545 lines
13 KiB
Go
545 lines
13 KiB
Go
// Copyright 2010 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package textproto
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import (
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"bufio"
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"bytes"
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"io"
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"io/ioutil"
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"strconv"
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"strings"
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)
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// BUG(rsc): To let callers manage exposure to denial of service
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// attacks, Reader should allow them to set and reset a limit on
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// the number of bytes read from the connection.
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// A Reader implements convenience methods for reading requests
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// or responses from a text protocol network connection.
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type Reader struct {
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R *bufio.Reader
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dot *dotReader
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}
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// NewReader returns a new Reader reading from r.
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func NewReader(r *bufio.Reader) *Reader {
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return &Reader{R: r}
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}
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// ReadLine reads a single line from r,
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// eliding the final \n or \r\n from the returned string.
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func (r *Reader) ReadLine() (string, error) {
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line, err := r.readLineSlice()
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return string(line), err
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}
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// ReadLineBytes is like ReadLine but returns a []byte instead of a string.
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func (r *Reader) ReadLineBytes() ([]byte, error) {
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line, err := r.readLineSlice()
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if line != nil {
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buf := make([]byte, len(line))
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copy(buf, line)
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line = buf
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}
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return line, err
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}
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func (r *Reader) readLineSlice() ([]byte, error) {
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r.closeDot()
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var line []byte
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for {
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l, more, err := r.R.ReadLine()
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if err != nil {
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return nil, err
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}
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// Avoid the copy if the first call produced a full line.
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if line == nil && !more {
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return l, nil
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}
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line = append(line, l...)
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if !more {
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break
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}
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}
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return line, nil
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}
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// ReadContinuedLine reads a possibly continued line from r,
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// eliding the final trailing ASCII white space.
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// Lines after the first are considered continuations if they
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// begin with a space or tab character. In the returned data,
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// continuation lines are separated from the previous line
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// only by a single space: the newline and leading white space
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// are removed.
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//
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// For example, consider this input:
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//
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// Line 1
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// continued...
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// Line 2
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//
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// The first call to ReadContinuedLine will return "Line 1 continued..."
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// and the second will return "Line 2".
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//
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// A line consisting of only white space is never continued.
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//
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func (r *Reader) ReadContinuedLine() (string, error) {
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line, err := r.readContinuedLineSlice()
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return string(line), err
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}
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// trim returns s with leading and trailing spaces and tabs removed.
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// It does not assume Unicode or UTF-8.
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func trim(s []byte) []byte {
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i := 0
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for i < len(s) && (s[i] == ' ' || s[i] == '\t') {
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i++
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}
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n := len(s)
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for n > i && (s[n-1] == ' ' || s[n-1] == '\t') {
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n--
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}
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return s[i:n]
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}
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// ReadContinuedLineBytes is like ReadContinuedLine but
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// returns a []byte instead of a string.
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func (r *Reader) ReadContinuedLineBytes() ([]byte, error) {
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line, err := r.readContinuedLineSlice()
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if line != nil {
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buf := make([]byte, len(line))
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copy(buf, line)
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line = buf
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}
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return line, err
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}
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func (r *Reader) readContinuedLineSlice() ([]byte, error) {
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// Read the first line.
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line, err := r.readLineSlice()
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if err != nil {
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return line, err
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}
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if len(line) == 0 { // blank line - no continuation
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return line, nil
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}
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line = trim(line)
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copied := false
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if r.R.Buffered() < 1 {
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// ReadByte will flush the buffer; make a copy of the slice.
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copied = true
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line = append([]byte(nil), line...)
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}
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// Look for a continuation line.
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c, err := r.R.ReadByte()
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if err != nil {
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// Delay err until we read the byte next time.
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return line, nil
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}
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if c != ' ' && c != '\t' {
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// Not a continuation.
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r.R.UnreadByte()
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return line, nil
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}
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if !copied {
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// The next readLineSlice will invalidate the previous one.
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line = append(make([]byte, 0, len(line)*2), line...)
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}
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// Read continuation lines.
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for {
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// Consume leading spaces; one already gone.
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for {
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c, err = r.R.ReadByte()
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if err != nil {
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break
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}
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if c != ' ' && c != '\t' {
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r.R.UnreadByte()
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break
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}
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}
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var cont []byte
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cont, err = r.readLineSlice()
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cont = trim(cont)
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line = append(line, ' ')
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line = append(line, cont...)
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if err != nil {
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break
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}
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// Check for leading space on next line.
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if c, err = r.R.ReadByte(); err != nil {
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break
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}
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if c != ' ' && c != '\t' {
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r.R.UnreadByte()
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break
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}
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}
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// Delay error until next call.
