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-rw-r--r--vendor/github.com/klauspost/compress/s2/reader.go1055
1 files changed, 1055 insertions, 0 deletions
diff --git a/vendor/github.com/klauspost/compress/s2/reader.go b/vendor/github.com/klauspost/compress/s2/reader.go
new file mode 100644
index 000000000..8b84baa6d
--- /dev/null
+++ b/vendor/github.com/klauspost/compress/s2/reader.go
@@ -0,0 +1,1055 @@
+// Copyright 2011 The Snappy-Go Authors. All rights reserved.
+// Copyright (c) 2019+ Klaus Post. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package s2
+
+import (
+ "errors"
+ "fmt"
+ "io"
+ "io/ioutil"
+ "math"
+ "runtime"
+ "sync"
+)
+
+// ErrCantSeek is returned if the stream cannot be seeked.
+type ErrCantSeek struct {
+ Reason string
+}
+
+// Error returns the error as string.
+func (e ErrCantSeek) Error() string {
+ return fmt.Sprintf("s2: Can't seek because %s", e.Reason)
+}
+
+// NewReader returns a new Reader that decompresses from r, using the framing
+// format described at
+// https://github.com/google/snappy/blob/master/framing_format.txt with S2 changes.
+func NewReader(r io.Reader, opts ...ReaderOption) *Reader {
+ nr := Reader{
+ r: r,
+ maxBlock: maxBlockSize,
+ }
+ for _, opt := range opts {
+ if err := opt(&nr); err != nil {
+ nr.err = err
+ return &nr
+ }
+ }
+ nr.maxBufSize = MaxEncodedLen(nr.maxBlock) + checksumSize
+ if nr.lazyBuf > 0 {
+ nr.buf = make([]byte, MaxEncodedLen(nr.lazyBuf)+checksumSize)
+ } else {
+ nr.buf = make([]byte, MaxEncodedLen(defaultBlockSize)+checksumSize)
+ }
+ nr.readHeader = nr.ignoreStreamID
+ nr.paramsOK = true
+ return &nr
+}
+
+// ReaderOption is an option for creating a decoder.
+type ReaderOption func(*Reader) error
+
+// ReaderMaxBlockSize allows to control allocations if the stream
+// has been compressed with a smaller WriterBlockSize, or with the default 1MB.
+// Blocks must be this size or smaller to decompress,
+// otherwise the decoder will return ErrUnsupported.
+//
+// For streams compressed with Snappy this can safely be set to 64KB (64 << 10).
+//
+// Default is the maximum limit of 4MB.
+func ReaderMaxBlockSize(blockSize int) ReaderOption {
+ return func(r *Reader) error {
+ if blockSize > maxBlockSize || blockSize <= 0 {
+ return errors.New("s2: block size too large. Must be <= 4MB and > 0")
+ }
+ if r.lazyBuf == 0 && blockSize < defaultBlockSize {
+ r.lazyBuf = blockSize
+ }
+ r.maxBlock = blockSize
+ return nil
+ }
+}
+
+// ReaderAllocBlock allows to control upfront stream allocations
+// and not allocate for frames bigger than this initially.
+// If frames bigger than this is seen a bigger buffer will be allocated.
+//
+// Default is 1MB, which is default output size.
+func ReaderAllocBlock(blockSize int) ReaderOption {
+ return func(r *Reader) error {
+ if blockSize > maxBlockSize || blockSize < 1024 {
+ return errors.New("s2: invalid ReaderAllocBlock. Must be <= 4MB and >= 1024")
+ }
+ r.lazyBuf = blockSize
+ return nil
+ }
+}
+
+// ReaderIgnoreStreamIdentifier will make the reader skip the expected
+// stream identifier at the beginning of the stream.
+// This can be used when serving a stream that has been forwarded to a specific point.
+func ReaderIgnoreStreamIdentifier() ReaderOption {
+ return func(r *Reader) error {
+ r.ignoreStreamID = true
+ return nil
+ }
+}
+
+// ReaderSkippableCB will register a callback for chuncks with the specified ID.
+// ID must be a Reserved skippable chunks ID, 0x80-0xfd (inclusive).
+// For each chunk with the ID, the callback is called with the content.
+// Any returned non-nil error will abort decompression.
+// Only one callback per ID is supported, latest sent will be used.
