139 lines
3.4 KiB
Go
139 lines
3.4 KiB
Go
// Package gitdiff parses and applies patches generated by Git. It supports
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// line-oriented text patches, binary patches, and can also parse standard
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// unified diffs generated by other tools.
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package gitdiff
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import (
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"bufio"
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"fmt"
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"io"
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)
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// Parse parses a patch with changes to one or more files. Any content before
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// the first file is returned as the second value. If an error occurs while
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// parsing, it returns all files parsed before the error.
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func Parse(r io.Reader) ([]*File, string, error) {
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p := newParser(r)
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if err := p.Next(); err != nil {
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if err == io.EOF {
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return nil, "", nil
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}
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return nil, "", err
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}
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var preamble string
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var files []*File
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for {
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file, pre, err := p.ParseNextFileHeader()
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if err != nil {
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return files, preamble, err
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}
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if file == nil {
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break
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}
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for _, fn := range []func(*File) (int, error){
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p.ParseTextFragments,
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p.ParseBinaryFragments,
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} {
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n, err := fn(file)
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if err != nil {
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return files, preamble, err
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}
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if n > 0 {
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break
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}
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}
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if len(files) == 0 {
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preamble = pre
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}
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files = append(files, file)
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}
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return files, preamble, nil
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}
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// TODO(bkeyes): consider exporting the parser type with configuration
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// this would enable OID validation, p-value guessing, and prefix stripping
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// by allowing users to set or override defaults
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// parser invariants:
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// - methods that parse objects:
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// - start with the parser on the first line of the first object
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// - if returning nil, do not advance
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// - if returning an error, do not advance past the object
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// - if returning an object, advance to the first line after the object
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// - any exported parsing methods must initialize the parser by calling Next()
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type stringReader interface {
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ReadString(delim byte) (string, error)
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}
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type parser struct {
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r stringReader
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eof bool
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lineno int64
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lines [3]string
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}
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func newParser(r io.Reader) *parser {
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if r, ok := r.(stringReader); ok {
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return &parser{r: r}
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}
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return &parser{r: bufio.NewReader(r)}
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}
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// Next advances the parser by one line. It returns any error encountered while
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// reading the line, including io.EOF when the end of stream is reached.
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func (p *parser) Next() error {
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if p.eof {
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return io.EOF
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}
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if p.lineno == 0 {
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// on first call to next, need to shift in all lines
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for i := 0; i < len(p.lines)-1; i++ {
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if err := p.shiftLines(); err != nil && err != io.EOF {
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return err
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}
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}
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}
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err := p.shiftLines()
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if err != nil && err != io.EOF {
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return err
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}
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p.lineno++
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if p.lines[0] == "" {
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p.eof = true
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return io.EOF
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}
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return nil
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}
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func (p *parser) shiftLines() (err error) {
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for i := 0; i < len(p.lines)-1; i++ {
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p.lines[i] = p.lines[i+1]
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}
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p.lines[len(p.lines)-1], err = p.r.ReadString('\n')
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return
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}
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// Line returns a line from the parser without advancing it. A delta of 0
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// returns the current line, while higher deltas return read-ahead lines. It
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// returns an empty string if the delta is higher than the available lines,
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// either because of the buffer size or because the parser reached the end of
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// the input. Valid lines always contain at least a newline character.
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func (p *parser) Line(delta uint) string {
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return p.lines[delta]
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}
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// Errorf generates an error and appends the current line information.
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func (p *parser) Errorf(delta int64, msg string, args ...interface{}) error {
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return fmt.Errorf("gitdiff: line %d: %s", p.lineno+delta, fmt.Sprintf(msg, args...))
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}
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