netramesh

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