+func ReaderSkippableCB(id uint8, fn func(r io.Reader) error) ReaderOption {
+ return func(r *Reader) error {
+ if id < 0x80 || id > 0xfd {
+ return fmt.Errorf("ReaderSkippableCB: Invalid id provided, must be 0x80-0xfd (inclusive)")
+ }
+ r.skippableCB[id] = fn
+ return nil
+ }
+}
+
+// ReaderIgnoreCRC will make the reader skip CRC calculation and checks.
+func ReaderIgnoreCRC() ReaderOption {
+ return func(r *Reader) error {
+ r.ignoreCRC = true
+ return nil
+ }
+}
+
+// Reader is an io.Reader that can read Snappy-compressed bytes.
+type Reader struct {
+ r io.Reader
+ err error
+ decoded []byte
+ buf []byte
+ skippableCB [0x80]func(r io.Reader) error
+ blockStart int64 // Uncompressed offset at start of current.
+ index *Index
+
+ // decoded[i:j] contains decoded bytes that have not yet been passed on.
+ i, j int
+ // maximum block size allowed.
+ maxBlock int
+ // maximum expected buffer size.
+ maxBufSize int
+ // alloc a buffer this size if > 0.
+ lazyBuf int
+ readHeader bool
+ paramsOK bool
+ snappyFrame bool
+ ignoreStreamID bool
+ ignoreCRC bool
+}
+
+// ensureBufferSize will ensure that the buffer can take at least n bytes.
+// If false is returned the buffer exceeds maximum allowed size.
+func (r *Reader) ensureBufferSize(n int) bool {
+ if n > r.maxBufSize {
+ r.err = ErrCorrupt
+ return false
+ }
+ if cap(r.buf) >= n {
+ return true
+ }
+ // Realloc buffer.
+ r.buf = make([]byte, n)
+ return true
+}
+
+// Reset discards any buffered data, resets all state, and switches the Snappy
+// reader to read from r. This permits reusing a Reader rather than allocating
+// a new one.
+func (r *Reader) Reset(reader io.Reader) {
+ if !r.paramsOK {
+ return
+ }
+ r.index = nil
+ r.r = reader
+ r.err = nil
+ r.i = 0
+ r.j = 0
+ r.blockStart = 0
+ r.readHeader = r.ignoreStreamID
+}
+
+func (r *Reader) readFull(p []byte, allowEOF bool) (ok bool) {
+ if _, r.err = io.ReadFull(r.r, p); r.err != nil {
+ if r.err == io.ErrUnexpectedEOF || (r.err == io.EOF && !allowEOF) {
+ r.err = ErrCorrupt
+ }
+ return false
+ }
+ return true
+}
+
+// skippable will skip n bytes.
+// If the supplied reader supports seeking that is used.
+// tmp is used as a temporary buffer for reading.
+// The supplied slice does not need to be the size of the read.
+func (r *Reader) skippable(tmp []byte, n int, allowEOF bool, id uint8) (ok bool) {
+ if id < 0x80 {
+ r.err = fmt.Errorf("interbal error: skippable id < 0x80")
+ return false
+ }
+ if fn := r.skippableCB[id-0x80]; fn != nil {
+ rd := io.LimitReader(r.r, int64(n))
+ r.err = fn(rd)
+ if r.err != nil {
+ return false
+ }
+ _, r.err = io.CopyBuffer(ioutil.Discard, rd, tmp)
+ return r.err == nil
+ }
+ if rs, ok := r.r.(io.ReadSeeker); ok {
+ _, err := rs.Seek(int64(n), io.SeekCurrent)
+ if err == nil {
+ return true
+ }
+ if err == io.ErrUnexpectedEOF || (r.err == io.EOF && !allowEOF) {
+ r.err = ErrCorrupt
+ return false
+ }
+ }
+ for n > 0 {
+ if n < len(tmp) {
+ tmp = tmp[:n]
+ }
+ if _, r.err = io.ReadFull(r.r, tmp); r.err != nil {
+ if r.err == io.ErrUnexpectedEOF || (r.err == io.EOF && !allowEOF) {
+ r.err = ErrCorrupt
+ }
+ return false
+ }
+ n -= len(tmp)
+ }
+ return true
+}
+
+// Read satisfies the io.Reader interface.
