internal/edit: copy cmd/internal/edit
Make a copy of cmd/internal/edit for use in this repo.
This copy is taken from rsc.io/edit which is the cleaned up
external version of cmd/internal/edit. (We don't want
an rsc.io dependency in golang.org/x either.)
Change-Id: I9d8ed5d58f61f14e032c613af711fafa050c7f3e
Reviewed-on: https://go-review.googlesource.com/c/tools/+/513736
TryBot-Result: Gopher Robot <gobot@golang.org>
gopls-CI: kokoro <noreply+kokoro@google.com>
Auto-Submit: Russ Cox <rsc@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>
diff --git a/internal/edit/edit.go b/internal/edit/edit.go
new file mode 100644
index 0000000..effb326
--- /dev/null
+++ b/internal/edit/edit.go
@@ -0,0 +1,96 @@
+// 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(old []byte) *Buffer {
+ return &Buffer{old: old}
+}
+
+// Insert inserts the new string at old[pos:pos].
+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})
+}
+
+// Delete deletes the text old[start:end].
+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, ""})
+}
+
+// Replace replaces old[start:end] with new.
+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())
+}
diff --git a/internal/edit/edit_test.go b/internal/edit/edit_test.go
new file mode 100644
index 0000000..0e0c564
--- /dev/null
+++ b/internal/edit/edit_test.go
@@ -0,0 +1,28 @@
+// 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
+
+import "testing"
+
+func TestEdit(t *testing.T) {
+ b := NewBuffer([]byte("0123456789"))
+ b.Insert(8, ",7½,")
+ b.Replace(9, 10, "the-end")
+ b.Insert(10, "!")
+ b.Insert(4, "3.14,")
+ b.Insert(4, "π,")
+ b.Insert(4, "3.15,")
+ b.Replace(3, 4, "three,")
+ want := "012three,3.14,π,3.15,4567,7½,8the-end!"
+
+ s := b.String()
+ if s != want {
+ t.Errorf("b.String() = %q, want %q", s, want)
+ }
+ sb := b.Bytes()
+ if string(sb) != want {
+ t.Errorf("b.Bytes() = %q, want %q", sb, want)
+ }
+}
