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gitea/vendor/github.com/couchbase/gomemcached/flexibleFraming.go

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package gomemcached
import (
"encoding/binary"
"fmt"
)
type FrameObjType int
const (
FrameBarrier FrameObjType = iota
FrameDurability FrameObjType = iota
FrameDcpStreamId FrameObjType = iota
FrameOpenTracing FrameObjType = iota
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FrameImpersonate FrameObjType = iota
)
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const MAX_USER_LEN = 15 // TODO half byte shifting to be implemented
// it's not very efficient so we currently truncate user names
const FAST_USER_LEN = 15
type FrameInfo struct {
ObjId FrameObjType
ObjLen int
ObjData []byte
}
var ErrorInvalidOp error = fmt.Errorf("Specified method is not applicable")
var ErrorObjLenNotMatch error = fmt.Errorf("Object length does not match data")
func (f *FrameInfo) Validate() error {
switch f.ObjId {
case FrameBarrier:
if f.ObjLen != 0 {
return fmt.Errorf("Invalid FrameBarrier - length is %v\n", f.ObjLen)
} else if f.ObjLen != len(f.ObjData) {
return ErrorObjLenNotMatch
}
case FrameDurability:
if f.ObjLen != 1 && f.ObjLen != 3 {
return fmt.Errorf("Invalid FrameDurability - length is %v\n", f.ObjLen)
} else if f.ObjLen != len(f.ObjData) {
return ErrorObjLenNotMatch
}
case FrameDcpStreamId:
if f.ObjLen != 2 {
return fmt.Errorf("Invalid FrameDcpStreamId - length is %v\n", f.ObjLen)
} else if f.ObjLen != len(f.ObjData) {
return ErrorObjLenNotMatch
}
case FrameOpenTracing:
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if f.ObjLen != 1 {
return fmt.Errorf("Invalid FrameImpersonate - length is %v\n", f.ObjLen)
} else if f.ObjLen != len(f.ObjData) {
return ErrorObjLenNotMatch
}
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case FrameImpersonate:
default:
return fmt.Errorf("Unknown FrameInfo type")
}
return nil
}
func (f *FrameInfo) GetStreamId() (uint16, error) {
if f.ObjId != FrameDcpStreamId {
return 0, ErrorInvalidOp
}
var output uint16
output = uint16(f.ObjData[0])
output = output << 8
output |= uint16(f.ObjData[1])
return output, nil
}
type DurabilityLvl uint8
const (
DuraInvalid DurabilityLvl = iota // Not used (0x0)
DuraMajority DurabilityLvl = iota // (0x01)
DuraMajorityAndPersistOnMaster DurabilityLvl = iota // (0x02)
DuraPersistToMajority DurabilityLvl = iota // (0x03)
)
func (f *FrameInfo) GetDurabilityRequirements() (lvl DurabilityLvl, timeoutProvided bool, timeoutMs uint16, err error) {
if f.ObjId != FrameDurability {
err = ErrorInvalidOp
return
}
if f.ObjLen != 1 && f.ObjLen != 3 {
err = ErrorObjLenNotMatch
return
}
lvl = DurabilityLvl(uint8(f.ObjData[0]))
if f.ObjLen == 3 {
timeoutProvided = true
timeoutMs = binary.BigEndian.Uint16(f.ObjData[1:2])
}
return
}
func incrementMarker(bitsToBeIncremented, byteIncrementCnt *int, framingElen, curObjIdx int) (int, error) {
for *bitsToBeIncremented >= 8 {
*byteIncrementCnt++
*bitsToBeIncremented -= 8
}
marker := curObjIdx + *byteIncrementCnt
if marker > framingElen {
return -1, fmt.Errorf("Out of bounds")
}
return marker, nil
}
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func (f *FrameInfo) Bytes() ([]byte, bool) {
return obj2Bytes(f.ObjId, f.ObjLen, f.ObjData)
}
// TODO implement half byte shifting for impersonate user names
// halfByteRemaining will always be false, because ObjID and Len haven't gotten that large yet
// and user names are truncated
func obj2Bytes(id FrameObjType, len int, data []byte) (output []byte, halfByteRemaining bool) {
if len < 16 {
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// ObjIdentifier - 4 bits + ObjLength - 4 bits
var idAndLen uint8
idAndLen |= uint8(id) << 4
idAndLen |= uint8(len)
output = append(output, byte(idAndLen))
// Rest is Data
output = append(output, data[:len]...)
