Refactor primitives.

substrate/codec/src/endiansensitive.rs

@@ -0,0 +1,81 @@
+// Copyright 2017 Parity Technologies (UK) Ltd.
+// This file is part of Polkadot.
+
+// Polkadot is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Polkadot is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Polkadot.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Endian manager.
+
+/// Trait to allow conversion to a know endian representation when sensitive.
+/// Types implementing this trait must have a size > 0.
+// note: the copy bound and static lifetimes are necessary for safety of `Slicable` blanket
+// implementation.
+pub trait EndianSensitive: Copy + 'static {
+	fn to_le(self) -> Self { self }
+	fn to_be(self) -> Self { self }
+	fn from_le(self) -> Self { self }
+	fn from_be(self) -> Self { self }
+	fn as_be_then<T, F: FnOnce(&Self) -> T>(&self, f: F) -> T { f(&self) }
+	fn as_le_then<T, F: FnOnce(&Self) -> T>(&self, f: F) -> T { f(&self) }
+}
+
+macro_rules! impl_endians {
+	( $( $t:ty ),* ) => { $(
+		impl EndianSensitive for $t {
+			fn to_le(self) -> Self { <$t>::to_le(self) }
+			fn to_be(self) -> Self { <$t>::to_be(self) }
+			fn from_le(self) -> Self { <$t>::from_le(self) }
+			fn from_be(self) -> Self { <$t>::from_be(self) }
+			fn as_be_then<T, F: FnOnce(&Self) -> T>(&self, f: F) -> T { let d = self.to_be(); f(&d) }
+			fn as_le_then<T, F: FnOnce(&Self) -> T>(&self, f: F) -> T { let d = self.to_le(); f(&d) }
+		}
+	)* }
+}
+macro_rules! impl_non_endians {
+	( $( $t:ty ),* ) => { $(
+		impl EndianSensitive for $t {}
+	)* }
+}
+
+// NOTE: See test to ensure correctness.
+impl EndianSensitive for bool {}
+
+impl_endians!(u16, u32, u64, usize, i16, i32, i64, isize);
+impl_non_endians!(u8, i8, [u8; 1], [u8; 2], [u8; 3], [u8; 4], [u8; 5], [u8; 6], [u8; 7], [u8; 8],
+	[u8; 10], [u8; 12], [u8; 14], [u8; 16], [u8; 20], [u8; 24], [u8; 28], [u8; 32], [u8; 40],
+	[u8; 48], [u8; 56], [u8; 64], [u8; 80], [u8; 96], [u8; 112], [u8; 128]);
+
+#[cfg(test)]
+mod tests {
+	use super::EndianSensitive;
+
+	#[test]
+	fn endian_sensitive_is_copy() {
+		fn _takes_copy<T: Copy>() { }
+		fn _takes_endian_sensitive<T: EndianSensitive>() { _takes_copy::<T>() }
+	}
+
+	#[test]
+	fn endian_sensitive_outlives_static() {
+		fn _takes_static<T: 'static>() { }
+		fn _takes_endian_sensitive<T: EndianSensitive>() { _takes_static::<T>() }
+	}
+
+	#[test]
+	fn bool_is_not_endian_sensitive() {
+		let b = true;
+		assert_eq!(b.to_be(), b.to_le());
+		let b = false;
+		assert_eq!(b.to_be(), b.to_le());
+	}
+}