diff options
Diffstat (limited to 'internal/zlib/reader.go')
| -rw-r--r-- | internal/zlib/reader.go | 198 |
1 files changed, 0 insertions, 198 deletions
diff --git a/internal/zlib/reader.go b/internal/zlib/reader.go deleted file mode 100644 index 2c8fd215..00000000 --- a/internal/zlib/reader.go +++ /dev/null @@ -1,198 +0,0 @@ -// Copyright 2009 The Go Authors. All rights reserved. -// Use of this source code is governed by a BSD-style -// license that can be found in the LICENSE file. - -/* -Package zlib implements reading and writing of zlib format compressed data, -as specified in RFC 1950. - -This package differs from the standard library's compress/zlib package -in that it pools readers to reduce allocations. Writers are unchanged. - -Note that closing the reader causes it to be returned to a pool for -reuse. Therefore, the caller must not retain references to the -reader after closing it; in the standard library's compress/zlib package, -it is legal to Reset a closed reader and continue using it; that is -not allowed here, so there is simply no Resetter interface. - -The implementation provides filters that uncompress during reading -and compress during writing. For example, to write compressed data -to a buffer: - - var b bytes.Buffer - w := zlib.NewWriter(&b) - w.Write([]byte("hello, world\n")) - w.Close() - -and to read that data back: - - r, err := zlib.NewReader(&b) - io.Copy(os.Stdout, r) - r.Close() -*/ -package zlib - -import ( - "bufio" - "encoding/binary" - "errors" - "hash" - "io" - "sync" - - "git.sr.ht/~runxiyu/furgit/internal/adler32" - "git.sr.ht/~runxiyu/furgit/internal/flate" -) - -const ( - zlibDeflate = 8 - zlibMaxWindow = 7 -) - -var ( - // ErrChecksum is returned when reading ZLIB data that has an invalid checksum. - ErrChecksum = errors.New("zlib: invalid checksum") - // ErrDictionary is returned when reading ZLIB data that has an invalid dictionary. - ErrDictionary = errors.New("zlib: invalid dictionary") - // ErrHeader is returned when reading ZLIB data that has an invalid header. - ErrHeader = errors.New("zlib: invalid header") -) - -var pool = sync.Pool{ - New: func() any { - r := new(reader) - return r - }, -} - -type reader struct { - r flate.Reader - decompressor io.ReadCloser - digest hash.Hash32 - err error - scratch [4]byte -} - -// NewReader creates a new ReadCloser. -// Reads from the returned ReadCloser read and decompress data from r. -// If r does not implement [io.ByteReader], the decompressor may read more -// data than necessary from r. -// It is the caller's responsibility to call Close on the ReadCloser when done. -func NewReader(r io.Reader) (io.ReadCloser, error) { - return NewReaderDict(r, nil) -} - -// NewReaderDict is like [NewReader] but uses a preset dictionary. -// NewReaderDict ignores the dictionary if the compressed data does not refer to it. -// If the compressed data refers to a different dictionary, NewReaderDict returns [ErrDictionary]. -func NewReaderDict(r io.Reader, dict []byte) (io.ReadCloser, error) { - v := pool.Get() - z, ok := v.(*reader) - if !ok { - panic("zlib: pool returned unexpected type") - } - err := z.Reset(r, dict) - if err != nil { - return nil, err - } - return z, nil -} - -func (z *reader) Read(p []byte) (int, error) { - if z.err != nil { - return 0, z.err - } - - var n int - n, z.err = z.decompressor.Read(p) - z.digest.Write(p[0:n]) - if z.err != io.EOF { - // In the normal case we return here. - return n, z.err - } - - // Finished file; check checksum. - if _, err := io.ReadFull(z.r, z.scratch[0:4]); err != nil { - if err == io.EOF { - err = io.ErrUnexpectedEOF - } - z.err = err - return n, z.err - } - // ZLIB (RFC 1950) is big-endian, unlike GZIP (RFC 1952). - checksum := binary.BigEndian.Uint32(z.scratch[:4]) - if checksum != z.digest.Sum32() { - z.err = ErrChecksum - return n, z.err - } - return n, io.EOF -} - -// Calling Close does not close the wrapped [io.Reader] originally passed to [NewReader]. -// In order for the ZLIB checksum to be verified, the reader must be -// fully consumed until the [io.EOF]. -func (z *reader) Close() error { - if z.err != nil && z.err != io.EOF { - return z.err - } - z.err = z.decompressor.Close() - if z.err != nil { - return z.err - } - - pool.Put(z) - return nil -} - -func (z *reader) Reset(r io.Reader, dict []byte) error { - *z = reader{decompressor: z.decompressor} - if fr, ok := r.(flate.Reader); ok { - z.r = fr - } else { - z.r = bufio.NewReader(r) - } - - // Read the header (RFC 1950 section 2.2.). - _, z.err = io.ReadFull(z.r, z.scratch[0:2]) - if z.err != nil { - if z.err == io.EOF { - z.err = io.ErrUnexpectedEOF - } - return z.err - } - h := binary.BigEndian.Uint16(z.scratch[:2]) - if (z.scratch[0]&0x0f != zlibDeflate) || (z.scratch[0]>>4 > zlibMaxWindow) || (h%31 != 0) { - z.err = ErrHeader - return z.err - } - haveDict := z.scratch[1]&0x20 != 0 - if haveDict { - _, z.err = io.ReadFull(z.r, z.scratch[0:4]) - if z.err != nil { - if z.err == io.EOF { - z.err = io.ErrUnexpectedEOF - } - return z.err - } - checksum := binary.BigEndian.Uint32(z.scratch[:4]) - if checksum != adler32.Checksum(dict) { - z.err = ErrDictionary - return z.err - } - } - - if z.decompressor == nil { - if haveDict { - z.decompressor = flate.NewReaderDict(z.r, dict) - } else { - z.decompressor = flate.NewReader(z.r) - } - } else { - z.err = z.decompressor.(flate.Resetter).Reset(z.r, dict) - if z.err != nil { - return z.err - } - } - z.digest = adler32.New() - return nil -} |