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// Copyright 2009 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 patch implements parsing and execution of the textual and
// binary patch descriptions used by version control tools such as
// CVS, Git, Mercurial, and Subversion.
package patch
import (
"bytes"
"os"
"path"
"strings"
)
// A Set represents a set of patches to be applied as a single atomic unit.
// Patch sets are often preceded by a descriptive header.
type Set struct {
Header string // free-form text
File []*File
}
// A File represents a collection of changes to be made to a single file.
type File struct {
Verb Verb
Src string // source for Verb == Copy, Verb == Rename
Dst string
OldMode, NewMode int // 0 indicates not used
Diff // changes to data; == NoDiff if operation does not edit file
}
// A Verb is an action performed on a file.
type Verb string
const (
Add Verb = "add"
Copy Verb = "copy"
Delete Verb = "delete"
Edit Verb = "edit"
Rename Verb = "rename"
)
// A Diff is any object that describes changes to transform
// an old byte stream to a new one.
type Diff interface {
// Apply applies the changes listed in the diff
// to the string s, returning the new version of the string.
// Note that the string s need not be a text string.
Apply(old []byte) (new []byte, err os.Error)
}
// NoDiff is a no-op Diff implementation: it passes the
// old data through unchanged.
var NoDiff Diff = noDiffType(0)
type noDiffType int
func (noDiffType) Apply(old []byte) ([]byte, os.Error) {
return old, nil
}
// A SyntaxError represents a syntax error encountered while parsing a patch.
type SyntaxError string
func (e SyntaxError) String() string { return string(e) }
var newline = []byte{'\n'}
// Parse patches the patch text to create a patch Set.
// The patch text typically comprises a textual header and a sequence
// of file patches, as would be generated by CVS, Subversion,
// Mercurial, or Git.
func Parse(text []byte) (*Set, os.Error) {
// Split text into files.
// CVS and Subversion begin new files with
// Index: file name.
// ==================
// diff -u blah blah
//
// Mercurial and Git use
// diff [--git] a/file/path b/file/path.
//
// First look for Index: lines. If none, fall back on diff lines.
text, files := sections(text, "Index: ")
if len(files) == 0 {
text, files = sections(text, "diff ")
}
set := &Set{string(text), make([]*File, len(files))}
// Parse file header and then
// parse files into patch chunks.
// Each chunk begins with @@.
for i, raw := range files {
p := new(File)
set.File[i] = p
// First line of hdr is the Index: that
// begins the section. After that is the file name.
s, raw, _ := getLine(raw, 1)
if hasPrefix(s, "Index: ") {
p.Dst = string(bytes.TrimSpace(s[7:]))
goto HaveName
} else if hasPrefix(s, "diff ") {
str := string(bytes.TrimSpace(s))
i := strings.LastIndex(str, " b/")
if i >= 0 {
p.Dst = str[i+3:]
goto HaveName
}
}
return nil, SyntaxError("unexpected patch header line: " + string(s))
HaveName:
p.Dst = path.Clean(p.Dst)
if strings.HasPrefix(p.Dst, "../") || strings.HasPrefix(p.Dst, "/") {
return nil, SyntaxError("invalid path: " + p.Dst)
}
// Parse header lines giving file information:
// new file mode %o - file created
// deleted file mode %o - file deleted
// old file mode %o - file mode changed
// new file mode %o - file mode changed
// rename from %s - file renamed from other file
// rename to %s
// copy from %s - file copied from other file
// copy to %s
p.Verb = Edit
for len(raw) > 0 {
oldraw := raw
var l []byte
l, raw, _ = getLine(raw, 1)
l = bytes.TrimSpace(l)
if m, s, ok := atoi(l, "new file mode ", 8); ok && len(s) == 0 {
p.NewMode = m
p.Verb = Add
continue
}
if m, s, ok := atoi(l, "deleted file mode ", 8); ok && len(s) == 0 {
p.OldMode = m
p.Verb = Delete
p.Src = p.Dst
p.Dst = ""
continue
}
if m, s, ok := atoi(l, "old file mode ", 8); ok && len(s) == 0 {
// usually implies p.Verb = "rename" or "copy"
// but we'll get that from the rename or copy line.
