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6835abd953
((a*b)>>18) & mask has higher throughput than (a*b)>>shift, and produces the same results when the hash table size is 2**14. In other cases, the hash function is still good, but it's not as necessary for that to be the case as the input is small anyway. This speeds up in encoding, especially in cases where hashing is a significant part of the encoding critical path (small or uncompressible files). PiperOrigin-RevId: 341498741
1741 lines
62 KiB
C++
1741 lines
62 KiB
C++
// Copyright 2005 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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#include "snappy-internal.h"
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#include "snappy-sinksource.h"
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#include "snappy.h"
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#if !defined(SNAPPY_HAVE_SSSE3)
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// __SSSE3__ is defined by GCC and Clang. Visual Studio doesn't target SIMD
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// support between SSE2 and AVX (so SSSE3 instructions require AVX support), and
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// defines __AVX__ when AVX support is available.
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#if defined(__SSSE3__) || defined(__AVX__)
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#define SNAPPY_HAVE_SSSE3 1
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#else
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#define SNAPPY_HAVE_SSSE3 0
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#endif
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#endif // !defined(SNAPPY_HAVE_SSSE3)
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#if !defined(SNAPPY_HAVE_BMI2)
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// __BMI2__ is defined by GCC and Clang. Visual Studio doesn't target BMI2
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// specifically, but it does define __AVX2__ when AVX2 support is available.
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// Fortunately, AVX2 was introduced in Haswell, just like BMI2.
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//
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// BMI2 is not defined as a subset of AVX2 (unlike SSSE3 and AVX above). So,
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// GCC and Clang can build code with AVX2 enabled but BMI2 disabled, in which
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// case issuing BMI2 instructions results in a compiler error.
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#if defined(__BMI2__) || (defined(_MSC_VER) && defined(__AVX2__))
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#define SNAPPY_HAVE_BMI2 1
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#else
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#define SNAPPY_HAVE_BMI2 0
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#endif
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#endif // !defined(SNAPPY_HAVE_BMI2)
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#if SNAPPY_HAVE_SSSE3
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// Please do not replace with <x86intrin.h>. or with headers that assume more
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// advanced SSE versions without checking with all the OWNERS.
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#include <tmmintrin.h>
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#endif
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#if SNAPPY_HAVE_BMI2
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// Please do not replace with <x86intrin.h>. or with headers that assume more
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// advanced SSE versions without checking with all the OWNERS.
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#include <immintrin.h>
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#endif
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#include <algorithm>
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#include <cstdio>
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#include <cstring>
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#include <string>
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#include <vector>
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namespace snappy {
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// The amount of slop bytes writers are using for unconditional copies.
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constexpr int kSlopBytes = 64;
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using internal::char_table;
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using internal::COPY_1_BYTE_OFFSET;
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using internal::COPY_2_BYTE_OFFSET;
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using internal::COPY_4_BYTE_OFFSET;
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using internal::kMaximumTagLength;
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using internal::LITERAL;
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// Any hash function will produce a valid compressed bitstream, but a good
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// hash function reduces the number of collisions and thus yields better
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// compression for compressible input, and more speed for incompressible
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// input. Of course, it doesn't hurt if the hash function is reasonably fast
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// either, as it gets called a lot.
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static inline uint32_t HashBytes(uint32_t bytes, uint32_t mask) {
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constexpr uint32_t kMagic = 0x1e35a7bd;
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return ((kMagic * bytes) >> (32 - kMaxHashTableBits)) & mask;
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}
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size_t MaxCompressedLength(size_t source_bytes) {
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// Compressed data can be defined as:
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// compressed := item* literal*
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// item := literal* copy
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//
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// The trailing literal sequence has a space blowup of at most 62/60
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// since a literal of length 60 needs one tag byte + one extra byte
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// for length information.
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//
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// Item blowup is trickier to measure. Suppose the "copy" op copies
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// 4 bytes of data. Because of a special check in the encoding code,
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// we produce a 4-byte copy only if the offset is < 65536. Therefore
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// the copy op takes 3 bytes to encode, and this type of item leads
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// to at most the 62/60 blowup for representing literals.
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//
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// Suppose the "copy" op copies 5 bytes of data. If the offset is big
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// enough, it will take 5 bytes to encode the copy op. Therefore the
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// worst case here is a one-byte literal followed by a five-byte copy.
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// I.e., 6 bytes of input turn into 7 bytes of "compressed" data.
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//
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// This last factor dominates the blowup, so the final estimate is:
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return 32 + source_bytes + source_bytes / 6;
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}
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namespace {
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void UnalignedCopy64(const void* src, void* dst) {
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char tmp[8];
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std::memcpy(tmp, src, 8);
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std::memcpy(dst, tmp, 8);
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}
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void UnalignedCopy128(const void* src, void* dst) {
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// std::memcpy() gets vectorized when the appropriate compiler options are
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// used. For example, x86 compilers targeting SSE2+ will optimize to an SSE2
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// load and store.
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char tmp[16];
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std::memcpy(tmp, src, 16);
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std::memcpy(dst, tmp, 16);
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}
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// Copy [src, src+(op_limit-op)) to [op, (op_limit-op)) a byte at a time. Used
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// for handling COPY operations where the input and output regions may overlap.
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// For example, suppose:
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// src == "ab"
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// op == src + 2
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// op_limit == op + 20
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// After IncrementalCopySlow(src, op, op_limit), the result will have eleven
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// copies of "ab"
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// ababababababababababab
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// Note that this does not match the semantics of either std::memcpy() or
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// std::memmove().
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inline char* IncrementalCopySlow(const char* src, char* op,
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char* const op_limit) {
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// TODO: Remove pragma when LLVM is aware this
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// function is only called in cold regions and when cold regions don't get
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// vectorized or unrolled.
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#ifdef __clang__
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#pragma clang loop unroll(disable)
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#endif
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while (op < op_limit) {
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*op++ = *src++;
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}
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return op_limit;
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}
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#if SNAPPY_HAVE_SSSE3
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// This is a table of shuffle control masks that can be used as the source
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// operand for PSHUFB to permute the contents of the destination XMM register
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// into a repeating byte pattern.
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alignas(16) const char pshufb_fill_patterns[7][16] = {
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{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
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{0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1},
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{0, 1, 2, 0, 1, 2, 0, 1, 2, 0, 1, 2, 0, 1, 2, 0},
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{0, 1, 2, 3, 0, 1, 2, 3, 0, 1, 2, 3, 0, 1, 2, 3},
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{0, 1, 2, 3, 4, 0, 1, 2, 3, 4, 0, 1, 2, 3, 4, 0},
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{0, 1, 2, 3, 4, 5, 0, 1, 2, 3, 4, 5, 0, 1, 2, 3},
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{0, 1, 2, 3, 4, 5, 6, 0, 1, 2, 3, 4, 5, 6, 0, 1},
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};
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// j * (16 / j) for all j from 0 to 7. 0 is not actually used.
