68 lines
1.1 KiB
Go
68 lines
1.1 KiB
Go
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package packer
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import "errors"
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func PackInt(num int) ([]byte, error) {
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dstLen := 4
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res := []byte{0x00}
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idx := 0
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if num < 0 {
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res[0] |= 0x40 // set sign bit
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num = ^num
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}
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res[0] |= byte(num & 0x3F) // pack 6 bit into dst
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num >>= 6 // discard 6 bits
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for num != 0 {
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if idx > dstLen {
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return nil, errors.New("Int too big")
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}
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res = append(res, 0x00)
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res[idx] |= 0x80 // set extend bit
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idx++
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res[idx] = byte(num & 0x7F) // pack 7 bit
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num >>= 7 // discard 7 bits
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}
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return res, nil
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}
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func UnpackInt(data []byte) int {
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sign := int(data[0]>>6) & 1
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res := int(data[0] & 0x3F)
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i := 0
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// fake loop should only loop once
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// its the poor mans goto hack
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for {
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if (data[i] & 0x80) == 0 {
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break
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}
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i += 1
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res |= int(data[i]&0x7F) << 6
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if (data[i] & 0x80) == 0 {
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break
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}
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i += 1
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res |= int(data[i]&0x7F) << (6 + 7)
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if (data[i] & 0x80) == 0 {
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break
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}
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i += 1
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res |= int(data[i]&0x7F) << (6 + 7 + 7)
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if (data[i] & 0x80) == 0 {
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break
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}
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i += 1
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res |= int(data[i]&0x7F) << (6 + 7 + 7 + 7)
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break
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}
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res ^= -sign
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return res
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}
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