writer.go

Documentation: net/textproto

		 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  	wstateBegin		 = iota // initial state; must be zero
		62  	wstateBeginLine				// beginning of line
		63  	wstateCR							 // wrote \r (possibly at end of line)
		64  	wstateData						 // writing data in middle of line
		65  )
		66  
		67  func (d *dotWriter) Write(b []byte) (n int, err error) {
		68  	bw := d.w.W
		69  	for n < len(b) {
		70  		c := b[n]
		71  		switch d.state {
		72  		case wstateBegin, wstateBeginLine:
		73  			d.state = wstateData
		74  			if c == '.' {
		75  				// escape leading dot
		76  				bw.WriteByte('.')
		77  			}
		78  			fallthrough
		79  
		80  		case wstateData:
		81  			if c == '\r' {
		82  				d.state = wstateCR
		83  			}
		84  			if c == '\n' {
		85  				bw.WriteByte('\r')
		86  				d.state = wstateBeginLine
		87  			}
		88  
		89  		case wstateCR:
		90  			d.state = wstateData
		91  			if c == '\n' {
		92  				d.state = wstateBeginLine
		93  			}
		94  		}
		95  		if err = bw.WriteByte(c); err != nil {
		96  			break
		97  		}
		98  		n++
		99  	}
	 100  	return
	 101  }
	 102  
	 103  func (d *dotWriter) Close() error {
	 104  	if d.w.dot == d {
	 105  		d.w.dot = nil
	 106  	}
	 107  	bw := d.w.W
	 108  	switch d.state {
	 109  	default:
	 110  		bw.WriteByte('\r')
	 111  		fallthrough
	 112  	case wstateCR:
	 113  		bw.WriteByte('\n')
	 114  		fallthrough
	 115  	case wstateBeginLine:
	 116  		bw.Write(dotcrnl)
	 117  	}
	 118  	return bw.Flush()
	 119  }
	 120
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