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const uint8_t pattern_size_table[8] = {0, 16, 16, 15, 16, 15, 12, 14};
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#endif // SNAPPY_HAVE_SSSE3
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// Copy [src, src+(op_limit-op)) to [op, (op_limit-op)) but faster than
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// IncrementalCopySlow. buf_limit is the address past the end of the writable
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// region of the buffer.
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inline char* IncrementalCopy(const char* src, char* op, char* const op_limit,
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char* const buf_limit) {
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// Terminology:
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//
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// slop = buf_limit - op
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// pat = op - src
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// len = limit - op
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assert(src < op);
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assert(op <= op_limit);
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assert(op_limit <= buf_limit);
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// NOTE: The copy tags use 3 or 6 bits to store the copy length, so len <= 64.
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assert(op_limit - op <= 64);
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// NOTE: In practice the compressor always emits len >= 4, so it is ok to
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// assume that to optimize this function, but this is not guaranteed by the
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// compression format, so we have to also handle len < 4 in case the input
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// does not satisfy these conditions.
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size_t pattern_size = op - src;
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// The cases are split into different branches to allow the branch predictor,
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// FDO, and static prediction hints to work better. For each input we list the
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// ratio of invocations that match each condition.
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//
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// input slop < 16 pat < 8 len > 16
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// ------------------------------------------
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// html|html4|cp 0% 1.01% 27.73%
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// urls 0% 0.88% 14.79%
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// jpg 0% 64.29% 7.14%
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// pdf 0% 2.56% 58.06%
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// txt[1-4] 0% 0.23% 0.97%
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// pb 0% 0.96% 13.88%
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// bin 0.01% 22.27% 41.17%
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//
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// It is very rare that we don't have enough slop for doing block copies. It
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// is also rare that we need to expand a pattern. Small patterns are common
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// for incompressible formats and for those we are plenty fast already.
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// Lengths are normally not greater than 16 but they vary depending on the
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// input. In general if we always predict len <= 16 it would be an ok
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// prediction.
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//
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// In order to be fast we want a pattern >= 8 bytes and an unrolled loop
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// copying 2x 8 bytes at a time.
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// Handle the uncommon case where pattern is less than 8 bytes.
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if (SNAPPY_PREDICT_FALSE(pattern_size < 8)) {
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#if SNAPPY_HAVE_SSSE3
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// Load the first eight bytes into an 128-bit XMM register, then use PSHUFB
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// to permute the register's contents in-place into a repeating sequence of
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// the first "pattern_size" bytes.
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// For example, suppose:
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// src == "abc"
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// op == op + 3
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// After _mm_shuffle_epi8(), "pattern" will have five copies of "abc"
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// followed by one byte of slop: abcabcabcabcabca.
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//
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// The non-SSE fallback implementation suffers from store-forwarding stalls
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// because its loads and stores partly overlap. By expanding the pattern
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// in-place, we avoid the penalty.
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if (SNAPPY_PREDICT_TRUE(op <= buf_limit - 16)) {
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const __m128i shuffle_mask = _mm_load_si128(
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reinterpret_cast<const __m128i*>(pshufb_fill_patterns) +
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pattern_size - 1);
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const __m128i pattern = _mm_shuffle_epi8(
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_mm_loadl_epi64(reinterpret_cast<const __m128i*>(src)), shuffle_mask);
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// Uninitialized bytes are masked out by the shuffle mask.
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// TODO: remove annotation and macro defs once MSan is fixed.
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SNAPPY_ANNOTATE_MEMORY_IS_INITIALIZED(&pattern, sizeof(pattern));
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pattern_size = pattern_size_table[pattern_size];
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char* op_end = std::min(op_limit, buf_limit - 15);
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while (op < op_end) {
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_mm_storeu_si128(reinterpret_cast<__m128i*>(op), pattern);
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op += pattern_size;
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}
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if (SNAPPY_PREDICT_TRUE(op >= op_limit)) return op_limit;
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}
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return IncrementalCopySlow(src, op, op_limit);
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#else // !SNAPPY_HAVE_SSSE3
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// If plenty of buffer space remains, expand the pattern to at least 8
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// bytes. The way the following loop is written, we need 8 bytes of buffer
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// space if pattern_size >= 4, 11 bytes if pattern_size is 1 or 3, and 10
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// bytes if pattern_size is 2. Precisely encoding that is probably not
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// worthwhile; instead, invoke the slow path if we cannot write 11 bytes
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// (because 11 are required in the worst case).
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if (SNAPPY_PREDICT_TRUE(op <= buf_limit - 11)) {
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while (pattern_size < 8) {
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UnalignedCopy64(src, op);
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op += pattern_size;
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pattern_size *= 2;
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}
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if (SNAPPY_PREDICT_TRUE(op >= op_limit)) return op_limit;
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} else {
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return IncrementalCopySlow(src, op, op_limit);
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}
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#endif // SNAPPY_HAVE_SSSE3
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}
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assert(pattern_size >= 8);
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// Copy 2x 8 bytes at a time. Because op - src can be < 16, a single
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// UnalignedCopy128 might overwrite data in op. UnalignedCopy64 is safe
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// because expanding the pattern to at least 8 bytes guarantees that
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// op - src >= 8.
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//
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// Typically, the op_limit is the gating factor so try to simplify the loop
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// based on that.
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if (SNAPPY_PREDICT_TRUE(op_limit <= buf_limit - 16)) {
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// There is at least one, and at most four 16-byte blocks. Writing four
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// conditionals instead of a loop allows FDO to layout the code with respect
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// to the actual probabilities of each length.
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// TODO: Replace with loop with trip count hint.
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UnalignedCopy64(src, op);
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UnalignedCopy64(src + 8, op + 8);
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if (op + 16 < op_limit) {
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UnalignedCopy64(src + 16, op + 16);
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UnalignedCopy64(src + 24, op + 24);
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}
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if (op + 32 < op_limit) {
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UnalignedCopy64(src + 32, op + 32);
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UnalignedCopy64(src + 40, op + 40);
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}
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if (op + 48 < op_limit) {
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UnalignedCopy64(src + 48, op + 48);
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UnalignedCopy64(src + 56, op + 56);
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}
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return op_limit;
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}
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// Fall back to doing as much as we can with the available slop in the
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// buffer. This code path is relatively cold however so we save code size by
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// avoiding unrolling and vectorizing.
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//
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// TODO: Remove pragma when when cold regions don't get vectorized
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// or unrolled.
