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parser.go
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parser.go
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package memcache
import "bytes"
type parser struct {
data []byte
binaries [][]byte
}
func initParser(p *parser,
data []byte,
binaries [][]byte,
) {
p.data = data
p.binaries = binaries
}
// MGetResponseType ...
type MGetResponseType int
var serverErrorPrefix = []byte("SERVER_ERROR")
var clientErrorPrefix = []byte("CLIENT_ERROR")
const (
// MGetResponseTypeVA ...
MGetResponseTypeVA MGetResponseType = iota + 1
// MGetResponseTypeHD ...
MGetResponseTypeHD
// MGetResponseTypeEN ...
MGetResponseTypeEN
)
// MGetFlags ...
type MGetFlags uint64
const (
// MGetFlagW ...
MGetFlagW MGetFlags = 1 << iota // won cache lease
// MGetFlagX ...
MGetFlagX // stale data
// MGetFlagZ ...
MGetFlagZ // already has winning flag
)
// MGetResponse ...
type MGetResponse struct {
Type MGetResponseType
Data []byte
Flags MGetFlags
CAS uint64
}
// MSetResponseType ...
type MSetResponseType int
const (
// MSetResponseTypeHD ...
MSetResponseTypeHD MSetResponseType = iota + 1 // STORED
// MSetResponseTypeNS ...
MSetResponseTypeNS // NOT STORED
// MSetResponseTypeEX ...
MSetResponseTypeEX // EXISTS, cas modified
// MSetResponseTypeNF ...
MSetResponseTypeNF // NOT FOUND, cas not found
)
// MSetResponse ...
type MSetResponse struct {
Type MSetResponseType
}
// MDelResponseType ...
type MDelResponseType int
const (
// MDelResponseTypeHD ...
MDelResponseTypeHD MDelResponseType = iota + 1 // DELETED
// MDelResponseTypeNF ...
MDelResponseTypeNF // NOT FOUND
// MDelResponseTypeEX ...
MDelResponseTypeEX // EXISTS, cas not match
)
// MDelResponse ...
type MDelResponse struct {
Type MDelResponseType
}
// ErrInvalidMGet ...
var ErrInvalidMGet = ErrBrokenPipe{reason: "can not parse mget response"}
// ErrInvalidMSet ...
var ErrInvalidMSet = ErrBrokenPipe{reason: "can not parse mset response"}
// ErrInvalidMDel ...
var ErrInvalidMDel = ErrBrokenPipe{reason: "can not parse mdel response"}
// ErrInvalidResponse ...
var ErrInvalidResponse = ErrBrokenPipe{reason: "can not parse response"}
func (p *parser) findCRLF(index int) int {
for i := index + 1; i < len(p.data); i++ {
if p.isCRLF(i - 1) {
return i + 1
}
}
return -1
}
func (p *parser) prefixEqual(a, b byte) bool {
return p.data[0] == a && p.data[1] == b
}
func (p *parser) pairEqual(i int, a, b byte) bool {
return p.data[i] == a && p.data[i+1] == b
}
func (p *parser) isCRLF(index int) bool {
return p.pairEqual(index, '\r', '\n')
}
func isDigit(c byte) bool {
return c >= '0' && c <= '9'
}
func findNumber(data []byte, index int) (uint64, int) {
foundIndex := -1
var firstChar byte
for i := index; i < len(data); i++ {
if isDigit(data[i]) {
foundIndex = i
firstChar = data[i]
break
}
}
num := uint64(firstChar - '0')
var i int
for i = foundIndex + 1; i < len(data); i++ {
if !isDigit(data[i]) {
break
}
num *= 10
num += uint64(data[i] - '0')
}
return num, i // next index right after number
}
func (p *parser) returnIfCRLF(index int, resp MGetResponse) (MGetResponse, error) {
nextIndex := p.findCRLF(index)
if nextIndex < 0 {
return MGetResponse{}, ErrInvalidMGet
}
p.skipData(nextIndex)
return resp, nil
}
func (p *parser) parseMGetFlags(index int, resp *MGetResponse) (int, error) {
flags := MGetFlags(0)
for i := index; i < len(p.data)-1; i++ {
if p.data[i] == 'W' {
flags |= MGetFlagW
continue
}
if p.data[i] == 'X' {
flags |= MGetFlagX
continue
}
if p.data[i] == 'Z' {
flags |= MGetFlagZ
continue
}
if p.data[i] == 'c' {
cas, nextIndex := findNumber(p.data, i+1)
resp.CAS = cas
i = nextIndex - 1
continue
}
if p.isCRLF(i) {
resp.Flags = flags
return i + 2, nil
}
}
return 0, ErrInvalidMGet
}
func (p *parser) skipData(nextIndex int) {
p.data = p.data[nextIndex:]
}
func (p *parser) readMGetHD() (MGetResponse, error) {
