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