--- /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.
+
+// This test tests some internals of the flate package.
+// The tests in package compress/gzip serve as the
+// end-to-end test of the inflater.
+
+package flate
+
+import (
+ "bufio";
+ "compress/flate";
+ "io";
+ "os";
+ "reflect";
+ "strconv";
+ "testing";
+)
+
+// The Huffman code lengths used by the fixed-format Huffman blocks.
+var fixedHuffmanBits = [...]int {
+ // 0-143 length 8
+ 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
+ 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
+ 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
+ 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
+ 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
+ 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
+ 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
+ 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
+ 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
+
+ // 144-255 length 9
+ 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
+ 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
+ 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
+ 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
+ 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
+ 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
+ 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
+
+ // 256-279 length 7
+ 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
+ 7, 7, 7, 7, 7, 7, 7, 7,
+
+ // 280-287 length 8
+ 8, 8, 8, 8, 8, 8, 8, 8,
+}
+
+type InitDecoderTest struct {
+ in []int;
+ out huffmanDecoder;
+ ok bool;
+}
+
+var initDecoderTests = []*InitDecoderTest{
+ // Example from Connell 1973,
+ &InitDecoderTest{
+ []int{ 3, 5, 2, 4, 3, 5, 5, 4, 4, 3, 4, 5 },
+ huffmanDecoder {
+ 2, 5,
+ [maxCodeLen+1]int{ 2: 0, 4, 13, 31 },
+ [maxCodeLen+1]int{ 2: 0, 1, 6, 20 },
+ // Paper used different code assignment:
+ // 2, 9, 4, 0, 10, 8, 3, 7, 1, 5, 11, 6
+ // Reordered here so that codes of same length
+ // are assigned to increasing numbers.
+ []int{ 2, 0, 4, 9, 3, 7, 8, 10, 1, 5, 6, 11 },
+ },
+ true,
+ },
+
+ // Example from RFC 1951 section 3.2.2
+ &InitDecoderTest{
+ []int{ 2, 1, 3, 3 },
+ huffmanDecoder {
+ 1, 3,
+ [maxCodeLen+1]int{ 1: 0, 2, 7, },
+ [maxCodeLen+1]int{ 1: 0, 1, 4, },
+ []int{ 1, 0, 2, 3 },
+ },
+ true,
+ },
+
+ // Second example from RFC 1951 section 3.2.2
+ &InitDecoderTest{
+ []int{ 3, 3, 3, 3, 3, 2, 4, 4 },
+ huffmanDecoder{
+ 2, 4,
+ [maxCodeLen+1]int{ 2: 0, 6, 15, },
+ [maxCodeLen+1]int{ 2: 0, 1, 8, },
+ []int{ 5, 0, 1, 2, 3, 4, 6, 7 },
+ },
+ true,
+ },
+
+ // Static Huffman codes (RFC 1951 section 3.2.6)
+ &InitDecoderTest{
+ &fixedHuffmanBits,
+ fixedHuffmanDecoder,
+ true,
+ },
+
+ // Illegal input.
+ &InitDecoderTest{
+ []int{ },
+ huffmanDecoder{ },
+ false,
+ },
+
+ // Illegal input.
+ &InitDecoderTest{
+ []int{ 0, 0, 0, 0, 0, 0, 0, },
+ huffmanDecoder{ },
+ false,
+ },
+}
+
+func TestInitDecoder(t *testing.T) {
+ for i, tt := range initDecoderTests {
+ var h huffmanDecoder;
+ if h.init(tt.in) != tt.ok {
+ t.Errorf("test %d: init = %v", i, !tt.ok);
+ continue;
+ }
+ if !reflect.DeepEqual(&h, &tt.out) {
+ t.Errorf("test %d:\nhave %v\nwant %v", i, h, tt.out);
+ }
+ }
+}
--- /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 flate package implements the DEFLATE compressed data
+// format, described in RFC 1951. The gzip and zlib packages
+// implement access to DEFLATE-based file formats.
