header.go

Documentation: net/http

  // Copyright 2010 The Go Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style
  // license that can be found in the LICENSE file.
  
  package http
  
  import (
  	"io"
  	"net/textproto"
  	"sort"
  	"strings"
  	"sync"
  	"time"
  )
  
  var raceEnabled = false // set by race.go
  
  // A Header represents the key-value pairs in an HTTP header.
  type Header map[string][]string
  
  // Add adds the key, value pair to the header.
  // It appends to any existing values associated with key.
  func (h Header) Add(key, value string) {
  	textproto.MIMEHeader(h).Add(key, value)
  }
  
  // Set sets the header entries associated with key to
  // the single element value. It replaces any existing
  // values associated with key.
  func (h Header) Set(key, value string) {
  	textproto.MIMEHeader(h).Set(key, value)
  }
  
  // Get gets the first value associated with the given key.
  // It is case insensitive; textproto.CanonicalMIMEHeaderKey is used
  // to canonicalize the provided key.
  // If there are no values associated with the key, Get returns "".
  // To access multiple values of a key, or to use non-canonical keys,
  // access the map directly.
  func (h Header) Get(key string) string {
  	return textproto.MIMEHeader(h).Get(key)
  }
  
  // get is like Get, but key must already be in CanonicalHeaderKey form.
  func (h Header) get(key string) string {
  	if v := h[key]; len(v) > 0 {
  		return v[0]
  	}
  	return ""
  }
  
  // Del deletes the values associated with key.
  func (h Header) Del(key string) {
  	textproto.MIMEHeader(h).Del(key)
  }
  
  // Write writes a header in wire format.
  func (h Header) Write(w io.Writer) error {
  	return h.WriteSubset(w, nil)
  }
  
  func (h Header) clone() Header {
  	h2 := make(Header, len(h))
  	for k, vv := range h {
  		vv2 := make([]string, len(vv))
  		copy(vv2, vv)
  		h2[k] = vv2
  	}
  	return h2
  }
  
  var timeFormats = []string{
  	TimeFormat,
  	time.RFC850,
  	time.ANSIC,
  }
  
  // ParseTime parses a time header (such as the Date: header),
  // trying each of the three formats allowed by HTTP/1.1:
  // TimeFormat, time.RFC850, and time.ANSIC.
  func ParseTime(text string) (t time.Time, err error) {
  	for _, layout := range timeFormats {
  		t, err = time.Parse(layout, text)
  		if err == nil {
  			return
  		}
  	}
  	return
  }
  
  var headerNewlineToSpace = strings.NewReplacer("\n", " ", "\r", " ")
  
  type writeStringer interface {
  	WriteString(string) (int, error)
  }
  
  // stringWriter implements WriteString on a Writer.
  type stringWriter struct {
  	w io.Writer
  }
  
  func (w stringWriter) WriteString(s string) (n int, err error) {
  	return w.w.Write([]byte(s))
  }
  
  type keyValues struct {
  	key    string
  	values []string
  }
  
  // A headerSorter implements sort.Interface by sorting a []keyValues
  // by key. It's used as a pointer, so it can fit in a sort.Interface
  // interface value without allocation.
  type headerSorter struct {
  	kvs []keyValues
  }
  
  func (s *headerSorter) Len() int           { return len(s.kvs) }
  func (s *headerSorter) Swap(i, j int)      { s.kvs[i], s.kvs[j] = s.kvs[j], s.kvs[i] }
  func (s *headerSorter) Less(i, j int) bool { return s.kvs[i].key < s.kvs[j].key }
  
  var headerSorterPool = sync.Pool{
  	New: func() interface{} { return new(headerSorter) },
  }
  
  // sortedKeyValues returns h's keys sorted in the returned kvs
  // slice. The headerSorter used to sort is also returned, for possible
  // return to headerSorterCache.
  func (h Header) sortedKeyValues(exclude map[string]bool) (kvs []keyValues, hs *headerSorter) {
  	hs = headerSorterPool.Get().(*headerSorter)
  	if cap(hs.kvs) < len(h) {
  		hs.kvs = make([]keyValues, 0, len(h))
  	}
  	kvs = hs.kvs[:0]
  	for k, vv := range h {
  		if !exclude[k] {
  			kvs = append(kvs, keyValues{k, vv})
  		}
  	}
  	hs.kvs = kvs
  	sort.Sort(hs)
  	return kvs, hs
  }
  
  // WriteSubset writes a header in wire format.
  // If exclude is not nil, keys where exclude[key] == true are not written.
  func (h Header) WriteSubset(w io.Writer, exclude map[string]bool) error {
  	ws, ok := w.(writeStringer)
  	if !ok {
  		ws = stringWriter{w}
  	}
  	kvs, sorter := h.sortedKeyValues(exclude)
  	for _, kv := range kvs {
  		for _, v := range kv.values {
  			v = headerNewlineToSpace.Replace(v)
  			v = textproto.TrimString(v)
  			for _, s := range []string{kv.key, ": ", v, "\r\n"} {
  				if _, err := ws.WriteString(s); err != nil {
  					return err
  				}
  			}
  		}
  	}
  	headerSorterPool.Put(sorter)
  	return nil
  }
  
  // CanonicalHeaderKey returns the canonical format of the
  // header key s. The canonicalization converts the first
  // letter and any letter following a hyphen to upper case;
  // the rest are converted to lowercase. For example, the
  // canonical key for "accept-encoding" is "Accept-Encoding".
  // If s contains a space or invalid header field bytes, it is
  // returned without modifications.
  func CanonicalHeaderKey(s string) string { return textproto.CanonicalMIMEHeaderKey(s) }
  
  // hasToken reports whether token appears with v, ASCII
  // case-insensitive, with space or comma boundaries.
  // token must be all lowercase.
  // v may contain mixed cased.
  func hasToken(v, token string) bool {
  	if len(token) > len(v) || token == "" {
  		return false
  	}
  	if v == token {
  		return true
  	}
  	for sp := 0; sp <= len(v)-len(token); sp++ {
  		// Check that first character is good.
  		// The token is ASCII, so checking only a single byte
  		// is sufficient. We skip this potential starting
  		// position if both the first byte and its potential
  		// ASCII uppercase equivalent (b|0x20) don't match.
  		// False positives ('^' => '~') are caught by EqualFold.
  		if b := v[sp]; b != token[0] && b|0x20 != token[0] {
  			continue
  		}
  		// Check that start pos is on a valid token boundary.
  		if sp > 0 && !isTokenBoundary(v[sp-1]) {
  			continue
  		}
  		// Check that end pos is on a valid token boundary.
  		if endPos := sp + len(token); endPos != len(v) && !isTokenBoundary(v[endPos]) {
  			continue
  		}
  		if strings.EqualFold(v[sp:sp+len(token)], token) {
  			return true
  		}
  	}
  	return false
  }
  
  func isTokenBoundary(b byte) bool {
  	return b == ' ' || b == ',' || b == '\t'
  }
  
  func cloneHeader(h Header) Header {
  	h2 := make(Header, len(h))
  	for k, vv := range h {
  		vv2 := make([]string, len(vv))
  		copy(vv2, vv)
  		h2[k] = vv2
  	}
  	return h2
  }
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