diff --git a/src/compress/flate/fixedhuff.go b/src/compress/flate/fixedhuff.go deleted file mode 100644 index 7df8b9a293..0000000000 --- a/src/compress/flate/fixedhuff.go +++ /dev/null @@ -1,78 +0,0 @@ -// Copyright 2013 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 flate - -// autogenerated by go run gen.go -output fixedhuff.go, DO NOT EDIT - -var fixedHuffmanDecoder = huffmanDecoder{ - 7, - [huffmanNumChunks]uint32{ - 0x1007, 0x0508, 0x0108, 0x1188, 0x1107, 0x0708, 0x0308, 0x0c09, - 0x1087, 0x0608, 0x0208, 0x0a09, 0x0008, 0x0808, 0x0408, 0x0e09, - 0x1047, 0x0588, 0x0188, 0x0909, 0x1147, 0x0788, 0x0388, 0x0d09, - 0x10c7, 0x0688, 0x0288, 0x0b09, 0x0088, 0x0888, 0x0488, 0x0f09, - 0x1027, 0x0548, 0x0148, 0x11c8, 0x1127, 0x0748, 0x0348, 0x0c89, - 0x10a7, 0x0648, 0x0248, 0x0a89, 0x0048, 0x0848, 0x0448, 0x0e89, - 0x1067, 0x05c8, 0x01c8, 0x0989, 0x1167, 0x07c8, 0x03c8, 0x0d89, - 0x10e7, 0x06c8, 0x02c8, 0x0b89, 0x00c8, 0x08c8, 0x04c8, 0x0f89, - 0x1017, 0x0528, 0x0128, 0x11a8, 0x1117, 0x0728, 0x0328, 0x0c49, - 0x1097, 0x0628, 0x0228, 0x0a49, 0x0028, 0x0828, 0x0428, 0x0e49, - 0x1057, 0x05a8, 0x01a8, 0x0949, 0x1157, 0x07a8, 0x03a8, 0x0d49, - 0x10d7, 0x06a8, 0x02a8, 0x0b49, 0x00a8, 0x08a8, 0x04a8, 0x0f49, - 0x1037, 0x0568, 0x0168, 0x11e8, 0x1137, 0x0768, 0x0368, 0x0cc9, - 0x10b7, 0x0668, 0x0268, 0x0ac9, 0x0068, 0x0868, 0x0468, 0x0ec9, - 0x1077, 0x05e8, 0x01e8, 0x09c9, 0x1177, 0x07e8, 0x03e8, 0x0dc9, - 0x10f7, 0x06e8, 0x02e8, 0x0bc9, 0x00e8, 0x08e8, 0x04e8, 0x0fc9, - 0x1007, 0x0518, 0x0118, 0x1198, 0x1107, 0x0718, 0x0318, 0x0c29, - 0x1087, 0x0618, 0x0218, 0x0a29, 0x0018, 0x0818, 0x0418, 0x0e29, - 0x1047, 0x0598, 0x0198, 0x0929, 0x1147, 0x0798, 0x0398, 0x0d29, - 0x10c7, 0x0698, 0x0298, 0x0b29, 0x0098, 0x0898, 0x0498, 0x0f29, - 0x1027, 0x0558, 0x0158, 0x11d8, 0x1127, 0x0758, 0x0358, 0x0ca9, - 0x10a7, 0x0658, 0x0258, 0x0aa9, 0x0058, 0x0858, 0x0458, 0x0ea9, - 0x1067, 0x05d8, 0x01d8, 0x09a9, 0x1167, 0x07d8, 0x03d8, 0x0da9, - 0x10e7, 0x06d8, 0x02d8, 0x0ba9, 0x00d8, 0x08d8, 0x04d8, 0x0fa9, - 0x1017, 0x0538, 0x0138, 0x11b8, 0x1117, 0x0738, 0x0338, 0x0c69, - 0x1097, 0x0638, 0x0238, 0x0a69, 0x0038, 0x0838, 0x0438, 0x0e69, - 0x1057, 0x05b8, 0x01b8, 0x0969, 0x1157, 0x07b8, 0x03b8, 0x0d69, - 0x10d7, 0x06b8, 0x02b8, 0x0b69, 0x00b8, 0x08b8, 0x04b8, 0x0f69, - 0x1037, 0x0578, 0x0178, 0x11f8, 0x1137, 0x0778, 0x0378, 0x0ce9, - 0x10b7, 0x0678, 0x0278, 0x0ae9, 0x0078, 0x0878, 0x0478, 0x0ee9, - 0x1077, 0x05f8, 0x01f8, 0x09e9, 0x1177, 0x07f8, 0x03f8, 0x0de9, - 0x10f7, 0x06f8, 0x02f8, 0x0be9, 0x00f8, 0x08f8, 0x04f8, 0x0fe9, - 0x1007, 0x0508, 0x0108, 0x1188, 0x1107, 0x0708, 0x0308, 0x0c19, - 0x1087, 0x0608, 0x0208, 0x0a19, 0x0008, 0x0808, 0x0408, 0x0e19, - 0x1047, 0x0588, 0x0188, 0x0919, 0x1147, 0x0788, 0x0388, 0x0d19, - 0x10c7, 0x0688, 0x0288, 0x0b19, 0x0088, 0x0888, 0x0488, 0x0f19, - 0x1027, 0x0548, 0x0148, 0x11c8, 0x1127, 0x0748, 0x0348, 0x0c99, - 0x10a7, 0x0648, 0x0248, 0x0a99, 0x0048, 0x0848, 0x0448, 0x0e99, - 0x1067, 0x05c8, 