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		"time"
    13	)
    14	
    15	// A Header represents the key-value pairs in an HTTP header.
    16	type Header map[string][]string
    17	
    18	// Add adds the key, value pair to the header.
    19	// It appends to any existing values associated with key.
    20	func (h Header) Add(key, value string) {
    21		textproto.MIMEHeader(h).Add(key, value)
    22	}
    23	
    24	// Set sets the header entries associated with key to
    25	// the single element value.  It replaces any existing
    26	// values associated with key.
    27	func (h Header) Set(key, value string) {
    28		textproto.MIMEHeader(h).Set(key, value)
    29	}
    30	
    31	// Get gets the first value associated with the given key.
    32	// If there are no values associated with the key, Get returns "".
    33	// To access multiple values of a key, access the map directly
    34	// with CanonicalHeaderKey.
    35	func (h Header) Get(key string) string {
    36		return textproto.MIMEHeader(h).Get(key)
    37	}
    38	
    39	// get is like Get, but key must already be in CanonicalHeaderKey form.
    40	func (h Header) get(key string) string {
    41		if v := h[key]; len(v) > 0 {
    42			return v[0]
    43		}
    44		return ""
    45	}
    46	
    47	// Del deletes the values associated with key.
    48	func (h Header) Del(key string) {
    49		textproto.MIMEHeader(h).Del(key)
    50	}
    51	
    52	// Write writes a header in wire format.
    53	func (h Header) Write(w io.Writer) error {
    54		return h.WriteSubset(w, nil)
    55	}
    56	
    57	func (h Header) clone() Header {
    58		h2 := make(Header, len(h))
    59		for k, vv := range h {
    60			vv2 := make([]string, len(vv))
    61			copy(vv2, vv)
    62			h2[k] = vv2
    63		}
    64		return h2
    65	}
    66	
    67	var timeFormats = []string{
    68		TimeFormat,
    69		time.RFC850,
    70		time.ANSIC,
    71	}
    72	
    73	// ParseTime parses a time header (such as the Date: header),
    74	// trying each of the three formats allowed by HTTP/1.1:
    75	// TimeFormat, time.RFC850, and time.ANSIC.
    76	func ParseTime(text string) (t time.Time, err error) {
    77		for _, layout := range timeFormats {
    78			t, err = time.Parse(layout, text)
    79			if err == nil {
    80				return
    81			}
    82		}
    83		return
    84	}
    85	
    86	var headerNewlineToSpace = strings.NewReplacer("\n", " ", "\r", " ")
    87	
    88	type writeStringer interface {
    89		WriteString(string) (int, error)
    90	}
    91	
    92	// stringWriter implements WriteString on a Writer.
    93	type stringWriter struct {
    94		w io.Writer
    95	}
    96	
    97	func (w stringWriter) WriteString(s string) (n int, err error) {
    98		return w.w.Write([]byte(s))
    99	}
   100	
   101	type keyValues struct {
   102		key    string
   103		values []string
   104	}
   105	
   106	// A headerSorter implements sort.Interface by sorting a []keyValues
   107	// by key. It's used as a pointer, so it can fit in a sort.Interface
   108	// interface value without allocation.
   109	type headerSorter struct {
   110		kvs []keyValues
   111	}
   112	
   113	func (s *headerSorter) Len() int           { return len(s.kvs) }
   114	func (s *headerSorter) Swap(i, j int)      { s.kvs[i], s.kvs[j] = s.kvs[j], s.kvs[i] }
   115	func (s *headerSorter) Less(i, j int) bool { return s.kvs[i].key < s.kvs[j].key }
   116	
   117	// TODO: convert this to a sync.Cache (issue 4720)
   118	var headerSorterCache = make(chan *headerSorter, 8)
   119	
   120	// sortedKeyValues returns h's keys sorted in the returned kvs
   121	// slice. The headerSorter used to sort is also returned, for possible
   122	// return to headerSorterCache.
   123	func (h Header) sortedKeyValues(exclude map[string]bool) (kvs []keyValues, hs *headerSorter) {
   124		select {
   125		case hs = <-headerSorterCache:
   126		default:
   127			hs = new(headerSorter)
   128		}
   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		select {
   163		case headerSorterCache <- sorter:
   164		default:
   165		}
   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	func CanonicalHeaderKey(s string) string { return textproto.CanonicalMIMEHeaderKey(s) }
   175	
   176	// hasToken returns whether token appears with v, ASCII
   177	// case-insensitive, with space or comma boundaries.
   178	// token must be all lowercase.
   179	// v may contain mixed cased.
   180	func hasToken(v, token string) bool {
   181		if len(token) > len(v) || token == "" {
   182			return false
   183		}
   184		if v == token {
   185			return true
   186		}
   187		for sp := 0; sp <= len(v)-len(token); sp++ {
   188			// Check that first character is good.
   189			// The token is ASCII, so checking only a single byte
   190			// is sufficient.  We skip this potential starting
   191			// position if both the first byte and its potential
   192			// ASCII uppercase equivalent (b|0x20) don't match.
   193			// False positives ('^' => '~') are caught by EqualFold.
   194			if b := v[sp]; b != token[0] && b|0x20 != token[0] {
   195				continue
   196			}
   197			// Check that start pos is on a valid token boundary.
   198			if sp > 0 && !isTokenBoundary(v[sp-1]) {
   199				continue
   200			}
   201			// Check that end pos is on a valid token boundary.
   202			if endPos := sp + len(token); endPos != len(v) && !isTokenBoundary(v[endPos]) {
   203				continue
   204			}
   205			if strings.EqualFold(v[sp:sp+len(token)], token) {
   206				return true
   207			}
   208		}
   209		return false
   210	}
   211	
   212	func isTokenBoundary(b byte) bool {
   213		return b == ' ' || b == ',' || b == '\t'
   214	}

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