--- /dev/null
+// Copyright 2011 The LevelDB-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.
+
+// Taken from: https://code.google.com/p/leveldb-go/source/browse/leveldb/record/record.go?r=1d5ccbe03246da926391ee12d1c6caae054ff4b0
+// License, authors and contributors informations can be found at bellow URLs respectively:
+// https://code.google.com/p/leveldb-go/source/browse/LICENSE
+// https://code.google.com/p/leveldb-go/source/browse/AUTHORS
+// https://code.google.com/p/leveldb-go/source/browse/CONTRIBUTORS
+
+// Package journal reads and writes sequences of journals. Each journal is a stream
+// of bytes that completes before the next journal starts.
+//
+// When reading, call Next to obtain an io.Reader for the next journal. Next will
+// return io.EOF when there are no more journals. It is valid to call Next
+// without reading the current journal to exhaustion.
+//
+// When writing, call Next to obtain an io.Writer for the next journal. Calling
+// Next finishes the current journal. Call Close to finish the final journal.
+//
+// Optionally, call Flush to finish the current journal and flush the underlying
+// writer without starting a new journal. To start a new journal after flushing,
+// call Next.
+//
+// Neither Readers or Writers are safe to use concurrently.
+//
+// Example code:
+// func read(r io.Reader) ([]string, error) {
+// var ss []string
+// journals := journal.NewReader(r, nil, true, true)
+// for {
+// j, err := journals.Next()
+// if err == io.EOF {
+// break
+// }
+// if err != nil {
+// return nil, err
+// }
+// s, err := ioutil.ReadAll(j)
+// if err != nil {
+// return nil, err
+// }
+// ss = append(ss, string(s))
+// }
+// return ss, nil
+// }
+//
+// func write(w io.Writer, ss []string) error {
+// journals := journal.NewWriter(w)
+// for _, s := range ss {
+// j, err := journals.Next()
+// if err != nil {
+// return err
+// }
+// if _, err := j.Write([]byte(s)), err != nil {
+// return err
+// }
+// }
+// return journals.Close()
+// }
+//
+// The wire format is that the stream is divided into 32KiB blocks, and each
+// block contains a number of tightly packed chunks. Chunks cannot cross block
+// boundaries. The last block may be shorter than 32 KiB. Any unused bytes in a
+// block must be zero.
+//
+// A journal maps to one or more chunks. Each chunk has a 7 byte header (a 4
+// byte checksum, a 2 byte little-endian uint16 length, and a 1 byte chunk type)
+// followed by a payload. The checksum is over the chunk type and the payload.
+//
+// There are four chunk types: whether the chunk is the full journal, or the
+// first, middle or last chunk of a multi-chunk journal. A multi-chunk journal
+// has one first chunk, zero or more middle chunks, and one last chunk.
+//
+// The wire format allows for limited recovery in the face of data corruption:
+// on a format error (such as a checksum mismatch), the reader moves to the
+// next block and looks for the next full or first chunk.
+package journal
+
+import (
+ "encoding/binary"
+ "fmt"
+ "io"
+
+ "github.com/syndtr/goleveldb/leveldb/errors"
+ "github.com/syndtr/goleveldb/leveldb/storage"
+ "github.com/syndtr/goleveldb/leveldb/util"
+)
+
+// These constants are part of the wire format and should not be changed.
+const (
+ fullChunkType = 1
+ firstChunkType = 2
+ middleChunkType = 3
+ lastChunkType = 4
+)
+
+const (
+ blockSize = 32 * 1024
+ headerSize = 7
+)
+
+type flusher interface {
+ Flush() error
+}
+
+// ErrCorrupted is the error type that generated by corrupted block or chunk.
+type ErrCorrupted struct {
+ Size int
+ Reason string
+}
+
+func (e *ErrCorrupted) Error() string {
+ return fmt.Sprintf("leveldb/journal: block/chunk corrupted: %s (%d bytes)", e.Reason, e.Size)
+}
+
+// Dropper is the interface that wrap simple Drop method. The Drop
+// method will be called when the journal reader dropping a block or chunk.
