encoding/binary: give LittleEndian, BigEndian specific types
Giving them specific types has the benefit that
binary.BigEndian.Uint32(b) is now a direct call, not an
indirect via a mutable interface value, so it can potentially
be inlined.
Recent changes to the spec relaxed the rules for comparison,
so this code is still valid:
func isLittle(o binary.ByteOrder) { return o == binary.LittleEndian }
The change does break this potential idiom:
o := binary.BigEndian
if foo {
o = binary.LittleEndian
}
That must rewrite to give o an explicit binary.ByteOrder type.
On balance I think the benefit from the direct call and inlining
outweigh the cost of breaking that idiom.
R=r, r2
CC=golang-dev
https://golang.org/cl/
2427042