+package flate
+
+import (
+ "bufio";
+ "io";
+ "os";
+ "strconv";
+)
+
+const (
+ maxCodeLen = 16; // max length of Huffman code
+ maxHist = 32768; // max history required
+ maxLit = 286;
+ maxDist = 32;
+ numCodes = 19; // number of codes in Huffman meta-code
+)
+
+// TODO(rsc): Publish in another package?
+var reverseByte = [256]byte {
+ 0x00, 0x80, 0x40, 0xc0, 0x20, 0xa0, 0x60, 0xe0,
+ 0x10, 0x90, 0x50, 0xd0, 0x30, 0xb0, 0x70, 0xf0,
+ 0x08, 0x88, 0x48, 0xc8, 0x28, 0xa8, 0x68, 0xe8,
+ 0x18, 0x98, 0x58, 0xd8, 0x38, 0xb8, 0x78, 0xf8,
+ 0x04, 0x84, 0x44, 0xc4, 0x24, 0xa4, 0x64, 0xe4,
+ 0x14, 0x94, 0x54, 0xd4, 0x34, 0xb4, 0x74, 0xf4,
+ 0x0c, 0x8c, 0x4c, 0xcc, 0x2c, 0xac, 0x6c, 0xec,
+ 0x1c, 0x9c, 0x5c, 0xdc, 0x3c, 0xbc, 0x7c, 0xfc,
+ 0x02, 0x82, 0x42, 0xc2, 0x22, 0xa2, 0x62, 0xe2,
+ 0x12, 0x92, 0x52, 0xd2, 0x32, 0xb2, 0x72, 0xf2,
+ 0x0a, 0x8a, 0x4a, 0xca, 0x2a, 0xaa, 0x6a, 0xea,
+ 0x1a, 0x9a, 0x5a, 0xda, 0x3a, 0xba, 0x7a, 0xfa,
+ 0x06, 0x86, 0x46, 0xc6, 0x26, 0xa6, 0x66, 0xe6,
+ 0x16, 0x96, 0x56, 0xd6, 0x36, 0xb6, 0x76, 0xf6,
+ 0x0e, 0x8e, 0x4e, 0xce, 0x2e, 0xae, 0x6e, 0xee,
+ 0x1e, 0x9e, 0x5e, 0xde, 0x3e, 0xbe, 0x7e, 0xfe,
+ 0x01, 0x81, 0x41, 0xc1, 0x21, 0xa1, 0x61, 0xe1,
+ 0x11, 0x91, 0x51, 0xd1, 0x31, 0xb1, 0x71, 0xf1,
+ 0x09, 0x89, 0x49, 0xc9, 0x29, 0xa9, 0x69, 0xe9,
+ 0x19, 0x99, 0x59, 0xd9, 0x39, 0xb9, 0x79, 0xf9,
+ 0x05, 0x85, 0x45, 0xc5, 0x25, 0xa5, 0x65, 0xe5,
+ 0x15, 0x95, 0x55, 0xd5, 0x35, 0xb5, 0x75, 0xf5,
+ 0x0d, 0x8d, 0x4d, 0xcd, 0x2d, 0xad, 0x6d, 0xed,
+ 0x1d, 0x9d, 0x5d, 0xdd, 0x3d, 0xbd, 0x7d, 0xfd,
+ 0x03, 0x83, 0x43, 0xc3, 0x23, 0xa3, 0x63, 0xe3,
+ 0x13, 0x93, 0x53, 0xd3, 0x33, 0xb3, 0x73, 0xf3,
+ 0x0b, 0x8b, 0x4b, 0xcb, 0x2b, 0xab, 0x6b, 0xeb,
+ 0x1b, 0x9b, 0x5b, 0xdb, 0x3b, 0xbb, 0x7b, 0xfb,
+ 0x07, 0x87, 0x47, 0xc7, 0x27, 0xa7, 0x67, 0xe7,
+ 0x17, 0x97, 0x57, 0xd7, 0x37, 0xb7, 0x77, 0xf7,
+ 0x0f, 0x8f, 0x4f, 0xcf, 0x2f, 0xaf, 0x6f, 0xef,
+ 0x1f, 0x9f, 0x5f, 0xdf, 0x3f, 0xbf, 0x7f, 0xff,
+}
+
+// A CorruptInputError reports the presence of corrupt input at a given offset.
