|
| 1 | +package main |
| 2 | + |
| 3 | +import ( |
| 4 | + "bufio" |
| 5 | + "bytes" |
| 6 | + "fmt" |
| 7 | + "io" |
| 8 | + "strconv" |
| 9 | +) |
| 10 | + |
| 11 | +type transformerFn func(code byte, line []byte) []byte |
| 12 | + |
| 13 | +func newRespReader(b *bufio.Reader, w *bytes.Buffer, fn transformerFn) RespReader { |
| 14 | + return RespReader{ |
| 15 | + br: b, |
| 16 | + bw: w, |
| 17 | + fn: fn, |
| 18 | + } |
| 19 | +} |
| 20 | + |
| 21 | +type RespReader struct { |
| 22 | + br *bufio.Reader |
| 23 | + bw *bytes.Buffer |
| 24 | + fn transformerFn |
| 25 | +} |
| 26 | + |
| 27 | +type readerError string |
| 28 | + |
| 29 | +func (pe readerError) Error() string { |
| 30 | + return fmt.Sprintf("parse erro: %s", string(pe)) |
| 31 | +} |
| 32 | + |
| 33 | +func (c *RespReader) readReply() error { |
| 34 | + line, err := c.readLine() |
| 35 | + if err != nil { |
| 36 | + return err |
| 37 | + } |
| 38 | + if len(line) < 2 { |
| 39 | + return readerError("short response line") |
| 40 | + } |
| 41 | + switch line[0] { |
| 42 | + case '+', '-', ':': |
| 43 | + c.bw.Write(line) |
| 44 | + return nil |
| 45 | + case '$': |
| 46 | + n, err := parseLen(line[1:]) |
| 47 | + if n < 0 || err != nil { |
| 48 | + return err |
| 49 | + } |
| 50 | + p := make([]byte, n+2) |
| 51 | + _, err = io.ReadFull(c.br, p) |
| 52 | + if err != nil { |
| 53 | + return err |
| 54 | + } |
| 55 | + if c.fn != nil { |
| 56 | + p = c.fn('$', p) |
| 57 | + } |
| 58 | + c.bw.WriteString("$" + strconv.Itoa(len(p)-2) + "\r\n") |
| 59 | + c.bw.Write(p) |
| 60 | + return nil |
| 61 | + case '*': |
| 62 | + n, err := parseLen(line[1:]) |
| 63 | + if n < 0 || err != nil { |
| 64 | + return err |
| 65 | + } |
| 66 | + c.bw.Write(line) |
| 67 | + for range n { |
| 68 | + err = c.readReply() |
| 69 | + if err != nil { |
| 70 | + return err |
| 71 | + } |
| 72 | + } |
| 73 | + return nil |
| 74 | + } |
| 75 | + return readerError("unexpected response line") |
| 76 | +} |
| 77 | + |
| 78 | +func (c *RespReader) readLine() ([]byte, error) { |
| 79 | + // To avoid allocations, attempt to read the line using ReadSlice. This |
| 80 | + // call typically succeeds. The known case where the call fails is when |
| 81 | + // reading the output from the MONITOR command. |
| 82 | + p, err := c.br.ReadSlice('\n') |
| 83 | + if err == bufio.ErrBufferFull { |
| 84 | + // The line does not fit in the bufio.Reader's buffer. Fall back to |
| 85 | + // allocating a buffer for the line. |
| 86 | + buf := append([]byte{}, p...) |
| 87 | + for err == bufio.ErrBufferFull { |
| 88 | + p, err = c.br.ReadSlice('\n') |
| 89 | + buf = append(buf, p...) |
| 90 | + } |
| 91 | + p = buf |
| 92 | + } |
| 93 | + if err != nil { |
| 94 | + return nil, err |
| 95 | + } |
| 96 | + i := len(p) - 2 |
| 97 | + if i < 0 || p[i] != '\r' { |
| 98 | + return nil, readerError("bad response line terminator") |
| 99 | + } |
| 100 | + return p, nil |
| 101 | +} |
| 102 | + |
| 103 | +// parseLen parses bulk string and array lengths. |
| 104 | +func parseLen(p []byte) (int, error) { |
| 105 | + if len(p) == 0 { |
| 106 | + return -1, readerError("malformed length") |
| 107 | + } |
| 108 | + |
| 109 | + if p[0] == '-' && len(p) == 4 && p[1] == '1' { |
| 110 | + // handle $-1 and $-1 null replies. |
| 111 | + return -1, nil |
| 112 | + } |
| 113 | + |
| 114 | + var n int |
| 115 | + for _, b := range p[:len(p)-2] { |
| 116 | + n *= 10 |
| 117 | + if b < '0' || b > '9' { |
| 118 | + return -1, readerError("illegal bytes in length") |
| 119 | + } |
| 120 | + n += int(b - '0') |
| 121 | + } |
| 122 | + |
| 123 | + return n, nil |
| 124 | +} |
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