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#ifdef __clang__
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#pragma clang loop unroll(disable)
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#endif
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for (char* op_end = buf_limit - 16; op < op_end; op += 16, src += 16) {
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UnalignedCopy64(src, op);
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UnalignedCopy64(src + 8, op + 8);
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}
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if (op >= op_limit) return op_limit;
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// We only take this branch if we didn't have enough slop and we can do a
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// single 8 byte copy.
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if (SNAPPY_PREDICT_FALSE(op <= buf_limit - 8)) {
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UnalignedCopy64(src, op);
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src += 8;
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op += 8;
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}
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return IncrementalCopySlow(src, op, op_limit);
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}
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} // namespace
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template <bool allow_fast_path>
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static inline char* EmitLiteral(char* op, const char* literal, int len) {
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// The vast majority of copies are below 16 bytes, for which a
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// call to std::memcpy() is overkill. This fast path can sometimes
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// copy up to 15 bytes too much, but that is okay in the
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// main loop, since we have a bit to go on for both sides:
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//
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// - The input will always have kInputMarginBytes = 15 extra
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// available bytes, as long as we're in the main loop, and
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// if not, allow_fast_path = false.
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// - The output will always have 32 spare bytes (see
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// MaxCompressedLength).
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assert(len > 0); // Zero-length literals are disallowed
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int n = len - 1;
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if (allow_fast_path && len <= 16) {
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// Fits in tag byte
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*op++ = LITERAL | (n << 2);
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UnalignedCopy128(literal, op);
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return op + len;
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}
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if (n < 60) {
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// Fits in tag byte
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*op++ = LITERAL | (n << 2);
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} else {
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int count = (Bits::Log2Floor(n) >> 3) + 1;
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assert(count >= 1);
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assert(count <= 4);
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*op++ = LITERAL | ((59 + count) << 2);
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// Encode in upcoming bytes.
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// Write 4 bytes, though we may care about only 1 of them. The output buffer
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// is guaranteed to have at least 3 more spaces left as 'len >= 61' holds
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// here and there is a std::memcpy() of size 'len' below.
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LittleEndian::Store32(op, n);
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op += count;
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}
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std::memcpy(op, literal, len);
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return op + len;
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}
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template <bool len_less_than_12>
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static inline char* EmitCopyAtMost64(char* op, size_t offset, size_t len) {
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assert(len <= 64);
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assert(len >= 4);
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assert(offset < 65536);
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assert(len_less_than_12 == (len < 12));
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if (len_less_than_12) {
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uint32_t u = (len << 2) + (offset << 8);
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uint32_t copy1 = COPY_1_BYTE_OFFSET - (4 << 2) + ((offset >> 3) & 0xe0);
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uint32_t copy2 = COPY_2_BYTE_OFFSET - (1 << 2);
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// It turns out that offset < 2048 is a difficult to predict branch.
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// `perf record` shows this is the highest percentage of branch misses in
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// benchmarks. This code produces branch free code, the data dependency
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// chain that bottlenecks the throughput is so long that a few extra
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// instructions are completely free (IPC << 6 because of data deps).
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u += offset < 2048 ? copy1 : copy2;
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LittleEndian::Store32(op, u);
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op += offset < 2048 ? 2 : 3;
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} else {
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// Write 4 bytes, though we only care about 3 of them. The output buffer
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// is required to have some slack, so the extra byte won't overrun it.
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uint32_t u = COPY_2_BYTE_OFFSET + ((len - 1) << 2) + (offset << 8);
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LittleEndian::Store32(op, u);
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op += 3;
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}
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return op;
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}
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template <bool len_less_than_12>
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static inline char* EmitCopy(char* op, size_t offset, size_t len) {
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assert(len_less_than_12 == (len < 12));
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if (len_less_than_12) {
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return EmitCopyAtMost64</*len_less_than_12=*/true>(op, offset, len);
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} else {
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// A special case for len <= 64 might help, but so far measurements suggest
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// it's in the noise.
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// Emit 64 byte copies but make sure to keep at least four bytes reserved.
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while (SNAPPY_PREDICT_FALSE(len >= 68)) {
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op = EmitCopyAtMost64</*len_less_than_12=*/false>(op, offset, 64);
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len -= 64;
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}
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|
|
// One or two copies will now finish the job.
|
|
if (len > 64) {
|
|
op = EmitCopyAtMost64</*len_less_than_12=*/false>(op, offset, 60);
|
|
len -= 60;
|
|
}
|
|
|
|
// Emit remainder.
|
|
if (len < 12) {
|
|
op = EmitCopyAtMost64</*len_less_than_12=*/true>(op, offset, len);
|
|
} else {
|
|
op = EmitCopyAtMost64</*len_less_than_12=*/false>(op, offset, len);
|
|
}
|
|
return op;
|
|
}
|
|
}
|
|
|
|
bool GetUncompressedLength(const char* start, size_t n, size_t* result) {
|
|
uint32_t v = 0;
|
|
const char* limit = start + n;
|
|
if (Varint::Parse32WithLimit(start, limit, &v) != NULL) {
|
|
*result = v;
|
|
return true;
|
|
} else {
|
|
return false;
|
|
}
|
|
}
|
|
|
|
namespace {
|
|
uint32_t CalculateTableSize(uint32_t input_size) {
|
|
static_assert(
|
|
kMaxHashTableSize >= kMinHashTableSize,
|
|
"kMaxHashTableSize should be greater or equal to kMinHashTableSize.");
|
|
if (input_size > kMaxHashTableSize) {
|
|
return kMaxHashTableSize;
|
|
}
|
|
if (input_size < kMinHashTableSize) {
|
|
return kMinHashTableSize;
|
|
}
|
|
// This is equivalent to Log2Ceiling(input_size), assuming input_size > 1.
|
|
// 2 << Log2Floor(x - 1) is equivalent to 1 << (1 + Log2Floor(x - 1)).
|
|
return 2u << Bits::Log2Floor(input_size - 1);
|
|
}
|
|
} // namespace
|
|
|
|
namespace internal {
|
|
WorkingMemory::WorkingMemory(size_t input_size) {
|
|
const size_t max_fragment_size = std::min(input_size, kBlockSize);
|
|
const size_t table_size = CalculateTableSize(max_fragment_size);
|
|
size_ = table_size * sizeof(*table_) + max_fragment_size +
|
|
MaxCompressedLength(max_fragment_size);
|
|
mem_ = std::allocator<char>().allocate(size_);
|
|
table_ = reinterpret_cast<uint16_t*>(mem_);
|
|
input_ = mem_ + table_size * sizeof(*table_);
|
|
output_ = input_ + max_fragment_size;
|
|
}
|
|
|
|
WorkingMemory::~WorkingMemory() {
|
|
std::allocator<char>().deallocate(mem_, size_);
|
|
}
|
|
|
|
uint16_t* WorkingMemory::GetHashTable(size_t fragment_size,
|
|
int* table_size) const {
|
|
const size_t htsize = CalculateTableSize(fragment_size);
|
|
memset(table_, 0, htsize * sizeof(*table_));
|
|
*table_size = htsize;
|
|
return table_;
|
|
}
|
|
} // end namespace internal
|
|
|
|
// Flat array compression that does not emit the "uncompressed length"
|
|
// prefix. Compresses "input" string to the "*op" buffer.