0x01c8, 0x0999, 0x1167, 0x07c8, 0x03c8, 0x0d99, - 0x10e7, 0x06c8, 0x02c8, 0x0b99, 0x00c8, 0x08c8, 0x04c8, 0x0f99, - 0x1017, 0x0528, 0x0128, 0x11a8, 0x1117, 0x0728, 0x0328, 0x0c59, - 0x1097, 0x0628, 0x0228, 0x0a59, 0x0028, 0x0828, 0x0428, 0x0e59, - 0x1057, 0x05a8, 0x01a8, 0x0959, 0x1157, 0x07a8, 0x03a8, 0x0d59, - 0x10d7, 0x06a8, 0x02a8, 0x0b59, 0x00a8, 0x08a8, 0x04a8, 0x0f59, - 0x1037, 0x0568, 0x0168, 0x11e8, 0x1137, 0x0768, 0x0368, 0x0cd9, - 0x10b7, 0x0668, 0x0268, 0x0ad9, 0x0068, 0x0868, 0x0468, 0x0ed9, - 0x1077, 0x05e8, 0x01e8, 0x09d9, 0x1177, 0x07e8, 0x03e8, 0x0dd9, - 0x10f7, 0x06e8, 0x02e8, 0x0bd9, 0x00e8, 0x08e8, 0x04e8, 0x0fd9, - 0x1007, 0x0518, 0x0118, 0x1198, 0x1107, 0x0718, 0x0318, 0x0c39, - 0x1087, 0x0618, 0x0218, 0x0a39, 0x0018, 0x0818, 0x0418, 0x0e39, - 0x1047, 0x0598, 0x0198, 0x0939, 0x1147, 0x0798, 0x0398, 0x0d39, - 0x10c7, 0x0698, 0x0298, 0x0b39, 0x0098, 0x0898, 0x0498, 0x0f39, - 0x1027, 0x0558, 0x0158, 0x11d8, 0x1127, 0x0758, 0x0358, 0x0cb9, - 0x10a7, 0x0658, 0x0258, 0x0ab9, 0x0058, 0x0858, 0x0458, 0x0eb9, - 0x1067, 0x05d8, 0x01d8, 0x09b9, 0x1167, 0x07d8, 0x03d8, 0x0db9, - 0x10e7, 0x06d8, 0x02d8, 0x0bb9, 0x00d8, 0x08d8, 0x04d8, 0x0fb9, - 0x1017, 0x0538, 0x0138, 0x11b8, 0x1117, 0x0738, 0x0338, 0x0c79, - 0x1097, 0x0638, 0x0238, 0x0a79, 0x0038, 0x0838, 0x0438, 0x0e79, - 0x1057, 0x05b8, 0x01b8, 0x0979, 0x1157, 0x07b8, 0x03b8, 0x0d79, - 0x10d7, 0x06b8, 0x02b8, 0x0b79, 0x00b8, 0x08b8, 0x04b8, 0x0f79, - 0x1037, 0x0578, 0x0178, 0x11f8, 0x1137, 0x0778, 0x0378, 0x0cf9, - 0x10b7, 0x0678, 0x0278, 0x0af9, 0x0078, 0x0878, 0x0478, 0x0ef9, - 0x1077, 0x05f8, 0x01f8, 0x09f9, 0x1177, 0x07f8, 0x03f8, 0x0df9, - 0x10f7, 0x06f8, 0x02f8, 0x0bf9, 0x00f8, 0x08f8, 0x04f8, 0x0ff9, - }, - nil, 0, -} diff --git a/src/compress/flate/gen.go b/src/compress/flate/gen.go deleted file mode 100644 index 154c89a488..0000000000 --- a/src/compress/flate/gen.go +++ /dev/null @@ -1,265 +0,0 @@ -// Copyright 2012 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. - -// +build ignore - -// This program generates fixedhuff.go -// Invoke as -// -// go run gen.go -output fixedhuff.go - -package main - -import ( - "bytes" - "flag" - "fmt" - "go/format" - "io/ioutil" - "log" -) - -var filename = flag.String("output", "fixedhuff.go", "output file name") - -const maxCodeLen = 16 - -// Note: the definition of the huffmanDecoder struct is copied from -// inflate.go, as it is private to the implementation. - -// chunk & 15 is number of bits -// chunk >> 4 is value, including table link - -const ( - huffmanChunkBits = 9 - huffmanNumChunks = 1 << huffmanChunkBits - huffmanCountMask = 15 - huffmanValueShift = 4 -) - -type huffmanDecoder struct { - min int // the minimum code length - chunks [huffmanNumChunks]uint32 // chunks as described above - links [][]uint32 // overflow links - linkMask uint32 // mask the width of the link table -} - -// Initialize Huffman decoding tables from array of code lengths. -// Following this function, h