+type Dropper interface {
+ Drop(err error)
+}
+
+// Reader reads journals from an underlying io.Reader.
+type Reader struct {
+ // r is the underlying reader.
+ r io.Reader
+ // the dropper.
+ dropper Dropper
+ // strict flag.
+ strict bool
+ // checksum flag.
+ checksum bool
+ // seq is the sequence number of the current journal.
+ seq int
+ // buf[i:j] is the unread portion of the current chunk's payload.
+ // The low bound, i, excludes the chunk header.
+ i, j int
+ // n is the number of bytes of buf that are valid. Once reading has started,
+ // only the final block can have n < blockSize.
+ n int
+ // last is whether the current chunk is the last chunk of the journal.
+ last bool
+ // err is any accumulated error.
+ err error
+ // buf is the buffer.
+ buf [blockSize]byte
+}
+
+// NewReader returns a new reader. The dropper may be nil, and if
+// strict is true then corrupted or invalid chunk will halt the journal
+// reader entirely.
+func NewReader(r io.Reader, dropper Dropper, strict, checksum bool) *Reader {
+ return &Reader{
+ r: r,
+ dropper: dropper,
+ strict: strict,
+ checksum: checksum,
+ last: true,
+ }
+}
+
+var errSkip = errors.New("leveldb/journal: skipped")
+
+func (r *Reader) corrupt(n int, reason string, skip bool) error {
+ if r.dropper != nil {
+ r.dropper.Drop(&ErrCorrupted{n, reason})
+ }
+ if r.strict && !skip {
+ r.err = errors.NewErrCorrupted(storage.FileDesc{}, &ErrCorrupted{n, reason})
+ return r.err
+ }
+ return errSkip
+}
+
+// nextChunk sets r.buf[r.i:r.j] to hold the next chunk's payload, reading the
+// next block into the buffer if necessary.
+func (r *Reader) nextChunk(first bool) error {
+ for {
+ if r.j+headerSize <= r.n {
+ checksum := binary.LittleEndian.Uint32(r.buf[r.j+0 : r.j+4])
+ length := binary.LittleEndian.Uint16(r.buf[r.j+4 : r.j+6])
+ chunkType := r.buf[r.j+6]
+ unprocBlock := r.n - r.j
+ if checksum == 0 && length == 0 && chunkType == 0 {
+ // Drop entire block.
+ r.i = r.n
+ r.j = r.n
+ return r.corrupt(unprocBlock, "zero header", false)
+ }
+ if chunkType < fullChunkType || chunkType > lastChunkType {
+ // Drop entire block.
+ r.i = r.n
+ r.j = r.n
+ return r.corrupt(unprocBlock, fmt.Sprintf("invalid chunk type %#x", chunkType), false)
+ }
+ r.i = r.j + headerSize
+ r.j = r.j + headerSize + int(length)
+ if r.j > r.n {
+ // Drop entire block.
+ r.i = r.n
+ r.j = r.n
+ return r.corrupt(unprocBlock, "chunk length overflows block", false)
+ } else if r.checksum && checksum != util.NewCRC(r.buf[r.i-1:r.j]).Value() {
+ // Drop entire block.
+ r.i = r.n
+ r.j = r.n
+ return r.corrupt(unprocBlock, "checksum mismatch", false)
+ }
+ if first && chunkType != fullChunkType && chunkType != firstChunkType {
+ chunkLength := (r.j - r.i) + headerSize
+ r.i = r.j
+ // Report the error, but skip it.
+ return r.corrupt(chunkLength, "orphan chunk", true)
+ }
+ r.last = chunkType == fullChunkType || chunkType == lastChunkType
+ return nil
+ }
+
+ // The last block.
+ if r.n < blockSize && r.n > 0 {
+ if !first {
+ return r.corrupt(0, "missing chunk part", false)
+ }
+ r.err = io.EOF
+ return r.err
+ }
+
+ // Read block.