|
|
//
|
|
// REQUIRES: "input" is at most "kBlockSize" bytes long.
|
|
// REQUIRES: "op" points to an array of memory that is at least
|
|
// "MaxCompressedLength(input.size())" in size.
|
|
// REQUIRES: All elements in "table[0..table_size-1]" are initialized to zero.
|
|
// REQUIRES: "table_size" is a power of two
|
|
//
|
|
// Returns an "end" pointer into "op" buffer.
|
|
// "end - op" is the compressed size of "input".
|
|
namespace internal {
|
|
char* CompressFragment(const char* input, size_t input_size, char* op,
|
|
uint16_t* table, const int table_size) {
|
|
// "ip" is the input pointer, and "op" is the output pointer.
|
|
const char* ip = input;
|
|
assert(input_size <= kBlockSize);
|
|
assert((table_size & (table_size - 1)) == 0); // table must be power of two
|
|
const uint32_t mask = table_size - 1;
|
|
const char* ip_end = input + input_size;
|
|
const char* base_ip = ip;
|
|
|
|
const size_t kInputMarginBytes = 15;
|
|
if (SNAPPY_PREDICT_TRUE(input_size >= kInputMarginBytes)) {
|
|
const char* ip_limit = input + input_size - kInputMarginBytes;
|
|
|
|
for (uint32_t preload = LittleEndian::Load32(ip + 1);;) {
|
|
// Bytes in [next_emit, ip) will be emitted as literal bytes. Or
|
|
// [next_emit, ip_end) after the main loop.
|
|
const char* next_emit = ip++;
|
|
uint64_t data = LittleEndian::Load64(ip);
|
|
// The body of this loop calls EmitLiteral once and then EmitCopy one or
|
|
// more times. (The exception is that when we're close to exhausting
|
|
// the input we goto emit_remainder.)
|
|
//
|
|
// In the first iteration of this loop we're just starting, so
|
|
// there's nothing to copy, so calling EmitLiteral once is
|
|
// necessary. And we only start a new iteration when the
|
|
// current iteration has determined that a call to EmitLiteral will
|
|
// precede the next call to EmitCopy (if any).
|
|
//
|
|
// Step 1: Scan forward in the input looking for a 4-byte-long match.
|
|
// If we get close to exhausting the input then goto emit_remainder.
|
|
//
|
|
// Heuristic match skipping: If 32 bytes are scanned with no matches
|
|
// found, start looking only at every other byte. If 32 more bytes are
|
|
// scanned (or skipped), look at every third byte, etc.. When a match is
|
|
// found, immediately go back to looking at every byte. This is a small
|
|
// loss (~5% performance, ~0.1% density) for compressible data due to more
|
|
// bookkeeping, but for non-compressible data (such as JPEG) it's a huge
|
|
// win since the compressor quickly "realizes" the data is incompressible
|
|
// and doesn't bother looking for matches everywhere.
|
|
//
|
|
// The "skip" variable keeps track of how many bytes there are since the
|
|
// last match; dividing it by 32 (ie. right-shifting by five) gives the
|
|
// number of bytes to move ahead for each iteration.
|
|
uint32_t skip = 32;
|
|
|
|
const char* candidate;
|
|
if (ip_limit - ip >= 16) {
|
|
auto delta = ip - base_ip;
|
|
for (int j = 0; j < 4; ++j) {
|
|
for (int k = 0; k < 4; ++k) {
|
|
int i = 4 * j + k;
|
|
// These for-loops are meant to be unrolled. So we can freely
|
|
// special case the first iteration to use the value already
|
|
// loaded in preload.
|
|
uint32_t dword = i == 0 ? preload : static_cast<uint32_t>(data);
|
|
assert(dword == LittleEndian::Load32(ip + i));
|
|
uint32_t hash = HashBytes(dword, mask);
|
|
candidate = base_ip + table[hash];
|
|
assert(candidate >= base_ip);
|
|
assert(candidate < ip + i);
|
|
table[hash] = delta + i;
|
|
if (SNAPPY_PREDICT_FALSE(LittleEndian::Load32(candidate) == dword)) {
|
|
*op = LITERAL | (i << 2);
|
|
UnalignedCopy128(next_emit, op + 1);
|
|
ip += i;
|
|
op = op + i + 2;
|
|
goto emit_match;
|
|
}
|
|
data >>= 8;
|
|
}
|
|
data = LittleEndian::Load64(ip + 4 * j + 4);
|
|
}
|
|
ip += 16;
|
|
skip += 16;
|
|
}
|
|
while (true) {
|
|
assert(static_cast<uint32_t>(data) == LittleEndian::Load32(ip));
|
|
uint32_t hash = HashBytes(data, mask);
|
|
uint32_t bytes_between_hash_lookups = skip >> 5;
|
|
skip += bytes_between_hash_lookups;
|
|
const char* next_ip = ip + bytes_between_hash_lookups;
|
|
if (SNAPPY_PREDICT_FALSE(next_ip > ip_limit)) {
|
|
ip = next_emit;
|
|
goto emit_remainder;
|
|
}
|
|
candidate = base_ip + table[hash];
|
|
assert(candidate >= base_ip);
|
|
assert(candidate < ip);
|
|
|
|
table[hash] = ip - base_ip;
|
|
if (SNAPPY_PREDICT_FALSE(static_cast<uint32_t>(data) ==
|
|
LittleEndian::Load32(candidate))) {
|
|
break;
|
|
}
|
|
data = LittleEndian::Load32(next_ip);
|
|
ip = next_ip;
|
|
}
|
|
|
|
// Step 2: A 4-byte match has been found. We'll later see if more
|
|
// than 4 bytes match. But, prior to the match, input
|
|
// bytes [next_emit, ip) are unmatched. Emit them as "literal bytes."
|
|
assert(next_emit + 16 <= ip_end);
|
|
op = EmitLiteral</*allow_fast_path=*/true>(op, next_emit, ip - next_emit);
|
|
|
|
// Step 3: Call EmitCopy, and then see if another EmitCopy could
|
|
// be our next move. Repeat until we find no match for the
|
|
// input immediately after what was consumed by the last EmitCopy call.
