565 lines
14 KiB
Go
565 lines
14 KiB
Go
// Copyright 2011 The Snappy-Go Authors. All rights reserved.
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// Copyright (c) 2019 Klaus Post. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package s2
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import (
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"encoding/binary"
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"errors"
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"io"
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)
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var (
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// ErrCorrupt reports that the input is invalid.
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ErrCorrupt = errors.New("s2: corrupt input")
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// ErrCRC reports that the input failed CRC validation (streams only)
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ErrCRC = errors.New("s2: corrupt input, crc mismatch")
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// ErrTooLarge reports that the uncompressed length is too large.
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ErrTooLarge = errors.New("s2: decoded block is too large")
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// ErrUnsupported reports that the input isn't supported.
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ErrUnsupported = errors.New("s2: unsupported input")
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)
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// DecodedLen returns the length of the decoded block.
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func DecodedLen(src []byte) (int, error) {
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v, _, err := decodedLen(src)
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return v, err
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}
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// decodedLen returns the length of the decoded block and the number of bytes
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// that the length header occupied.
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func decodedLen(src []byte) (blockLen, headerLen int, err error) {
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v, n := binary.Uvarint(src)
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if n <= 0 || v > 0xffffffff {
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return 0, 0, ErrCorrupt
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}
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const wordSize = 32 << (^uint(0) >> 32 & 1)
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if wordSize == 32 && v > 0x7fffffff {
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return 0, 0, ErrTooLarge
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}
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return int(v), n, nil
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}
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const (
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decodeErrCodeCorrupt = 1
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)
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// Decode returns the decoded form of src. The returned slice may be a sub-
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// slice of dst if dst was large enough to hold the entire decoded block.
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// Otherwise, a newly allocated slice will be returned.
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//
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// The dst and src must not overlap. It is valid to pass a nil dst.
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func Decode(dst, src []byte) ([]byte, error) {
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dLen, s, err := decodedLen(src)
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if err != nil {
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return nil, err
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}
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if dLen <= cap(dst) {
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dst = dst[:dLen]
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} else {
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dst = make([]byte, dLen)
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}
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if s2Decode(dst, src[s:]) != 0 {
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return nil, ErrCorrupt
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}
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return dst, nil
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}
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// NewReader returns a new Reader that decompresses from r, using the framing
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// format described at
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// https://github.com/google/snappy/blob/master/framing_format.txt with S2 changes.
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func NewReader(r io.Reader, opts ...ReaderOption) *Reader {
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nr := Reader{
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r: r,
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maxBlock: maxBlockSize,
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}
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for _, opt := range opts {
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if err := opt(&nr); err != nil {
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nr.err = err
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return &nr
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}
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}
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nr.maxBufSize = MaxEncodedLen(nr.maxBlock) + checksumSize
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if nr.lazyBuf > 0 {
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nr.buf = make([]byte, MaxEncodedLen(nr.lazyBuf)+checksumSize)
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} else {
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nr.buf = make([]byte, MaxEncodedLen(defaultBlockSize)+checksumSize)
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}
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nr.paramsOK = true
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return &nr
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}
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// ReaderOption is an option for creating a decoder.
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type ReaderOption func(*Reader) error
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// ReaderMaxBlockSize allows to control allocations if the stream
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// has been compressed with a smaller WriterBlockSize, or with the default 1MB.
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// Blocks must be this size or smaller to decompress,
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// otherwise the decoder will return ErrUnsupported.
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//
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// For streams compressed with Snappy this can safely be set to 64KB (64 << 10).
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//
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// Default is the maximum limit of 4MB.
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func ReaderMaxBlockSize(blockSize int) ReaderOption {
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return func(r *Reader) error {
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if blockSize > maxBlockSize || blockSize <= 0 {
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return errors.New("s2: block size too large. Must be <= 4MB and > 0")
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}
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if r.lazyBuf == 0 && blockSize < defaultBlockSize {
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r.lazyBuf = blockSize
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}
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r.maxBlock = blockSize
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return nil
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}
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}
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// ReaderAllocBlock allows to control upfront stream allocations
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// and not allocate for frames bigger than this initially.
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// If frames bigger than this is seen a bigger buffer will be allocated.
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//
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// Default is 1MB, which is default output size.