p.OldMode = m
continue
}
if m, s, ok := atoi(l, "old mode ", 8); ok && len(s) == 0 {
p.OldMode = m
continue
}
if m, s, ok := atoi(l, "new mode ", 8); ok && len(s) == 0 {
p.NewMode = m
continue
}
if s, ok := skip(l, "rename from "); ok && len(s) > 0 {
p.Src = string(s)
p.Verb = Rename
continue
}
if s, ok := skip(l, "rename to "); ok && len(s) > 0 {
p.Verb = Rename
continue
}
if s, ok := skip(l, "copy from "); ok && len(s) > 0 {
p.Src = string(s)
p.Verb = Copy
continue
}
if s, ok := skip(l, "copy to "); ok && len(s) > 0 {
p.Verb = Copy
continue
}
if s, ok := skip(l, "Binary file "); ok && len(s) > 0 {
// Hg prints
// Binary file foo has changed
// when deleting a binary file.
continue
}
if s, ok := skip(l, "RCS file: "); ok && len(s) > 0 {
// CVS prints
// RCS file: /cvs/plan9/bin/yesterday,v
// retrieving revision 1.1
// for each file.
continue
}
if s, ok := skip(l, "retrieving revision "); ok && len(s) > 0 {
// CVS prints
// RCS file: /cvs/plan9/bin/yesterday,v
// retrieving revision 1.1
// for each file.
continue
}
if hasPrefix(l, "===") || hasPrefix(l, "---") || hasPrefix(l, "+++") || hasPrefix(l, "diff ") {
continue
}
if hasPrefix(l, "@@ -") {
diff, err := ParseTextDiff(oldraw)
if err != nil {
return nil, err
}
p.Diff = diff
break
}
if hasPrefix(l, "GIT binary patch") || (hasPrefix(l, "index ") && !hasPrefix(raw, "--- ")) {
diff, err := ParseGitBinary(oldraw)
if err != nil {
return nil, err
}
p.Diff = diff
break
}
if hasPrefix(l, "index ") {
continue
}
return nil, SyntaxError("unexpected patch header line: " + string(l))
}
if p.Diff == nil {
p.Diff = NoDiff
}
if p.Verb == Edit {
p.Src = p.Dst
}
}
return set, nil
}
// getLine returns the first n lines of data and the remainder.
// If data has no newline, getLine returns data, nil, false
func getLine(data []byte, n int) (first []byte, rest []byte, ok bool) {
rest = data
ok = true
for ; n > 0; n-- {
nl := bytes.Index(rest, newline)
if nl < 0 {
rest = nil
ok = false
break
}
rest = rest[nl+1:]
}
first = data[0 : len(data)-len(rest)]
return
}
// sections returns a collection of file sections,
// each of which begins with a line satisfying prefix.
// text before the first instance of such a line is
// returned separately.
func sections(text []byte, prefix string) ([]byte, [][]byte) {
n := 0
for b := text; ; {
if hasPrefix(b, prefix) {
n++
}
nl := bytes.Index(b, newline)
if nl < 0 {
break
}
b = b[nl+1:]
}
sect := make([][]byte, n+1)
n = 0
for b := text; ; {
if hasPrefix(b, prefix) {
sect[n] = text[0 : len(text)-len(b)]
n++
text = b
}
nl := bytes.Index(b, newline)
if nl < 0 {
sect[n] = text
break
}
b = b[nl+1:]
}
return sect[0], sect[1:]
}
// if s begins with the prefix t, skip returns
// s with that prefix removed and ok == true.
func skip(s []byte, t string) (ss []byte, ok bool) {
if len(s) < len(t) || string(s[0:len(t)]) != t {
return nil, false
}
return s[len(t):], true
}
// if s begins with the prefix t and then is a sequence
// of digits in the given base, atoi returns the number
// represented by the digits and s with the
// prefix and the digits removed.
func atoi(s []byte, t string, base int) (n int, ss []byte, ok bool) {
if s, ok = skip(s, t); !ok {
return
}
var i int
for i = 0; i < len(s) && '0' <= s[i] && s[i] <= byte('0'+base-1); i++ {
n = n*base + int(s[i]-'0')
}
if i == 0 {
return
}
return n, s[i:], true
}
// hasPrefix returns true if s begins with t.
func hasPrefix(s []byte, t string) bool {
_, ok := skip(s, t)
return ok
}
// splitLines returns the result of splitting s into lines.
// The \n on each line is preserved.
func splitLines(s []byte) [][]byte { return bytes.SplitAfter(s, newline, -1) }