|
|
//
|
|
// If we exit this loop normally then we need to call EmitLiteral next,
|
|
// though we don't yet know how big the literal will be. We handle that
|
|
// by proceeding to the next iteration of the main loop. We also can exit
|
|
// this loop via goto if we get close to exhausting the input.
|
|
emit_match:
|
|
do {
|
|
// We have a 4-byte match at ip, and no need to emit any
|
|
// "literal bytes" prior to ip.
|
|
const char* base = ip;
|
|
std::pair<size_t, bool> p =
|
|
FindMatchLength(candidate + 4, ip + 4, ip_end, &data);
|
|
size_t matched = 4 + p.first;
|
|
ip += matched;
|
|
size_t offset = base - candidate;
|
|
assert(0 == memcmp(base, candidate, matched));
|
|
if (p.second) {
|
|
op = EmitCopy</*len_less_than_12=*/true>(op, offset, matched);
|
|
} else {
|
|
op = EmitCopy</*len_less_than_12=*/false>(op, offset, matched);
|
|
}
|
|
if (SNAPPY_PREDICT_FALSE(ip >= ip_limit)) {
|
|
goto emit_remainder;
|
|
}
|
|
// Expect 5 bytes to match
|
|
assert((data & 0xFFFFFFFFFF) ==
|
|
(LittleEndian::Load64(ip) & 0xFFFFFFFFFF));
|
|
// We are now looking for a 4-byte match again. We read
|
|
// table[Hash(ip, shift)] for that. To improve compression,
|
|
// we also update table[Hash(ip - 1, mask)] and table[Hash(ip, mask)].
|
|
table[HashBytes(LittleEndian::Load32(ip - 1), mask)] = ip - base_ip - 1;
|
|
uint32_t hash = HashBytes(data, mask);
|
|
candidate = base_ip + table[hash];
|
|
table[hash] = ip - base_ip;
|
|
// Measurements on the benchmarks have shown the following probabilities
|
|
// for the loop to exit (ie. avg. number of iterations is reciprocal).
|
|
// BM_Flat/6 txt1 p = 0.3-0.4
|
|
// BM_Flat/7 txt2 p = 0.35
|
|
// BM_Flat/8 txt3 p = 0.3-0.4
|
|
// BM_Flat/9 txt3 p = 0.34-0.4
|
|
// BM_Flat/10 pb p = 0.4
|
|
// BM_Flat/11 gaviota p = 0.1
|
|
// BM_Flat/12 cp p = 0.5
|
|
// BM_Flat/13 c p = 0.3
|
|
} while (static_cast<uint32_t>(data) == LittleEndian::Load32(candidate));
|
|
// Because the least significant 5 bytes matched, we can utilize data
|
|
// for the next iteration.
|
|
preload = data >> 8;
|
|
}
|
|
}
|
|
|
|
emit_remainder:
|
|
// Emit the remaining bytes as a literal
|
|
if (ip < ip_end) {
|
|
op = EmitLiteral</*allow_fast_path=*/false>(op, ip, ip_end - ip);
|
|
}
|
|
|
|
return op;
|
|
}
|
|
} // end namespace internal
|
|
|
|
// Called back at avery compression call to trace parameters and sizes.
|
|
static inline void Report(const char *algorithm, size_t compressed_size,
|
|
size_t uncompressed_size) {
|
|
// TODO: Switch to [[maybe_unused]] when we can assume C++17.
|
|
(void)algorithm;
|
|
(void)compressed_size;
|
|
(void)uncompressed_size;
|
|
}
|
|
|
|
// Signature of output types needed by decompression code.
|
|
// The decompression code is templatized on a type that obeys this
|
|
// signature so that we do not pay virtual function call overhead in
|
|
// the middle of a tight decompression loop.
|
|
//
|
|
// class DecompressionWriter {
|
|
// public:
|
|
// // Called before decompression
|
|
// void SetExpectedLength(size_t length);
|
|
//
|
|
// // For performance a writer may choose to donate the cursor variable to the
|
|
// // decompression function. The decompression will inject it in all its
|
|
// // function calls to the writer. Keeping the important output cursor as a
|
|
// // function local stack variable allows the compiler to keep it in
|
|
// // register, which greatly aids performance by avoiding loads and stores of
|
|
// // this variable in the fast path loop iterations.
|
|
// T GetOutputPtr() const;
|
|
//
|
|
// // At end of decompression the loop donates the ownership of the cursor
|
|
// // variable back to the writer by calling this function.
|
|
// void SetOutputPtr(T op);
|
|
//
|
|
// // Called after decompression
|
|
// bool CheckLength() const;
|
|
//
|
|
// // Called repeatedly during decompression
|
|
// // Each function get a pointer to the op (output pointer), that the writer
|
|
// // can use and update. Note it's important that these functions get fully
|
|
// // inlined so that no actual address of the local variable needs to be
|
|
// // taken.
|
|
// bool Append(const char* ip, size_t length, T* op);
|
|
// bool AppendFromSelf(uint32_t offset, size_t length, T* op);
|
|
//
|
|
// // The rules for how TryFastAppend differs from Append are somewhat
|
|
// // convoluted:
|
|
// //
|
|
// // - TryFastAppend is allowed to decline (return false) at any
|
|
// // time, for any reason -- just "return false" would be
|
|
// // a perfectly legal implementation of TryFastAppend.
|
|
// // The intention is for TryFastAppend to allow a fast path
|
|
// // in the common case of a small append.
|
|
// // - TryFastAppend is allowed to read up to <available> bytes
|
|
// // from the input buffer, whereas Append is allowed to read
|
|
// // <length>. However, if it returns true, it must leave
|
|
// // at least five (kMaximumTagLength) bytes in the input buffer
|
|
// // afterwards, so that there is always enough space to read the
|
|
// // next tag without checking for a refill.
|
|
// // - TryFastAppend must always return decline (return false)
|
|
// // if <length> is 61 or more, as in this case the literal length is not
|
|
// // decoded fully. In practice, this should not be a big problem,
|
|
// // as it is unlikely that one would implement a fast path accepting
|
|
// // this much data.
|
|
// //
|
|
// bool TryFastAppend(const char* ip, size_t available, size_t length, T* op);
|
|
// };
|
|
|
|
static inline uint32_t ExtractLowBytes(uint32_t v, int n) {
|
|
assert(n >= 0);
|
|
assert(n <= 4);
|
|
#if SNAPPY_HAVE_BMI2
|
|
return _bzhi_u32(v, 8 * n);
|
|
#else
|
|
// This needs to be wider than uint32_t otherwise `mask << 32` will be
|
|
// undefined.