is guaranteed to be initialized into a complete -// tree (i.e., neither over-subscribed nor under-subscribed). The exception is a -// degenerate case where the tree has only a single symbol with length 1. Empty -// trees are permitted. -func (h *huffmanDecoder) init(bits []int) bool { - // Sanity enables additional runtime tests during Huffman - // table construction. It's intended to be used during - // development to supplement the currently ad-hoc unit tests. - const sanity = false - - if h.min != 0 { - *h = huffmanDecoder{} - } - - // Count number of codes of each length, - // compute min and max length. - var count [maxCodeLen]int - var min, max int - for _, n := range bits { - if n == 0 { - continue - } - if min == 0 || n < min { - min = n - } - if n > max { - max = n - } - count[n]++ - } - - // Empty tree. The decompressor.huffSym function will fail later if the tree - // is used. Technically, an empty tree is only valid for the HDIST tree and - // not the HCLEN and HLIT tree. However, a stream with an empty HCLEN tree - // is guaranteed to fail since it will attempt to use the tree to decode the - // codes for the HLIT and HDIST trees. Similarly, an empty HLIT tree is - // guaranteed to fail later since the compressed data section must be - // composed of at least one symbol (the end-of-block marker). - if max == 0 { - return true - } - - code := 0 - var nextcode [maxCodeLen]int - for i := min; i <= max; i++ { - code <<= 1 - nextcode[i] = code - code += count[i] - } - - // Check that the coding is complete (i.e., that we've - // assigned all 2-to-the-max possible bit sequences). - // Exception: To be compatible with zlib, we also need to - // accept degenerate single-code codings. See also - // TestDegenerateHuffmanCoding. - if code != 1< huffmanChunkBits { - numLinks := 1 << (uint(max) - huffmanChunkBits) - h.linkMask = uint32(numLinks - 1) - - // create link tables - link := nextcode[huffmanChunkBits+1] >> 1 - h.links = make([][]uint32, huffmanNumChunks-link) - for j := uint(link); j < huffmanNumChunks; j++ { - reverse := int(reverseByte[j>>8]) | int(reverseByte[j&0xff])<<8 - reverse >>= uint(16 - huffmanChunkBits) - off := j - uint(link) - if sanity && h.chunks[reverse] != 0 { - panic("impossible: overwriting existing chunk") - } - h.chunks[reverse] = uint32(off<>8]) | int(reverseByte[code&0xff])<<8 - reverse >>= uint(16 - n) - if n <= huffmanChunkBits { - for off := reverse; off < len(h.chunks); off += 1 << uint(n) { - // We should never need to overwrite - // an existing chunk. Also, 0 is - // never a valid chunk, because the - // lower 4 "count" bits should be - // between 1 and 15. - if sanity && h.chunks[off] != 0 { - panic("impossible: overwriting existing chunk") - } - h.chunks[off] = chunk - } - } else { - j := reverse & (huffmanNumChunks - 1) - if sanity && h.chunks[j]&huffmanCountMask != huffmanChunkBits+1 { - // Longer codes should have been - // associated with a link table