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