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

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