+func (r *Reader) Read(p []byte) (int, error) {
+ if r.err != nil {
+ return 0, r.err
+ }
+ for {
+ if r.i < r.j {
+ n := copy(p, r.decoded[r.i:r.j])
+ r.i += n
+ return n, nil
+ }
+ if !r.readFull(r.buf[:4], true) {
+ return 0, r.err
+ }
+ chunkType := r.buf[0]
+ if !r.readHeader {
+ if chunkType != chunkTypeStreamIdentifier {
+ r.err = ErrCorrupt
+ return 0, r.err
+ }
+ r.readHeader = true
+ }
+ chunkLen := int(r.buf[1]) | int(r.buf[2])<<8 | int(r.buf[3])<<16
+
+ // The chunk types are specified at
+ // https://github.com/google/snappy/blob/master/framing_format.txt
+ switch chunkType {
+ case chunkTypeCompressedData:
+ r.blockStart += int64(r.j)
+ // Section 4.2. Compressed data (chunk type 0x00).
+ if chunkLen < checksumSize {
+ r.err = ErrCorrupt
+ return 0, r.err
+ }
+ if !r.ensureBufferSize(chunkLen) {
+ if r.err == nil {
+ r.err = ErrUnsupported
+ }
+ return 0, r.err
+ }
+ buf := r.buf[:chunkLen]
+ if !r.readFull(buf, false) {
+ return 0, r.err
+ }
+ checksum := uint32(buf[0]) | uint32(buf[1])<<8 | uint32(buf[2])<<16 | uint32(buf[3])<<24
+ buf = buf[checksumSize:]
+
+ n, err := DecodedLen(buf)
+ if err != nil {
+ r.err = err
+ return 0, r.err
+ }
+ if r.snappyFrame && n > maxSnappyBlockSize {
+ r.err = ErrCorrupt
+ return 0, r.err
+ }
+
+ if n > len(r.decoded) {
+ if n > r.maxBlock {
+ r.err = ErrCorrupt
+ return 0, r.err
+ }
+ r.decoded = make([]byte, n)
+ }
+ if _, err := Decode(r.decoded, buf); err != nil {
+ r.err = err
+ return 0, r.err
+ }
+ if !r.ignoreCRC && crc(r.decoded[:n]) != checksum {
+ r.err = ErrCRC
+ return 0, r.err
+ }
+ r.i, r.j = 0, n
+ continue
+
+ case chunkTypeUncompressedData:
+ r.blockStart += int64(r.j)
+ // Section 4.3. Uncompressed data (chunk type 0x01).
+ if chunkLen < checksumSize {
+ r.err = ErrCorrupt
+ return 0, r.err
+ }
+ if !r.ensureBufferSize(chunkLen) {
+ if r.err == nil {
+ r.err = ErrUnsupported
+ }
+ return 0, r.err
+ }
+ buf := r.buf[:checksumSize]
+ if !r.readFull(buf, false) {
+ return 0, r.err
+ }
+ checksum := uint32(buf[0]) | uint32(buf[1])<<8 | uint32(buf[2])<<16 | uint32(buf[3])<<24
+ // Read directly into r.decoded instead of via r.buf.
+ n := chunkLen - checksumSize
+ if r.snappyFrame && n > maxSnappyBlockSize {
+ r.err = ErrCorrupt
+ return 0, r.err
+ }
+ if n > len(r.decoded) {
+ if n > r.maxBlock {
+ r.err = ErrCorrupt
+ return 0, r.err
+ }
+ r.decoded = make([]byte, n)
+ }
+ if !r.readFull(r.decoded[:n], false) {
+ return 0, r.err
+ }
+ if !r.ignoreCRC && crc(r.decoded[:n]) != checksum {
+ r.err = ErrCRC
+ return 0, r.err
+ }
+ r.i, r.j = 0, n
+ continue
+
+ case chunkTypeStreamIdentifier:
+ // Section 4.1. Stream identifier (chunk type 0xff).
+ if chunkLen != len(magicBody) {
+ r.err = ErrCorrupt
+ return 0, r.err
+ }
+ if !r.readFull(r.buf[:len(magicBody)], false) {
+ return 0, r.err
+ }
+ if string(r.buf[:len(magicBody)]) != magicBody {
+ if string(r.buf[:len(magicBody)]) != magicBodySnappy {
+ r.err = ErrCorrupt
+ return 0, r.err
+ } else {
+ r.snappyFrame = true
+ }
+ } else {
+ r.snappyFrame = false
+ }
+ continue
+ }
+
+ if chunkType <= 0x7f {
+ // Section 4.5. Reserved unskippable chunks (chunk types 0x02-0x7f).
+ // fmt.Printf("ERR chunktype: 0x%x\n", chunkType)
+ r.err = ErrUnsupported
+ return 0, r.err
+ }
+ // Section 4.4 Padding (chunk type 0xfe).
+ // Section 4.6. Reserved skippable chunks (chunk types 0x80-0xfd).