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func ReaderAllocBlock(blockSize int) ReaderOption {
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return func(r *Reader) error {
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if blockSize > maxBlockSize || blockSize < 1024 {
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return errors.New("s2: invalid ReaderAllocBlock. Must be <= 4MB and >= 1024")
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}
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r.lazyBuf = blockSize
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return nil
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}
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}
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// Reader is an io.Reader that can read Snappy-compressed bytes.
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type Reader struct {
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r io.Reader
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err error
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decoded []byte
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buf []byte
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// decoded[i:j] contains decoded bytes that have not yet been passed on.
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i, j int
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// maximum block size allowed.
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maxBlock int
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// maximum expected buffer size.
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maxBufSize int
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// alloc a buffer this size if > 0.
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lazyBuf int
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readHeader bool
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paramsOK bool
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snappyFrame bool
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}
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// ensureBufferSize will ensure that the buffer can take at least n bytes.
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// If false is returned the buffer exceeds maximum allowed size.
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func (r *Reader) ensureBufferSize(n int) bool {
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if len(r.buf) >= n {
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return true
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}
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if n > r.maxBufSize {
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r.err = ErrCorrupt
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return false
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}
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// Realloc buffer.
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r.buf = make([]byte, n)
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return true
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}
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// Reset discards any buffered data, resets all state, and switches the Snappy
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// reader to read from r. This permits reusing a Reader rather than allocating
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// a new one.
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func (r *Reader) Reset(reader io.Reader) {
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if !r.paramsOK {
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return
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}
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r.r = reader
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r.err = nil
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r.i = 0
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r.j = 0
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r.readHeader = false
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}
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func (r *Reader) readFull(p []byte, allowEOF bool) (ok bool) {
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if _, r.err = io.ReadFull(r.r, p); r.err != nil {
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if r.err == io.ErrUnexpectedEOF || (r.err == io.EOF && !allowEOF) {
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r.err = ErrCorrupt
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}
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return false
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}
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return true
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}
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// skipN will skip n bytes.
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// If the supplied reader supports seeking that is used.
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// tmp is used as a temporary buffer for reading.
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// The supplied slice does not need to be the size of the read.
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func (r *Reader) skipN(tmp []byte, n int, allowEOF bool) (ok bool) {
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if rs, ok := r.r.(io.ReadSeeker); ok {
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_, err := rs.Seek(int64(n), io.SeekCurrent)
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if err == nil {
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return true
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}
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if err == io.ErrUnexpectedEOF || (r.err == io.EOF && !allowEOF) {
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r.err = ErrCorrupt
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return false
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}
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}
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for n > 0 {
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if n < len(tmp) {
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tmp = tmp[:n]
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}
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if _, r.err = io.ReadFull(r.r, tmp); r.err != nil {
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if r.err == io.ErrUnexpectedEOF || (r.err == io.EOF && !allowEOF) {
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r.err = ErrCorrupt
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}
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return false
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}
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n -= len(tmp)
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}
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return true
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}
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// Read satisfies the io.Reader interface.
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func (r *Reader) Read(p []byte) (int, error) {
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if r.err != nil {
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return 0, r.err
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}
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for {
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if r.i < r.j {
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n := copy(p, r.decoded[r.i:r.j])
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r.i += n
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return n, nil
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}
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if !r.readFull(r.buf[:4], true) {
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return 0, r.err
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}
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chunkType := r.buf[0]
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if !r.readHeader {
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if chunkType != chunkTypeStreamIdentifier {
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r.err = ErrCorrupt
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return 0, r.err
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}
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r.readHeader = true
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}
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chunkLen := int(r.buf[1]) | int(r.buf[2])<<8 | int(r.buf[3])<<16
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// The chunk types are specified at
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// https://github.com/google/snappy/blob/master/framing_format.txt
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switch chunkType {
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case chunkTypeCompressedData:
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// Section 4.2. Compressed data (chunk type 0x00).
