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resp.go
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resp.go
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package main
import (
"bufio"
"fmt"
"io"
"strconv"
)
const (
INTEGER = ':'
ARRAY = '*'
ERROR = '-' // simple errors
BULK = '$' // bulk strings
STRING = '+' // simple string
CRLF = "\r\n"
)
type Value struct {
typ string
str string
// num int
bulk string
arr []Value
}
// TODO: Maybe RespMessage is better than Resp
type RespMessage struct {
reader *bufio.Reader
}
func NewResp(rd io.Reader) *RespMessage {
return &RespMessage{reader: bufio.NewReader(rd)}
}
// Example: "+OK\r\n" --> "+", "O", "K", "\r", "\n"
// then we slice off the last 2 bytes '\r' '\n'
// finally we return ["+", "O", "K"] with n = 5 (5 reads)
// len(line)>=2 condition is necessary to prevent
// out of range access
func (r *RespMessage) ReadLine() (line []byte, n int, err error) {
for {
b, err := r.reader.ReadByte()
if err != nil {
return nil, 0, err
}
line = append(line, b)
n += 1
if len(line)>=2 && line[len(line)-2] == '\r' {
break
}
}
return line[:len(line)-2], n, err
}
func (r *RespMessage) ReadInteger() (x int, n int, err error) {
line, n, err := r.ReadLine()
if err != nil {
return -1, 0, err // TODO: x->"0" is not a good option to be returned
}
i64, err := strconv.ParseInt(string(line), 10, 64)
if err != nil {
return -1, 0, err
}
return int(i64), n, nil
}
/* func (r *Resp) ReadInteger() (x int, n int, err error) {
line, n, err := r.ReadLine()
if err != nil {
return 0, 0, err // TODO: "0" is not a good option to be returned
}
i64, err := strconv.ParseInt(string(line[1:]), 10, 64)
if err != nil {
return 0, 0, err
}
return int(i64), n-1, nil
} */
func (r *RespMessage) Read() (Value, error) {
_type, err := r.reader.ReadByte()
if err != nil {
return Value{}, err
}
switch _type {
case ARRAY:
return r.readArray()
case BULK:
return r.readBulk()
default:
fmt.Printf("Unknown type: %v", string(_type))
return Value{}, nil
}
}
// *3\r\n$3\r\nset\r\n$6\r\nplayer\r\n$7\r\nMolinex
func (r *RespMessage) readArray() (Value , error) {
v := Value{}
v.typ = "array"
len, _, err := r.ReadInteger()
if err != nil {
return v, err
}
v.arr = make([]Value, 0)
for i:=0; i<len; i++ {
b, err := r.Read()
if err != nil {
return v, err
}
v.arr = append(v.arr, b)
}
return v, nil
}
func (r *RespMessage) readBulk() (v Value, err error){
v = Value{}
v.typ = "bulk"
len, _, err := r.ReadInteger()
if err != nil {
return v, err
}
bulk := make([]byte, len)
_, err = r.reader.Read(bulk)
if err != nil {
return v, err
}
v.bulk = string(bulk)
// Read the CRLF, the pointer is left there
// Without using readLine things will messed up
r.ReadLine()
return v, nil
}
//========================================================
// The first part represents the implementation of the parser.
// Our parser is used to parse the received RESP message.
// Each RESP message is represented using "value" stuct.
// Now, we should consider how our program will send RESP compatible response.
// For every type(string, bulk, array,...) a method will be used to represent our message
// to the client in the RESP format (as bytes to send over the conn).
func (v Value) Marshal() []byte {
resp := []byte{}
switch v.typ {
case "string":
return v.marshalString()
case "bulk":
return v.marshalBulk()
// case "ineteger":
// return v.marshalInteger()
case "error":
return v.marshalError()
case "array":
return v.marshalArray()
case "null" :
return v.marshalNull()
default:
return resp
}
}
func (v Value) marshalString() []byte {
var bytes []byte
bytes = append(bytes, STRING)
bytes = append(bytes, []byte(v.str)...)
bytes = append(bytes, '\r', '\n')
return bytes
}
func (v Value) marshalBulk() []byte {
var bytes []byte
bytes = append(bytes, BULK)
bytes = append(bytes, strconv.Itoa(len(v.bulk))...)
bytes = append(bytes, '\r', '\n')
bytes = append(bytes, v.bulk...)
bytes = append(bytes, '\r', '\n')
return bytes
}
func (v Value) marshalArray() []byte {
var bytes []byte
arr_len := len(v.arr)
bytes = append(bytes, ARRAY) // "*"
bytes = append(bytes, strconv.Itoa(arr_len)...)
bytes = append(bytes, '\r', '\n')
for i:=0; i<arr_len; i++ {
bytes = append(bytes, v.arr[i].Marshal()...)
// bytes = append(bytes, '\r', '\n') --> fix the HGETALL command problem
// Error: Protocol error, got "\r" as reply type byte
}
return bytes
}
func (v Value) marshalError() []byte {
var bytes []byte
bytes = append(bytes, ERROR)
bytes = append(bytes, v.str...)
bytes = append(bytes, '\r', '\n')
return bytes
}
func (v Value) marshalNull() []byte {
return []byte("$-1\r\n")
}
type Writer struct {
writer io.Writer
}
func NewWriter(w io.Writer) *Writer {
return &Writer{writer: w}
}
func (w Writer) Write(v Value) error {
var bytes = v.Marshal()
_, err := w.writer.Write(bytes)
if err != nil {
return err
}
return nil
}