381 lines
10 KiB
Go
381 lines
10 KiB
Go
package gomemcached
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import (
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"encoding/binary"
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"fmt"
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)
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type FrameObjType int
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const (
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FrameBarrier FrameObjType = iota
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FrameDurability FrameObjType = iota
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FrameDcpStreamId FrameObjType = iota
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FrameOpenTracing FrameObjType = iota
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)
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type FrameInfo struct {
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ObjId FrameObjType
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ObjLen int
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ObjData []byte
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}
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var ErrorInvalidOp error = fmt.Errorf("Specified method is not applicable")
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var ErrorObjLenNotMatch error = fmt.Errorf("Object length does not match data")
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func (f *FrameInfo) Validate() error {
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switch f.ObjId {
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case FrameBarrier:
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if f.ObjLen != 0 {
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return fmt.Errorf("Invalid FrameBarrier - length is %v\n", f.ObjLen)
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} else if f.ObjLen != len(f.ObjData) {
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return ErrorObjLenNotMatch
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}
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case FrameDurability:
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if f.ObjLen != 1 && f.ObjLen != 3 {
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return fmt.Errorf("Invalid FrameDurability - length is %v\n", f.ObjLen)
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} else if f.ObjLen != len(f.ObjData) {
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return ErrorObjLenNotMatch
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}
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case FrameDcpStreamId:
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if f.ObjLen != 2 {
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return fmt.Errorf("Invalid FrameDcpStreamId - length is %v\n", f.ObjLen)
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} else if f.ObjLen != len(f.ObjData) {
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return ErrorObjLenNotMatch
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}
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case FrameOpenTracing:
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if f.ObjLen == 0 {
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return fmt.Errorf("Invalid FrameOpenTracing - length must be > 0")
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} else if f.ObjLen != len(f.ObjData) {
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return ErrorObjLenNotMatch
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}
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default:
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return fmt.Errorf("Unknown FrameInfo type")
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}
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return nil
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}
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func (f *FrameInfo) GetStreamId() (uint16, error) {
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if f.ObjId != FrameDcpStreamId {
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return 0, ErrorInvalidOp
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}
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var output uint16
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output = uint16(f.ObjData[0])
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output = output << 8
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output |= uint16(f.ObjData[1])
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return output, nil
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}
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type DurabilityLvl uint8
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const (
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DuraInvalid DurabilityLvl = iota // Not used (0x0)
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DuraMajority DurabilityLvl = iota // (0x01)
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DuraMajorityAndPersistOnMaster DurabilityLvl = iota // (0x02)
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DuraPersistToMajority DurabilityLvl = iota // (0x03)
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)
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func (f *FrameInfo) GetDurabilityRequirements() (lvl DurabilityLvl, timeoutProvided bool, timeoutMs uint16, err error) {
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if f.ObjId != FrameDurability {
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err = ErrorInvalidOp
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return
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}
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if f.ObjLen != 1 && f.ObjLen != 3 {
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err = ErrorObjLenNotMatch
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return
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}
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lvl = DurabilityLvl(uint8(f.ObjData[0]))
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if f.ObjLen == 3 {
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timeoutProvided = true
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timeoutMs = binary.BigEndian.Uint16(f.ObjData[1:2])
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}
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return
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}
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func incrementMarker(bitsToBeIncremented, byteIncrementCnt *int, framingElen, curObjIdx int) (int, error) {
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for *bitsToBeIncremented >= 8 {
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*byteIncrementCnt++
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*bitsToBeIncremented -= 8
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}
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marker := curObjIdx + *byteIncrementCnt
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if marker > framingElen {
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return -1, fmt.Errorf("Out of bounds")
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}
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return marker, nil
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}
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// Right now, halfByteRemaining will always be false, because ObjID and Len haven't gotten that large yet
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func (f *FrameInfo) Bytes() (output []byte, halfByteRemaining bool) {
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// ObjIdentifier - 4 bits + ObjLength - 4 bits
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var idAndLen uint8
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idAndLen |= uint8(f.ObjId) << 4
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idAndLen |= uint8(f.ObjLen)
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output = append(output, byte(idAndLen))
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// Rest is Data
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output = append(output, f.ObjData...)
