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Diffstat (limited to 'src/pkg/compress/zlib/writer.go')
-rw-r--r--src/pkg/compress/zlib/writer.go198
1 files changed, 0 insertions, 198 deletions
diff --git a/src/pkg/compress/zlib/writer.go b/src/pkg/compress/zlib/writer.go
deleted file mode 100644
index 3b4313a8b..000000000
--- a/src/pkg/compress/zlib/writer.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
-
-import (
- "compress/flate"
- "fmt"
- "hash"
- "hash/adler32"
- "io"
-)
-
-// 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
- level int
- dict []byte
- compressor *flate.Writer
- digest hash.Hash32
- err error
- scratch [4]byte
- wroteHeader bool
-}
-
-// NewWriter creates a new Writer.
-// Writes to the returned Writer are compressed and written to w.
-//
-// It is the caller's responsibility to call Close on the WriteCloser when done.
-// Writes may be buffered and not flushed until Close.
-func NewWriter(w io.Writer) *Writer {
- z, _ := NewWriterLevelDict(w, DefaultCompression, nil)
- return z
-}
-
-// NewWriterLevel is like NewWriter but specifies the compression level instead
-// of assuming DefaultCompression.
-//
-// The compression level can be DefaultCompression, NoCompression, or any
-// integer value between BestSpeed and BestCompression inclusive. The error
-// returned will be nil if the level is valid.
-func NewWriterLevel(w io.Writer, level int) (*Writer, error) {
- return NewWriterLevelDict(w, level, nil)
-}
-
-// NewWriterLevelDict is like NewWriterLevel but specifies a dictionary to
-// compress with.
-//
-// The dictionary may be nil. If not, its contents should not be modified until
-// the Writer is closed.
-func NewWriterLevelDict(w io.Writer, level int, dict []byte) (*Writer, error) {
- if level < DefaultCompression || level > BestCompression {
- return nil, fmt.Errorf("zlib: invalid compression level: %d", level)
- }
- return &Writer{
- w: w,
- level: level,
- dict: dict,
- }, nil
-}
-
-// Reset clears the state of the Writer z such that it is equivalent to its
-// initial state from NewWriterLevel or NewWriterLevelDict, but instead writing
-// to w.
-func (z *Writer) Reset(w io.Writer) {
- z.w = w
- // z.level and z.dict left unchanged.
- if z.compressor != nil {
- z.compressor.Reset(w)
- }
- if z.digest != nil {
- z.digest.Reset()
- }
- z.err = nil
- z.scratch = [4]byte{}
- z.wroteHeader = false
-}
-
-// writeHeader writes the ZLIB header.
-func (z *Writer) writeHeader() (err error) {
- z.wroteHeader = true
- // 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 z.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:
- panic("unreachable")
- }
- if z.dict != nil {
- z.scratch[1] |= 1 << 5
- }
- z.scratch[1] += uint8(31 - (uint16(z.scratch[0])<<8+uint16(z.scratch[1]))%31)
- if _, err = z.w.Write(z.scratch[0:2]); err != nil {
- return err
- }
- if z.dict != nil {
- // The next four bytes are the Adler-32 checksum of the dictionary.
- checksum := adler32.Checksum(z.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)
- if _, err = z.w.Write(z.scratch[0:4]); err != nil {
- return err
- }
- }
- if z.compressor == nil {
- // Initialize deflater unless the Writer is being reused
- // after a Reset call.
- z.compressor, err = flate.NewWriterDict(z.w, z.level, z.dict)
- if err != nil {
- return err
- }
- z.digest = adler32.New()
- }
- return nil
-}
-
-// Write writes a compressed form of p to the underlying io.Writer. The
-// compressed bytes are not necessarily flushed until the Writer is closed or
-// explicitly flushed.
-func (z *Writer) Write(p []byte) (n int, err error) {
- if !z.wroteHeader {
- z.err = z.writeHeader()
- }
- 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 Writer to its underlying io.Writer.
-func (z *Writer) Flush() error {
- if !z.wroteHeader {
- z.err = z.writeHeader()
- }
- if z.err != nil {
- return z.err
- }
- z.err = z.compressor.Flush()
- return z.err
-}
-
-// Close closes the Writer, flushing any unwritten data to the underlying
-// io.Writer, but does not close the underlying io.Writer.
-func (z *Writer) Close() error {
- if !z.wroteHeader {
- z.err = z.writeHeader()
- }
- 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
-}