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// 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.
// You can peek the stream, triggering the callback, by doing a Read with a 0
// byte buffer.
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-0x80] = 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 [0xff - 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
}
// GetBufferCapacity returns the capacity of the internal buffer.
// This might be useful to know when reusing the same reader in combination
// with the lazy buffer option.
func (r *Reader) GetBufferCapacity() int {
return cap(r.buf)
}
// 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("internal 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() || entry == nil {
if entry != nil {
writtenBlocks <- entry
}
continue
}
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)
}
}()
defer func() {
if r.err != nil {
setErr(r.err)
} else if err != nil {
setErr(err)
}
close(queue)
wg.Wait()
if err == nil {
err = aErr
}
written = aWritten
}()
// Reader
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)
entry <- nil
return
}
if !r.ignoreCRC && crc(decoded) != checksum {
writtenBlocks <- decoded
setErr(ErrCRC)
entry <- nil
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, 0x80-0xfd (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.
// Sending a nil function will disable previous callbacks.
// You can peek the stream, triggering the callback, by doing a Read with a 0
// byte buffer.
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-0x80] = fn
return nil
}
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