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return
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}
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func parseFrameInfoObjects(buf []byte, framingElen int) (objs []FrameInfo, err error, halfByteRemaining bool) {
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var curObjIdx int
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var byteIncrementCnt int
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var bitsToBeIncremented int
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var marker int
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// Parse frameInfo objects
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for curObjIdx = 0; curObjIdx < framingElen; curObjIdx += byteIncrementCnt {
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byteIncrementCnt = 0
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var oneFrameObj FrameInfo
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// First get the objId
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// -------------------------
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var objId int
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var objHeader uint8 = buf[curObjIdx]
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var objIdentifierRaw uint8
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if bitsToBeIncremented == 0 {
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// ObjHeader
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// 0 1 2 3 4 5 6 7
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// ^-----^
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// ObjIdentifierRaw
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objIdentifierRaw = (objHeader & 0xf0) >> 4
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} else {
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// ObjHeader
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// 0 1 2 3 4 5 6 7
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// ^-----^
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// ObjIdentifierRaw
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objIdentifierRaw = (objHeader & 0x0f)
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}
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bitsToBeIncremented += 4
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marker, err = incrementMarker(&bitsToBeIncremented, &byteIncrementCnt, framingElen, curObjIdx)
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if err != nil {
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return
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}
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// Value is 0-14
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objId = int(objIdentifierRaw & 0xe)
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// If bit 15 is set, ID is 15 + value of next byte
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if objIdentifierRaw&0x1 > 0 {
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if bitsToBeIncremented > 0 {
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// ObjHeader
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// 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
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// ^-----^ ^---------------^
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// ObjId1 Extension
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// ^ marker
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buffer := uint16(buf[marker])
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buffer = buffer << 8
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buffer |= uint16(buf[marker+1])
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var extension uint8 = uint8(buffer & 0xff0 >> 4)
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objId += int(extension)
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} else {
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// ObjHeader
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// 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
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// ^-----^ ^-------------------^
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// ObjId1 extension
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// ^ marker
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var extension uint8 = uint8(buf[marker])
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objId += int(extension)
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}
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bitsToBeIncremented += 8
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}
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marker, err = incrementMarker(&bitsToBeIncremented, &byteIncrementCnt, framingElen, curObjIdx)
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if err != nil {
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return
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}
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oneFrameObj.ObjId = FrameObjType(objId)
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// Then get the obj length
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// -------------------------
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var objLenRaw uint8
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var objLen int
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if bitsToBeIncremented > 0 {
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// ObjHeader
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// 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
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// ^ ^---------^
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// marker objLen
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objLenRaw = uint8(buf[marker]) & 0x0f
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} else {
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// ObjHeader
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// 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
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// ^--------^
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// objLen
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// ^ marker
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objLenRaw = uint8(buf[marker]) & 0xf0 >> 4
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}
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bitsToBeIncremented += 4
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marker, err = incrementMarker(&bitsToBeIncremented, &byteIncrementCnt, framingElen, curObjIdx)
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if err != nil {
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return
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}
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// Length is 0-14
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objLen = int(objLenRaw & 0xe)
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// If bit 15 is set, lenghth is 15 + value of next byte
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if objLenRaw&0x1 > 0 {
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if bitsToBeIncremented == 0 {
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// ObjHeader
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// 12 13 14 15 16 17 18 19 20 21 22 23
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// ^---------^ ^--------------------^
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// objLen extension
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// ^ marker
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var extension uint8 = uint8(buf[marker])
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objLen += int(extension)
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} else {
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// ObjHeader
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// 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
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// ^--------^ ^---------------------^
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// objLen extension
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// ^ marker var buffer uint16
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buffer := uint16(buf[marker])
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buffer = buffer << 8
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buffer |= uint16(buf[marker+1])
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var extension uint8 = uint8(buffer & 0xff0 >> 4)
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objLen += int(extension)
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}
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bitsToBeIncremented += 8
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}
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marker, err = incrementMarker(&bitsToBeIncremented, &byteIncrementCnt, framingElen, curObjIdx)
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if err != nil {
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return