+ n, err := io.ReadFull(r.r, r.buf[:])
+ if err != nil && err != io.EOF && err != io.ErrUnexpectedEOF {
+ return err
+ }
+ if n == 0 {
+ if !first {
+ return r.corrupt(0, "missing chunk part", false)
+ }
+ r.err = io.EOF
+ return r.err
+ }
+ r.i, r.j, r.n = 0, 0, n
+ }
+}
+
+// Next returns a reader for the next journal. It returns io.EOF if there are no
+// more journals. The reader returned becomes stale after the next Next call,
+// and should no longer be used. If strict is false, the reader will returns
+// io.ErrUnexpectedEOF error when found corrupted journal.
+func (r *Reader) Next() (io.Reader, error) {
+ r.seq++
+ if r.err != nil {
+ return nil, r.err
+ }
+ r.i = r.j
+ for {
+ if err := r.nextChunk(true); err == nil {
+ break
+ } else if err != errSkip {
+ return nil, err
+ }
+ }
+ return &singleReader{r, r.seq, nil}, nil
+}
+
+// Reset resets the journal reader, allows reuse of the journal reader. Reset returns
+// last accumulated error.
+func (r *Reader) Reset(reader io.Reader, dropper Dropper, strict, checksum bool) error {
+ r.seq++
+ err := r.err
+ r.r = reader
+ r.dropper = dropper
+ r.strict = strict
+ r.checksum = checksum
+ r.i = 0
+ r.j = 0
+ r.n = 0
+ r.last = true
+ r.err = nil
+ return err
+}
+
+type singleReader struct {
+ r *Reader
+ seq int
+ err error
+}
+
+func (x *singleReader) Read(p []byte) (int, error) {
+ r := x.r
+ if r.seq != x.seq {
+ return 0, errors.New("leveldb/journal: stale reader")
+ }
+ if x.err != nil {
+ return 0, x.err
+ }
+ if r.err != nil {
+ return 0, r.err
+ }
+ for r.i == r.j {
+ if r.last {
+ return 0, io.EOF
+ }
+ x.err = r.nextChunk(false)
+ if x.err != nil {
+ if x.err == errSkip {
+ x.err = io.ErrUnexpectedEOF
+ }
+ return 0, x.err
+ }
+ }
+ n := copy(p, r.buf[r.i:r.j])
+ r.i += n
+ return n, nil
+}
+
+func (x *singleReader) ReadByte() (byte, error) {
+ r := x.r
+ if r.seq != x.seq {
+ return 0, errors.New("leveldb/journal: stale reader")
+ }
+ if x.err != nil {
+ return 0, x.err
+ }
+ if r.err != nil {
+ return 0, r.err
+ }
+ for r.i == r.j {
+ if r.last {
+ return 0, io.EOF
+ }
+ x.err = r.nextChunk(false)
+ if x.err != nil {
+ if x.err == errSkip {
+ x.err = io.ErrUnexpectedEOF
+ }
+ return 0, x.err
+ }
+ }
+ c := r.buf[r.i]
+ r.i++
+ return c, nil
+}
+
+// Writer writes journals to an underlying io.Writer.
+type Writer struct {
+ // w is the underlying writer.
+ w io.Writer
+ // seq is the sequence number of the current journal.
+ seq int
+ // f is w as a flusher.
+ f flusher
+ // buf[i:j] is the bytes that will become the current chunk.
+ // The low bound, i, includes the chunk header.
+ i, j int
+ // buf[:written] has already been written to w.
+ // written is zero unless Flush has been called.
+ written int
+ // first is whether the current chunk is the first chunk of the journal.
+ first bool
+ // pending is whether a chunk is buffered but not yet written.
+ pending bool
+ // err is any accumulated error.
+ err error
+ // buf is the buffer.
+ buf [blockSize]byte
+}
+
+// NewWriter returns a new Writer.
+func NewWriter(w io.Writer) *Writer {
+ f, _ := w.(flusher)
+ return &Writer{
+ w: w,
+ f: f,
+ }
+}
+
+// fillHeader fills in the header for the pending chunk.