|
|
uint64_t mask = 0xffffffff;
|
|
return v & ~(mask << (8 * n));
|
|
#endif
|
|
}
|
|
|
|
static inline bool LeftShiftOverflows(uint8_t value, uint32_t shift) {
|
|
assert(shift < 32);
|
|
static const uint8_t masks[] = {
|
|
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, //
|
|
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, //
|
|
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, //
|
|
0x00, 0x80, 0xc0, 0xe0, 0xf0, 0xf8, 0xfc, 0xfe};
|
|
return (value & masks[shift]) != 0;
|
|
}
|
|
|
|
// Helper class for decompression
|
|
class SnappyDecompressor {
|
|
private:
|
|
Source* reader_; // Underlying source of bytes to decompress
|
|
const char* ip_; // Points to next buffered byte
|
|
const char* ip_limit_; // Points just past buffered bytes
|
|
// If ip < ip_limit_min_maxtaglen_ it's safe to read kMaxTagLength from
|
|
// buffer.
|
|
const char* ip_limit_min_maxtaglen_;
|
|
uint32_t peeked_; // Bytes peeked from reader (need to skip)
|
|
bool eof_; // Hit end of input without an error?
|
|
char scratch_[kMaximumTagLength]; // See RefillTag().
|
|
|
|
// Ensure that all of the tag metadata for the next tag is available
|
|
// in [ip_..ip_limit_-1]. Also ensures that [ip,ip+4] is readable even
|
|
// if (ip_limit_ - ip_ < 5).
|
|
//
|
|
// Returns true on success, false on error or end of input.
|
|
bool RefillTag();
|
|
|
|
void ResetLimit(const char* ip) {
|
|
ip_limit_min_maxtaglen_ =
|
|
ip_limit_ - std::min<ptrdiff_t>(ip_limit_ - ip, kMaximumTagLength - 1);
|
|
}
|
|
|
|
public:
|
|
explicit SnappyDecompressor(Source* reader)
|
|
: reader_(reader), ip_(NULL), ip_limit_(NULL), peeked_(0), eof_(false) {}
|
|
|
|
~SnappyDecompressor() {
|
|
// Advance past any bytes we peeked at from the reader
|
|
reader_->Skip(peeked_);
|
|
}
|
|
|
|
// Returns true iff we have hit the end of the input without an error.
|
|
bool eof() const { return eof_; }
|
|
|
|
// Read the uncompressed length stored at the start of the compressed data.
|
|
// On success, stores the length in *result and returns true.
|
|
// On failure, returns false.
|
|
bool ReadUncompressedLength(uint32_t* result) {
|
|
assert(ip_ == NULL); // Must not have read anything yet
|
|
// Length is encoded in 1..5 bytes
|
|
*result = 0;
|
|
uint32_t shift = 0;
|
|
while (true) {
|
|
if (shift >= 32) return false;
|
|
size_t n;
|
|
const char* ip = reader_->Peek(&n);
|
|
if (n == 0) return false;
|
|
const unsigned char c = *(reinterpret_cast<const unsigned char*>(ip));
|
|
reader_->Skip(1);
|
|
uint32_t val = c & 0x7f;
|
|
if (LeftShiftOverflows(static_cast<uint8_t>(val), shift)) return false;
|
|
*result |= val << shift;
|
|
if (c < 128) {
|
|
break;
|
|
}
|
|
shift += 7;
|
|
}
|
|
return true;
|
|
}
|
|
|
|
// Process the next item found in the input.
|
|
// Returns true if successful, false on error or end of input.
|
|
template <class Writer>
|
|
#if defined(__GNUC__) && defined(__x86_64__)
|
|
__attribute__((aligned(32)))
|
|
#endif
|
|
void
|
|
DecompressAllTags(Writer* writer) {
|
|
const char* ip = ip_;
|
|
ResetLimit(ip);
|
|
auto op = writer->GetOutputPtr();
|
|
// We could have put this refill fragment only at the beginning of the loop.
|
|
// However, duplicating it at the end of each branch gives the compiler more
|
|
// scope to optimize the <ip_limit_ - ip> expression based on the local
|
|
// context, which overall increases speed.
|
|
#define MAYBE_REFILL() \
|
|
if (SNAPPY_PREDICT_FALSE(ip >= ip_limit_min_maxtaglen_)) { \
|
|
ip_ = ip; \
|
|
if (SNAPPY_PREDICT_FALSE(!RefillTag())) goto exit; \
|
|
ip = ip_; \
|
|
ResetLimit(ip); \
|
|
} \
|
|
preload = static_cast<uint8_t>(*ip)
|
|
|
|
// At the start of the for loop below the least significant byte of preload
|
|
// contains the tag.
|
|
uint32_t preload;
|
|
MAYBE_REFILL();
|
|
for (;;) {
|
|
const uint8_t c = static_cast<uint8_t>(preload);
|
|
ip++;
|
|
|
|
// Ratio of iterations that have LITERAL vs non-LITERAL for different
|
|
// inputs.
|
|
//
|
|
// input LITERAL NON_LITERAL
|
|
// -----------------------------------
|
|
// html|html4|cp 23% 77%
|
|
// urls 36% 64%
|
|
// jpg 47% 53%
|
|
// pdf 19% 81%
|
|
// txt[1-4] 25% 75%
|
|
// pb 24% 76%
|
|
// bin 24% 76%
|
|
if (SNAPPY_PREDICT_FALSE((c & 0x3) == LITERAL)) {
|
|
size_t literal_length = (c >> 2) + 1u;
|
|
if (writer->TryFastAppend(ip, ip_limit_ - ip, literal_length, &op)) {
|
|
assert(literal_length < 61);
|
|
ip += literal_length;
|
|
// NOTE: There is no MAYBE_REFILL() here, as TryFastAppend()
|
|
// will not return true unless there's already at least five spare
|
|
// bytes in addition to the literal.
|
|
preload = static_cast<uint8_t>(*ip);
|
|
continue;
|
|
}
|
|
if (SNAPPY_PREDICT_FALSE(literal_length >= 61)) {
|
|
// Long literal.
