header.go

Documentation: net/http

     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 http
     6  
     7  import (
     8  	"io"
     9  	"net/http/httptrace"
    10  	"net/textproto"
    11  	"sort"
    12  	"strings"
    13  	"sync"
    14  	"time"
    15  )
    16  
    17  var raceEnabled = false // set by race.go
    18  
    19  // A Header represents the key-value pairs in an HTTP header.
    20  type Header map[string][]string
    21  
    22  // Add adds the key, value pair to the header.
    23  // It appends to any existing values associated with key.
    24  func (h Header) Add(key, value string) {
    25  	textproto.MIMEHeader(h).Add(key, value)
    26  }
    27  
    28  // Set sets the header entries associated with key to
    29  // the single element value. It replaces any existing
    30  // values associated with key.
    31  func (h Header) Set(key, value string) {
    32  	textproto.MIMEHeader(h).Set(key, value)
    33  }
    34  
    35  // Get gets the first value associated with the given key.
    36  // It is case insensitive; textproto.CanonicalMIMEHeaderKey is used
    37  // to canonicalize the provided key.
    38  // If there are no values associated with the key, Get returns "".
    39  // To access multiple values of a key, or to use non-canonical keys,
    40  // access the map directly.
    41  func (h Header) Get(key string) string {
    42  	return textproto.MIMEHeader(h).Get(key)
    43  }
    44  
    45  // get is like Get, but key must already be in CanonicalHeaderKey form.
    46  func (h Header) get(key string) string {
    47  	if v := h[key]; len(v) > 0 {
    48  		return v[0]
    49  	}
    50  	return ""
    51  }
    52  
    53  // Del deletes the values associated with key.
    54  func (h Header) Del(key string) {
    55  	textproto.MIMEHeader(h).Del(key)
    56  }
    57  
    58  // Write writes a header in wire format.
    59  func (h Header) Write(w io.Writer) error {
    60  	return h.write(w, nil)
    61  }
    62  
    63  func (h Header) write(w io.Writer, trace *httptrace.ClientTrace) error {
    64  	return h.writeSubset(w, nil, trace)
    65  }
    66  
    67  func (h Header) clone() Header {
    68  	h2 := make(Header, len(h))
    69  	for k, vv := range h {
    70  		vv2 := make([]string, len(vv))
    71  		copy(vv2, vv)
    72  		h2[k] = vv2
    73  	}
    74  	return h2
    75  }
    76  
    77  var timeFormats = []string{
    78  	TimeFormat,
    79  	time.RFC850,
    80  	time.ANSIC,
    81  }
    82  
    83  // ParseTime parses a time header (such as the Date: header),
    84  // trying each of the three formats allowed by HTTP/1.1:
    85  // TimeFormat, time.RFC850, and time.ANSIC.
    86  func ParseTime(text string) (t time.Time, err error) {
    87  	for _, layout := range timeFormats {
    88  		t, err = time.Parse(layout, text)
    89  		if err == nil {
    90  			return
    91  		}
    92  	}
    93  	return
    94  }
    95  
    96  var headerNewlineToSpace = strings.NewReplacer("\n", " ", "\r", " ")
    97  
    98  type writeStringer interface {
    99  	WriteString(string) (int, error)
   100  }
   101  
   102  // stringWriter implements WriteString on a Writer.
   103  type stringWriter struct {
   104  	w io.Writer
   105  }
   106  
   107  func (w stringWriter) WriteString(s string) (n int, err error) {
   108  	return w.w.Write([]byte(s))
   109  }
   110  
   111  type keyValues struct {
   112  	key    string
   113  	values []string
   114  }
   115  
   116  // A headerSorter implements sort.Interface by sorting a []keyValues
   117  // by key. It's used as a pointer, so it can fit in a sort.Interface
   118  // interface value without allocation.
   119  type headerSorter struct {
   120  	kvs []keyValues
   121  }
   122  
   123  func (s *headerSorter) Len() int           { return len(s.kvs) }
   124  func (s *headerSorter) Swap(i, j int)      { s.kvs[i], s.kvs[j] = s.kvs[j], s.kvs[i] }
   125  func (s *headerSorter) Less(i, j int) bool { return s.kvs[i].key < s.kvs[j].key }
   126  
   127  var headerSorterPool = sync.Pool{
   128  	New: func() interface{} { return new(headerSorter) },
   129  }
   130  
   131  // sortedKeyValues returns h's keys sorted in the returned kvs
   132  // slice. The headerSorter used to sort is also returned, for possible
   133  // return to headerSorterCache.