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}
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oneFrameObj.ObjLen = objLen
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// The rest is N-bytes of data based on the length
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if bitsToBeIncremented == 0 {
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// No weird alignment needed
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oneFrameObj.ObjData = buf[marker : marker+objLen]
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} else {
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// 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
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// ^--------^ ^---------------------^ ^--------->
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// objLen extension data
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// ^ marker
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oneFrameObj.ObjData = ShiftByteSliceLeft4Bits(buf[marker : marker+objLen+1])
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}
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err = oneFrameObj.Validate()
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if err != nil {
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return
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}
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objs = append(objs, oneFrameObj)
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bitsToBeIncremented += 8 * objLen
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marker, err = incrementMarker(&bitsToBeIncremented, &byteIncrementCnt, framingElen, curObjIdx)
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}
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if bitsToBeIncremented > 0 {
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halfByteRemaining = true
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}
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return
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}
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func ShiftByteSliceLeft4Bits(slice []byte) (replacement []byte) {
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var buffer uint16
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var i int
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sliceLen := len(slice)
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if sliceLen < 2 {
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// Let's not shift less than 16 bits
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return
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}
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replacement = make([]byte, sliceLen, cap(slice))
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for i = 0; i < sliceLen-1; i++ {
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// 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
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// ^-----^ ^---------------^ ^-----------
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// garbage data byte 0 data byte 1
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buffer = uint16(slice[i])
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buffer = buffer << 8
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buffer |= uint16(slice[i+1])
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replacement[i] = uint8(buffer & 0xff0 >> 4)
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}
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if i < sliceLen {
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lastByte := slice[sliceLen-1]
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lastByte = lastByte << 4
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replacement[i] = lastByte
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}
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return
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}
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// The following is used to theoretically support frameInfo ObjID extensions
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// for completeness, but they are not very efficient though
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func ShiftByteSliceRight4Bits(slice []byte) (replacement []byte) {
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var buffer uint16
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var i int
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var leftovers uint8 // 4 bits only
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var replacementUnit uint16
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var first bool = true
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var firstLeftovers uint8
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var lastLeftovers uint8
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sliceLen := len(slice)
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if sliceLen < 2 {
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// Let's not shift less than 16 bits
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return
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}
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if slice[sliceLen-1]&0xf == 0 {
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replacement = make([]byte, sliceLen, cap(slice))
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} else {
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replacement = make([]byte, sliceLen+1, cap(slice)+1)
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}
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for i = 0; i < sliceLen-1; i++ {
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buffer = binary.BigEndian.Uint16(slice[i : i+2])
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// (buffer)
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// 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
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// ^-------------^ ^-------------------^
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// data byte 0 data byte 1
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//
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// into
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//
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// 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
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// ^-----^ ^---------------^ ^--------------------^ ^----------^
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// zeroes data byte 0 data byte 1 zeroes
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if first {
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// The leftover OR'ing will overwrite the first 4 bits of data byte 0. Save them
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firstLeftovers = uint8(buffer & 0xf000 >> 12)
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first = false
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}
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replacementUnit = 0
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replacementUnit |= uint16(leftovers) << 12
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replacementUnit |= (buffer & 0xff00) >> 4 // data byte 0
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replacementUnit |= buffer & 0xff >> 4 // data byte 1 first 4 bits
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lastLeftovers = uint8(buffer&0xf) << 4
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replacement[i+1] = byte(replacementUnit)
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leftovers = uint8((buffer & 0x000f) << 4)
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}
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replacement[0] = byte(uint8(replacement[0]) | firstLeftovers)
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if lastLeftovers > 0 {
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replacement[sliceLen] = byte(lastLeftovers)
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}
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return
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}
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func Merge2HalfByteSlices(src1, src2 []byte) (output []byte) {
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src1Len := len(src1)
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src2Len := len(src2)
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output = make([]byte, src1Len+src2Len-1)
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var mergeByte uint8 = src1[src1Len-1]
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mergeByte |= uint8(src2[0])
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copy(output, src1)
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copy(output[src1Len:], src2[1:])
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output[src1Len-1] = byte(mergeByte)
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return
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}
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