+ if chunkLen > maxChunkSize {
+ // fmt.Printf("ERR chunkLen: 0x%x\n", chunkLen)
+ r.err = ErrUnsupported
+ return 0, r.err
+ }
+
+ // fmt.Printf("skippable: ID: 0x%x, len: 0x%x\n", chunkType, chunkLen)
+ if !r.skippable(r.buf, chunkLen, false, chunkType) {
+ return 0, r.err
+ }
+ }
+}
+
+// DecodeConcurrent will decode the full stream to w.
+// This function should not be combined with reading, seeking or other operations.
+// Up to 'concurrent' goroutines will be used.
+// If <= 0, runtime.NumCPU will be used.
+// On success the number of bytes decompressed nil and is returned.
+// This is mainly intended for bigger streams.
+func (r *Reader) DecodeConcurrent(w io.Writer, concurrent int) (written int64, err error) {
+ if r.i > 0 || r.j > 0 || r.blockStart > 0 {
+ return 0, errors.New("DecodeConcurrent called after ")
+ }
+ if concurrent <= 0 {
+ concurrent = runtime.NumCPU()
+ }
+
+ // Write to output
+ var errMu sync.Mutex
+ var aErr error
+ setErr := func(e error) (ok bool) {
+ errMu.Lock()
+ defer errMu.Unlock()
+ if e == nil {
+ return aErr == nil
+ }
+ if aErr == nil {
+ aErr = e
+ }
+ return false
+ }
+ hasErr := func() (ok bool) {
+ errMu.Lock()
+ v := aErr != nil
+ errMu.Unlock()
+ return v
+ }
+
+ var aWritten int64
+ toRead := make(chan []byte, concurrent)
+ writtenBlocks := make(chan []byte, concurrent)
+ queue := make(chan chan []byte, concurrent)
+ reUse := make(chan chan []byte, concurrent)
+ for i := 0; i < concurrent; i++ {
+ toRead <- make([]byte, 0, r.maxBufSize)
+ writtenBlocks <- make([]byte, 0, r.maxBufSize)
+ reUse <- make(chan []byte, 1)
+ }
+ // Writer
+ var wg sync.WaitGroup
+ wg.Add(1)
+ go func() {
+ defer wg.Done()
+ for toWrite := range queue {
+ entry := <-toWrite
+ reUse <- toWrite
+ if hasErr() {
+ writtenBlocks <- entry
+ continue
+ }
+ n, err := w.Write(entry)
+ want := len(entry)
+ writtenBlocks <- entry
+ if err != nil {
+ setErr(err)
+ continue
+ }
+ if n != want {
+ setErr(io.ErrShortWrite)
+ continue
+ }
+ aWritten += int64(n)
+ }
+ }()
+
+ // Reader
+ defer func() {
+ close(queue)
+ if r.err != nil {
+ err = r.err
+ setErr(r.err)
+ }
+ wg.Wait()
+ if err == nil {
+ err = aErr
+ }
+ written = aWritten
+ }()
+
+ for !hasErr() {
+ if !r.readFull(r.buf[:4], true) {
+ if r.err == io.EOF {
+ r.err = nil
+ }
+ return 0, r.err
+ }
+ chunkType := r.buf[0]
+ if !r.readHeader {
+ if chunkType != chunkTypeStreamIdentifier {
+ r.err = ErrCorrupt
+ return 0, r.err
+ }
+ r.readHeader = true
+ }
+ chunkLen := int(r.buf[1]) | int(r.buf[2])<<8 | int(r.buf[3])<<16
+
+ // The chunk types are specified at
+ // https://github.com/google/snappy/blob/master/framing_format.txt
+ switch chunkType {
+ case chunkTypeCompressedData:
+ r.blockStart += int64(r.j)
+ // Section 4.2. Compressed data (chunk type 0x00).