+type CorruptInputError int64
+func (e CorruptInputError) String() string {
+ return "flate: corrupt input at offset " + strconv.Itoa64(int64(e));
+}
+
+// An InternalError reports an error in the flate code itself.
+type InternalError string
+func (e InternalError) String() string {
+ return "flate: internal error: " + string(e);
+}
+
+// A ReadError reports an error encountered while reading input.
+type ReadError struct {
+ Offset int64; // byte offset where error occurred
+ Error os.Error; // error returned by underlying Read
+}
+
+func (e *ReadError) String() string {
+ return "flate: read error at offset " + strconv.Itoa64(e.Offset)
+ + ": " + e.Error.String();
+}
+
+// A WriteError reports an error encountered while writing output.
+type WriteError struct {
+ Offset int64; // byte offset where error occurred
+ Error os.Error; // error returned by underlying Read
+}
+
+func (e *WriteError) String() string {
+ return "flate: write error at offset " + strconv.Itoa64(e.Offset)
+ + ": " + e.Error.String();
+}
+
+// Huffman decoder is based on
+// J. Brian Connell, ``A Huffman-Shannon-Fano Code,''
+// Proceedings of the IEEE, 61(7) (July 1973), pp 1046-1047.
+type huffmanDecoder struct {
+ // min, max code length
+ min, max int;
+
+ // limit[i] = largest code word of length i
+ // Given code v of length n,
+ // need more bits if v > limit[n].
+ limit [maxCodeLen+1]int;
+
+ // base[i] = smallest code word of length i - seq number
+ base [maxCodeLen+1]int;
+
+ // codes[seq number] = output code.
+ // Given code v of length n, value is
+ // codes[v - base[n]].
+ codes []int;
+}
+
+// Initialize Huffman decoding tables from array of code lengths.
+func (h *huffmanDecoder) init(bits []int) bool {
+ // TODO(rsc): Return false sometimes.
+
+ // Count number of codes of each length,
+ // compute min and max length.
+ var count [maxCodeLen+1]int;
+ var min, max int;
+ for i, n := range bits {
+ if n == 0 {
+ continue;
+ }
+ if min == 0 || n < min {
+ min = n;
+ }
+ if n > max {
+ max = n;
+ }
+ count[n]++;
+ }
+ if max == 0 {
+ return false;
+ }
+
+ h.min = min;
+ h.max = max;
+
+
+ // For each code range, compute
+ // nextcode (first code of that length),
+ // limit (last code of that length), and
+ // base (offset from first code to sequence number).
+ code := 0;
+ seq := 0;
+ var nextcode [maxCodeLen]int;
+ for i := min; i <= max; i++ {
+ n := count[i];
+ nextcode[i] = code;
+ h.base[i] = code - seq;
+ code += n;
+ seq += n;
+ h.limit[i] = code - 1;
+ code <<= 1;
+ }
+
+ // Make array mapping sequence numbers to codes.
+ if len(h.codes) < len(bits) {
+ h.codes = make([]int, len(bits));
+ }
+ for i, n := range bits {
+ if n == 0 {
+ continue;
+ }
+ code := nextcode[n];
+ nextcode[n]++;
+ seq := code - h.base[n];
+ h.codes[seq] = i;
+ }
+ return true;
+}
+
+// Hard-coded Huffman tables for DEFLATE algorithm.
+// See RFC 1951, section 3.2.6.