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if len(line) > 0 {
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err = nil
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}
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return line, err
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}
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func (r *Reader) readCodeLine(expectCode int) (code int, continued bool, message string, err error) {
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line, err := r.ReadLine()
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if err != nil {
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return
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}
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return parseCodeLine(line, expectCode)
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}
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func parseCodeLine(line string, expectCode int) (code int, continued bool, message string, err error) {
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if len(line) < 4 || line[3] != ' ' && line[3] != '-' {
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err = ProtocolError("short response: " + line)
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return
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}
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continued = line[3] == '-'
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code, err = strconv.Atoi(line[0:3])
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if err != nil || code < 100 {
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err = ProtocolError("invalid response code: " + line)
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return
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}
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message = line[4:]
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if 1 <= expectCode && expectCode < 10 && code/100 != expectCode ||
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10 <= expectCode && expectCode < 100 && code/10 != expectCode ||
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100 <= expectCode && expectCode < 1000 && code != expectCode {
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err = &Error{code, message}
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}
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return
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}
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// ReadCodeLine reads a response code line of the form
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// code message
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// where code is a 3-digit status code and the message
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// extends to the rest of the line. An example of such a line is:
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// 220 plan9.bell-labs.com ESMTP
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//
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// If the prefix of the status does not match the digits in expectCode,
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// ReadCodeLine returns with err set to &Error{code, message}.
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// For example, if expectCode is 31, an error will be returned if
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// the status is not in the range [310,319].
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//
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// If the response is multi-line, ReadCodeLine returns an error.
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//
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// An expectCode <= 0 disables the check of the status code.
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//
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func (r *Reader) ReadCodeLine(expectCode int) (code int, message string, err error) {
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code, continued, message, err := r.readCodeLine(expectCode)
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if err == nil && continued {
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err = ProtocolError("unexpected multi-line response: " + message)
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}
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return
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}
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// ReadResponse reads a multi-line response of the form:
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//
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// code-message line 1
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// code-message line 2
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// ...
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// code message line n
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//
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// where code is a 3-digit status code. The first line starts with the
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// code and a hyphen. The response is terminated by a line that starts
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// with the same code followed by a space. Each line in message is
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// separated by a newline (\n).
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//
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// See page 36 of RFC 959 (http://www.ietf.org/rfc/rfc959.txt) for
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// details.
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//
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// If the prefix of the status does not match the digits in expectCode,
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// ReadResponse returns with err set to &Error{code, message}.
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// For example, if expectCode is 31, an error will be returned if
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// the status is not in the range [310,319].
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//
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// An expectCode <= 0 disables the check of the status code.
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//
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func (r *Reader) ReadResponse(expectCode int) (code int, message string, err error) {
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code, continued, message, err := r.readCodeLine(expectCode)
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for err == nil && continued {
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line, err := r.ReadLine()
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if err != nil {
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return 0, "", err
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}
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var code2 int
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var moreMessage string
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code2, continued, moreMessage, err = parseCodeLine(line, expectCode)
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if err != nil || code2 != code {
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message += "\n" + strings.TrimRight(line, "\r\n")
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continued = true
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continue
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}
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message += "\n" + moreMessage
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}
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return
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}
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// DotReader returns a new Reader that satisfies Reads using the
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// decoded text of a dot-encoded block read from r.
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// The returned Reader is only valid until the next call
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// to a method on r.
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//
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// Dot encoding is a common framing used for data blocks
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// in text protocols such as SMTP. The data consists of a sequence
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// of lines, each of which ends in "\r\n". The sequence itself
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// ends at a line containing just a dot: ".\r\n". Lines beginning
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// with a dot are escaped with an additional dot to avoid
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// looking like the end of the sequence.
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//
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// The decoded form returned by the Reader's Read method
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// rewrites the "\r\n" line endings into the simpler "\n",
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// removes leading dot escapes if present, and stops with error io.EOF
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// after consuming (and discarding) the end-of-sequence line.
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func (r *Reader) DotReader() io.Reader {
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r.closeDot()
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r.dot = &dotReader{r: r}
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return r.dot
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}
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type dotReader struct {
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r *Reader
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state int
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}
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// Read satisfies reads by decoding dot-encoded data read from d.r.
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func (d *dotReader) Read(b []byte) (n int, err error) {
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// Run data through a simple state machine to
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// elide leading dots, rewrite trailing \r\n into \n,
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// and detect ending .\r\n line.
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const (
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stateBeginLine = iota // beginning of line; initial state; must be zero
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stateDot // read . at beginning of line
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stateDotCR // read .\r at beginning of line
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stateCR // read \r (possibly at end of line)
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stateData // reading data in middle of line
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stateEOF // reached .\r\n end marker line
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)
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br := d.r.R
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for n < len(b) && d.state != stateEOF {
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var c byte
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c, err = br.ReadByte()
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if err != nil {
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if err == io.EOF {
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err = io.ErrUnexpectedEOF
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}
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break
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}
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switch d.state {
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case stateBeginLine:
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if c == '.' {
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d.state = stateDot
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continue
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}
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if c == '\r' {
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d.state = stateCR
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continue
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}
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d.state = stateData
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case stateDot:
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if c == '\r' {
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d.state = stateDotCR
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continue
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}
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if c == '\n' {
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d.state = stateEOF
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continue
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}
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d.state = stateData
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case stateDotCR:
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if c == '\n' {
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d.state = stateEOF
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continue
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}
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// Not part of .\r\n.
