038a3329b1
snappy-stubs-public.h defined the DISALLOW_COPY_AND_ASSIGN macro, so the definition propagated to all translation units that included the open source headers. The macro is now inlined, thus avoiding polluting the macro environment of snappy users.
224 lines
9.1 KiB
C++
224 lines
9.1 KiB
C++
// Copyright 2008 Google Inc. All Rights Reserved.
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//
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// Redistribution and use in source and binary forms, with or without
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// modification, are permitted provided that the following conditions are
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// met:
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//
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// * Redistributions of source code must retain the above copyright
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// notice, this list of conditions and the following disclaimer.
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// * Redistributions in binary form must reproduce the above
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// copyright notice, this list of conditions and the following disclaimer
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// in the documentation and/or other materials provided with the
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// distribution.
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// * Neither the name of Google Inc. nor the names of its
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// contributors may be used to endorse or promote products derived from
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// this software without specific prior written permission.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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//
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// Internals shared between the Snappy implementation and its unittest.
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#ifndef THIRD_PARTY_SNAPPY_SNAPPY_INTERNAL_H_
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#define THIRD_PARTY_SNAPPY_SNAPPY_INTERNAL_H_
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#include "snappy-stubs-internal.h"
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namespace snappy {
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namespace internal {
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class WorkingMemory {
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public:
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WorkingMemory() : large_table_(NULL) { }
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~WorkingMemory() { delete[] large_table_; }
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// Allocates and clears a hash table using memory in "*this",
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// stores the number of buckets in "*table_size" and returns a pointer to
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// the base of the hash table.
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uint16* GetHashTable(size_t input_size, int* table_size);
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private:
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uint16 small_table_[1<<10]; // 2KB
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uint16* large_table_; // Allocated only when needed
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// No copying
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WorkingMemory(const WorkingMemory&);
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void operator=(const WorkingMemory&);
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};
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// Flat array compression that does not emit the "uncompressed length"
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// prefix. Compresses "input" string to the "*op" buffer.
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//
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// REQUIRES: "input_length <= kBlockSize"
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// REQUIRES: "op" points to an array of memory that is at least
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// "MaxCompressedLength(input_length)" in size.
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// REQUIRES: All elements in "table[0..table_size-1]" are initialized to zero.
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// REQUIRES: "table_size" is a power of two
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//
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// Returns an "end" pointer into "op" buffer.
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// "end - op" is the compressed size of "input".
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char* CompressFragment(const char* input,
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size_t input_length,
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char* op,
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uint16* table,
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const int table_size);
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// Find the largest n such that
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//
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// s1[0,n-1] == s2[0,n-1]
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// and n <= (s2_limit - s2).
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//
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// Return make_pair(n, n < 8).
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// Does not read *s2_limit or beyond.
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// Does not read *(s1 + (s2_limit - s2)) or beyond.
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// Requires that s2_limit >= s2.
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//
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// Separate implementation for 64-bit, little-endian cpus.
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#if defined(ARCH_K8) || (defined(ARCH_PPC) && !defined(WORDS_BIGENDIAN))
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static inline std::pair<size_t, bool> FindMatchLength(const char* s1,
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const char* s2,
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const char* s2_limit) {
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assert(s2_limit >= s2);
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size_t matched = 0;
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// This block isn't necessary for correctness; we could just start looping
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// immediately. As an optimization though, it is useful. It creates some not
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// uncommon code paths that determine, without extra effort, whether the match
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// length is less than 8. In short, we are hoping to avoid a conditional
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// branch, and perhaps get better code layout from the C++ compiler.
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if (PREDICT_TRUE(s2 <= s2_limit - 8)) {
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uint64 a1 = UNALIGNED_LOAD64(s1);
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uint64 a2 = UNALIGNED_LOAD64(s2);
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if (a1 != a2) {
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return std::pair<size_t, bool>(Bits::FindLSBSetNonZero64(a1 ^ a2) >> 3,
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true);
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} else {
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matched = 8;
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s2 += 8;
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}
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}
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// Find out how long the match is. We loop over the data 64 bits at a
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// time until we find a 64-bit block that doesn't match; then we find
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// the first non-matching bit and use that to calculate the total
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// length of the match.
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while (PREDICT_TRUE(s2 <= s2_limit - 8)) {
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if (UNALIGNED_LOAD64(s2) == UNALIGNED_LOAD64(s1 + matched)) {
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s2 += 8;
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matched += 8;
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} else {
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uint64 x = UNALIGNED_LOAD64(s2) ^ UNALIGNED_LOAD64(s1 + matched);
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int matching_bits = Bits::FindLSBSetNonZero64(x);
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matched += matching_bits >> 3;
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assert(matched >= 8);
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return std::pair<size_t, bool>(matched, false);
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}
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}
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while (PREDICT_TRUE(s2 < s2_limit)) {
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if (s1[matched] == *s2) {
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++s2;
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++matched;
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} else {
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return std::pair<size_t, bool>(matched, matched < 8);
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}
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}
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return std::pair<size_t, bool>(matched, matched < 8);
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}
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#else
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static inline std::pair<size_t, bool> FindMatchLength(const char* s1,
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const char* s2,
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const char* s2_limit) {
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// Implementation based on the x86-64 version, above.
