diff options
Diffstat (limited to 'libgo/go/compress/zlib/reader.go')
-rw-r--r-- | libgo/go/compress/zlib/reader.go | 81 |
1 files changed, 55 insertions, 26 deletions
diff --git a/libgo/go/compress/zlib/reader.go b/libgo/go/compress/zlib/reader.go index 9e1aafd..816f1bf 100644 --- a/libgo/go/compress/zlib/reader.go +++ b/libgo/go/compress/zlib/reader.go @@ -51,45 +51,36 @@ type reader struct { scratch [4]byte } -// NewReader creates a new io.ReadCloser. -// Reads from the returned io.ReadCloser read and decompress data from r. +// Resetter resets a ReadCloser returned by NewReader or NewReaderDict to +// to switch to a new underlying Reader. This permits reusing a ReadCloser +// instead of allocating a new one. +type Resetter interface { + // Reset discards any buffered data and resets the Resetter as if it was + // newly initialized with the given reader. + Reset(r io.Reader, dict []byte) error +} + +// NewReader creates a new ReadCloser. +// Reads from the returned ReadCloser read and decompress data from r. // The implementation buffers input and may read more data than necessary from r. // It is the caller's responsibility to call Close on the ReadCloser when done. +// +// The ReadCloser returned by NewReader also implements Resetter. 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. +// +// The ReadCloser returned by NewReaderDict also implements Resetter. func NewReaderDict(r io.Reader, dict []byte) (io.ReadCloser, error) { z := new(reader) - if fr, ok := r.(flate.Reader); ok { - z.r = fr - } else { - z.r = bufio.NewReader(r) - } - _, err := io.ReadFull(z.r, z.scratch[0:2]) + err := z.Reset(r, dict) if err != nil { return nil, err } - h := uint(z.scratch[0])<<8 | uint(z.scratch[1]) - if (z.scratch[0]&0x0f != zlibDeflate) || (h%31 != 0) { - return nil, ErrHeader - } - if z.scratch[1]&0x20 != 0 { - _, err = io.ReadFull(z.r, z.scratch[0:4]) - if err != nil { - return nil, err - } - checksum := uint32(z.scratch[0])<<24 | uint32(z.scratch[1])<<16 | uint32(z.scratch[2])<<8 | uint32(z.scratch[3]) - if checksum != adler32.Checksum(dict) { - return nil, ErrDictionary - } - z.decompressor = flate.NewReaderDict(z.r, dict) - } else { - z.decompressor = flate.NewReader(z.r) - } - z.digest = adler32.New() return z, nil } @@ -130,3 +121,41 @@ func (z *reader) Close() error { z.err = z.decompressor.Close() return z.err } + +func (z *reader) Reset(r io.Reader, dict []byte) error { + if fr, ok := r.(flate.Reader); ok { + z.r = fr + } else { + z.r = bufio.NewReader(r) + } + _, err := io.ReadFull(z.r, z.scratch[0:2]) + if err != nil { + return err + } + h := uint(z.scratch[0])<<8 | uint(z.scratch[1]) + if (z.scratch[0]&0x0f != zlibDeflate) || (h%31 != 0) { + return ErrHeader + } + haveDict := z.scratch[1]&0x20 != 0 + if haveDict { + _, err = io.ReadFull(z.r, z.scratch[0:4]) + if err != nil { + return err + } + checksum := uint32(z.scratch[0])<<24 | uint32(z.scratch[1])<<16 | uint32(z.scratch[2])<<8 | uint32(z.scratch[3]) + if checksum != adler32.Checksum(dict) { + return ErrDictionary + } + } + if z.decompressor == nil { + if haveDict { + z.decompressor = flate.NewReaderDict(z.r, dict) + } else { + z.decompressor = flate.NewReader(z.r) + } + } else { + z.decompressor.(flate.Resetter).Reset(z.r, dict) + } + z.digest = adler32.New() + return nil +} |