} else {
}
return
}
func parseFrameInfoObjects(buf []byte, framingElen int) (objs []FrameInfo, err error, halfByteRemaining bool) {
var curObjIdx int
var byteIncrementCnt int
var bitsToBeIncremented int
var marker int
// Parse frameInfo objects
for curObjIdx = 0; curObjIdx < framingElen; curObjIdx += byteIncrementCnt {
byteIncrementCnt = 0
var oneFrameObj FrameInfo
// First get the objId
// -------------------------
var objId int
var objHeader uint8 = buf[curObjIdx]
var objIdentifierRaw uint8
if bitsToBeIncremented == 0 {
// ObjHeader
// 0 1 2 3 4 5 6 7
// ^-----^
// ObjIdentifierRaw
objIdentifierRaw = (objHeader & 0xf0) >> 4
} else {
// ObjHeader
// 0 1 2 3 4 5 6 7
// ^-----^
// ObjIdentifierRaw
objIdentifierRaw = (objHeader & 0x0f)
}
bitsToBeIncremented += 4
marker, err = incrementMarker(&bitsToBeIncremented, &byteIncrementCnt, framingElen, curObjIdx)
if err != nil {
return
}
// Value is 0-14
objId = int(objIdentifierRaw & 0xe)
// If bit 15 is set, ID is 15 + value of next byte
if objIdentifierRaw&0x1 > 0 {
if bitsToBeIncremented > 0 {
// ObjHeader
// 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
// ^-----^ ^---------------^
// ObjId1 Extension
// ^ marker
buffer := uint16(buf[marker])
buffer = buffer << 8
buffer |= uint16(buf[marker+1])
var extension uint8 = uint8(buffer & 0xff0 >> 4)
objId += int(extension)
} else {
// ObjHeader
// 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
// ^-----^ ^-------------------^
// ObjId1 extension
// ^ marker
var extension uint8 = uint8(buf[marker])
objId += int(extension)
}
bitsToBeIncremented += 8
}
marker, err = incrementMarker(&bitsToBeIncremented, &byteIncrementCnt, framingElen, curObjIdx)
if err != nil {
return
}
oneFrameObj.ObjId = FrameObjType(objId)
// Then get the obj length
// -------------------------
var objLenRaw uint8
var objLen int
if bitsToBeIncremented > 0 {
// ObjHeader
// 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
// ^ ^---------^
// marker objLen
objLenRaw = uint8(buf[marker]) & 0x0f
} else {
// ObjHeader
// 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
// ^--------^
// objLen
// ^ marker
objLenRaw = uint8(buf[marker]) & 0xf0 >> 4
}
bitsToBeIncremented += 4
marker, err = incrementMarker(&bitsToBeIncremented, &byteIncrementCnt, framingElen, curObjIdx)
if err != nil {
return
}
// Length is 0-14
objLen = int(objLenRaw & 0xe)
// If bit 15 is set, lenghth is 15 + value of next byte
if objLenRaw&0x1 > 0 {
if bitsToBeIncremented == 0 {
// ObjHeader
// 12 13 14 15 16 17 18 19 20 21 22 23
// ^---------^ ^--------------------^
// objLen extension
// ^ marker
var extension uint8 = uint8(buf[marker])
objLen += int(extension)
} else {
// ObjHeader
// 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
// ^--------^ ^---------------------^
// objLen extension
// ^ marker var buffer uint16
buffer := uint16(buf[marker])
buffer = buffer << 8
buffer |= uint16(buf[marker+1])
var extension uint8 = uint8(buffer & 0xff0 >> 4)
objLen += int(extension)
}
bitsToBeIncremented += 8
}
marker, err = incrementMarker(&bitsToBeIncremented, &byteIncrementCnt, framingElen, curObjIdx)
if err != nil {
return
}
oneFrameObj.ObjLen = objLen
// The rest is N-bytes of data based on the length