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if chunkLen < checksumSize {
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r.err = ErrCorrupt
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return 0, r.err
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}
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if !r.ensureBufferSize(chunkLen) {
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if r.err == nil {
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r.err = ErrUnsupported
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}
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return 0, r.err
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}
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buf := r.buf[:chunkLen]
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if !r.readFull(buf, false) {
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return 0, r.err
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}
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checksum := uint32(buf[0]) | uint32(buf[1])<<8 | uint32(buf[2])<<16 | uint32(buf[3])<<24
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buf = buf[checksumSize:]
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n, err := DecodedLen(buf)
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if err != nil {
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r.err = err
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return 0, r.err
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}
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if r.snappyFrame && n > maxSnappyBlockSize {
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r.err = ErrCorrupt
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return 0, r.err
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}
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if n > len(r.decoded) {
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if n > r.maxBlock {
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r.err = ErrCorrupt
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return 0, r.err
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}
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r.decoded = make([]byte, n)
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}
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if _, err := Decode(r.decoded, buf); err != nil {
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r.err = err
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return 0, r.err
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}
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if crc(r.decoded[:n]) != checksum {
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r.err = ErrCRC
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return 0, r.err
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}
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r.i, r.j = 0, n
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continue
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case chunkTypeUncompressedData:
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// Section 4.3. Uncompressed data (chunk type 0x01).
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if chunkLen < checksumSize {
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r.err = ErrCorrupt
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return 0, r.err
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}
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if !r.ensureBufferSize(chunkLen) {
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if r.err == nil {
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r.err = ErrUnsupported
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}
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return 0, r.err
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}
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buf := r.buf[:checksumSize]
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if !r.readFull(buf, false) {
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return 0, r.err
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}
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checksum := uint32(buf[0]) | uint32(buf[1])<<8 | uint32(buf[2])<<16 | uint32(buf[3])<<24
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// Read directly into r.decoded instead of via r.buf.
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n := chunkLen - checksumSize
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if r.snappyFrame && n > maxSnappyBlockSize {
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r.err = ErrCorrupt
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return 0, r.err
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}
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if n > len(r.decoded) {
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if n > r.maxBlock {
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r.err = ErrCorrupt
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return 0, r.err
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}
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r.decoded = make([]byte, n)
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}
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if !r.readFull(r.decoded[:n], false) {
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return 0, r.err
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}
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if crc(r.decoded[:n]) != checksum {
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r.err = ErrCRC
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return 0, r.err
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}
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r.i, r.j = 0, n
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continue
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case chunkTypeStreamIdentifier:
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// Section 4.1. Stream identifier (chunk type 0xff).
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if chunkLen != len(magicBody) {
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r.err = ErrCorrupt
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return 0, r.err
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}
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if !r.readFull(r.buf[:len(magicBody)], false) {
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return 0, r.err
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}
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if string(r.buf[:len(magicBody)]) != magicBody {
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if string(r.buf[:len(magicBody)]) != magicBodySnappy {
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r.err = ErrCorrupt
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return 0, r.err
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} else {
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r.snappyFrame = true
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}
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} else {
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r.snappyFrame = false
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}
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continue
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}
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if chunkType <= 0x7f {
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// Section 4.5. Reserved unskippable chunks (chunk types 0x02-0x7f).
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r.err = ErrUnsupported
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return 0, r.err
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}
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// Section 4.4 Padding (chunk type 0xfe).
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// Section 4.6. Reserved skippable chunks (chunk types 0x80-0xfd).
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if chunkLen > maxBlockSize {
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r.err = ErrUnsupported
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return 0, r.err
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}
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if !r.skipN(r.buf, chunkLen, false) {
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return 0, r.err
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}
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}
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}
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// Skip will skip n bytes forward in the decompressed output.
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// For larger skips this consumes less CPU and is faster than reading output and discarding it.
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// CRC is not checked on skipped blocks.
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// io.ErrUnexpectedEOF is returned if the stream ends before all bytes have been skipped.
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// If a decoding error is encountered subsequent calls to Read will also fail.
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func (r *Reader) Skip(n int64) error {
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if n < 0 {
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return errors.New("attempted negative skip")
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}
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if r.err != nil {
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return r.err
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}
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for n > 0 {
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if r.i < r.j {
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// Skip in buffer.
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// decoded[i:j] contains decoded bytes that have not yet been passed on.
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left := int64(r.j - r.i)
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if left >= n {
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r.i += int(n)
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return nil
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}
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n -= int64(r.j - r.i)
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r.i, r.j = 0, 0
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}
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// Buffer empty; read blocks until we have content.