+ if chunkLen < checksumSize {
+ r.err = ErrCorrupt
+ return 0, r.err
+ }
+ if chunkLen > r.maxBufSize {
+ r.err = ErrCorrupt
+ return 0, r.err
+ }
+ orgBuf := <-toRead
+ buf := orgBuf[:chunkLen]
+
+ if !r.readFull(buf, false) {
+ return 0, r.err
+ }
+
+ checksum := uint32(buf[0]) | uint32(buf[1])<<8 | uint32(buf[2])<<16 | uint32(buf[3])<<24
+ buf = buf[checksumSize:]
+
+ n, err := DecodedLen(buf)
+ if err != nil {
+ r.err = err
+ return 0, r.err
+ }
+ if r.snappyFrame && n > maxSnappyBlockSize {
+ r.err = ErrCorrupt
+ return 0, r.err
+ }
+
+ if n > r.maxBlock {
+ r.err = ErrCorrupt
+ return 0, r.err
+ }
+ wg.Add(1)
+
+ decoded := <-writtenBlocks
+ entry := <-reUse
+ queue <- entry
+ go func() {
+ defer wg.Done()
+ decoded = decoded[:n]
+ _, err := Decode(decoded, buf)
+ toRead <- orgBuf
+ if err != nil {
+ writtenBlocks <- decoded
+ setErr(err)
+ return
+ }
+ if !r.ignoreCRC && crc(decoded) != checksum {
+ writtenBlocks <- decoded
+ setErr(ErrCRC)
+ return
+ }
+ entry <- decoded
+ }()
+ continue
+
+ case chunkTypeUncompressedData:
+
+ // Section 4.3. Uncompressed data (chunk type 0x01).
+ if chunkLen < checksumSize {
+ r.err = ErrCorrupt
+ return 0, r.err
+ }
+ if chunkLen > r.maxBufSize {
+ r.err = ErrCorrupt
+ return 0, r.err
+ }
+ // Grab write buffer
+ orgBuf := <-writtenBlocks
+ buf := orgBuf[:checksumSize]
+ if !r.readFull(buf, false) {
+ return 0, r.err
+ }
+ checksum := uint32(buf[0]) | uint32(buf[1])<<8 | uint32(buf[2])<<16 | uint32(buf[3])<<24
+ // Read content.
+ n := chunkLen - checksumSize
+
+ if r.snappyFrame && n > maxSnappyBlockSize {
+ r.err = ErrCorrupt
+ return 0, r.err
+ }
+ if n > r.maxBlock {
+ r.err = ErrCorrupt
+ return 0, r.err
+ }
+ // Read uncompressed
+ buf = orgBuf[:n]
+ if !r.readFull(buf, false) {
+ return 0, r.err
+ }
+
+ if !r.ignoreCRC && crc(buf) != checksum {
+ r.err = ErrCRC
+ return 0, r.err
+ }
+ entry := <-reUse
+ queue <- entry
+ entry <- buf
+ continue
+
+ case chunkTypeStreamIdentifier:
+ // Section 4.1. Stream identifier (chunk type 0xff).
+ if chunkLen != len(magicBody) {
+ r.err = ErrCorrupt
+ return 0, r.err
+ }
+ if !r.readFull(r.buf[:len(magicBody)], false) {
+ return 0, r.err
+ }
+ if string(r.buf[:len(magicBody)]) != magicBody {
+ if string(r.buf[:len(magicBody)]) != magicBodySnappy {
+ r.err = ErrCorrupt
+ return 0, r.err
+ } else {
+ r.snappyFrame = true
+ }
+ } else {
+ r.snappyFrame = false
+ }
+ continue
+ }
+
+ if chunkType <= 0x7f {
+ // Section 4.5. Reserved unskippable chunks (chunk types 0x02-0x7f).
+ // fmt.Printf("ERR chunktype: 0x%x\n", chunkType)
+ r.err = ErrUnsupported
+ return 0, r.err
+ }
+ // Section 4.4 Padding (chunk type 0xfe).
+ // Section 4.6. Reserved skippable chunks (chunk types 0x80-0xfd).
+ if chunkLen > maxChunkSize {
+ // fmt.Printf("ERR chunkLen: 0x%x\n", chunkLen)
+ r.err = ErrUnsupported
+ return 0, r.err
+ }
+
+ // fmt.Printf("skippable: ID: 0x%x, len: 0x%x\n", chunkType, chunkLen)
+ if !r.skippable(r.buf, chunkLen, false, chunkType) {
+ return 0, r.err
+ }
+ }
+ return 0, r.err
+}
+
+// Skip will skip n bytes forward in the decompressed output.
+// For larger skips this consumes less CPU and is faster than reading output and discarding it.
+// CRC is not checked on skipped blocks.
+// io.ErrUnexpectedEOF is returned if the stream ends before all bytes have been skipped.
+// If a decoding error is encountered subsequent calls to Read will also fail.
+func (r *Reader) Skip(n int64) error {
+ if n < 0 {
+ return errors.New("attempted negative skip")
+ }
+ if r.err != nil {
+ return r.err
+ }
+
+ for n > 0 {
+ if r.i < r.j {
+ // Skip in buffer.
