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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/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						return err
   160					}
   161				}
   162			}
   163		}
   164		headerSorterPool.Put(sorter)
   165		return nil
   166	}
   167	
   168	// CanonicalHeaderKey returns the canonical format of the
   169	// header key s. The canonicalization converts the first
   170	// letter and any letter following a hyphen to upper case;
   171	// the rest are converted to lowercase. For example, the
   172	// canonical key for "accept-encoding" is "Accept-Encoding".
   173	// If s contains a space or invalid header field bytes, it is
   174	// returned without modifications.
   175	func CanonicalHeaderKey(s string) string { return textproto.CanonicalMIMEHeaderKey(s) }
   176	
   177	// hasToken reports whether token appears with v, ASCII
   178	// case-insensitive, with space or comma boundaries.
   179	// token must be all lowercase.
   180	// v may contain mixed cased.
   181	func hasToken(v, token string) bool {
   182		if len(token) > len(v) || token == "" {
   183			return false
   184		}
   185		if v == token {
   186			return true
   187		}
   188		for sp := 0; sp <= len(v)-len(token); sp++ {
   189			// Check that first character is good.
   190			// The token is ASCII, so checking only a single byte
   191			// is sufficient. We skip this potential starting
   192			// position if both the first byte and its potential
   193			// ASCII uppercase equivalent (b|0x20) don't match.
   194			// False positives ('^' => '~') are caught by EqualFold.
   195			if b := v[sp]; b != token[0] && b|0x20 != token[0] {
   196				continue
   197			}
   198			// Check that start pos is on a valid token boundary.
   199			if sp > 0 && !isTokenBoundary(v[sp-1]) {
   200				continue
   201			}
   202			// Check that end pos is on a valid token boundary.
   203			if endPos := sp + len(token); endPos != len(v) && !isTokenBoundary(v[endPos]) {
   204				continue
   205			}
   206			if strings.EqualFold(v[sp:sp+len(token)], token) {
   207				return true
   208			}
   209		}
   210		return false
   211	}
   212	
   213	func isTokenBoundary(b byte) bool {
   214		return b == ' ' || b == ',' || b == '\t'
   215	}
   216	
   217	func cloneHeader(h Header) Header {
   218		h2 := make(Header, len(h))
   219		for k, vv := range h {
   220			vv2 := make([]string, len(vv))
   221			copy(vv2, vv)
   222			h2[k] = vv2
   223		}
   224		return h2
   225	}
   226	

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