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if !r.readFull(r.buf[:4], true) {
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if r.err == io.EOF {
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r.err = io.ErrUnexpectedEOF
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}
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return r.err
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}
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chunkType := r.buf[0]
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if !r.readHeader {
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if chunkType != chunkTypeStreamIdentifier {
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r.err = ErrCorrupt
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return r.err
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}
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r.readHeader = true
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}
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chunkLen := int(r.buf[1]) | int(r.buf[2])<<8 | int(r.buf[3])<<16
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// The chunk types are specified at
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// https://github.com/google/snappy/blob/master/framing_format.txt
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switch chunkType {
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case chunkTypeCompressedData:
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// Section 4.2. Compressed data (chunk type 0x00).
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if chunkLen < checksumSize {
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r.err = ErrCorrupt
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return r.err
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}
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if !r.ensureBufferSize(chunkLen) {
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if r.err == nil {
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r.err = ErrUnsupported
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}
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return r.err
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}
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buf := r.buf[:chunkLen]
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if !r.readFull(buf, false) {
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return r.err
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}
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checksum := uint32(buf[0]) | uint32(buf[1])<<8 | uint32(buf[2])<<16 | uint32(buf[3])<<24
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buf = buf[checksumSize:]
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dLen, err := DecodedLen(buf)
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if err != nil {
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r.err = err
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return r.err
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}
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if dLen > r.maxBlock {
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r.err = ErrCorrupt
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return r.err
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}
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// Check if destination is within this block
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if int64(dLen) > n {
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if len(r.decoded) < dLen {
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r.decoded = make([]byte, dLen)
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}
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if _, err := Decode(r.decoded, buf); err != nil {
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r.err = err
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return r.err
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}
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if crc(r.decoded[:dLen]) != checksum {
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r.err = ErrCorrupt
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return r.err
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}
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} else {
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// Skip block completely
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n -= int64(dLen)
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dLen = 0
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}
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r.i, r.j = 0, dLen
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continue
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case chunkTypeUncompressedData:
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// Section 4.3. Uncompressed data (chunk type 0x01).
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if chunkLen < checksumSize {
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r.err = ErrCorrupt
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return r.err
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}
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if !r.ensureBufferSize(chunkLen) {
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if r.err != nil {
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r.err = ErrUnsupported
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}
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return r.err
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}
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buf := r.buf[:checksumSize]
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if !r.readFull(buf, false) {
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return r.err
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}
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checksum := uint32(buf[0]) | uint32(buf[1])<<8 | uint32(buf[2])<<16 | uint32(buf[3])<<24
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// Read directly into r.decoded instead of via r.buf.
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n2 := chunkLen - checksumSize
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if n2 > len(r.decoded) {
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if n2 > r.maxBlock {
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r.err = ErrCorrupt
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return r.err
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}
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r.decoded = make([]byte, n2)
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}
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if !r.readFull(r.decoded[:n2], false) {
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return r.err
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}
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if int64(n2) < n {
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if crc(r.decoded[:n2]) != checksum {
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r.err = ErrCorrupt
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return r.err
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}
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}
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r.i, r.j = 0, n2
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continue
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case chunkTypeStreamIdentifier:
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// Section 4.1. Stream identifier (chunk type 0xff).
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if chunkLen != len(magicBody) {
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r.err = ErrCorrupt
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return r.err
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}
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if !r.readFull(r.buf[:len(magicBody)], false) {
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return r.err
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}
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if string(r.buf[:len(magicBody)]) != magicBody {
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if string(r.buf[:len(magicBody)]) != magicBodySnappy {
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r.err = ErrCorrupt
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return r.err
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}
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}
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continue
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}
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|
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if chunkType <= 0x7f {
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// Section 4.5. Reserved unskippable chunks (chunk types 0x02-0x7f).
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r.err = ErrUnsupported
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return r.err
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}
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if chunkLen > maxBlockSize {
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r.err = ErrUnsupported
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return r.err
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}
|
|
// Section 4.4 Padding (chunk type 0xfe).
|
|
// Section 4.6. Reserved skippable chunks (chunk types 0x80-0xfd).
|
|
if !r.skipN(r.buf, chunkLen, false) {
|
|
return r.err
|
|
}
|
|
}
|
|
return 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
|
|
}
|