mirror of
https://github.com/nadoo/glider.git
synced 2025-02-24 09:45:40 +08:00
53 lines
1.1 KiB
Go
53 lines
1.1 KiB
Go
package ssr
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import "encoding/binary"
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var (
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crc32Table = make([]uint32, 256)
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)
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func init() {
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createCRC32Table()
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}
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func createCRC32Table() {
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for i := 0; i < 256; i++ {
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crc := uint32(i)
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for j := 8; j > 0; j-- {
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if crc&1 == 1 {
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crc = (crc >> 1) ^ 0xEDB88320
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} else {
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crc >>= 1
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}
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}
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crc32Table[i] = crc
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}
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}
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func CalcCRC32(input []byte, length int, value uint32) uint32 {
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value = 0xFFFFFFFF
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return DoCalcCRC32(input, 0, length, value)
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}
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func DoCalcCRC32(input []byte, index int, length int, value uint32) uint32 {
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buffer := input
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for i := index; i < length; i++ {
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value = (value >> 8) ^ crc32Table[byte(value&0xFF)^buffer[i]]
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}
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return value ^ 0xFFFFFFFF
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}
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func DoSetCRC32(buffer []byte, index int, length int) {
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crc := CalcCRC32(buffer[:length-4], length-4, 0xFFFFFFFF)
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binary.LittleEndian.PutUint32(buffer[length-4:], crc^0xFFFFFFFF)
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}
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func SetCRC32(buffer []byte, length int) {
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DoSetCRC32(buffer, 0, length)
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}
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func CheckCRC32(buffer []byte, length int) bool {
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crc := CalcCRC32(buffer, length, 0xFFFFFFFF)
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return crc == 0xFFFFFFFF
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}
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