+var fixedHuffmanDecoder = huffmanDecoder{
+ 7, 9,
+ [maxCodeLen+1]int{ 7: 23, 199, 511, },
+ [maxCodeLen+1]int{ 7: 0, 24, 224, },
+ []int{
+ // length 7: 256-279
+ 256, 257, 258, 259, 260, 261, 262,
+ 263, 264, 265, 266, 267, 268, 269,
+ 270, 271, 272, 273, 274, 275, 276,
+ 277, 278, 279,
+
+ // length 8: 0-143
+ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11,
+ 12, 13, 14, 15, 16, 17, 18, 19, 20, 21,
+ 22, 23, 24, 25, 26, 27, 28, 29, 30, 31,
+ 32, 33, 34, 35, 36, 37, 38, 39, 40, 41,
+ 42, 43, 44, 45, 46, 47, 48, 49, 50, 51,
+ 52, 53, 54, 55, 56, 57, 58, 59, 60, 61,
+ 62, 63, 64, 65, 66, 67, 68, 69, 70, 71,
+ 72, 73, 74, 75, 76, 77, 78, 79, 80, 81,
+ 82, 83, 84, 85, 86, 87, 88, 89, 90, 91,
+ 92, 93, 94, 95, 96, 97, 98, 99, 100,
+ 101, 102, 103, 104, 105, 106, 107, 108,
+ 109, 110, 111, 112, 113, 114, 115, 116,
+ 117, 118, 119, 120, 121, 122, 123, 124,
+ 125, 126, 127, 128, 129, 130, 131, 132,
+ 133, 134, 135, 136, 137, 138, 139, 140,
+ 141, 142, 143,
+
+ // length 8: 280-287
+ 280, 281, 282, 283, 284, 285, 286, 287,
+
+ // length 9: 144-255
+ 144, 145, 146, 147, 148, 149, 150, 151,
+ 152, 153, 154, 155, 156, 157, 158, 159,
+ 160, 161, 162, 163, 164, 165, 166, 167,
+ 168, 169, 170, 171, 172, 173, 174, 175,
+ 176, 177, 178, 179, 180, 181, 182, 183,
+ 184, 185, 186, 187, 188, 189, 190, 191,
+ 192, 193, 194, 195, 196, 197, 198, 199,
+ 200, 201, 202, 203, 204, 205, 206, 207,
+ 208, 209, 210, 211, 212, 213, 214, 215,
+ 216, 217, 218, 219, 220, 221, 222, 223,
+ 224, 225, 226, 227, 228, 229, 230, 231,
+ 232, 233, 234, 235, 236, 237, 238, 239,
+ 240, 241, 242, 243, 244, 245, 246, 247,
+ 248, 249, 250, 251, 252, 253, 254, 255,
+ }
+}
+
+// The actual read interface needed by NewInflater.
+// If the passed in io.Reader does not also have ReadByte,
+// the NewInflater will introduce its own buffering.
+type Reader interface {
+ io.Reader;
+ ReadByte() (c byte, err os.Error);
+}
+
+// Inflate state.
+// TODO(rsc): Expose this or not?
+type inflater struct {
+ // Input/output sources.
+ r Reader;
+ w io.Writer;
+ roffset int64;
+ woffset int64;
+
+ // Input bits, in top of b.
+ b uint32;
+ nb uint;
+
+ // Huffman decoders for literal/length, distance.
+ h1, h2 huffmanDecoder;
+
+ // Length arrays used to define Huffman codes.
+ bits [maxLit+maxDist]int;
+ codebits [numCodes]int;
+
+ // Output history, buffer.
+ hist [maxHist]byte;
+ hp int; // current output position in buffer
+ hfull bool; // buffer has filled at least once
+
+ // Temporary buffer (avoids repeated allocation).
+ buf [4]byte;
+}
+
+// TODO(rsc): This works around a 6g bug.
