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  	"golang.org/x/net/http/httpguts"
    18  )
    19  
    20  // A Header represents the key-value pairs in an HTTP header.
    21  //
    22  // The keys should be in canonical form, as returned by
    23  // CanonicalHeaderKey.
    24  type Header map[string][]string
    25  
    26  // Add adds the key, value pair to the header.
    27  // It appends to any existing values associated with key.
    28  // The key is case insensitive; it is canonicalized by
    29  // CanonicalHeaderKey.
    30  func (h Header) Add(key, value string) {
    31  	textproto.MIMEHeader(h).Add(key, value)
    32  }
    33  
    34  // Set sets the header entries associated with key to the
    35  // single element value. It replaces any existing values
    36  // associated with key. The key is case insensitive; it is
    37  // canonicalized by textproto.CanonicalMIMEHeaderKey.
    38  // To use non-canonical keys, assign to the map directly.
    39  func (h Header) Set(key, value string) {
    40  	textproto.MIMEHeader(h).Set(key, value)
    41  }
    42  
    43  // Get gets the first value associated with the given key. If
    44  // there are no values associated with the key, Get returns "".
    45  // It is case insensitive; textproto.CanonicalMIMEHeaderKey is
    46  // used to canonicalize the provided key. To use non-canonical keys,
    47  // access the map directly.
    48  func (h Header) Get(key string) string {
    49  	return textproto.MIMEHeader(h).Get(key)
    50  }
    51  
    52  // Values returns all values associated with the given key.
    53  // It is case insensitive; textproto.CanonicalMIMEHeaderKey is
    54  // used to canonicalize the provided key. To use non-canonical
    55  // keys, access the map directly.
    56  // The returned slice is not a copy.
    57  func (h Header) Values(key string) []string {
    58  	return textproto.MIMEHeader(h).Values(key)
    59  }
    60  
    61  // get is like Get, but key must already be in CanonicalHeaderKey form.
    62  func (h Header) get(key string) string {
    63  	if v := h[key]; len(v) > 0 {
    64  		return v[0]
    65  	}
    66  	return ""
    67  }
    68  
    69  // has reports whether h has the provided key defined, even if it's
    70  // set to 0-length slice.
    71  func (h Header) has(key string) bool {
    72  	_, ok := h[key]
    73  	return ok
    74  }
    75  
    76  // Del deletes the values associated with key.
    77  // The key is case insensitive; it is canonicalized by
    78  // CanonicalHeaderKey.
    79  func (h Header) Del(key string) {
    80  	textproto.MIMEHeader(h).Del(key)
    81  }
    82  
    83  // Write writes a header in wire format.
    84  func (h Header) Write(w io.Writer) error {
    85  	return h.write(w, nil)
    86  }
    87  
    88  func (h Header) write(w io.Writer, trace *httptrace.ClientTrace) error {
    89  	return h.writeSubset(w, nil, trace)
    90  }
    91  
    92  // Clone returns a copy of h or nil if h is nil.
    93  func (h Header) Clone() Header {
    94  	if h == nil {
    95  		return nil
    96  	}
    97  
    98  	// Find total number of values.
    99  	nv := 0
   100  	for _, vv := range h {
   101  		nv += len(vv)
   102  	}
   103  	sv := make([]string, nv) // shared backing array for headers' values
   104  	h2 := make(Header, len(h))
   105  	for k, vv := range h {
   106  		n := copy(sv, vv)
   107  		h2[k] = sv[:n:n]
   108  		sv = sv[n:]
   109  	}
   110  	return h2
   111  }
   112  
   113  var timeFormats = []string{
   114  	TimeFormat,
   115  	time.RFC850,
   116  	time.ANSIC,
   117  }
   118  
   119  // ParseTime parses a time header (such as the Date: header),
   120  // trying each of the three formats allowed by HTTP/1.1:
   121  // TimeFormat, time.RFC850, and time.ANSIC.
   122  func ParseTime(text string) (t time.Time, err error) {
   123  	for _, layout := range timeFormats {
   124  		t, err = time.Parse(layout, text)
   125  		if err == nil {
   126  			return
   127  		}
   128  	}
   129  	return
   130  }
   131  
   132  var headerNewlineToSpace = strings.NewReplacer("\n", " ", "\r", " ")
   133  
   134  // stringWriter implements WriteString on a Writer.
   135  type stringWriter struct {
   136  	w io.Writer
   137  }
   138  
   139  func (w stringWriter) WriteString(s string) (n int, err error) {
   140  	return w.w.Write([]byte(s))
   141  }
   142  
   143  type keyValues struct {
   144  	key    string
   145  	values []string
   146  }
   147  
   148  // A headerSorter implements sort.Interface by sorting a []keyValues
   149  // by key. It's used as a pointer, so it can fit in a sort.Interface
   150  // interface value without allocation.
