package patch

R=r
http://go/go-review/1018043

1 files changed, 323 insertions, 0 deletions

diff --git a/src/pkg/patch/patch.go b/src/pkg/patch/patch.go
new file mode 100644
index 000000000..c0fdadb84
--- /dev/null
+++ b/src/pkg/patch/patch.go
@@ -0,0 +1,323 @@
+// 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:len(s)]));
+			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 : len(str)];
+				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, "index ") || hasPrefix(l, "GIT binary patch") {
+				diff, err := ParseGITBinary(oldraw);
+				if err != nil {
+					return nil, err;
+				}
+				p.Diff = diff;
+				break;
+			}
+			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 : len(rest)];
+	}
+	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 : len(b)];
+	}
+
+	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 : len(b)];
+	}
+	return sect[0], sect[1:len(sect)];
+}
+
+// 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):len(s)], 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:len(s)], 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, 0);
+}