source: code/trunk/vendor/github.com/andybalholm/brotli/find_match_length.go@ 145

package brotli

import (
        "encoding/binary"
        "math/bits"
        "runtime"
)

/* Copyright 2010 Google Inc. All Rights Reserved.

   Distributed under MIT license.
   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
*/

/* Function to find maximal matching prefixes of strings. */
func findMatchLengthWithLimit(s1 []byte, s2 []byte, limit uint) uint {
        var matched uint = 0
        _, _ = s1[limit-1], s2[limit-1] // bounds check
        switch runtime.GOARCH {
        case "amd64":
                // Compare 8 bytes at at time.
                for matched+8 <= limit {
                        w1 := binary.LittleEndian.Uint64(s1[matched:])
                        w2 := binary.LittleEndian.Uint64(s2[matched:])
                        if w1 != w2 {
                                return matched + uint(bits.TrailingZeros64(w1^w2)>>3)
                        }
                        matched += 8
                }
        case "386":
                // Compare 4 bytes at at time.
                for matched+4 <= limit {
                        w1 := binary.LittleEndian.Uint32(s1[matched:])
                        w2 := binary.LittleEndian.Uint32(s2[matched:])
                        if w1 != w2 {
                                return matched + uint(bits.TrailingZeros32(w1^w2)>>3)
                        }
                        matched += 4
                }
        }
        for matched < limit && s1[matched] == s2[matched] {
                matched++
        }
        return matched
}