   134  func (h Header) sortedKeyValues(exclude map[string]bool) (kvs []keyValues, hs *headerSorter) {
   135  	hs = headerSorterPool.Get().(*headerSorter)
   136  	if cap(hs.kvs) < len(h) {
   137  		hs.kvs = make([]keyValues, 0, len(h))
   138  	}
   139  	kvs = hs.kvs[:0]
   140  	for k, vv := range h {
   141  		if !exclude[k] {
   142  			kvs = append(kvs, keyValues{k, vv})
   143  		}
   144  	}
   145  	hs.kvs = kvs
   146  	sort.Sort(hs)
   147  	return kvs, hs
   148  }
   149  
   150  // WriteSubset writes a header in wire format.
   151  // If exclude is not nil, keys where exclude[key] == true are not written.
   152  func (h Header) WriteSubset(w io.Writer, exclude map[string]bool) error {
   153  	return h.writeSubset(w, exclude, nil)
   154  }
   155  
   156  func (h Header) writeSubset(w io.Writer, exclude map[string]bool, trace *httptrace.ClientTrace) error {
   157  	ws, ok := w.(writeStringer)
   158  	if !ok {
   159  		ws = stringWriter{w}
   160  	}
   161  	kvs, sorter := h.sortedKeyValues(exclude)
   162  	var formattedVals []string
   163  	for _, kv := range kvs {
   164  		for _, v := range kv.values {
   165  			v = headerNewlineToSpace.Replace(v)
   166  			v = textproto.TrimString(v)
   167  			for _, s := range []string{kv.key, ": ", v, "\r\n"} {
   168  				if _, err := ws.WriteString(s); err != nil {
   169  					headerSorterPool.Put(sorter)
   170  					return err
   171  				}
   172  			}
   173  			if trace != nil && trace.WroteHeaderField != nil {
   174  				formattedVals = append(formattedVals, v)
   175  			}
   176  		}
   177  		if trace != nil && trace.WroteHeaderField != nil {
   178  			trace.WroteHeaderField(kv.key, formattedVals)
   179  			formattedVals = nil
   180  		}
   181  	}
   182  	headerSorterPool.Put(sorter)
   183  	return nil
   184  }
   185  
   186  // CanonicalHeaderKey returns the canonical format of the
   187  // header key s. The canonicalization converts the first
   188  // letter and any letter following a hyphen to upper case;
   189  // the rest are converted to lowercase. For example, the
   190  // canonical key for "accept-encoding" is "Accept-Encoding".
   191  // If s contains a space or invalid header field bytes, it is
   192  // returned without modifications.
   193  func CanonicalHeaderKey(s string) string { return textproto.CanonicalMIMEHeaderKey(s) }
   194  
   195  // hasToken reports whether token appears with v, ASCII
   196  // case-insensitive, with space or comma boundaries.
   197  // token must be all lowercase.
   198  // v may contain mixed cased.
   199  func hasToken(v, token string) bool {
   200  	if len(token) > len(v) || token == "" {
   201  		return false
   202  	}
   203  	if v == token {
   204  		return true
   205  	}
   206  	for sp := 0; sp <= len(v)-len(token); sp++ {
   207  		// Check that first character is good.
   208  		// The token is ASCII, so checking only a single byte
   209  		// is sufficient. We skip this potential starting
   210  		// position if both the first byte and its potential
   211  		// ASCII uppercase equivalent (b|0x20) don't match.
   212  		// False positives ('^' => '~') are caught by EqualFold.
   213  		if b := v[sp]; b != token[0] && b|0x20 != token[0] {
   214  			continue
   215  		}
   216  		// Check that start pos is on a valid token boundary.
   217  		if sp > 0 && !isTokenBoundary(v[sp-1]) {
   218  			continue
   219  		}
   220  		// Check that end pos is on a valid token boundary.
   221  		if endPos := sp + len(token); endPos != len(v) && !isTokenBoundary(v[endPos]) {
   222  			continue
   223  		}
   224  		if strings.EqualFold(v[sp:sp+len(token)], token) {
   225  			return true
   226  		}
   227  	}
   228  	return false
   229  }
   230  
   231  func isTokenBoundary(b byte) bool {
   232  	return b == ' ' || b == ',' || b == '\t'
   233  }
   234  
   235  func cloneHeader(h Header) Header {
   236  	h2 := make(Header, len(h))
   237  	for k, vv := range h {
   238  		vv2 := make([]string, len(vv))
   239  		copy(vv2, vv)
   240  		h2[k] = vv2
   241  	}
   242  	return h2
   243  }
   244
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