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// Copyright 2011 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 strings
import (
"io"
"os"
)
// Can't import ioutil for ioutil.Discard, due to ioutil/tempfile.go -> strconv -> strings
var discard io.Writer = devNull(0)
type devNull int
func (devNull) Write(p []byte) (int, os.Error) {
return len(p), nil
}
type pair struct{ old, new string }
// A Replacer replaces a list of strings with replacements.
type Replacer struct {
p []pair
}
// NewReplacer returns a new Replacer from a list of old, new string pairs.
// Replacements are performed in order, without overlapping matches.
func NewReplacer(oldnew ...string) *Replacer {
if len(oldnew)%2 == 1 {
panic("strings.NewReplacer: odd argument count")
}
r := new(Replacer)
for len(oldnew) >= 2 {
r.p = append(r.p, pair{oldnew[0], oldnew[1]})
oldnew = oldnew[2:]
}
return r
}
type appendSliceWriter struct {
b []byte
}
func (w *appendSliceWriter) Write(p []byte) (int, os.Error) {
w.b = append(w.b, p...)
return len(p), nil
}
// Replace returns a copy of s with all replacements performed.
func (r *Replacer) Replace(s string) string {
// TODO(bradfitz): optimized version
n, _ := r.WriteString(discard, s)
w := appendSliceWriter{make([]byte, 0, n)}
r.WriteString(&w, s)
return string(w.b)
}
// WriteString writes s to w with all replacements performed.
func (r *Replacer) WriteString(w io.Writer, s string) (n int, err os.Error) {
Input:
// TODO(bradfitz): optimized version
for i := 0; i < len(s); {
for _, p := range r.p {
if HasPrefix(s[i:], p.old) {
wn, err := w.Write([]byte(p.new))
n += wn
if err != nil {
return n, err
}
i += len(p.old)
continue Input
}
}
wn, err := w.Write([]byte{s[i]})
n += wn
if err != nil {
return n, err
}
i++
}
return n, nil
}
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