+func (f *inflater) getRoffset() int64 {
+ return f.roffset;
+}
+
+func (f *inflater) dataBlock() os.Error
+func (f *inflater) readHuffman() os.Error
+func (f *inflater) decodeBlock(hl, hd *huffmanDecoder) os.Error
+func (f *inflater) moreBits() os.Error
+func (f *inflater) huffSym(h *huffmanDecoder) (int, os.Error)
+func (f *inflater) flush() os.Error
+
+func (f *inflater) inflate() (err os.Error) {
+ final := false;
+ for err == nil && !final {
+ for f.nb < 1+2 {
+ if err = f.moreBits(); err != nil {
+ return;
+ }
+ }
+ final = f.b & 1 == 1;
+ f.b >>= 1;
+ typ := f.b & 3;
+ f.b >>= 2;
+ f.nb -= 1+2;
+ switch typ {
+ case 0:
+ err = f.dataBlock();
+ case 1:
+ // compressed, fixed Huffman tables
+ err = f.decodeBlock(&fixedHuffmanDecoder, nil);
+ case 2:
+ // compressed, dynamic Huffman tables
+ if err = f.readHuffman(); err == nil {
+ err = f.decodeBlock(&f.h1, &f.h2);
+ }
+ default:
+ // 3 is reserved.
+ // TODO(rsc): Works around the same 6g bug.
+ var i int64 = f.getRoffset();
+ i--;
+ err = CorruptInputError(i);
+ }
+ }
+ return;
+}
+
+// RFC 1951 section 3.2.7.
+// Compression with dynamic Huffman codes
+
+var codeOrder = [...]int {
+ 16, 17, 18, 0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15
+}
+
+func (f *inflater) readHuffman() os.Error {
+ // HLIT[5], HDIST[5], HCLEN[4].
+ for f.nb < 5+5+4 {
+ if err := f.moreBits(); err != nil {
+ return err;
+ }
+ }
+ nlit := int(f.b & 0x1F) + 257;
+ f.b >>= 5;
+ ndist := int(f.b & 0x1F) + 1;
+ f.b >>= 5;
+ nclen := int(f.b & 0xF) + 4;
+ f.b >>= 4;
+ f.nb -= 5+5+4;
+
+ // (HCLEN+4)*3 bits: code lengths in the magic codeOrder order.
+ for i := 0; i < nclen; i++ {
+ for f.nb < 3 {
+ if err := f.moreBits(); err != nil {
+ return err;
+ }
+ }
+ f.codebits[codeOrder[i]] = int(f.b & 0x7);
+ f.b >>= 3;
+ f.nb -= 3;
+ }
+ for i := nclen; i < len(codeOrder); i++ {
+ f.codebits[codeOrder[i]] = 0;
+ }
+ if !f.h1.init(&f.codebits) {
+ return os.ErrorString("huff and puff");
+ }
+
+ // HLIT + 257 code lengths, HDIST + 1 code lengths,
+ // using the code length Huffman code.
+ for i, n := 0, nlit+ndist; i < n; {
+ x, err := f.huffSym(&f.h1);
+ if err != nil {
+ return err;
+ }
+ if x < 16 {
+ // Actual length.
+ f.bits[i] = x;
+ i++;
+ continue;
+ }
+ // Repeat previous length or zero.
+ var rep int;
+ var nb uint;
+ var b int;
+ switch x {
+ default:
+ return InternalError("unexpected length code");
+ case 16:
+ rep = 3;
+ nb = 2;
+ if i == 0 {
+ return CorruptInputError(f.getRoffset());
+ }
+ b = f.bits[i-1];
+ case 17:
+ rep = 3;
+ nb = 3;
+ b = 0;
+ case 18:
+ rep = 11;
+ nb = 7;
+ b = 0;
+ }
+ for f.nb < nb {
+ if err := f.moreBits(); err != nil {
+ return err;
+ }
+ }
+ rep += int(f.b & uint32(1<<nb - 1));
+ f.b >>= nb;
+ f.nb -= nb;
+ if i+rep > n {
+ return CorruptInputError(f.getRoffset());
+ }
+ for j := 0; j < rep; j++ {
+ f.bits[i] = b;
+ i++;
+ }
+ }
+
+ if !f.h1.init(f.bits[0:nlit]) || !f.h2.init(f.bits[nlit:nlit+ndist]) {
+ return CorruptInputError(f.getRoffset());
+ }
+
+ return nil;
+}
+
+// Decode a single Huffman block from f.
