Source file src/pkg/net/textproto/writer.go

     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	}