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// Copyright 2017 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 edit implements buffered position-based editing of byte slices.
package edit
import (
"fmt"
"sort"
)
// A Buffer is a queue of edits to apply to a given byte slice.
type Buffer struct {
old []byte
q edits
}
// An edit records a single text modification: change the bytes in [start,end) to new.
type edit struct {
start int
end int
new string
}
// An edits is a list of edits that is sortable by start offset, breaking ties by end offset.
type edits []edit
func (x edits) Len() int { return len(x) }
func (x edits) Swap(i, j int) { x[i], x[j] = x[j], x[i] }
func (x edits) Less(i, j int) bool {
if x[i].start != x[j].start {
return x[i].start < x[j].start
}
return x[i].end < x[j].end
}
// NewBuffer returns a new buffer to accumulate changes to an initial data slice.
// The returned buffer maintains a reference to the data, so the caller must ensure
// the data is not modified until after the Buffer is done being used.
func NewBuffer(data []byte) *Buffer {
return &Buffer{old: data}
}
func (b *Buffer) Insert(pos int, new string) {
if pos < 0 || pos > len(b.old) {
panic("invalid edit position")
}
b.q = append(b.q, edit{pos, pos, new})
}
func (b *Buffer) Delete(start, end int) {
if end < start || start < 0 || end > len(b.old) {
panic("invalid edit position")
}
b.q = append(b.q, edit{start, end, ""})
}
func (b *Buffer) Replace(start, end int, new string) {
if end < start || start < 0 || end > len(b.old) {
panic("invalid edit position")
}
b.q = append(b.q, edit{start, end, new})
}
// Bytes returns a new byte slice containing the original data
// with the queued edits applied.
func (b *Buffer) Bytes() []byte {
// Sort edits by starting position and then by ending position.
// Breaking ties by ending position allows insertions at point x
// to be applied before a replacement of the text at [x, y).
sort.Stable(b.q)
var new []byte
offset := 0
for i, e := range b.q {
if e.start < offset {
e0 := b.q[i-1]
panic(fmt.Sprintf("overlapping edits: [%d,%d)->%q, [%d,%d)->%q", e0.start, e0.end, e0.new, e.start, e.end, e.new))
}
new = append(new, b.old[offset:e.start]...)
offset = e.end
new = append(new, e.new...)
}
new = append(new, b.old[offset:]...)
return new
}
// String returns a string containing the original data
// with the queued edits applied.
func (b *Buffer) String() string {
return string(b.Bytes())
}
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