diff options
author | Russ Cox <rsc@golang.org> | 2014-09-08 00:08:51 -0400 |
---|---|---|
committer | Russ Cox <rsc@golang.org> | 2014-09-08 00:08:51 -0400 |
commit | 8528da672cc093d4dd06732819abc1f7b6b5a46e (patch) | |
tree | 334be80d4a4c85b77db6f6fdb67cbf0528cba5f5 /src/compress/gzip/gzip.go | |
parent | 73bcb69f272cbf34ddcc9daa56427a8683b5a95d (diff) | |
download | go-8528da672cc093d4dd06732819abc1f7b6b5a46e.tar.gz |
build: move package sources from src/pkg to src
Preparation was in CL 134570043.
This CL contains only the effect of 'hg mv src/pkg/* src'.
For more about the move, see golang.org/s/go14nopkg.
Diffstat (limited to 'src/compress/gzip/gzip.go')
-rw-r--r-- | src/compress/gzip/gzip.go | 272 |
1 files changed, 272 insertions, 0 deletions
diff --git a/src/compress/gzip/gzip.go b/src/compress/gzip/gzip.go new file mode 100644 index 000000000..5131d128e --- /dev/null +++ b/src/compress/gzip/gzip.go @@ -0,0 +1,272 @@ +// Copyright 2010 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 gzip + +import ( + "compress/flate" + "errors" + "fmt" + "hash" + "hash/crc32" + "io" +) + +// These constants are copied from the flate package, so that code that imports +// "compress/gzip" does not also have to import "compress/flate". +const ( + NoCompression = flate.NoCompression + BestSpeed = flate.BestSpeed + BestCompression = flate.BestCompression + DefaultCompression = flate.DefaultCompression +) + +// A Writer is an io.WriteCloser. +// Writes to a Writer are compressed and written to w. +type Writer struct { + Header + w io.Writer + level int + wroteHeader bool + compressor *flate.Writer + digest hash.Hash32 + size uint32 + closed bool + buf [10]byte + err error +} + +// NewWriter returns 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. +// +// Callers that wish to set the fields in Writer.Header must do so before +// the first call to Write or Close. The Comment and Name header fields are +// UTF-8 strings in Go, but the underlying format requires NUL-terminated ISO +// 8859-1 (Latin-1). NUL or non-Latin-1 runes in those strings will lead to an +// error on Write. +func NewWriter(w io.Writer) *Writer { + z, _ := NewWriterLevel(w, DefaultCompression) + 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) { + if level < DefaultCompression || level > BestCompression { + return nil, fmt.Errorf("gzip: invalid compression level: %d", level) + } + z := new(Writer) + z.init(w, level) + return z, nil +} + +func (z *Writer) init(w io.Writer, level int) { + digest := z.digest + if digest != nil { + digest.Reset() + } else { + digest = crc32.NewIEEE() + } + compressor := z.compressor + if compressor != nil { + compressor.Reset(w) + } + *z = Writer{ + Header: Header{ + OS: 255, // unknown + }, + w: w, + level: level, + digest: digest, + compressor: compressor, + } +} + +// Reset discards the Writer z's state and makes it equivalent to the +// result of its original state from NewWriter or NewWriterLevel, but +// writing to w instead. This permits reusing a Writer rather than +// allocating a new one. +func (z *Writer) Reset(w io.Writer) { + z.init(w, z.level) +} + +// GZIP (RFC 1952) is little-endian, unlike ZLIB (RFC 1950). +func put2(p []byte, v uint16) { + p[0] = uint8(v >> 0) + p[1] = uint8(v >> 8) +} + +func put4(p []byte, v uint32) { + p[0] = uint8(v >> 0) + p[1] = uint8(v >> 8) + p[2] = uint8(v >> 16) + p[3] = uint8(v >> 