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62 lines
1.5 KiB
62 lines
1.5 KiB
package structure
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import (
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"RedisShake/internal/log"
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"encoding/binary"
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"fmt"
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"io"
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)
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const (
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RDB6ByteLen = 0 // RDB_6BITLEN
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RDB14ByteLen = 1 // RDB_14BITLEN
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len32or64Bit = 2
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lenSpecial = 3 // RDB_ENCVAL
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RDB32ByteLen = 0x80
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RDB64ByteLen = 0x81
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)
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func ReadLength(rd io.Reader) uint64 {
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length, special, err := readEncodedLength(rd)
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if special {
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log.Panicf("illegal length special=true, encoding: %d", length)
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}
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if err != nil {
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log.Panicf(err.Error())
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}
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return length
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}
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func readEncodedLength(rd io.Reader) (length uint64, special bool, err error) {
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var lengthBuffer = make([]byte, 8)
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firstByte := ReadByte(rd)
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first2bits := (firstByte & 0xc0) >> 6 // first 2 bits of encoding
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switch first2bits {
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case RDB6ByteLen:
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length = uint64(firstByte) & 0x3f
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case RDB14ByteLen:
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nextByte := ReadByte(rd)
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length = (uint64(firstByte)&0x3f)<<8 | uint64(nextByte)
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case len32or64Bit:
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if firstByte == RDB32ByteLen {
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_, err = io.ReadFull(rd, lengthBuffer[0:4])
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if err != nil {
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return 0, false, fmt.Errorf("read len32Bit failed: %s", err.Error())
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}
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length = uint64(binary.BigEndian.Uint32(lengthBuffer))
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} else if firstByte == RDB64ByteLen {
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_, err = io.ReadFull(rd, lengthBuffer)
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if err != nil {
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return 0, false, fmt.Errorf("read len64Bit failed: %s", err.Error())
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}
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length = binary.BigEndian.Uint64(lengthBuffer)
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} else {
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return 0, false, fmt.Errorf("illegal length encoding: %x", firstByte)
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}
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case lenSpecial:
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special = true
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length = uint64(firstByte) & 0x3f
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}
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return length, special, nil
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}
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