1 files changed, 230 insertions, 0 deletions
diff --git a/libgo/go/compress/gzip/gunzip.go b/libgo/go/compress/gzip/gunzip.go
new file mode 100644
index 000000000..3c0b3c5e5
--- /dev/null
+++ b/libgo/go/compress/gzip/gunzip.go
@@ -0,0 +1,230 @@
+// 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.
+
+// The gzip package implements reading and writing of
+// gzip format compressed files, as specified in RFC 1952.
+package gzip
+
+import (
+	"bufio"
+	"compress/flate"
+	"hash"
+	"hash/crc32"
+	"io"
+	"os"
+)
+
+// BUG(nigeltao): Comments and Names don't properly map UTF-8 character codes outside of
+// the 0x00-0x7f range to ISO 8859-1 (Latin-1).
+
+const (
+	gzipID1     = 0x1f
+	gzipID2     = 0x8b
+	gzipDeflate = 8
+	flagText    = 1 << 0
+	flagHdrCrc  = 1 << 1
+	flagExtra   = 1 << 2
+	flagName    = 1 << 3
+	flagComment = 1 << 4
+)
+
+func makeReader(r io.Reader) flate.Reader {
+	if rr, ok := r.(flate.Reader); ok {
+		return rr
+	}
+	return bufio.NewReader(r)
+}
+
+var HeaderError os.Error = os.ErrorString("invalid gzip header")
+var ChecksumError os.Error = os.ErrorString("gzip checksum error")
+
+// The gzip file stores a header giving metadata about the compressed file.
+// That header is exposed as the fields of the Compressor and Decompressor structs.
+type Header struct {
+	Comment string // comment
+	Extra   []byte // "extra data"
+	Mtime   uint32 // modification time (seconds since January 1, 1970)
+	Name    string // file name
+	OS      byte   // operating system type
+}
+
+// An Decompressor is an io.Reader that can be read to retrieve
+// uncompressed data from a gzip-format compressed file.
+//
+// In general, a gzip file can be a concatenation of gzip files,
+// each with its own header.  Reads from the Decompressor
+// return the concatenation of the uncompressed data of each.
+// Only the first header is recorded in the Decompressor fields.
+//
+// Gzip files store a length and checksum of the uncompressed data.
+// The Decompressor will return a ChecksumError when Read
+// reaches the end of the uncompressed data if it does not
+// have the expected length or checksum.  Clients should treat data
+// returned by Read as tentative until they receive the successful
+// (zero length, nil error) Read marking the end of the data.
+type Decompressor struct {
+	Header
+	r            flate.Reader
+	decompressor io.ReadCloser
+	digest       hash.Hash32
+	size         uint32
+	flg          byte
+	buf          [512]byte
+	err          os.Error
+}
+
+// NewReader creates a new Decompressor reading the given reader.
+// The implementation buffers input and may read more data than necessary from r.
+// It is the caller's responsibility to call Close on the Decompressor when done.
+func NewReader(r io.Reader) (*Decompressor, os.Error) {
+	z := new(Decompressor)
+	z.r = makeReader(r)
+	z.digest = crc32.NewIEEE()
+	if err := z.readHeader(true); err != nil {
+		z.err = err
+		return nil, err
+	}
+	return z, nil
+}
+
+// GZIP (RFC 1952) is little-endian, unlike ZLIB (RFC 1950).
+func get4(p []byte) uint32 {
+	return uint32(p[0]) | uint32(p[1])<<8 | uint32(p[2])<<16 | uint32(p[3])<<24
+}
+
+func (z *Decompressor) readString() (string, os.Error) {
+	var err os.Error
+	for i := 0; ; i++ {
+		if i >= len(z.buf) {
+			return "", HeaderError
+		}
+		z.buf[i], err = z.r.ReadByte()
+		if err != nil {
+			return "", err
+		}
+		if z.buf[i] == 0 {
+			// GZIP (RFC 1952) specifies that strings are NUL-terminated ISO 8859-1 (Latin-1).
+			// TODO(nigeltao): Convert from ISO 8859-1 (Latin-1) to UTF-8.
+			return string(z.buf[0:i]), nil
+		}
+	}
+	panic("not reached")
+}
+
+func (z *Decompressor) read2() (uint32, os.Error) {
+	_, err := io.ReadFull(z.r, z.buf[0:2])
+	if err != nil {
+		return 0, err
+	}
+	return uint32(z.buf[0]) | uint32(z.buf[1])<<8, nil
+}
+
+func (z *Decompressor) readHeader(save bool) os.Error {
+	_, err := io.ReadFull(z.r, z.buf[0:10])
+	if err != nil {
+		return err
+	}
+	if z.buf[0] != gzipID1 || z.buf[1] != gzipID2 || z.buf[2] != gzipDeflate {
+		return HeaderError
+	}
+	z.flg = z.buf[3]
+	if save {
+		z.Mtime = get4(z.buf[4:8])
+		// z.buf[8] is xfl, ignored
+		z.OS = z.buf[9]
+	}
+	z.digest.Reset()
+	z.digest.Write(z.buf[0:10])
+
+	if z.flg&flagExtra != 0 {
+		n, err := z.read2()
+		if err != nil {
+			return err
+		}
+		data := make([]byte, n)
+		if _, err = io.ReadFull(z.r, data); err != nil {
+			return err
+		}
+		if save {
+			z.Extra = data
+		}
+	}
+
+	var s string
+	if z.flg&flagName != 0 {
+		if s, err = z.readString(); err != nil {
+			return err
+		}
+		if save {
+			z.Name = s
+		}
+	}
+
+	if z.flg&flagComment != 0 {
+		if s, err = z.readString(); err != nil {
+			return err
+		}
+		if save {
+			z.Comment = s
+		}
+	}
+
+	if z.flg&flagHdrCrc != 0 {
+		n, err := z.read2()
+		if err != nil {
+			return err
+		}
+		sum := z.digest.Sum32() & 0xFFFF
+		if n != sum {
+			return HeaderError
+		}
+	}
+
+	z.digest.Reset()
+	z.decompressor = flate.NewReader(z.r)
+	return nil
+}
+
+func (z *Decompressor) Read(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.decompressor.Read(p)
+	z.digest.Write(p[0:n])
+	z.size += uint32(n)
+	if n != 0 || err != os.EOF {
+		z.err = err
+		return
+	}
+
+	// Finished file; check checksum + size.
+	if _, err := io.ReadFull(z.r, z.buf[0:8]); err != nil {
+		z.err = err
+		return 0, err
+	}
+	crc32, isize := get4(z.buf[0:4]), get4(z.buf[4:8])
+	sum := z.digest.Sum32()
+	if sum != crc32 || isize != z.size {
+		z.err = ChecksumError
+		return 0, z.err
+	}
+
+	// File is ok; is there another?
+	if err = z.readHeader(false); err != nil {
+		z.err = err
+		return
+	}
+
+	// Yes.  Reset and read from it.
+	z.digest.Reset()
+	z.size = 0
+	return z.Read(p)
+}
+
+// Calling Close does not close the wrapped io.Reader originally passed to NewReader.
+func (z *Decompressor) Close() os.Error { return z.decompressor.Close() }