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|
package patch
import (
"bytes"
"os"
)
type TextDiff []TextChunk
// A TextChunk specifies an edit to a section of a file:
// the text beginning at Line, which should be exactly Old,
// is to be replaced with New.
type TextChunk struct {
Line int
Old []byte
New []byte
}
func ParseTextDiff(raw []byte) (TextDiff, os.Error) {
var chunkHeader []byte
// Copy raw so it is safe to keep references to slices.
_, chunks := sections(raw, "@@ -")
delta := 0
diff := make(TextDiff, len(chunks))
for i, raw := range chunks {
c := &diff[i]
// Parse start line: @@ -oldLine,oldCount +newLine,newCount @@ junk
chunk := splitLines(raw)
chunkHeader = chunk[0]
var ok bool
var oldLine, oldCount, newLine, newCount int
s := chunkHeader
if oldLine, s, ok = atoi(s, "@@ -", 10); !ok {
goto ErrChunkHdr
}
if len(s) == 0 || s[0] != ',' {
oldCount = 1
} else if oldCount, s, ok = atoi(s, ",", 10); !ok {
goto ErrChunkHdr
}
if newLine, s, ok = atoi(s, " +", 10); !ok {
goto ErrChunkHdr
}
if len(s) == 0 || s[0] != ',' {
newCount = 1
} else if newCount, s, ok = atoi(s, ",", 10); !ok {
goto ErrChunkHdr
}
if !hasPrefix(s, " @@") {
goto ErrChunkHdr
}
// Special case: for created or deleted files, the empty half
// is given as starting at line 0. Translate to line 1.
if oldCount == 0 && oldLine == 0 {
oldLine = 1
}
if newCount == 0 && newLine == 0 {
newLine = 1
}
// Count lines in text
var dropOldNL, dropNewNL bool
var nold, nnew int
var lastch byte
chunk = chunk[1:]
for _, l := range chunk {
if nold == oldCount && nnew == newCount && (len(l) == 0 || l[0] != '\\') {
if len(bytes.TrimSpace(l)) != 0 {
return nil, SyntaxError("too many chunk lines")
}
continue
}
if len(l) == 0 {
return nil, SyntaxError("empty chunk line")
}
switch l[0] {
case '+':
nnew++
case '-':
nold++
case ' ':
nnew++
nold++
case '\\':
if _, ok := skip(l, "\\ No newline at end of file"); ok {
switch lastch {
case '-':
dropOldNL = true
case '+':
dropNewNL = true
case ' ':
dropOldNL = true
dropNewNL = true
default:
return nil, SyntaxError("message `\\ No newline at end of file' out of context")
}
break
}
fallthrough
default:
return nil, SyntaxError("unexpected chunk line: " + string(l))
}
lastch = l[0]
}
// Does it match the header?
if nold != oldCount || nnew != newCount {
return nil, SyntaxError("chunk header does not match line count: " + string(chunkHeader))
}
if oldLine+delta != newLine {
return nil, SyntaxError("chunk delta is out of sync with previous chunks")
}
delta += nnew - nold
c.Line = oldLine
var old, new bytes.Buffer
nold = 0
nnew = 0
for _, l := range chunk {
if nold == oldCount && nnew == newCount {
break
}
ch, l := l[0], l[1:]
if ch == '\\' {
continue
}
if ch != '+' {
old.Write(l)
nold++
}
if ch != '-' {
new.Write(l)
nnew++
}
}
c.Old = old.Bytes()
c.New = new.Bytes()
if dropOldNL {
c.Old = c.Old[0 : len(c.Old)-1]
}
if dropNewNL {
c.New = c.New[0 : len(c.New)-1]
}
}
return diff, nil
ErrChunkHdr:
return nil, SyntaxError("unexpected chunk header line: " + string(chunkHeader))
}
var ErrPatchFailure = os.NewError("patch did not apply cleanly")
// Apply applies the changes listed in the diff
// to the data, returning the new version.
func (d TextDiff) Apply(data []byte) ([]byte, os.Error) {
var buf bytes.Buffer
line := 1
for _, c := range d {
var ok bool
var prefix []byte
prefix, data, ok = getLine(data, c.Line-line)
if !ok || !bytes.HasPrefix(data, c.Old) {
return nil, ErrPatchFailure
}
buf.Write(prefix)
data = data[len(c.Old):]
buf.Write(c.New)
line = c.Line + bytes.Count(c.Old, newline)
}
buf.Write(data)
return buf.Bytes(), nil
}
|
