Compile triehash for no_std

triehash/CHANGELOG.md

@@ -5,7 +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 (https://github.com/paritytech/parity-common/pull/280)
 ## [0.8.1] - 2019-10-24
 - Migrated to 2018 edition (https://github.com/paritytech/parity-common/pull/214)
 ### Dependencies

triehash/Cargo.toml

@@ -1,15 +1,15 @@
 [package]
 name = "triehash"
-version = "0.8.1"
+version = "0.8.2"
 authors = ["Parity Technologies <admin@parity.io>"]
 description = "In-memory patricia trie operations"
 repository = "https://github.com/paritytech/parity-common"
 license = "GPL-3.0"
 edition = "2018"
 
 [dependencies]
-hash-db = "0.15.2"
-rlp = { version = "0.4", path = "../rlp" }
+hash-db = { version = "0.15.2", default-features = false }
+rlp = { version = "0.4", path = "../rlp", default-features = false }
 
 [dev-dependencies]
 criterion = "0.3.0"
@@ -19,6 +19,13 @@ tiny-keccak = { version = "2.0", features = ["keccak"] }
 trie-standardmap = "0.15.2"
 hex-literal = "0.2.1"
 
+[features]
+default = ["std"]
+std = [
+	"hash-db/std",
+	"rlp/std",
+]
+
 [[bench]]
 name = "triehash"
 path = "benches/triehash.rs"

triehash/src/lib.rs

@@ -18,9 +18,26 @@
 //!
 //! This module should be used to generate trie root hash.
 
-use std::cmp;
-use std::collections::BTreeMap;
-use std::iter::once;
+#![cfg_attr(not(feature = "std"), no_std)]
+
+#[cfg(not(feature = "std"))]
+extern crate alloc;
+
+#[cfg(feature = "std")]
+mod rstd {
+	pub use std::collections::BTreeMap;
+}
+
+#[cfg(not(feature = "std"))]
+mod rstd {
+	pub use alloc::vec::Vec;
+	pub use alloc::collections::BTreeMap;
+}
+
+use core::cmp;
+use core::iter::once;
+use rstd::*;
+
 
 use hash_db::Hasher;
 use rlp::RlpStream;