--- /dev/null
+// 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 zlib package implements reading (and eventually writing) of
+// zlib format compressed files, as specified in RFC 1950.
+package zlib
+
+import (
+ "bufio";
+ "compress/flate";
+ "hash";
+ "hash/adler32";
+ "io";
+ "os";
+)
+
+const zlibDeflate = 8
+
+var ChecksumError os.Error = os.ErrorString("zlib checksum error")
+var HeaderError os.Error = os.ErrorString("invalid zlib header")
+var UnsupportedError os.Error = os.ErrorString("unsupported zlib format")
+
+type reader struct {
+ r flate.Reader;
+ inflater io.Reader;
+ digest hash.Hash32;
+ err os.Error;
+}
+
+// NewZlibInflater creates a new io.Reader that satisfies reads by decompressing data read from r.
+// The implementation buffers input and may read more data than necessary from r.
+func NewZlibInflater(r io.Reader) (io.Reader, os.Error) {
+ z := new(reader);
+ if fr, ok := r.(flate.Reader); ok {
+ z.r = fr;
+ } else {
+ z.r = bufio.NewReader(r);
+ }
+ var buf [2]byte;
+ n, err := io.ReadFull(z.r, buf[0:2]);
+ if err != nil {
+ return nil, err;
+ }
+ h := uint(buf[0])<<8 | uint(buf[1]);
+ if (buf[0] & 0x0f != zlibDeflate) || (h % 31 != 0) {
+ return nil, HeaderError;
+ }
+ if buf[1] & 0x20 != 0 {
+ // BUG(nigeltao): The zlib package does not implement the FDICT flag.
+ return nil, UnsupportedError;
+ }
+ z.digest = adler32.New();
+ z.inflater = flate.NewInflater(z.r);
+ return z, nil;
+}
+
+func (z *reader) 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.inflater.Read(p);
+ z.digest.Write(p[0:n]);
+ if n != 0 || err != os.EOF {
+ z.err = err;
+ return;
+ }
+
+ // Finished file; check checksum.
+ var buf [4]byte;
+ if _, err := io.ReadFull(z.r, buf[0:4]); err != nil {
+ z.err = err;
+ return 0, err;
+ }
+ // ZLIB (RFC 1950) is big-endian, unlike GZIP (RFC 1952).
+ checksum := uint32(buf[0])<<24 | uint32(buf[1])<<16 | uint32(buf[2])<<8 | uint32(buf[3]);
+ if checksum != z.digest.Sum32() {
+ z.err = ChecksumError;
+ return 0, z.err;
+ }
+ return;
+}
+
--- /dev/null
+// 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 (
+ "bytes";
+ "io";
+ "os";
+ "testing";
+)
+
+type zlibTest struct {
+ desc string;
+ raw string;
+ compressed []byte;
+ err os.Error;
+}
+
+// Compare-to-golden test data was generated by the ZLIB example program at
+// http://www.zlib.net/zpipe.c
+
+var zlibTests = []zlibTest {
+ zlibTest {
+ "empty",
+ "",
+ []byte {
+ 0x78, 0x9c, 0x03, 0x00, 0x00, 0x00, 0x00, 0x01,
+ },
+ nil
+ },
+ zlibTest {
+ "goodbye",
+ "goodbye, world",
+ []byte {
+ 0x78, 0x9c, 0x4b, 0xcf, 0xcf, 0x4f, 0x49, 0xaa,
+ 0x4c, 0xd5, 0x51, 0x28, 0xcf, 0x2f, 0xca, 0x49,
+ 0x01, 0x00, 0x28, 0xa5, 0x05, 0x5e,
+ },
+ nil
+ },
+ zlibTest {
+ "bad header",
+ "",
+ []byte {
+ 0x78, 0x9f, 0x03, 0x00, 0x00, 0x00, 0x00, 0x01,
+ },
+ HeaderError
+ },
+ zlibTest {
+ "bad checksum",
+ "",
+ []byte {
+ 0x78, 0x9c, 0x03, 0x00, 0x00, 0x00, 0x00, 0xff,
+ },
+ ChecksumError,
+ },
+ zlibTest {
+ "not enough data",
+ "",
+ []byte {
+ 0x78, 0x9c, 0x03, 0x00, 0x00, 0x00,
+ },
+ io.ErrUnexpectedEOF,
+ },
+ zlibTest {
+ "excess data is silently ignored",
+ "",
+ []byte {
+ 0x78, 0x9c, 0x03, 0x00, 0x00, 0x00, 0x00, 0x01,
+ 0x78, 0x9c, 0xff,
+ },
+ nil,
+ },
+}
+
+func TestZlibInflater(t *testing.T) {
+ b := new(bytes.Buffer);
+ for i, tt := range zlibTests {
+ in := io.NewByteReader(tt.compressed);
+ zlib, err := NewZlibInflater(in);
+ if err != nil {
+ if err != tt.err {
+ t.Errorf("%s: NewZlibInflater: %s", tt.desc, err);
+ }
+ continue;
+ }
+ b.Reset();
+ n, err := io.Copy(zlib, b);
+ if err != nil {
+ if err != tt.err {
+ t.Errorf("%s: io.Copy: %v want %v", tt.desc, err, tt.err);
+ }
+ continue;
+ }
+ s := string(b.Data());
+ if s != tt.raw {
+ t.Errorf("%s: got %d-byte %q want %d-byte %q", tt.desc, n, s, len(tt.raw), tt.raw);
+ }
+ }
+}