   151  type headerSorter struct {
   152  	kvs []keyValues
   153  }
   154  
   155  func (s *headerSorter) Len() int           { return len(s.kvs) }
   156  func (s *headerSorter) Swap(i, j int)      { s.kvs[i], s.kvs[j] = s.kvs[j], s.kvs[i] }
   157  func (s *headerSorter) Less(i, j int) bool { return s.kvs[i].key < s.kvs[j].key }
   158  
   159  var headerSorterPool = sync.Pool{
   160  	New: func() any { return new(headerSorter) },
   161  }
   162  
   163  // sortedKeyValues returns h's keys sorted in the returned kvs
   164  // slice. The headerSorter used to sort is also returned, for possible
   165  // return to headerSorterCache.
   166  func (h Header) sortedKeyValues(exclude map[string]bool) (kvs []keyValues, hs *headerSorter) {
   167  	hs = headerSorterPool.Get().(*headerSorter)
   168  	if cap(hs.kvs) < len(h) {
   169  		hs.kvs = make([]keyValues, 0, len(h))
   170  	}
   171  	kvs = hs.kvs[:0]
   172  	for k, vv := range h {
   173  		if !exclude[k] {
   174  			kvs = append(kvs, keyValues{k, vv})
   175  		}
   176  	}
   177  	hs.kvs = kvs
   178  	sort.Sort(hs)
   179  	return kvs, hs
   180  }
   181  
   182  // WriteSubset writes a header in wire format.
   183  // If exclude is not nil, keys where exclude[key] == true are not written.
   184  // Keys are not canonicalized before checking the exclude map.
   185  func (h Header) WriteSubset(w io.Writer, exclude map[string]bool) error {
   186  	return h.writeSubset(w, exclude, nil)
   187  }
   188  
   189  func (h Header) writeSubset(w io.Writer, exclude map[string]bool, trace *httptrace.ClientTrace) error {
   190  	ws, ok := w.(io.StringWriter)
   191  	if !ok {
   192  		ws = stringWriter{w}
   193  	}
   194  	kvs, sorter := h.sortedKeyValues(exclude)
   195  	var formattedVals []string
   196  	for _, kv := range kvs {
   197  		if !httpguts.ValidHeaderFieldName(kv.key) {
   198  			// This could be an error. In the common case of
   199  			// writing response headers, however, we have no good
   200  			// way to provide the error back to the server
   201  			// handler, so just drop invalid headers instead.
   202  			continue
   203  		}
   204  		for _, v := range kv.values {
   205  			v = headerNewlineToSpace.Replace(v)
   206  			v = textproto.TrimString(v)
   207  			for _, s := range []string{kv.key, ": ", v, "\r\n"} {
   208  				if _, err := ws.WriteString(s); err != nil {
   209  					headerSorterPool.Put(sorter)
   210  					return err
   211  				}
   212  			}
   213  			if trace != nil && trace.WroteHeaderField != nil {
   214  				formattedVals = append(formattedVals, v)
   215  			}
   216  		}
   217  		if trace != nil && trace.WroteHeaderField != nil {
   218  			trace.WroteHeaderField(kv.key, formattedVals)
   219  			formattedVals = nil
   220  		}
   221  	}
   222  	headerSorterPool.Put(sorter)
   223  	return nil
   224  }
   225  
   226  // CanonicalHeaderKey returns the canonical format of the
   227  // header key s. The canonicalization converts the first
   228  // letter and any letter following a hyphen to upper case;
   229  // the rest are converted to lowercase. For example, the
   230  // canonical key for "accept-encoding" is "Accept-Encoding".
   231  // If s contains a space or invalid header field bytes, it is
   232  // returned without modifications.
   233  func CanonicalHeaderKey(s string) string { return textproto.CanonicalMIMEHeaderKey(s) }
   234  
   235  // hasToken reports whether token appears with v, ASCII
   236  // case-insensitive, with space or comma boundaries.
   237  // token must be all lowercase.
   238  // v may contain mixed cased.
   239  func hasToken(v, token string) bool {
   240  	if len(token) > len(v) || token == "" {
   241  		return false
   242  	}
   243  	if v == token {
   244  		return true
   245  	}
   246  	for sp := 0; sp <= len(v)-len(token); sp++ {
   247  		// Check that first character is good.
   248  		// The token is ASCII, so checking only a single byte
   249  		// is sufficient. We skip this potential starting
   250  		// position if both the first byte and its potential
   251  		// ASCII uppercase equivalent (b|0x20) don't match.
   252  		// False positives ('^' => '~') are caught by EqualFold.
   253  		if b := v[sp]; b != token[0] && b|0x20 != token[0] {
   254  			continue
   255  		}
   256  		// Check that start pos is on a valid token boundary.
   257  		if sp > 0 && !isTokenBoundary(v[sp-1]) {
   258  			continue
   259  		}
   260  		// Check that end pos is on a valid token boundary.
   261  		if endPos := sp + len(token); endPos != len(v) && !isTokenBoundary(v[endPos]) {
   262  			continue
   263  		}
   264  		if ascii.EqualFold(v[sp:sp+len(token)], token) {
   265  			return true
   266  		}
   267  	}
   268  	return false
   269  }
   270  
   271  func isTokenBoundary(b byte) bool {
   272  	return b == ' ' || b == ',' || b == '\t'
   273  }
   274  

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