above. - panic("impossible: not an indirect chunk") - } - value := h.chunks[j] >> huffmanValueShift - linktab := h.links[value] - reverse >>= huffmanChunkBits - for off := reverse; off < len(linktab); off += 1 << uint(n-huffmanChunkBits) { - if sanity && linktab[off] != 0 { - panic("impossible: overwriting existing chunk") - } - linktab[off] = chunk - } - } - } - - if sanity { - // Above we've sanity checked that we never overwrote - // an existing entry. Here we additionally check that - // we filled the tables completely. - for i, chunk := range h.chunks { - if chunk == 0 { - // As an exception, in the degenerate - // single-code case, we allow odd - // chunks to be missing. - if code == 1 && i%2 == 1 { - continue - } - panic("impossible: missing chunk") - } - } - for _, linktab := range h.links { - for _, chunk := range linktab { - if chunk == 0 { - panic("impossible: missing chunk") - } - } - } - } - - return true -} - -func main() { - flag.Parse() - - var h huffmanDecoder - var bits [288]int - initReverseByte() - for i := 0; i < 144; i++ { - bits[i] = 8 - } - for i := 144; i < 256; i++ { - bits[i] = 9 - } - for i := 256; i < 280; i++ { - bits[i] = 7 - } - for i := 280; i < 288; i++ { - bits[i] = 8 - } - h.init(bits[:]) - if h.links != nil { - log.Fatal("Unexpected links table in fixed Huffman decoder") - } - - var buf bytes.Buffer - - fmt.Fprintf(&buf, `// Copyright 2013 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.`+"\n\n") - - fmt.Fprintln(&buf, "package flate") - fmt.Fprintln(&buf) - fmt.Fprintln(&buf, "// autogenerated by go run gen.go -output fixedhuff.go, DO NOT EDIT") - fmt.Fprintln(&buf) - fmt.Fprintln(&buf, "var fixedHuffmanDecoder = huffmanDecoder{") - fmt.Fprintf(&buf, "\t%d,\n", h.min) - fmt.Fprintln(&buf, "\t[huffmanNumChunks]uint32{") - for i := 0; i < huffmanNumChunks; i++ { - if i&7 == 0 { - fmt.Fprintf(&buf, "\t\t") - } else { - fmt.Fprintf(&buf, " ") - } - fmt.Fprintf(&buf, "0x%04x,", h.chunks[i]) - if i&7 == 7 { - fmt.Fprintln(&buf) - } - } - fmt.Fprintln(&buf, "\t},") - fmt.Fprintln(&buf, "\tnil, 0,") - fmt.Fprintln(&buf, "}") - - data, err := format.Source(buf.Bytes()) - if err != nil { - log.Fatal(err) - } - err = ioutil.WriteFile(*filename, data, 0644) - if err != nil { - log.Fatal(err) - } -} - -var reverseByte [256]byte - -func initReverseByte() { - for x := 0; x < 256; x++ { - var result byte - for i := uint(0); i < 8; i++ { - result |= byte(((x >> i) & 1) << (7 - i)) - } - reverseByte[x] = result - } -} diff --git a/src/compress/flate/inflate.go b/src/compress/flate/inflate.go index 04372dec24..09f6115804 100644 --- a/src/compress/flate/inflate.go +++ b/src/compress/flate/inflate.go @@ -2,8 +2,6 @@ // Use of this source code is governed by a BSD-style // license that can be found in the LICENSE file. -//go:generate go run gen.go -output fixedhuff.go - // Package flate implements the DEFLATE compressed data format, described in // RFC 1951. The gzip and zlib packages