|
|
const size_t literal_length_length = literal_length - 60;
|
|
literal_length =
|
|
ExtractLowBytes(LittleEndian::Load32(ip), literal_length_length) +
|
|
1;
|
|
ip += literal_length_length;
|
|
}
|
|
|
|
size_t avail = ip_limit_ - ip;
|
|
while (avail < literal_length) {
|
|
if (!writer->Append(ip, avail, &op)) goto exit;
|
|
literal_length -= avail;
|
|
reader_->Skip(peeked_);
|
|
size_t n;
|
|
ip = reader_->Peek(&n);
|
|
avail = n;
|
|
peeked_ = avail;
|
|
if (avail == 0) goto exit;
|
|
ip_limit_ = ip + avail;
|
|
ResetLimit(ip);
|
|
}
|
|
if (!writer->Append(ip, literal_length, &op)) goto exit;
|
|
ip += literal_length;
|
|
MAYBE_REFILL();
|
|
} else {
|
|
if (SNAPPY_PREDICT_FALSE((c & 3) == COPY_4_BYTE_OFFSET)) {
|
|
const size_t copy_offset = LittleEndian::Load32(ip);
|
|
const size_t length = (c >> 2) + 1;
|
|
ip += 4;
|
|
|
|
if (!writer->AppendFromSelf(copy_offset, length, &op)) goto exit;
|
|
} else {
|
|
const uint32_t entry = char_table[c];
|
|
preload = LittleEndian::Load32(ip);
|
|
const uint32_t trailer = ExtractLowBytes(preload, c & 3);
|
|
const uint32_t length = entry & 0xff;
|
|
|
|
// copy_offset/256 is encoded in bits 8..10. By just fetching
|
|
// those bits, we get copy_offset (since the bit-field starts at
|
|
// bit 8).
|
|
const uint32_t copy_offset = (entry & 0x700) + trailer;
|
|
if (!writer->AppendFromSelf(copy_offset, length, &op)) goto exit;
|
|
|
|
ip += (c & 3);
|
|
// By using the result of the previous load we reduce the critical
|
|
// dependency chain of ip to 4 cycles.
|
|
preload >>= (c & 3) * 8;
|
|
if (ip < ip_limit_min_maxtaglen_) continue;
|
|
}
|
|
MAYBE_REFILL();
|
|
}
|
|
}
|
|
#undef MAYBE_REFILL
|
|
exit:
|
|
writer->SetOutputPtr(op);
|
|
}
|
|
};
|
|
|
|
bool SnappyDecompressor::RefillTag() {
|
|
const char* ip = ip_;
|
|
if (ip == ip_limit_) {
|
|
// Fetch a new fragment from the reader
|
|
reader_->Skip(peeked_); // All peeked bytes are used up
|
|
size_t n;
|
|
ip = reader_->Peek(&n);
|
|
peeked_ = n;
|
|
eof_ = (n == 0);
|
|
if (eof_) return false;
|
|
ip_limit_ = ip + n;
|
|
}
|
|
|
|
// Read the tag character
|
|
assert(ip < ip_limit_);
|
|
const unsigned char c = *(reinterpret_cast<const unsigned char*>(ip));
|
|
const uint32_t entry = char_table[c];
|
|
const uint32_t needed = (entry >> 11) + 1; // +1 byte for 'c'
|
|
assert(needed <= sizeof(scratch_));
|
|
|
|
// Read more bytes from reader if needed
|
|
uint32_t nbuf = ip_limit_ - ip;
|
|
if (nbuf < needed) {
|
|
// Stitch together bytes from ip and reader to form the word
|
|
// contents. We store the needed bytes in "scratch_". They
|
|
// will be consumed immediately by the caller since we do not
|
|
// read more than we need.
|
|
std::memmove(scratch_, ip, nbuf);
|
|
reader_->Skip(peeked_); // All peeked bytes are used up
|
|
peeked_ = 0;
|
|
while (nbuf < needed) {
|
|
size_t length;
|
|
const char* src = reader_->Peek(&length);
|
|
if (length == 0) return false;
|
|
uint32_t to_add = std::min<uint32_t>(needed - nbuf, length);
|
|
std::memcpy(scratch_ + nbuf, src, to_add);
|
|
nbuf += to_add;
|
|
reader_->Skip(to_add);
|
|
}
|
|
assert(nbuf == needed);
|
|
ip_ = scratch_;
|
|
ip_limit_ = scratch_ + needed;
|
|
} else if (nbuf < kMaximumTagLength) {
|
|
// Have enough bytes, but move into scratch_ so that we do not
|
|
// read past end of input
|
|
std::memmove(scratch_, ip, nbuf);
|
|
reader_->Skip(peeked_); // All peeked bytes are used up
|
|
peeked_ = 0;
|
|
ip_ = scratch_;
|
|
ip_limit_ = scratch_ + nbuf;
|
|
} else {
|
|
// Pass pointer to buffer returned by reader_.
|
|
ip_ = ip;
|
|
}
|
|
return true;
|
|
}
|
|
|
|
template <typename Writer>
|
|
static bool InternalUncompress(Source* r, Writer* writer) {
|
|
// Read the uncompressed length from the front of the compressed input
|
|
SnappyDecompressor decompressor(r);
|
|
uint32_t uncompressed_len = 0;
|
|
if (!decompressor.ReadUncompressedLength(&uncompressed_len)) return false;
|
|
|
|
return InternalUncompressAllTags(&decompressor, writer, r->Available(),
|
|
uncompressed_len);
|
|
}
|
|
|
|
template <typename Writer>
|
|
static bool InternalUncompressAllTags(SnappyDecompressor* decompressor,
|
|
Writer* writer, uint32_t compressed_len,
|
|
uint32_t uncompressed_len) {
|
|
Report("snappy_uncompress", compressed_len, uncompressed_len);
|
|
|
|
writer->SetExpectedLength(uncompressed_len);
|
|
|
|
// Process the entire input
|
|
decompressor->DecompressAllTags(writer);
|
|
writer->Flush();
|
|
return (decompressor->eof() && writer->CheckLength());
|
|
}
|
|
|
|
bool GetUncompressedLength(Source* source, uint32_t* result) {
|
|
SnappyDecompressor decompressor(source);
|
|
return decompressor.ReadUncompressedLength(result);
|
|
}
|
|
|
|
size_t Compress(Source* reader, Sink* writer) {
|
|
size_t written = 0;
|
|
size_t N = reader->Available();
|
|
const size_t uncompressed_size = N;
|
|
char ulength[Varint::kMax32];
|
|
char* p = Varint::Encode32(ulength, N);
|
|
writer->Append(ulength, p - ulength);
|
|
written += (p - ulength);
|
|
|
|
internal::WorkingMemory wmem(N);
|
|
|
|
while (N > 0) {
|
|
// Get next block to compress (without copying if possible)
|
|
size_t fragment_size;
|
|
const char* fragment = reader->Peek(&fragment_size);
|
|
assert(fragment_size != 0); // premature end of input
|
|
const size_t num_to_read = std::min(N, kBlockSize);
|
|
size_t bytes_read = fragment_size;
|
|
|
|
size_t pending_advance = 0;
|
|
if (bytes_read >= num_to_read) {
|
|
// Buffer returned by reader is large enough
|
|
pending_advance = num_to_read;
|
|
fragment_size = num_to_read;
|
|
} else {
|
|
char* scratch = wmem.GetScratchInput();
|
|
std::memcpy(scratch, fragment, bytes_read);
|
|
reader->Skip(bytes_read);
|
|
|
|
while (bytes_read < num_to_read) {
|
|
fragment = reader->Peek(&fragment_size);
|
|
size_t n = std::min<size_t>(fragment_size, num_to_read - bytes_read);
|
|
std::memcpy(scratch + bytes_read, fragment, n);
|
|
bytes_read += n;
|
|
reader->Skip(n);
|
|
}
|
|
assert(bytes_read == num_to_read);
|
|
fragment = scratch;
|
|
fragment_size = num_to_read;
|
|
}
|
|
assert(fragment_size == num_to_read);
|
|
|
|
// Get encoding table for compression
|
|
int table_size;
|
|
uint16_t* table = wmem.GetHashTable(num_to_read, &table_size);
|
|
|
|
// Compress input_fragment and append to dest
|
|
const int max_output = MaxCompressedLength(num_to_read);
|
|
|
|
// Need a scratch buffer for the output, in case the byte sink doesn't
|
|
// have room for us directly.