+// hl and hd are the Huffman states for the lit/length values
+// and the distance values, respectively. If hd == nil, using the
+// fixed distance encoding assocated with fixed Huffman blocks.
+func (f *inflater) decodeBlock(hl, hd *huffmanDecoder) os.Error {
+ for {
+ v, err := f.huffSym(hl);
+ if err != nil {
+ return err;
+ }
+ var n uint; // number of bits extra
+ var length int;
+ switch {
+ case v < 256:
+ f.hist[f.hp] = byte(v);
+ f.hp++;
+ if f.hp == len(f.hist) {
+ if err = f.flush(); err != nil {
+ return err;
+ }
+ }
+ continue;
+ case v == 256:
+ return nil;
+ // otherwise, reference to older data
+ case v < 265:
+ length = v - (257 - 3);
+ n = 0;
+ case v < 269:
+ length = v*2 - (265*2 - 11);
+ n = 1;
+ case v < 273:
+ length = v*4 - (269*4 - 19);
+ n = 2;
+ case v < 277:
+ length = v*8 - (273*8 - 35);
+ n = 3;
+ case v < 281:
+ length = v*16 - (277*16 - 67);
+ n = 4;
+ case v < 285:
+ length = v*32 - (281*32 - 131);
+ n = 5;
+ default:
+ length = 258;
+ n = 0;
+ }
+ if n > 0 {
+ for f.nb < n {
+ if err = f.moreBits(); err != nil {
+ return err;
+ }
+ }
+ length += int(f.b & uint32(1<<n - 1));
+ f.b >>= n;
+ f.nb -= n;
+ }
+
+ var dist int;
+ if hd == nil {
+ for f.nb < 5 {
+ if err = f.moreBits(); err != nil {
+ return err;
+ }
+ }
+ dist = int(f.b & 0x1F);
+ f.b >>= 5;
+ f.nb -= 5;
+ } else {
+ if dist, err = f.huffSym(hd); err != nil {
+ return err;
+ }
+ }
+
+ switch {
+ case dist < 4:
+ dist++;
+ case dist >= 30:
+ return CorruptInputError(f.getRoffset());
+ default:
+ nb := uint(dist - 2) >> 1;
+ // have 1 bit in bottom of dist, need nb more.
+ extra := (dist&1) << nb;
+ for f.nb < nb {
+ if err = f.moreBits(); err != nil {
+ return err;
+ }
+ }
+ extra |= int(f.b & uint32(1<<nb - 1));
+ f.b >>= nb;
+ f.nb -= nb;
+ dist = 1<<(nb+1) + 1 + extra;
+ }
+
+ // Copy history[-dist:-dist+length] into output.
+ if dist > len(f.hist) {
+ return InternalError("bad history distance");
+ }
+
+ // No check on length; encoding can be prescient.
+ if !f.hfull && dist > f.hp {
+ return CorruptInputError(f.getRoffset());
+ }
+
+ p := f.hp - dist;
+ if p < 0 {
+ p += len(f.hist);
+ }
+ for i := 0; i < length; i++ {
+ f.hist[f.hp] = f.hist[p];
+ f.hp++;
+ p++;
+ if f.hp == len(f.hist) {
+ if err = f.flush(); err != nil {
+ return err;
+ }
+ }
+ if p == len(f.hist) {
+ p = 0;
+ }
+ }
+ }
+ panic("unreached");
+}
+
+// Copy a single uncompressed data block from input to output.
+func (f *inflater) dataBlock() os.Error {
+ // Uncompressed.
+ // Discard current half-byte.
+ f.nb = 0;
+ f.b = 0;
+
+ // Length then ones-complement of length.