implement access to DEFLATE-based file // formats. @@ -13,6 +11,7 @@ import ( "bufio" "io" "strconv" + "sync" ) const ( @@ -26,6 +25,10 @@ const ( numCodes = 19 // number of codes in Huffman meta-code ) +// Initialize the fixedHuffmanDecoder only once upon first use. +var fixedOnce sync.Once +var fixedHuffmanDecoder huffmanDecoder + // A CorruptInputError reports the presence of corrupt input at a given offset. type CorruptInputError int64 @@ -67,10 +70,6 @@ type Resetter interface { Reset(r io.Reader, dict []byte) error } -// Note that much of the implementation of huffmanDecoder is also copied -// into gen.go (in package main) for the purpose of precomputing the -// fixed huffman tables so they can be included statically. - // The data structure for decoding Huffman tables is based on that of // zlib. There is a lookup table of a fixed bit width (huffmanChunkBits), // For codes smaller than the table width, there are multiple entries @@ -78,12 +77,15 @@ type Resetter interface { // larger than the table width, the table contains a link to an overflow // table. The width of each entry in the link table is the maximum code // size minus the chunk width. - +// // Note that you can do a lookup in the table even without all bits // filled. Since the extra bits are zero, and the DEFLATE Huffman codes // have the property that shorter codes come before longer ones, the // bit length estimate in the result is a lower bound on the actual // number of bits. +// +// See the following: +// http://www.gzip.org/algorithm.txt // chunk & 15 is number of bits // chunk >> 4 is value, including table link @@ -760,6 +762,26 @@ func makeReader(r io.Reader) Reader { return bufio.NewReader(r) } +func fixedHuffmanDecoderInit() { + fixedOnce.Do(func() { + // These come from the RFC section 3.2.6. + var bits [288]int + for i := 0; i < 144; i++ { + bits[i] = 8 + } + for i := 144; i < 256; i++ { + bits[i] = 9 + } + for i := 256; i < 280; i++ { + bits[i] = 7 + } + for i := 280; i < 288; i++ { + bits[i] = 8 + } + fixedHuffmanDecoder.init(bits[:]) + }) +} + func (f *decompressor) Reset(r io.Reader, dict []byte) error { *f = decompressor{ r: makeReader(r), @@ -783,11 +805,13 @@ func (f *decompressor) Reset(r io.Reader, dict []byte) error { // // The ReadCloser returned by NewReader also implements Resetter. func NewReader(r io.Reader) io.ReadCloser { + fixedHuffmanDecoderInit() + var f decompressor - f.bits = new([maxNumLit + maxNumDist]int) - f.codebits = new([numCodes]int) f.r = makeReader(r) f.hist = new([maxHist]byte) + f.bits = new([maxNumLit + maxNumDist]int) + f.codebits = new([numCodes]int) f.step = (*decompressor).nextBlock return &f } @@ -800,6 +824,8 @@ func NewReader(r io.Reader) io.ReadCloser { // // The ReadCloser returned by NewReader also implements Resetter. func NewReaderDict(r io.Reader, dict []byte) io.ReadCloser { + fixedHuffmanDecoderInit() + var f decompressor f.r = makeReader(r) f.hist = new([maxHist]byte)