+ // decoded[i:j] contains decoded bytes that have not yet been passed on.
+ left := int64(r.j - r.i)
+ if left >= n {
+ tmp := int64(r.i) + n
+ if tmp > math.MaxInt32 {
+ return errors.New("s2: internal overflow in skip")
+ }
+ r.i = int(tmp)
+ return nil
+ }
+ n -= int64(r.j - r.i)
+ r.i = r.j
+ }
+
+ // Buffer empty; read blocks until we have content.
+ if !r.readFull(r.buf[:4], true) {
+ if r.err == io.EOF {
+ r.err = io.ErrUnexpectedEOF
+ }
+ return r.err
+ }
+ chunkType := r.buf[0]
+ if !r.readHeader {
+ if chunkType != chunkTypeStreamIdentifier {
+ r.err = ErrCorrupt
+ return r.err
+ }
+ r.readHeader = true
+ }
+ chunkLen := int(r.buf[1]) | int(r.buf[2])<<8 | int(r.buf[3])<<16
+
+ // The chunk types are specified at
+ // https://github.com/google/snappy/blob/master/framing_format.txt
+ switch chunkType {
+ case chunkTypeCompressedData:
+ r.blockStart += int64(r.j)
+ // Section 4.2. Compressed data (chunk type 0x00).
+ if chunkLen < checksumSize {
+ r.err = ErrCorrupt
+ return r.err
+ }
+ if !r.ensureBufferSize(chunkLen) {
+ if r.err == nil {
+ r.err = ErrUnsupported
+ }
+ return r.err
+ }
+ buf := r.buf[:chunkLen]
+ if !r.readFull(buf, false) {
+ return r.err
+ }
+ checksum := uint32(buf[0]) | uint32(buf[1])<<8 | uint32(buf[2])<<16 | uint32(buf[3])<<24
+ buf = buf[checksumSize:]
+
+ dLen, err := DecodedLen(buf)
+ if err != nil {
+ r.err = err
+ return r.err
+ }
+ if dLen > r.maxBlock {
+ r.err = ErrCorrupt
+ return r.err
+ }
+ // Check if destination is within this block
+ if int64(dLen) > n {
+ if len(r.decoded) < dLen {
+ r.decoded = make([]byte, dLen)
+ }
+ if _, err := Decode(r.decoded, buf); err != nil {
+ r.err = err
+ return r.err
+ }
+ if crc(r.decoded[:dLen]) != checksum {
+ r.err = ErrCorrupt
+ return r.err
+ }
+ } else {
+ // Skip block completely
+ n -= int64(dLen)
+ r.blockStart += int64(dLen)
+ dLen = 0
+ }
+ r.i, r.j = 0, dLen
+ continue
+ case chunkTypeUncompressedData:
+ r.blockStart += int64(r.j)
+ // Section 4.3. Uncompressed data (chunk type 0x01).
+ if chunkLen < checksumSize {
+ r.err = ErrCorrupt
+ return r.err
+ }
+ if !r.ensureBufferSize(chunkLen) {
+ if r.err != nil {
+ r.err = ErrUnsupported
+ }
+ return r.err
+ }
+ buf := r.buf[:checksumSize]
+ if !r.readFull(buf, false) {
+ return r.err
+ }
+ checksum := uint32(buf[0]) | uint32(buf[1])<<8 | uint32(buf[2])<<16 | uint32(buf[3])<<24
+ // Read directly into r.decoded instead of via r.buf.
+ n2 := chunkLen - checksumSize
+ if n2 > len(r.decoded) {
+ if n2 > r.maxBlock {
+ r.err = ErrCorrupt
+ return r.err
+ }
+ r.decoded = make([]byte, n2)
+ }
+ if !r.readFull(r.decoded[:n2], false) {
+ return r.err
+ }
+ if int64(n2) < n {
+ if crc(r.decoded[:n2]) != checksum {
+ r.err = ErrCorrupt
+ return r.err
+ }
+ }
+ r.i, r.j = 0, n2
+ continue
+ case chunkTypeStreamIdentifier:
+ // Section 4.1. Stream identifier (chunk type 0xff).
+ if chunkLen != len(magicBody) {
+ r.err = ErrCorrupt
+ return r.err
+ }
+ if !r.readFull(r.buf[:len(magicBody)], false) {
+ return r.err
+ }
+ if string(r.buf[:len(magicBody)]) != magicBody {
+ if string(r.buf[:len(magicBody)]) != magicBodySnappy {
+ r.err = ErrCorrupt
+ return r.err
+ }
+ }
+
+ continue
+ }
+
+ if chunkType <= 0x7f {
+ // Section 4.5. Reserved unskippable chunks (chunk types 0x02-0x7f).
