Tweak flatecut's huffman.decode
name old time/op new time/op delta
pkg:github.com/google/wuffs/lib/flatecut goos:linux goarch:amd64
Cut-56 1.05ms ± 0% 1.03ms ± 0% -2.32% (p=0.008 n=5+5)
pkg:github.com/google/wuffs/lib/zlibcut goos:linux goarch:amd64
Cut-56 2.48ms ± 0% 2.44ms ± 0% -1.44% (p=0.008 n=5+5)
diff --git a/lib/flatecut/flatecut.go b/lib/flatecut/flatecut.go
index c9ef653..b0b7391 100644
--- a/lib/flatecut/flatecut.go
+++ b/lib/flatecut/flatecut.go
@@ -156,26 +156,23 @@
func (h *huffman) decode(b *bitstream) int32 {
if b.nBits >= 8 {
- if x := h.lookUpTable[b.bits&0xFF]; x != 0 {
- n := x >> 16
- b.bits >>= n
- b.nBits -= n
- return int32(x & 0xFFFF)
- }
- }
-
- if b.index < len(b.bytes) {
+ // No-op.
+ } else if b.index < len(b.bytes) {
b.bits |= uint32(b.bytes[b.index]) << b.nBits
b.nBits += 8
b.index++
- if x := h.lookUpTable[b.bits&0xFF]; x != 0 {
- n := x >> 16
- b.bits >>= n
- b.nBits -= n
- return int32(x & 0xFFFF)
- }
+ } else {
+ goto slow
}
+ if x := h.lookUpTable[b.bits&0xFF]; x != 0 {
+ n := x >> 16
+ b.bits >>= n
+ b.nBits -= n
+ return int32(x & 0xFFFF)
+ }
+
+slow:
return h.slowDecode(b)
}
