1 files changed, 187 insertions, 0 deletions
diff --git a/libgo/go/compress/gzip/gzip.go b/libgo/go/compress/gzip/gzip.go
new file mode 100644
index 000000000..8860d10af
--- /dev/null
+++ b/libgo/go/compress/gzip/gzip.go
@@ -0,0 +1,187 @@
+// 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"
+	"hash"
+	"hash/crc32"
+	"io"
+	"os"
+)
+
+// 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 Compressor is an io.WriteCloser that satisfies writes by compressing data written
+// to its wrapped io.Writer.
+type Compressor struct {
+	Header
+	w          io.Writer
+	level      int
+	compressor io.WriteCloser
+	digest     hash.Hash32
+	size       uint32
+	closed     bool
+	buf        [10]byte
+	err        os.Error
+}
+
+// NewWriter calls NewWriterLevel with the default compression level.
+func NewWriter(w io.Writer) (*Compressor, os.Error) {
+	return NewWriterLevel(w, DefaultCompression)
+}
+
+// NewWriterLevel creates a new Compressor writing to the given writer.
+// Writes may be buffered and not flushed until Close.
+// Callers that wish to set the fields in Compressor.Header must
+// do so before the first call to Write or Close.
+// 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).
+func NewWriterLevel(w io.Writer, level int) (*Compressor, os.Error) {
+	z := new(Compressor)
+	z.OS = 255 // unknown
+	z.w = w
+	z.level = level
+	z.digest = crc32.NewIEEE()
+	return z, nil
+}
+
+// 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 *Compressor) writeBytes(b []byte) os.Error {
+	if len(b) > 0xffff {
+		return os.NewError("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 string (in ISO 8859-1 (Latin-1) format) to z.w.
+func (z *Compressor) writeString(s string) os.Error {
+	// GZIP (RFC 1952) specifies that strings are NUL-terminated ISO 8859-1 (Latin-1).
+	// TODO(nigeltao): Convert from UTF-8 to ISO 8859-1 (Latin-1).
+	for _, v := range s {
+		if v == 0 || v > 0x7f {
+			return os.NewError("gzip.Write: non-ASCII header string")
+		}
+	}
+	_, 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
+}
+
+func (z *Compressor) Write(p []byte) (int, os.Error) {
+	if z.err != nil {
+		return 0, z.err
+	}
+	var n int
+	// Write the GZIP header lazily.
+	if z.compressor == nil {
+		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], z.Mtime)
+		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
+			}
+		}
+		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
+}
+
+// Calling Close does not close the wrapped io.Writer originally passed to NewWriter.
+func (z *Compressor) Close() os.Error {
+	if z.err != nil {
+		return z.err
+	}
+	if z.closed {
+		return nil
+	}
+	z.closed = true
+	if z.compressor == nil {
+		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
+}