+ r.err = ErrUnsupported
+ return r.err
+ }
+ if chunkLen > maxChunkSize {
+ r.err = ErrUnsupported
+ return r.err
+ }
+ // Section 4.4 Padding (chunk type 0xfe).
+ // Section 4.6. Reserved skippable chunks (chunk types 0x80-0xfd).
+ if !r.skippable(r.buf, chunkLen, false, chunkType) {
+ return r.err
+ }
+ }
+ return nil
+}
+
+// ReadSeeker provides random or forward seeking in compressed content.
+// See Reader.ReadSeeker
+type ReadSeeker struct {
+ *Reader
+ readAtMu sync.Mutex
+}
+
+// ReadSeeker will return an io.ReadSeeker and io.ReaderAt
+// compatible version of the reader.
+// If 'random' is specified the returned io.Seeker can be used for
+// random seeking, otherwise only forward seeking is supported.
+// Enabling random seeking requires the original input to support
+// the io.Seeker interface.
+// A custom index can be specified which will be used if supplied.
+// When using a custom index, it will not be read from the input stream.
+// The ReadAt position will affect regular reads and the current position of Seek.
+// So using Read after ReadAt will continue from where the ReadAt stopped.
+// No functions should be used concurrently.
+// The returned ReadSeeker contains a shallow reference to the existing Reader,
+// meaning changes performed to one is reflected in the other.
+func (r *Reader) ReadSeeker(random bool, index []byte) (*ReadSeeker, error) {
+ // Read index if provided.
+ if len(index) != 0 {
+ if r.index == nil {
+ r.index = &Index{}
+ }
+ if _, err := r.index.Load(index); err != nil {
+ return nil, ErrCantSeek{Reason: "loading index returned: " + err.Error()}
+ }
+ }
+
+ // Check if input is seekable
+ rs, ok := r.r.(io.ReadSeeker)
+ if !ok {
+ if !random {
+ return &ReadSeeker{Reader: r}, nil
+ }
+ return nil, ErrCantSeek{Reason: "input stream isn't seekable"}
+ }
+
+ if r.index != nil {
+ // Seekable and index, ok...
+ return &ReadSeeker{Reader: r}, nil
+ }
+
+ // Load from stream.
+ r.index = &Index{}
+
+ // Read current position.
+ pos, err := rs.Seek(0, io.SeekCurrent)
+ if err != nil {
+ return nil, ErrCantSeek{Reason: "seeking input returned: " + err.Error()}
+ }
+ err = r.index.LoadStream(rs)
+ if err != nil {
+ if err == ErrUnsupported {
+ // If we don't require random seeking, reset input and return.
+ if !random {
+ _, err = rs.Seek(pos, io.SeekStart)
+ if err != nil {
+ return nil, ErrCantSeek{Reason: "resetting stream returned: " + err.Error()}
+ }
+ r.index = nil
+ return &ReadSeeker{Reader: r}, nil
+ }
+ return nil, ErrCantSeek{Reason: "input stream does not contain an index"}
+ }
+ return nil, ErrCantSeek{Reason: "reading index returned: " + err.Error()}
+ }
+
+ // reset position.
+ _, err = rs.Seek(pos, io.SeekStart)
+ if err != nil {
+ return nil, ErrCantSeek{Reason: "seeking input returned: " + err.Error()}
+ }
+ return &ReadSeeker{Reader: r}, nil
+}
+
+// Seek allows seeking in compressed data.
+func (r *ReadSeeker) Seek(offset int64, whence int) (int64, error) {
+ if r.err != nil {
+ if !errors.Is(r.err, io.EOF) {
+ return 0, r.err
+ }
+ // Reset on EOF
+ r.err = nil
+ }
+
+ // Calculate absolute offset.
+ absOffset := offset
+
+ switch whence {
+ case io.SeekStart:
+ case io.SeekCurrent:
+ absOffset = r.blockStart + int64(r.i) + offset
+ case io.SeekEnd:
+ if r.index == nil {
+ return 0, ErrUnsupported
+ }
+ absOffset = r.index.TotalUncompressed + offset
+ default:
+ r.err = ErrUnsupported
+ return 0, r.err
+ }
+
+ if absOffset < 0 {
+ return 0, errors.New("seek before start of file")
+ }
+
+ if !r.readHeader {
+ // Make sure we read the header.
