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46 lines
1.1 KiB
46 lines
1.1 KiB
package brotli
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import (
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"encoding/binary"
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"math/bits"
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"runtime"
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)
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/* Copyright 2010 Google Inc. All Rights Reserved.
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Distributed under MIT license.
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See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
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*/
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/* Function to find maximal matching prefixes of strings. */
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func findMatchLengthWithLimit(s1 []byte, s2 []byte, limit uint) uint {
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var matched uint = 0
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_, _ = s1[limit-1], s2[limit-1] // bounds check
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switch runtime.GOARCH {
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case "amd64":
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// Compare 8 bytes at at time.
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for matched+8 <= limit {
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w1 := binary.LittleEndian.Uint64(s1[matched:])
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w2 := binary.LittleEndian.Uint64(s2[matched:])
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if w1 != w2 {
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return matched + uint(bits.TrailingZeros64(w1^w2)>>3)
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}
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matched += 8
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}
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case "386":
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// Compare 4 bytes at at time.
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for matched+4 <= limit {
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w1 := binary.LittleEndian.Uint32(s1[matched:])
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w2 := binary.LittleEndian.Uint32(s2[matched:])
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if w1 != w2 {
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return matched + uint(bits.TrailingZeros32(w1^w2)>>3)
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}
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matched += 4
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}
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}
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for matched < limit && s1[matched] == s2[matched] {
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matched++
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}
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return matched
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}
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