Source file src/net/http/header.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 http
     6  
     7  import (
     8  	"io"
     9  	"net/http/httptrace"
    10  	"net/http/internal/ascii"
    11  	"net/textproto"
    12  	"sort"
    13  	"strings"
    14  	"sync"
    15  	"time"
    16  )
    17  
    18  // A Header represents the key-value pairs in an HTTP header.
    19  //
    20  // The keys should be in canonical form, as returned by
    21  // CanonicalHeaderKey.
    22  type Header map[string][]string
    23  
    24  // Add adds the key, value pair to the header.
    25  // It appends to any existing values associated with key.
    26  // The key is case insensitive; it is canonicalized by
    27  // CanonicalHeaderKey.
    28  func (h Header) Add(key, value string) {
    29  	textproto.MIMEHeader(h).Add(key, value)
    30  }
    31  
    32  // Set sets the header entries associated with key to the
    33  // single element value. It replaces any existing values
    34  // associated with key. The key is case insensitive; it is
    35  // canonicalized by textproto.CanonicalMIMEHeaderKey.
    36  // To use non-canonical keys, assign to the map directly.
    37  func (h Header) Set(key, value string) {
    38  	textproto.MIMEHeader(h).Set(key, value)
    39  }
    40  
    41  // Get gets the first value associated with the given key. If
    42  // there are no values associated with the key, Get returns "".
    43  // It is case insensitive; textproto.CanonicalMIMEHeaderKey is
    44  // used to canonicalize the provided key. To use non-canonical keys,
    45  // access the map directly.
    46  func (h Header) Get(key string) string {
    47  	return textproto.MIMEHeader(h).Get(key)
    48  }
    49  
    50  // Values returns all values associated with the given key.
    51  // It is case insensitive; textproto.CanonicalMIMEHeaderKey is
    52  // used to canonicalize the provided key. To use non-canonical
    53  // keys, access the map directly.
    54  // The returned slice is not a copy.
    55  func (h Header) Values(key string) []string {
    56  	return textproto.MIMEHeader(h).Values(key)
    57  }
    58  
    59  // get is like Get, but key must already be in CanonicalHeaderKey form.
    60  func (h Header) get(key string) string {
    61  	if v := h[key]; len(v) > 0 {
    62  		return v[0]
    63  	}
    64  	return ""
    65  }
    66  
    67  // has reports whether h has the provided key defined, even if it's
    68  // set to 0-length slice.
    69  func (h Header) has(key string) bool {
    70  	_, ok := h[key]
    71  	return ok
    72  }
    73  
    74  // Del deletes the values associated with key.
    75  // The key is case insensitive; it is canonicalized by
    76  // CanonicalHeaderKey.
    77  func (h Header) Del(key string) {
    78  	textproto.MIMEHeader(h).Del(key)
    79  }
    80  
    81  // Write writes a header in wire format.
    82  func (h Header) Write(w io.Writer) error {
    83  	return h.write(w, nil)
    84  }
    85  
    86  func (h Header) write(w io.Writer, trace *httptrace.ClientTrace) error {
    87  	return h.writeSubset(w, nil, trace)
    88  }
    89  
    90  // Clone returns a copy of h or nil if h is nil.
    91  func (h Header) Clone() Header {
    92  	if h == nil {
    93  		return nil
    94  	}
    95  
    96  	// Find total number of values.
    97  	nv := 0
    98  	for _, vv := range h {
    99  		nv += len(vv)
   100  	}
   101  	sv := make([]string, nv) // shared backing array for headers' values
   102  	h2 := make(Header, len(h))
   103  	for k, vv := range h {
   104  		n := copy(sv, vv)
   105  		h2[k] = sv[:n:n]
   106  		sv = sv[n:]
   107  	}
   108  	return h2
   109  }
   110  
   111  var timeFormats = []string{
   112  	TimeFormat,
   113  	time.RFC850,
   114  	time.ANSIC,
   115  }
   116  
   117  // ParseTime parses a time header (such as the Date: header),
   118  // trying each of the three formats allowed by HTTP/1.1:
   119  // TimeFormat, time.RFC850, and time.ANSIC.
   120  func ParseTime(text string) (t time.Time, err error) {
   121  	for _, layout := range timeFormats {
   122  		t, err = time.Parse(layout, text)
   123  		if err == nil {
   124  			return
   125  		}
   126  	}
   127  	return
   128  }
   129  
   130  var headerNewlineToSpace = strings.NewReplacer("\n", " ", "\r", " ")
   131  
   132  // stringWriter implements WriteString on a Writer.
   133  type stringWriter struct {
   134  	w io.Writer
   135  }
   136  
   137  func (w stringWriter) WriteString(s string) (n int, err error) {
   138  	return w.w.Write([]byte(s))
   139  }
   140  
   141  type keyValues struct {
   142  	key    string
   143  	values []string
   144  }
   145  
   146  // A headerSorter implements sort.Interface by sorting a []keyValues
   147  // by key. It's used as a pointer, so it can fit in a sort.Interface
   148  // interface value without allocation.