resp := MGetResponse{
Type: MGetResponseTypeHD,
}
nextIndex, err := p.parseMGetFlags(2, &resp)
if err != nil {
return MGetResponse{}, err
}
p.skipData(nextIndex)
return resp, nil
}
func (p *parser) readMGetVA() (MGetResponse, error) {
_, index := findNumber(p.data, 3)
resp := MGetResponse{
Type: MGetResponseTypeVA,
}
crlfIndex, err := p.parseMGetFlags(index, &resp)
if err != nil {
return MGetResponse{}, err
}
p.skipData(crlfIndex)
if len(p.binaries) == 0 {
return MGetResponse{}, ErrInvalidMGet
}
resp.Data = p.binaries[0]
p.binaries = p.binaries[1:]
return resp, nil
}
type errorType int
const (
errorTypeNone errorType = iota
errorTypeServer
errorTypeClient
)
func (p *parser) readError(errType errorType) error {
index := len(serverErrorPrefix)
crlfIndex := p.findCRLF(index + 1)
if crlfIndex < 0 {
return ErrInvalidResponse
}
data := make([]byte, crlfIndex-2-index-1)
copy(data, p.data[index+1:])
p.skipData(crlfIndex)
if errType == errorTypeServer {
return NewServerError(string(data))
}
return NewClientError(string(data))
}
func isBytesEqual(data []byte, err []byte) bool {
return len(data) > len(err) && bytes.Equal(data[:len(err)], err)
}
func (p *parser) isErrorPrefix() errorType {
if p.prefixEqual('S', 'E') {
if isBytesEqual(p.data, serverErrorPrefix) {
return errorTypeServer
}
} else if p.prefixEqual('C', 'L') {
if isBytesEqual(p.data, clientErrorPrefix) {
return errorTypeClient
}
}
return errorTypeNone
}
func (p *parser) readMGet() (MGetResponse, error) {
if len(p.data) < 4 {
return MGetResponse{}, ErrInvalidMGet
}
if p.prefixEqual('E', 'N') {
return p.returnIfCRLF(2, MGetResponse{
Type: MGetResponseTypeEN,
})
}
if p.prefixEqual('H', 'D') {
return p.readMGetHD()
}
if p.prefixEqual('V', 'A') {
return p.readMGetVA()
}
if errType := p.isErrorPrefix(); errType != errorTypeNone {
return MGetResponse{}, p.readError(errType)
}
return MGetResponse{}, ErrInvalidMGet
}
// Meta Set
func (p *parser) readMSetWithCRLF(respType MSetResponseType) (MSetResponse, error) {
index := p.findCRLF(2)
if index < 0 {
return MSetResponse{}, ErrInvalidMSet
}
p.skipData(index)
return MSetResponse{
Type: respType,
}, nil
}
func (p *parser) readMSet() (MSetResponse, error) {
if len(p.data) < 4 {
return MSetResponse{}, ErrInvalidMSet
}
if p.prefixEqual('H', 'D') {
return p.readMSetWithCRLF(MSetResponseTypeHD)
}
if p.prefixEqual('N', 'S') {
return p.readMSetWithCRLF(MSetResponseTypeNS)
}
if p.prefixEqual('E', 'X') {
return p.readMSetWithCRLF(MSetResponseTypeEX)
}
if p.prefixEqual('N', 'F') {
return p.readMSetWithCRLF(MSetResponseTypeNF)
}
if errType := p.isErrorPrefix(); errType != errorTypeNone {
return MSetResponse{}, p.readError(errType)
}
return MSetResponse{}, ErrInvalidMSet
}
// Meta Delete
func (p *parser) readMDelWithCRLF(respType MDelResponseType) (MDelResponse, error) {
index := p.findCRLF(2)
if index < 0 {
return MDelResponse{}, ErrInvalidMDel
}
p.skipData(index)
return MDelResponse{
Type: respType,
}, nil
}
func (p *parser) readMDel() (MDelResponse, error) {
if len(p.data) < 4 {
return MDelResponse{}, ErrInvalidMDel
}
if p.prefixEqual('H', 'D') {
return p.readMDelWithCRLF(MDelResponseTypeHD)
}
if p.prefixEqual('N', 'F') {
return p.readMDelWithCRLF(MDelResponseTypeNF)
}
if p.prefixEqual('E', 'X') {
return p.readMDelWithCRLF(MDelResponseTypeEX)
}
if errType := p.isErrorPrefix(); errType != errorTypeNone {
return MDelResponse{}, p.readError(errType)
}
return MDelResponse{}, ErrInvalidMDel
}
// flush_all
func (p *parser) readFlushAllWithCRLF() error {
index := p.findCRLF(2)
if index < 0 {
return ErrInvalidResponse
}
p.skipData(index)
return nil
}
func (p *parser) readFlushAll() error {
if p.prefixEqual('O', 'K') {
return p.readFlushAllWithCRLF()
}
if errType := p.isErrorPrefix(); errType != errorTypeNone {
return p.readError(errType)
}
return ErrInvalidResponse
}