24) +} + +// writeBytes writes a length-prefixed byte slice to z.w. +func (z *Writer) writeBytes(b []byte) error { + if len(b) > 0xffff { + return errors.New("gzip.Write: Extra data is too large") + } + put2(z.buf[0:2], uint16(len(b))) + _, err := z.w.Write(z.buf[0:2]) + if err != nil { + return err + } + _, err = z.w.Write(b) + return err +} + +// writeString writes a UTF-8 string s in GZIP's format to z.w. +// GZIP (RFC 1952) specifies that strings are NUL-terminated ISO 8859-1 (Latin-1). +func (z *Writer) writeString(s string) (err error) { + // GZIP stores Latin-1 strings; error if non-Latin-1; convert if non-ASCII. + needconv := false + for _, v := range s { + if v == 0 || v > 0xff { + return errors.New("gzip.Write: non-Latin-1 header string") + } + if v > 0x7f { + needconv = true + } + } + if needconv { + b := make([]byte, 0, len(s)) + for _, v := range s { + b = append(b, byte(v)) + } + _, err = z.w.Write(b) + } else { + _, err = io.WriteString(z.w, s) + } + if err != nil { + return err + } + // GZIP strings are NUL-terminated. + z.buf[0] = 0 + _, err = z.w.Write(z.buf[0:1]) + return err +} + +// Write writes a compressed form of p to the underlying io.Writer. The +// compressed bytes are not necessarily flushed until the Writer is closed. +func (z *Writer) Write(p []byte) (int, error) { + if z.err != nil { + return 0, z.err + } + var n int + // Write the GZIP header lazily. + if !z.wroteHeader { + z.wroteHeader = true + z.buf[0] = gzipID1 + z.buf[1] = gzipID2 + z.buf[2] = gzipDeflate + z.buf[3] = 0 + if z.Extra != nil { + z.buf[3] |= 0x04 + } + if z.Name != "" { + z.buf[3] |= 0x08 + } + if z.Comment != "" { + z.buf[3] |= 0x10 + } + put4(z.buf[4:8], uint32(z.ModTime.Unix())) + if z.level == BestCompression { + z.buf[8] = 2 + } else if z.level == BestSpeed { + z.buf[8] = 4 + } else { + z.buf[8] = 0 + } + z.buf[9] = z.OS + n, z.err = z.w.Write(z.buf[0:10]) + if z.err != nil { + return n, z.err + } + if z.Extra != nil { + z.err = z.writeBytes(z.Extra) + if z.err != nil { + return n, z.err + } + } + if z.Name != "" { + z.err = z.writeString(z.Name) + if z.err != nil { + return n, z.err + } + } + if z.Comment != "" { + z.err = z.writeString(z.Comment) + if z.err != nil { + return n, z.err + } + } + if z.compressor == nil { + z.compressor, _ = flate.NewWriter(z.w, z.level) + } + } + z.size += uint32(len(p)) + z.digest.Write(p) + n, z.err = z.compressor.Write(p) + return n, z.err +} + +// Flush flushes any pending compressed data to the underlying writer. +// +// It is useful mainly in compressed network protocols, to ensure that +// a remote reader has enough data to reconstruct a packet. Flush does +// not return until the data has been written. If the underlying +// writer returns an error, Flush returns that error. +// +// In the terminology of the zlib library, Flush is equivalent to Z_SYNC_FLUSH. +func (z *Writer) Flush() error { + if z.err != nil { + return z.err + } + if z.closed { + return nil + } + if !z.wroteHeader { + z.Write(nil) + 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.err != nil { + return z.err + } + if z.closed { + return nil + } + z.closed = true + if !z.wroteHeader { + z.Write(nil) + if z.err != nil { + return z.err + } + } + z.err = z.compressor.Close() + if z.err != nil { + return z.err + } + put4(z.buf[0:4], z.digest.Sum32()) + put4(z.buf[4:8], z.size) + _, z.err = z.w.Write(z.buf[0:8]) + return z.err +} |