if bitsToBeIncremented == 0 {
// No weird alignment needed
oneFrameObj.ObjData = buf[marker : marker+objLen]
} else {
// 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
// ^--------^ ^---------------------^ ^--------->
// objLen extension data
// ^ marker
oneFrameObj.ObjData = ShiftByteSliceLeft4Bits(buf[marker : marker+objLen+1])
}
err = oneFrameObj.Validate()
if err != nil {
return
}
objs = append(objs, oneFrameObj)
bitsToBeIncremented += 8 * objLen
marker, err = incrementMarker(&bitsToBeIncremented, &byteIncrementCnt, framingElen, curObjIdx)
}
if bitsToBeIncremented > 0 {
halfByteRemaining = true
}
return
}
func ShiftByteSliceLeft4Bits(slice []byte) (replacement []byte) {
var buffer uint16
var i int
sliceLen := len(slice)
if sliceLen < 2 {
// Let's not shift less than 16 bits
return
}
replacement = make([]byte, sliceLen, cap(slice))
for i = 0; i < sliceLen-1; i++ {
// 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
// ^-----^ ^---------------^ ^-----------
// garbage data byte 0 data byte 1
buffer = uint16(slice[i])
buffer = buffer << 8
buffer |= uint16(slice[i+1])
replacement[i] = uint8(buffer & 0xff0 >> 4)
}
if i < sliceLen {
lastByte := slice[sliceLen-1]
lastByte = lastByte << 4
replacement[i] = lastByte
}
return
}
// The following is used to theoretically support frameInfo ObjID extensions
// for completeness, but they are not very efficient though
func ShiftByteSliceRight4Bits(slice []byte) (replacement []byte) {
var buffer uint16
var i int
var leftovers uint8 // 4 bits only
var replacementUnit uint16
var first bool = true
var firstLeftovers uint8
var lastLeftovers uint8
sliceLen := len(slice)
if sliceLen < 2 {
// Let's not shift less than 16 bits
return
}
if slice[sliceLen-1]&0xf == 0 {
replacement = make([]byte, sliceLen, cap(slice))
} else {
replacement = make([]byte, sliceLen+1, cap(slice)+1)
}
for i = 0; i < sliceLen-1; i++ {
buffer = binary.BigEndian.Uint16(slice[i : i+2])
// (buffer)
// 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
// ^-------------^ ^-------------------^
// data byte 0 data byte 1
//
// into
//
// 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
// ^-----^ ^---------------^ ^--------------------^ ^----------^
// zeroes data byte 0 data byte 1 zeroes
if first {
// The leftover OR'ing will overwrite the first 4 bits of data byte 0. Save them
firstLeftovers = uint8(buffer & 0xf000 >> 12)
first = false
}
replacementUnit = 0
replacementUnit |= uint16(leftovers) << 12
replacementUnit |= (buffer & 0xff00) >> 4 // data byte 0
replacementUnit |= buffer & 0xff >> 4 // data byte 1 first 4 bits
lastLeftovers = uint8(buffer&0xf) << 4
replacement[i+1] = byte(replacementUnit)
leftovers = uint8((buffer & 0x000f) << 4)
}
replacement[0] = byte(uint8(replacement[0]) | firstLeftovers)
if lastLeftovers > 0 {
replacement[sliceLen] = byte(lastLeftovers)
}
return
}
func Merge2HalfByteSlices(src1, src2 []byte) (output []byte) {
src1Len := len(src1)
src2Len := len(src2)
output = make([]byte, src1Len+src2Len-1)
var mergeByte uint8 = src1[src1Len-1]
mergeByte |= uint8(src2[0])
copy(output, src1)
copy(output[src1Len:], src2[1:])
output[src1Len-1] = byte(mergeByte)
return
}