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assert(s2_limit >= s2);
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int matched = 0;
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while (s2 <= s2_limit - 4 &&
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UNALIGNED_LOAD32(s2) == UNALIGNED_LOAD32(s1 + matched)) {
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s2 += 4;
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matched += 4;
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}
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if (LittleEndian::IsLittleEndian() && s2 <= s2_limit - 4) {
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uint32 x = UNALIGNED_LOAD32(s2) ^ UNALIGNED_LOAD32(s1 + matched);
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int matching_bits = Bits::FindLSBSetNonZero(x);
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matched += matching_bits >> 3;
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} else {
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while ((s2 < s2_limit) && (s1[matched] == *s2)) {
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++s2;
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++matched;
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}
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}
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return std::pair<size_t, bool>(matched, matched < 8);
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}
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#endif
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// Lookup tables for decompression code. Give --snappy_dump_decompression_table
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// to the unit test to recompute char_table.
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enum {
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LITERAL = 0,
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COPY_1_BYTE_OFFSET = 1, // 3 bit length + 3 bits of offset in opcode
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COPY_2_BYTE_OFFSET = 2,
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COPY_4_BYTE_OFFSET = 3
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};
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static const int kMaximumTagLength = 5; // COPY_4_BYTE_OFFSET plus the actual offset.
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// Data stored per entry in lookup table:
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// Range Bits-used Description
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// ------------------------------------
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// 1..64 0..7 Literal/copy length encoded in opcode byte
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// 0..7 8..10 Copy offset encoded in opcode byte / 256
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// 0..4 11..13 Extra bytes after opcode
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//
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// We use eight bits for the length even though 7 would have sufficed
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// because of efficiency reasons:
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// (1) Extracting a byte is faster than a bit-field
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// (2) It properly aligns copy offset so we do not need a <<8
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static const uint16 char_table[256] = {
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0x0001, 0x0804, 0x1001, 0x2001, 0x0002, 0x0805, 0x1002, 0x2002,
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0x0003, 0x0806, 0x1003, 0x2003, 0x0004, 0x0807, 0x1004, 0x2004,
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0x0005, 0x0808, 0x1005, 0x2005, 0x0006, 0x0809, 0x1006, 0x2006,
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0x0007, 0x080a, 0x1007, 0x2007, 0x0008, 0x080b, 0x1008, 0x2008,
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0x0009, 0x0904, 0x1009, 0x2009, 0x000a, 0x0905, 0x100a, 0x200a,
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0x000b, 0x0906, 0x100b, 0x200b, 0x000c, 0x0907, 0x100c, 0x200c,
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0x000d, 0x0908, 0x100d, 0x200d, 0x000e, 0x0909, 0x100e, 0x200e,
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0x000f, 0x090a, 0x100f, 0x200f, 0x0010, 0x090b, 0x1010, 0x2010,
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0x0011, 0x0a04, 0x1011, 0x2011, 0x0012, 0x0a05, 0x1012, 0x2012,
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0x0013, 0x0a06, 0x1013, 0x2013, 0x0014, 0x0a07, 0x1014, 0x2014,
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0x0015, 0x0a08, 0x1015, 0x2015, 0x0016, 0x0a09, 0x1016, 0x2016,
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0x0017, 0x0a0a, 0x1017, 0x2017, 0x0018, 0x0a0b, 0x1018, 0x2018,
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0x0019, 0x0b04, 0x1019, 0x2019, 0x001a, 0x0b05, 0x101a, 0x201a,
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0x001b, 0x0b06, 0x101b, 0x201b, 0x001c, 0x0b07, 0x101c, 0x201c,
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0x001d, 0x0b08, 0x101d, 0x201d, 0x001e, 0x0b09, 0x101e, 0x201e,
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0x001f, 0x0b0a, 0x101f, 0x201f, 0x0020, 0x0b0b, 0x1020, 0x2020,
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0x0021, 0x0c04, 0x1021, 0x2021, 0x0022, 0x0c05, 0x1022, 0x2022,
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0x0023, 0x0c06, 0x1023, 0x2023, 0x0024, 0x0c07, 0x1024, 0x2024,
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0x0025, 0x0c08, 0x1025, 0x2025, 0x0026, 0x0c09, 0x1026, 0x2026,
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0x0027, 0x0c0a, 0x1027, 0x2027, 0x0028, 0x0c0b, 0x1028, 0x2028,
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0x0029, 0x0d04, 0x1029, 0x2029, 0x002a, 0x0d05, 0x102a, 0x202a,
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0x002b, 0x0d06, 0x102b, 0x202b, 0x002c, 0x0d07, 0x102c, 0x202c,
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0x002d, 0x0d08, 0x102d, 0x202d, 0x002e, 0x0d09, 0x102e, 0x202e,
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0x002f, 0x0d0a, 0x102f, 0x202f, 0x0030, 0x0d0b, 0x1030, 0x2030,
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0x0031, 0x0e04, 0x1031, 0x2031, 0x0032, 0x0e05, 0x1032, 0x2032,
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0x0033, 0x0e06, 0x1033, 0x2033, 0x0034, 0x0e07, 0x1034, 0x2034,
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0x0035, 0x0e08, 0x1035, 0x2035, 0x0036, 0x0e09, 0x1036, 0x2036,
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0x0037, 0x0e0a, 0x1037, 0x2037, 0x0038, 0x0e0b, 0x1038, 0x2038,
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0x0039, 0x0f04, 0x1039, 0x2039, 0x003a, 0x0f05, 0x103a, 0x203a,
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0x003b, 0x0f06, 0x103b, 0x203b, 0x003c, 0x0f07, 0x103c, 0x203c,
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0x0801, 0x0f08, 0x103d, 0x203d, 0x1001, 0x0f09, 0x103e, 0x203e,
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0x1801, 0x0f0a, 0x103f, 0x203f, 0x2001, 0x0f0b, 0x1040, 0x2040
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};
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} // end namespace internal
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} // end namespace snappy
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#endif // THIRD_PARTY_SNAPPY_SNAPPY_INTERNAL_H_
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