde feature (#385)

* primitive-types: add no_std support for serde feature

This adds no_std support to primitive-types with serde.

Due to rust-lang/cargo#3494,
a separate new feature `serde_no_std` is created.

* primitive-types: update changelog

* travis: add tests for primitive-types

.travis.yml

@@ -55,6 +55,8 @@ script:
   - cd parity-util-mem/ && cargo test --features=jemalloc-global && cd ..
   - cd parity-util-mem/ && cargo test --features=mimalloc-global && cd ..
   - cd parity-util-mem/ && cargo test --no-default-features --features=dlmalloc-global && cd ..
+  - cd primitive-types/ && cargo test --all-features && cd ..
+  - cd primitive-types/ && cargo test --no-default-features --features=serde_no_std && cd ..
   - cd rlp/ && cargo test --no-default-features && cargo check --benches && cd ..
   - cd triehash/ && cargo check --benches && cd ..
   - cd kvdb-web/ && wasm-pack test --headless --firefox && cd ..

primitive-types/CHANGELOG.md

@@ -5,6 +5,7 @@ The format is based on [Keep a Changelog].
 [Keep a Changelog]: http://keepachangelog.com/en/1.0.0/
 
 ## [Unreleased]
+- Added `no_std` support for `serde` feature. [#385](https://github.com/paritytech/parity-common/pull/385)
 
 ## [0.7.1] - 2020-04-27
 - Added `arbitrary` feature. [#378](https://github.com/paritytech/parity-common/pull/378)

primitive-types/Cargo.toml

@@ -19,7 +19,8 @@ default = ["std"]
 std = ["uint/std", "fixed-hash/std", "impl-codec/std"]
 byteorder = ["fixed-hash/byteorder"]
 rustc-hex = ["fixed-hash/rustc-hex"]
-serde = ["std", "impl-serde"]
+serde = ["std", "impl-serde", "impl-serde/std"]
+serde_no_std = ["impl-serde"]
 codec = ["impl-codec"]
 rlp = ["impl-rlp"]
 arbitrary = ["fixed-hash/arbitrary", "uint/arbitrary"]

primitive-types/impls/serde/Cargo.toml

@@ -7,8 +7,12 @@ license = "MIT OR Apache-2.0"
 homepage = "https://github.com/paritytech/parity-common"
 description = "Serde serialization support for uint and fixed hash."
 
+[features]
+default = ["std"]
+std = ["serde/std"]
+
 [dependencies]
-serde = "1.0.101"
+serde = { version = "1.0.101", default-features = false, features = ["alloc"] }
 
 [dev-dependencies]
 criterion = "0.3.0"

primitive-types/impls/serde/src/lib.rs

@@ -8,6 +8,14 @@
 
 //! Serde serialization support for uint and fixed hash.
 
+#![no_std]
+
+#[macro_use]
+extern crate alloc;
+
+#[cfg(feature = "std")]
+extern crate std;
+
 #[doc(hidden)]
 pub use serde;
 

primitive-types/impls/serde/src/serialize.rs

@@ -6,8 +6,11 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+use alloc::string::String;
+use alloc::vec::Vec;
+use core::fmt;
+use core::result::Result;
 use serde::{de, Deserializer, Serializer};
-use std::fmt;
 
 static CHARS: &[u8] = b"0123456789abcdef";
 
@@ -58,7 +61,7 @@ fn to_hex_raw<'a>(v: &'a mut [u8], bytes: &[u8], skip_leading_zero: bool) -> &'a
 	}
 
 	// SAFETY: all characters come either from CHARS or "0x", therefore valid UTF8
-	unsafe { std::str::from_utf8_unchecked(&v[0..idx]) }
+	unsafe { core::str::from_utf8_unchecked(&v[0..idx]) }
 }
 
 /// Decoding bytes from hex string error.
@@ -75,6 +78,7 @@ pub enum FromHexError {
 	},
 }
 
+#[cfg(feature = "std")]
 impl std::error::Error for FromHexError {}
 
 impl fmt::Display for FromHexError {