   149  type headerSorter struct {
   150  	kvs []keyValues
   151  }
   152  
   153  func (s *headerSorter) Len() int           { return len(s.kvs) }
   154  func (s *headerSorter) Swap(i, j int)      { s.kvs[i], s.kvs[j] = s.kvs[j], s.kvs[i] }
   155  func (s *headerSorter) Less(i, j int) bool { return s.kvs[i].key < s.kvs[j].key }
   156  
   157  var headerSorterPool = sync.Pool{
   158  	New: func() interface{} { return new(headerSorter) },
   159  }
   160  
   161  // sortedKeyValues returns h's keys sorted in the returned kvs
   162  // slice. The headerSorter used to sort is also returned, for possible
   163  // return to headerSorterCache.
   164  func (h Header) sortedKeyValues(exclude map[string]bool) (kvs []keyValues, hs *headerSorter) {
   165  	hs = headerSorterPool.Get().(*headerSorter)
   166  	if cap(hs.kvs) < len(h) {
   167  		hs.kvs = make([]keyValues, 0, len(h))
   168  	}
   169  	kvs = hs.kvs[:0]
   170  	for k, vv := range h {
   171  		if !exclude[k] {
   172  			kvs = append(kvs, keyValues{k, vv})
   173  		}
   174  	}
   175  	hs.kvs = kvs
   176  	sort.Sort(hs)
   177  	return kvs, hs
   178  }
   179  
   180  // WriteSubset writes a header in wire format.
   181  // If exclude is not nil, keys where exclude[key] == true are not written.
   182  // Keys are not canonicalized before checking the exclude map.
   183  func (h Header) WriteSubset(w io.Writer, exclude map[string]bool) error {
   184  	return h.writeSubset(w, exclude, nil)
   185  }
   186  
   187  func (h Header) writeSubset(w io.Writer, exclude map[string]bool, trace *httptrace.ClientTrace) error {
   188  	ws, ok := w.(io.StringWriter)
   189  	if !ok {
   190  		ws = stringWriter{w}
   191  	}
   192  	kvs, sorter := h.sortedKeyValues(exclude)
   193  	var formattedVals []string
   194  	for _, kv := range kvs {
   195  		for _, v := range kv.values {
   196  			v = headerNewlineToSpace.Replace(v)
   197  			v = textproto.TrimString(v)
   198  			for _, s := range []string{kv.key, ": ", v, "\r\n"} {
   199  				if _, err := ws.WriteString(s); err != nil {
   200  					headerSorterPool.Put(sorter)
   201  					return err
   202  				}
   203  			}
   204  			if trace != nil && trace.WroteHeaderField != nil {
   205  				formattedVals = append(formattedVals, v)
   206  			}
   207  		}
   208  		if trace != nil && trace.WroteHeaderField != nil {
   209  			trace.WroteHeaderField(kv.key, formattedVals)
   210  			formattedVals = nil
   211  		}
   212  	}
   213  	headerSorterPool.Put(sorter)
   214  	return nil
   215  }
   216  
   217  // CanonicalHeaderKey returns the canonical format of the
   218  // header key s. The canonicalization converts the first
   219  // letter and any letter following a hyphen to upper case;
   220  // the rest are converted to lowercase. For example, the
   221  // canonical key for "accept-encoding" is "Accept-Encoding".
   222  // If s contains a space or invalid header field bytes, it is
   223  // returned without modifications.
   224  func CanonicalHeaderKey(s string) string { return textproto.CanonicalMIMEHeaderKey(s) }
   225  
   226  // hasToken reports whether token appears with v, ASCII
   227  // case-insensitive, with space or comma boundaries.
   228  // token must be all lowercase.
   229  // v may contain mixed cased.
   230  func hasToken(v, token string) bool {
   231  	if len(token) > len(v) || token == "" {
   232  		return false
   233  	}
   234  	if v == token {
   235  		return true
   236  	}
   237  	for sp := 0; sp <= len(v)-len(token); sp++ {
   238  		// Check that first character is good.
   239  		// The token is ASCII, so checking only a single byte
   240  		// is sufficient. We skip this potential starting
   241  		// position if both the first byte and its potential
   242  		// ASCII uppercase equivalent (b|0x20) don't match.
   243  		// False positives ('^' => '~') are caught by EqualFold.
   244  		if b := v[sp]; b != token[0] && b|0x20 != token[0] {
   245  			continue
   246  		}
   247  		// Check that start pos is on a valid token boundary.
   248  		if sp > 0 && !isTokenBoundary(v[sp-1]) {
   249  			continue
   250  		}
   251  		// Check that end pos is on a valid token boundary.
   252  		if endPos := sp + len(token); endPos != len(v) && !isTokenBoundary(v[endPos]) {
   253  			continue
   254  		}
   255  		if ascii.EqualFold(v[sp:sp+len(token)], token) {
   256  			return true
   257  		}
   258  	}
   259  	return false
   260  }
   261  
   262  func isTokenBoundary(b byte) bool {
   263  	return b == ' ' || b == ',' || b == '\t'
   264  }
   265  

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