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// Consume leading dot and emit saved \r.
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br.UnreadByte()
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c = '\r'
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d.state = stateData
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case stateCR:
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if c == '\n' {
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d.state = stateBeginLine
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break
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}
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// Not part of \r\n. Emit saved \r
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br.UnreadByte()
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c = '\r'
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d.state = stateData
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case stateData:
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if c == '\r' {
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d.state = stateCR
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continue
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}
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if c == '\n' {
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d.state = stateBeginLine
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}
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}
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b[n] = c
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n++
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}
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if err == nil && d.state == stateEOF {
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err = io.EOF
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}
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if err != nil && d.r.dot == d {
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d.r.dot = nil
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}
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return
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}
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// closeDot drains the current DotReader if any,
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// making sure that it reads until the ending dot line.
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func (r *Reader) closeDot() {
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if r.dot == nil {
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return
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}
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buf := make([]byte, 128)
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for r.dot != nil {
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// When Read reaches EOF or an error,
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// it will set r.dot == nil.
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r.dot.Read(buf)
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}
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}
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// ReadDotBytes reads a dot-encoding and returns the decoded data.
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//
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// See the documentation for the DotReader method for details about dot-encoding.
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func (r *Reader) ReadDotBytes() ([]byte, error) {
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return ioutil.ReadAll(r.DotReader())
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}
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// ReadDotLines reads a dot-encoding and returns a slice
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// containing the decoded lines, with the final \r\n or \n elided from each.
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//
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// See the documentation for the DotReader method for details about dot-encoding.
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func (r *Reader) ReadDotLines() ([]string, error) {
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// We could use ReadDotBytes and then Split it,
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// but reading a line at a time avoids needing a
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// large contiguous block of memory and is simpler.
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var v []string
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var err error
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for {
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var line string
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line, err = r.ReadLine()
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if err != nil {
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if err == io.EOF {
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err = io.ErrUnexpectedEOF
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}
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break
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}
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// Dot by itself marks end; otherwise cut one dot.
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if len(line) > 0 && line[0] == '.' {
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if len(line) == 1 {
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break
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}
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line = line[1:]
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}
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v = append(v, line)
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}
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return v, err
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}
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// ReadMIMEHeader reads a MIME-style header from r.
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// The header is a sequence of possibly continued Key: Value lines
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// ending in a blank line.
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// The returned map m maps CanonicalMIMEHeaderKey(key) to a
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// sequence of values in the same order encountered in the input.
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//
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// For example, consider this input:
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//
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// My-Key: Value 1
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// Long-Key: Even
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// Longer Value
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// My-Key: Value 2
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//
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// Given that input, ReadMIMEHeader returns the map:
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//
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// map[string][]string{
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// "My-Key": {"Value 1", "Value 2"},
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// "Long-Key": {"Even Longer Value"},
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// }
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//
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func (r *Reader) ReadMIMEHeader() (MIMEHeader, error) {
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m := make(MIMEHeader)
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for {
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kv, err := r.readContinuedLineSlice()
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if len(kv) == 0 {
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return m, err
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}
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// Key ends at first colon; must not have spaces.
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i := bytes.IndexByte(kv, ':')
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if i < 0 || bytes.IndexByte(kv[0:i], ' ') >= 0 {
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return m, ProtocolError("malformed MIME header line: " + string(kv))
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}
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key := CanonicalMIMEHeaderKey(string(kv[0:i]))
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// Skip initial spaces in value.
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i++ // skip colon
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for i < len(kv) && (kv[i] == ' ' || kv[i] == '\t') {
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i++
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}
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value := string(kv[i:])
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m[key] = append(m[key], value)
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if err != nil {
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return m, err
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}
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}
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panic("unreachable")
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}
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// CanonicalMIMEHeaderKey returns the canonical format of the
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// MIME header key s. The canonicalization converts the first
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// letter and any letter following a hyphen to upper case;
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// the rest are converted to lowercase. For example, the
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// canonical key for "accept-encoding" is "Accept-Encoding".
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func CanonicalMIMEHeaderKey(s string) string {
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// Quick check for canonical encoding.
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needUpper := true
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for i := 0; i < len(s); i++ {
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c := s[i]
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if needUpper && 'a' <= c && c <= 'z' {
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goto MustRewrite
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}
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if !needUpper && 'A' <= c && c <= 'Z' {
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goto MustRewrite
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}
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needUpper = c == '-'
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}
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return s
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MustRewrite:
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// Canonicalize: first letter upper case
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// and upper case after each dash.
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// (Host, User-Agent, If-Modified-Since).
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// MIME headers are ASCII only, so no Unicode issues.
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a := []byte(s)
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upper := true
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for i, v := range a {
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if upper && 'a' <= v && v <= 'z' {
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a[i] = v + 'A' - 'a'
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}
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if !upper && 'A' <= v && v <= 'Z' {
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a[i] = v + 'a' - 'A'
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}
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upper = v == '-'
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}
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return string(a)
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}
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