[feature] add per-uri dereferencer locks (#2291)

vendor/github.com/klauspost/compress/flate/fast_encoder.go

@@ -8,7 +8,6 @@ package flate
 import (
 	"encoding/binary"
 	"fmt"
-	"math/bits"
 )
 
 type fastEnc interface {
@@ -192,25 +191,3 @@ func (e *fastGen) Reset() {
 	}
 	e.hist = e.hist[:0]
 }
-
-// matchLen returns the maximum length.
-// 'a' must be the shortest of the two.
-func matchLen(a, b []byte) int {
-	var checked int
-
-	for len(a) >= 8 {
-		if diff := binary.LittleEndian.Uint64(a) ^ binary.LittleEndian.Uint64(b); diff != 0 {
-			return checked + (bits.TrailingZeros64(diff) >> 3)
-		}
-		checked += 8
-		a = a[8:]
-		b = b[8:]
-	}
-	b = b[:len(a)]
-	for i := range a {
-		if a[i] != b[i] {
-			return i + checked
-		}
-	}
-	return len(a) + checked
-}