+func (w *Writer) fillHeader(last bool) {
+ if w.i+headerSize > w.j || w.j > blockSize {
+ panic("leveldb/journal: bad writer state")
+ }
+ if last {
+ if w.first {
+ w.buf[w.i+6] = fullChunkType
+ } else {
+ w.buf[w.i+6] = lastChunkType
+ }
+ } else {
+ if w.first {
+ w.buf[w.i+6] = firstChunkType
+ } else {
+ w.buf[w.i+6] = middleChunkType
+ }
+ }
+ binary.LittleEndian.PutUint32(w.buf[w.i+0:w.i+4], util.NewCRC(w.buf[w.i+6:w.j]).Value())
+ binary.LittleEndian.PutUint16(w.buf[w.i+4:w.i+6], uint16(w.j-w.i-headerSize))
+}
+
+// writeBlock writes the buffered block to the underlying writer, and reserves
+// space for the next chunk's header.
+func (w *Writer) writeBlock() {
+ _, w.err = w.w.Write(w.buf[w.written:])
+ w.i = 0
+ w.j = headerSize
+ w.written = 0
+}
+
+// writePending finishes the current journal and writes the buffer to the
+// underlying writer.
+func (w *Writer) writePending() {
+ if w.err != nil {
+ return
+ }
+ if w.pending {
+ w.fillHeader(true)
+ w.pending = false
+ }
+ _, w.err = w.w.Write(w.buf[w.written:w.j])
+ w.written = w.j
+}
+
+// Close finishes the current journal and closes the writer.
+func (w *Writer) Close() error {
+ w.seq++
+ w.writePending()
+ if w.err != nil {
+ return w.err
+ }
+ w.err = errors.New("leveldb/journal: closed Writer")
+ return nil
+}
+
+// Flush finishes the current journal, writes to the underlying writer, and
+// flushes it if that writer implements interface{ Flush() error }.
+func (w *Writer) Flush() error {
+ w.seq++
+ w.writePending()
+ if w.err != nil {
+ return w.err
+ }
+ if w.f != nil {
+ w.err = w.f.Flush()
+ return w.err
+ }
+ return nil
+}
+
+// Reset resets the journal writer, allows reuse of the journal writer. Reset
+// will also closes the journal writer if not already.
+func (w *Writer) Reset(writer io.Writer) (err error) {
+ w.seq++
+ if w.err == nil {
+ w.writePending()
+ err = w.err
+ }
+ w.w = writer
+ w.f, _ = writer.(flusher)
+ w.i = 0
+ w.j = 0
+ w.written = 0
+ w.first = false
+ w.pending = false
+ w.err = nil
+ return
+}
+
+// Next returns a writer for the next journal. The writer returned becomes stale
+// after the next Close, Flush or Next call, and should no longer be used.
+func (w *Writer) Next() (io.Writer, error) {
+ w.seq++
+ if w.err != nil {
+ return nil, w.err
+ }
+ if w.pending {
+ w.fillHeader(true)
+ }
+ w.i = w.j
+ w.j = w.j + headerSize
+ // Check if there is room in the block for the header.
+ if w.j > blockSize {
+ // Fill in the rest of the block with zeroes.
+ for k := w.i; k < blockSize; k++ {
+ w.buf[k] = 0
+ }
+ w.writeBlock()
+ if w.err != nil {
+ return nil, w.err
+ }
+ }
+ w.first = true
+ w.pending = true
+ return singleWriter{w, w.seq}, nil
+}
+
+type singleWriter struct {
+ w *Writer
+ seq int
+}
+
+func (x singleWriter) Write(p []byte) (int, error) {
+ w := x.w
+ if w.seq != x.seq {
+ return 0, errors.New("leveldb/journal: stale writer")
+ }
+ if w.err != nil {
+ return 0, w.err
+ }
+ n0 := len(p)
+ for len(p) > 0 {
+ // Write a block, if it is full.
+ if w.j == blockSize {
+ w.fillHeader(false)
+ w.writeBlock()
+ if w.err != nil {
+ return 0, w.err
+ }
+ w.first = false
+ }
+ // Copy bytes into the buffer.
+ n := copy(w.buf[w.j:], p)
+ w.j += n
+ p = p[n:]
+ }
+ return n0, nil
+}
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