+ nr, err := f.r.Read(f.buf[0:4]);
+ f.roffset += int64(nr);
+ if nr < 4 && err == nil {
+ err = io.ErrEOF;
+ }
+ if err != nil {
+ return &ReadError{f.roffset, err};
+ }
+ n := int(f.buf[0]) | int(f.buf[1])<<8;
+ nn := int(f.buf[2]) | int(f.buf[3])<<8;
+ if nn != ^n {
+ return CorruptInputError(f.getRoffset());
+ }
+
+ // Read len bytes into history,
+ // writing as history fills.
+ for n > 0 {
+ m := len(f.hist) - f.hp;
+ if m > n {
+ m = n;
+ }
+ m, err := f.r.Read(f.hist[f.hp:f.hp+m]);
+ f.roffset += int64(m);
+ if m == 0 && err == nil {
+ err = io.ErrEOF;
+ }
+ if err != nil {
+ return &ReadError{f.roffset, err};
+ }
+ n -= m;
+ f.hp += m;
+ if f.hp == len(f.hist) {
+ if err = f.flush(); err != nil {
+ return err;
+ }
+ }
+ }
+ return nil;
+}
+
+func (f *inflater) moreBits() os.Error {
+ c, err := f.r.ReadByte();
+ if err != nil {
+ return err;
+ }
+ f.roffset++;
+ f.b |= uint32(c) << f.nb;
+ f.nb += 8;
+ return nil;
+}
+
+// Read the next Huffman-encoded symbol from f according to h.
+func (f *inflater) huffSym(h *huffmanDecoder) (int, os.Error) {
+ for n := uint(h.min); n <= uint(h.max); n++ {
+ lim := h.limit[n];
+ if lim == -1 {
+ continue;
+ }
+ for f.nb < n {
+ if err := f.moreBits(); err != nil {
+ return 0, err;
+ }
+ }
+ v := int(f.b & uint32(1<<n - 1));
+ v <<= 16 - n;
+ v = int(reverseByte[v>>8]) | int(reverseByte[v&0xFF])<<8; // reverse bits
+ if v <= lim {
+ f.b >>= n;
+ f.nb -= n;
+ return h.codes[v - h.base[n]], nil;
+ }
+ }
+ return 0, CorruptInputError(f.getRoffset());
+}
+
+// Flush any buffered output to the underlying writer.
+func (f *inflater) flush() os.Error {
+ if f.hp == 0 {
+ return nil;
+ }
+ n, err := f.w.Write(f.hist[0:f.hp]);
+ if n != f.hp && err == nil {
+ err = io.ErrShortWrite;
+ }
+ if err != nil {
+ return &WriteError{f.woffset, err};
+ }
+ f.woffset += int64(f.hp);
+ f.hp = 0;
+ f.hfull = true;
+ return nil;
+}
+
+func makeReader(r io.Reader) Reader {
+ if rr, ok := r.(Reader); ok {
+ return rr;
+ }
+ return bufio.NewReader(r);
+}
+
+// Inflate reads DEFLATE-compressed data from r and writes
+// the uncompressed data to w.
+func (f *inflater) inflater(r io.Reader, w io.Writer) os.Error {
+ var ok bool; // TODO(rsc): why not := on next line?
+ f.r = makeReader(r);
+ f.w = w;
+ f.woffset = 0;
+ if err := f.inflate(); err != nil {
+ return err;
+ }
+ if err := f.flush(); err != nil {
+ return err;
+ }
+ return nil;
+}
+
+// NewInflater returns a new ReadCloser that can be used
+// to read the uncompressed version of r. It is the caller's
+// responsibility to call Close on the ReadClosed when
+// finished reading.
+func NewInflater(r io.Reader) io.ReadCloser {
+ var f inflater;
+ pr, pw := io.Pipe();
+ go func() {
+ pw.CloseWithError(f.inflater(r, pw));
+ }();
+ return pr;
+}