1 files changed, 236 insertions, 0 deletions
diff --git a/src/pkg/compress/gzip/gunzip.go b/src/pkg/compress/gzip/gunzip.go
new file mode 100644
index 000000000..32cc3ecb0
--- /dev/null
+++ b/src/pkg/compress/gzip/gunzip.go
@@ -0,0 +1,236 @@
+// 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 eventually writing) of
+// gzip format compressed files, as specified in RFC 1952.
+package gzip
+
+import (
+	"bufio";
+	"compress/flate";
+	"hash";
+	"hash/crc32";
+	"io";
+	"os";
+)
+
+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")
+
+// A GzipInflater is an io.Reader that can be read to retrieve
+// uncompressed data from a gzip-format compressed file.
+// The gzip file stores a header giving metadata about the compressed file.
+// That header is exposed as the fields of the GzipInflater struct.
+//
+// In general, a gzip file can be a concatenation of gzip files,
+// each with its own header.  Reads from the GzipInflater
+// return the concatenation of the uncompressed data of each.
+// Only the first header is recorded in the GzipInflater fields.
+//
+// Gzip files store a length and checksum of the uncompressed data.
+// The GzipInflater 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 GzipInflater 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
+
+	r flate.Reader;
+	inflater io.Reader;
+	digest hash.Hash32;
+	size uint32;
+	flg byte;
+	buf [512]byte;
+	err os.Error;
+	eof bool;
+}
+
+func (z *GzipInflater) readHeader(save bool) os.Error
+
+// NewGzipInflater creates a new GzipInflater reading the given reader.
+// The implementation buffers input and may read more data than necessary from r.
+func NewGzipInflater(r io.Reader) (*GzipInflater, os.Error) {
+	z := new(GzipInflater);
+	z.r = makeReader(r);
+	z.digest = crc32.NewIEEE();
+	if err := z.readHeader(true); err != nil {
+		z.err = err;
+		return nil, err;
+	}
+	return z, nil;
+}
+
+func get4(p []byte) uint32 {
+	return uint32(p[0]) | uint32(p[1])<<8 | uint32(p[2])<<16 | uint32(p[3])<<24;
+}
+
+func (z *GzipInflater) 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 {
+			return string(z.buf[0:i]), nil;
+		}
+	}
+	panic("not reached");
+}
+
+func (z *GzipInflater) read2() (uint32, os.Error) {
+	_, err := z.r.Read(z.buf[0:2]);
+	if err != nil {
+		return 0, err;
+	}
+	return uint32(z.buf[0]) | uint32(z.buf[1])<<8, nil;
+}
+
+func (z *GzipInflater) readHeader(save bool) os.Error {
+	n, err := io.FullRead(z.r, z.buf[0:10]);
+	if err != nil {
+		if n != 0 && err == io.ErrEOF {
+			return HeaderError;
+		}
+		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);
+		var nn int;
+		if nn, err = io.FullRead(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.inflater = flate.NewInflater(z.r);
+	return nil;
+}
+
+func (z *GzipInflater) Read(p []byte) (n int, err os.Error) {
+	if z.err != nil {
+		return 0, z.err;
+	}
+	if z.eof || len(p) == 0 {
+		return 0, nil;
+	}
+
+	n, err = z.inflater.Read(p);
+	z.digest.Write(p[0:n]);
+	z.size += uint32(n);
+	if n != 0 || err != nil {
+		z.err = err;
+		return;
+	}
+
+	// Finished file; check checksum + size.
+	if _, err := io.FullRead(z.r, z.buf[0:8]); err != nil {
+		z.err = err;
+		return 0, err;
+	}
+	if 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?
+	switch err = z.readHeader(false); {
+	case err == io.ErrEOF:
+		err = nil;
+		z.eof = true;
+		return;
+	case err != nil:
+		z.err = err;
+		return;
+	}
+
+	// Yes.  Reset and read from it.
+	z.digest.Reset();
+	z.size = 0;
+	return z.Read(p);
+}
+