1 // Copyright 2010 The Go Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style 3 // license that can be found in the LICENSE file. 4 5 package textproto 6 7 import ( 8 "bufio" 9 "fmt" 10 "io" 11 ) 12 13 // A Writer implements convenience methods for writing 14 // requests or responses to a text protocol network connection. 15 type Writer struct { 16 W *bufio.Writer 17 dot *dotWriter 18 } 19 20 // NewWriter returns a new Writer writing to w. 21 func NewWriter(w *bufio.Writer) *Writer { 22 return &Writer{W: w} 23 } 24 25 var crnl = []byte{'\r', '\n'} 26 var dotcrnl = []byte{'.', '\r', '\n'} 27 28 // PrintfLine writes the formatted output followed by \r\n. 29 func (w *Writer) PrintfLine(format string, args ...interface{}) error { 30 w.closeDot() 31 fmt.Fprintf(w.W, format, args...) 32 w.W.Write(crnl) 33 return w.W.Flush() 34 } 35 36 // DotWriter returns a writer that can be used to write a dot-encoding to w. 37 // It takes care of inserting leading dots when necessary, 38 // translating line-ending \n into \r\n, and adding the final .\r\n line 39 // when the DotWriter is closed. The caller should close the 40 // DotWriter before the next call to a method on w. 41 // 42 // See the documentation for Reader's DotReader method for details about dot-encoding. 43 func (w *Writer) DotWriter() io.WriteCloser { 44 w.closeDot() 45 w.dot = &dotWriter{w: w} 46 return w.dot 47 } 48 49 func (w *Writer) closeDot() { 50 if w.dot != nil { 51 w.dot.Close() // sets w.dot = nil 52 } 53 } 54 55 type dotWriter struct { 56 w *Writer 57 state int 58 } 59 60 const ( 61 wstateBeginLine = iota // beginning of line; initial state; must be zero 62 wstateCR // wrote \r (possibly at end of line) 63 wstateData // writing data in middle of line 64 ) 65 66 func (d *dotWriter) Write(b []byte) (n int, err error) { 67 bw := d.w.W 68 for n < len(b) { 69 c := b[n] 70 switch d.state { 71 case wstateBeginLine: 72 d.state = wstateData 73 if c == '.' { 74 // escape leading dot 75 bw.WriteByte('.') 76 } 77 fallthrough 78 79 case wstateData: 80 if c == '\r' { 81 d.state = wstateCR 82 } 83 if c == '\n' { 84 bw.WriteByte('\r') 85 d.state = wstateBeginLine 86 } 87 88 case wstateCR: 89 d.state = wstateData 90 if c == '\n' { 91 d.state = wstateBeginLine 92 } 93 } 94 if err = bw.WriteByte(c); err != nil { 95 break 96 } 97 n++ 98 } 99 return 100 } 101 102 func (d *dotWriter) Close() error { 103 if d.w.dot == d { 104 d.w.dot = nil 105 } 106 bw := d.w.W 107 switch d.state { 108 default: 109 bw.WriteByte('\r') 110 fallthrough 111 case wstateCR: 112 bw.WriteByte('\n') 113 fallthrough 114 case wstateBeginLine: 115 bw.Write(dotcrnl) 116 } 117 return bw.Flush() 118 } 119