+ _, r.err = r.Read([]byte{})
+ if r.err != nil {
+ return 0, r.err
+ }
+ }
+
+ // If we are inside current block no need to seek.
+ // This includes no offset changes.
+ if absOffset >= r.blockStart && absOffset < r.blockStart+int64(r.j) {
+ r.i = int(absOffset - r.blockStart)
+ return r.blockStart + int64(r.i), nil
+ }
+
+ rs, ok := r.r.(io.ReadSeeker)
+ if r.index == nil || !ok {
+ currOffset := r.blockStart + int64(r.i)
+ if absOffset >= currOffset {
+ err := r.Skip(absOffset - currOffset)
+ return r.blockStart + int64(r.i), err
+ }
+ return 0, ErrUnsupported
+ }
+
+ // We can seek and we have an index.
+ c, u, err := r.index.Find(absOffset)
+ if err != nil {
+ return r.blockStart + int64(r.i), err
+ }
+
+ // Seek to next block
+ _, err = rs.Seek(c, io.SeekStart)
+ if err != nil {
+ return 0, err
+ }
+
+ r.i = r.j // Remove rest of current block.
+ r.blockStart = u - int64(r.j) // Adjust current block start for accounting.
+ if u < absOffset {
+ // Forward inside block
+ return absOffset, r.Skip(absOffset - u)
+ }
+ if u > absOffset {
+ return 0, fmt.Errorf("s2 seek: (internal error) u (%d) > absOffset (%d)", u, absOffset)
+ }
+ return absOffset, nil
+}
+
+// ReadAt reads len(p) bytes into p starting at offset off in the
+// underlying input source. It returns the number of bytes
+// read (0 <= n <= len(p)) and any error encountered.
+//
+// When ReadAt returns n < len(p), it returns a non-nil error
+// explaining why more bytes were not returned. In this respect,
+// ReadAt is stricter than Read.
+//
+// Even if ReadAt returns n < len(p), it may use all of p as scratch
+// space during the call. If some data is available but not len(p) bytes,
+// ReadAt blocks until either all the data is available or an error occurs.
+// In this respect ReadAt is different from Read.
+//
+// If the n = len(p) bytes returned by ReadAt are at the end of the
+// input source, ReadAt may return either err == EOF or err == nil.
+//
+// If ReadAt is reading from an input source with a seek offset,
+// ReadAt should not affect nor be affected by the underlying
+// seek offset.
+//
+// Clients of ReadAt can execute parallel ReadAt calls on the
+// same input source. This is however not recommended.
+func (r *ReadSeeker) ReadAt(p []byte, offset int64) (int, error) {
+ r.readAtMu.Lock()
+ defer r.readAtMu.Unlock()
+ _, err := r.Seek(offset, io.SeekStart)
+ if err != nil {
+ return 0, err
+ }
+ n := 0
+ for n < len(p) {
+ n2, err := r.Read(p[n:])
+ if err != nil {
+ // This will include io.EOF
+ return n + n2, err
+ }
+ n += n2
+ }
+ return n, nil
+}
+
+// ReadByte satisfies the io.ByteReader interface.
+func (r *Reader) ReadByte() (byte, error) {
+ if r.err != nil {
+ return 0, r.err
+ }
+ if r.i < r.j {
+ c := r.decoded[r.i]
+ r.i++
+ return c, nil
+ }
+ var tmp [1]byte
+ for i := 0; i < 10; i++ {
+ n, err := r.Read(tmp[:])
+ if err != nil {
+ return 0, err
+ }
+ if n == 1 {
+ return tmp[0], nil
+ }
+ }
+ return 0, io.ErrNoProgress
+}
+
+// SkippableCB will register a callback for chunks with the specified ID.
+// ID must be a Reserved skippable chunks ID, 0x80-0xfe (inclusive).
+// For each chunk with the ID, the callback is called with the content.
+// Any returned non-nil error will abort decompression.
+// Only one callback per ID is supported, latest sent will be used.
+// Sending a nil function will disable previous callbacks.
+func (r *Reader) SkippableCB(id uint8, fn func(r io.Reader) error) error {
+ if id < 0x80 || id > chunkTypePadding {
+ return fmt.Errorf("ReaderSkippableCB: Invalid id provided, must be 0x80-0xfe (inclusive)")
+ }
+ r.skippableCB[id] = fn
+ return nil
+}
generated by cgit v1.2.3 (git 2.46.0) at 2025-08-02 16:29:29 +0000