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Diffstat (limited to 'src/pkg/compress/zlib/writer.go')
| -rw-r--r-- | src/pkg/compress/zlib/writer.go | 139 |
1 files changed, 0 insertions, 139 deletions
diff --git a/src/pkg/compress/zlib/writer.go b/src/pkg/compress/zlib/writer.go deleted file mode 100644 index 8f86e9c4c..000000000 --- a/src/pkg/compress/zlib/writer.go +++ /dev/null @@ -1,139 +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 - -import ( - "compress/flate" - "hash" - "hash/adler32" - "io" - "os" -) - -// These constants are copied from the flate package, so that code that imports -// "compress/zlib" does not also have to import "compress/flate". -const ( - NoCompression = flate.NoCompression - BestSpeed = flate.BestSpeed - BestCompression = flate.BestCompression - DefaultCompression = flate.DefaultCompression -) - -// A Writer takes data written to it and writes the compressed -// form of that data to an underlying writer (see NewWriter). -type Writer struct { - w io.Writer - compressor *flate.Writer - digest hash.Hash32 - err os.Error - scratch [4]byte -} - -// NewWriter calls NewWriterLevel with the default compression level. -func NewWriter(w io.Writer) (*Writer, os.Error) { - return NewWriterLevel(w, DefaultCompression) -} - -// NewWriterLevel calls NewWriterDict with no dictionary. -func NewWriterLevel(w io.Writer, level int) (*Writer, os.Error) { - return NewWriterDict(w, level, nil) -} - -// NewWriterDict creates a new io.WriteCloser that satisfies writes by compressing data written to w. -// It is the caller's responsibility to call Close on the WriteCloser when done. -// level is the compression level, which can be DefaultCompression, NoCompression, -// or any integer value between BestSpeed and BestCompression (inclusive). -// dict is the preset dictionary to compress with, or nil to use no dictionary. -func NewWriterDict(w io.Writer, level int, dict []byte) (*Writer, os.Error) { - z := new(Writer) - // ZLIB has a two-byte header (as documented in RFC 1950). - // The first four bits is the CINFO (compression info), which is 7 for the default deflate window size. - // The next four bits is the CM (compression method), which is 8 for deflate. - z.scratch[0] = 0x78 - // The next two bits is the FLEVEL (compression level). The four values are: - // 0=fastest, 1=fast, 2=default, 3=best. - // The next bit, FDICT, is set if a dictionary is given. - // The final five FCHECK bits form a mod-31 checksum. - switch level { - case 0, 1: - z.scratch[1] = 0 << 6 - case 2, 3, 4, 5: - z.scratch[1] = 1 << 6 - case 6, -1: - z.scratch[1] = 2 << 6 - case 7, 8, 9: - z.scratch[1] = 3 << 6 - default: - return nil, os.NewError("level out of range") - } - if dict != nil { - z.scratch[1] |= 1 << 5 - } - z.scratch[1] += uint8(31 - (uint16(z.scratch[0])<<8+uint16(z.scratch[1]))%31) - _, err := w.Write(z.scratch[0:2]) - if err != nil { - return nil, err - } - if dict != nil { - // The next four bytes are the Adler-32 checksum of the dictionary. - checksum := adler32.Checksum(dict) - z.scratch[0] = uint8(checksum >> 24) - z.scratch[1] = uint8(checksum >> 16) - z.scratch[2] = uint8(checksum >> 8) - z.scratch[3] = uint8(checksum >> 0) - _, err = w.Write(z.scratch[0:4]) - if err != nil { - return nil, err - } - } - z.w = w - z.compressor = flate.NewWriterDict(w, level, dict) - z.digest = adler32.New() - return z, nil -} - -func (z *Writer) Write(p []byte) (n int, err os.Error) { - if z.err != nil { - return 0, z.err - } - if len(p) == 0 { - return 0, nil - } - n, err = z.compressor.Write(p) - if err != nil { - z.err = err - return - } - z.digest.Write(p) - return -} - -// Flush flushes the underlying compressor. -func (z *Writer) Flush() os.Error { - if z.err != nil { - return z.err - } - z.err = z.compressor.Flush() - return z.err -} - -// Calling Close does not close the wrapped io.Writer originally passed to NewWriter. -func (z *Writer) Close() os.Error { - if z.err != nil { - return z.err - } - z.err = z.compressor.Close() - if z.err != nil { - return z.err - } - checksum := z.digest.Sum32() - // ZLIB (RFC 1950) is big-endian, unlike GZIP (RFC 1952). - z.scratch[0] = uint8(checksum >> 24) - z.scratch[1] = uint8(checksum >> 16) - z.scratch[2] = uint8(checksum >> 8) - z.scratch[3] = uint8(checksum >> 0) - _, z.err = z.w.Write(z.scratch[0:4]) - return z.err -} |