89 lines
2.0 KiB
Go
89 lines
2.0 KiB
Go
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package mq_coder
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import (
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"bytes"
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"errors"
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"fmt"
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"git.hpds.cc/Component/mq_coder/encoding"
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)
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// DecodeState represents the state of decoding
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type DecodeState struct {
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// ConsumedBytes is the bytes consumed by decoder
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ConsumedBytes int
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// SizeL is the bytes length of value
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SizeL int
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}
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// DecodeToPrimitivePacket parse out whole buffer to a PrimitivePacket
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//
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// Examples:
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// [0x01, 0x01, 0x01] -> Key=0x01, Value=0x01
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// [0x41, 0x06, 0x03, 0x01, 0x61, 0x04, 0x01, 0x62] -> key=0x03, value=0x61; key=0x04, value=0x62
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func DecodeToPrimitivePacket(buf []byte, p *PrimitivePacket) (*DecodeState, error) {
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decoder := &DecodeState{
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ConsumedBytes: 0,
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SizeL: 0,
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}
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if buf == nil || len(buf) < primitivePacketBufferMinimalLength {
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return decoder, errors.New("invalid packet minimal size")
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}
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p.packet = &packet{
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valBuf: []byte{},
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buf: &bytes.Buffer{},
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}
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var pos = 0
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// first byte is `Tag`
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p.tag = NewTag(buf[pos])
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p.buf.WriteByte(buf[pos])
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pos++
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decoder.ConsumedBytes = pos
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// read `Varint` from buf for `Length of value`
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tmpBuf := buf[pos:]
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var bufLen int32
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codec := encoding.VarCodec{}
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err := codec.DecodePVarInt32(tmpBuf, &bufLen)
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if err != nil {
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return decoder, err
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}
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if codec.Size < 1 {
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return decoder, errors.New("malformed, size of Length can not smaller than 1")
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}
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// codec.Size describes how many bytes used to represent `Length`
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p.buf.Write(buf[pos : pos+codec.Size])
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pos += codec.Size
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decoder.ConsumedBytes = pos
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decoder.SizeL = codec.Size
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// if length<0, error on decoding
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if bufLen < 0 {
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return decoder, errors.New("invalid packet, negative length")
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}
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// the length of value
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p.length = int(bufLen)
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if p.length == 0 {
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p.valBuf = nil
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return decoder, nil
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}
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// the next `p.length` bytes store value
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endPos := pos + p.length
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if pos > endPos || endPos > len(buf) || pos > len(buf) {
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return decoder, fmt.Errorf("beyond the boundary, pos=%v, endPos=%v", pos, endPos)
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}
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p.valBuf = buf[pos:endPos]
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p.buf.Write(buf[pos:endPos])
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decoder.ConsumedBytes = endPos
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return decoder, nil
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}
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