|
|
|
|
// Since we encode kBlockSize regions followed by a region
|
|
// which is <= kBlockSize in length, a previously allocated
|
|
// scratch_output[] region is big enough for this iteration.
|
|
char* dest = writer->GetAppendBuffer(max_output, wmem.GetScratchOutput());
|
|
char* end = internal::CompressFragment(fragment, fragment_size, dest, table,
|
|
table_size);
|
|
writer->Append(dest, end - dest);
|
|
written += (end - dest);
|
|
|
|
N -= num_to_read;
|
|
reader->Skip(pending_advance);
|
|
}
|
|
|
|
Report("snappy_compress", written, uncompressed_size);
|
|
|
|
return written;
|
|
}
|
|
|
|
// -----------------------------------------------------------------------
|
|
// IOVec interfaces
|
|
// -----------------------------------------------------------------------
|
|
|
|
// A type that writes to an iovec.
|
|
// Note that this is not a "ByteSink", but a type that matches the
|
|
// Writer template argument to SnappyDecompressor::DecompressAllTags().
|
|
class SnappyIOVecWriter {
|
|
private:
|
|
// output_iov_end_ is set to iov + count and used to determine when
|
|
// the end of the iovs is reached.
|
|
const struct iovec* output_iov_end_;
|
|
|
|
#if !defined(NDEBUG)
|
|
const struct iovec* output_iov_;
|
|
#endif // !defined(NDEBUG)
|
|
|
|
// Current iov that is being written into.
|
|
const struct iovec* curr_iov_;
|
|
|
|
// Pointer to current iov's write location.
|
|
char* curr_iov_output_;
|
|
|
|
// Remaining bytes to write into curr_iov_output.
|
|
size_t curr_iov_remaining_;
|
|
|
|
// Total bytes decompressed into output_iov_ so far.
|
|
size_t total_written_;
|
|
|
|
// Maximum number of bytes that will be decompressed into output_iov_.
|
|
size_t output_limit_;
|
|
|
|
static inline char* GetIOVecPointer(const struct iovec* iov, size_t offset) {
|
|
return reinterpret_cast<char*>(iov->iov_base) + offset;
|
|
}
|
|
|
|
public:
|
|
// Does not take ownership of iov. iov must be valid during the
|
|
// entire lifetime of the SnappyIOVecWriter.
|
|
inline SnappyIOVecWriter(const struct iovec* iov, size_t iov_count)
|
|
: output_iov_end_(iov + iov_count),
|
|
#if !defined(NDEBUG)
|
|
output_iov_(iov),
|
|
#endif // !defined(NDEBUG)
|
|
curr_iov_(iov),
|
|
curr_iov_output_(iov_count ? reinterpret_cast<char*>(iov->iov_base)
|
|
: nullptr),
|
|
curr_iov_remaining_(iov_count ? iov->iov_len : 0),
|
|
total_written_(0),
|
|
output_limit_(-1) {
|
|
}
|
|
|
|
inline void SetExpectedLength(size_t len) { output_limit_ = len; }
|
|
|
|
inline bool CheckLength() const { return total_written_ == output_limit_; }
|
|
|
|
inline bool Append(const char* ip, size_t len, char**) {
|
|
if (total_written_ + len > output_limit_) {
|
|
return false;
|
|
}
|
|
|
|
return AppendNoCheck(ip, len);
|
|
}
|
|
|
|
char* GetOutputPtr() { return nullptr; }
|
|
void SetOutputPtr(char* op) {
|
|
// TODO: Switch to [[maybe_unused]] when we can assume C++17.
|
|
(void)op;
|
|
}
|
|
|
|
inline bool AppendNoCheck(const char* ip, size_t len) {
|
|
while (len > 0) {
|
|
if (curr_iov_remaining_ == 0) {
|
|
// This iovec is full. Go to the next one.
|
|
if (curr_iov_ + 1 >= output_iov_end_) {
|
|
return false;
|
|
}
|
|
++curr_iov_;
|
|
curr_iov_output_ = reinterpret_cast<char*>(curr_iov_->iov_base);
|
|
curr_iov_remaining_ = curr_iov_->iov_len;
|
|
}
|
|
|
|
const size_t to_write = std::min(len, curr_iov_remaining_);
|
|
std::memcpy(curr_iov_output_, ip, to_write);
|
|
curr_iov_output_ += to_write;
|
|
curr_iov_remaining_ -= to_write;
|
|
total_written_ += to_write;
|
|
ip += to_write;
|
|
len -= to_write;
|
|
}
|
|
|
|
return true;
|
|
}
|
|
|
|
inline bool TryFastAppend(const char* ip, size_t available, size_t len,
|
|
char**) {
|
|
const size_t space_left = output_limit_ - total_written_;
|
|
if (len <= 16 && available >= 16 + kMaximumTagLength && space_left >= 16 &&
|
|
curr_iov_remaining_ >= 16) {
|
|
// Fast path, used for the majority (about 95%) of invocations.
|
|
UnalignedCopy128(ip, curr_iov_output_);
|
|
curr_iov_output_ += len;
|
|
curr_iov_remaining_ -= len;
|
|
total_written_ += len;
|
|
return true;
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
inline bool AppendFromSelf(size_t offset, size_t len, char**) {
|
|
// See SnappyArrayWriter::AppendFromSelf for an explanation of
|
|
// the "offset - 1u" trick.
|
|
if (offset - 1u >= total_written_) {
|
|
return false;
|
|
}
|
|
const size_t space_left = output_limit_ - total_written_;
|
|
if (len > space_left) {
|
|
return false;
|
|
}
|
|
|
|
// Locate the iovec from which we need to start the copy.
|
|
const iovec* from_iov = curr_iov_;
|
|
size_t from_iov_offset = curr_iov_->iov_len - curr_iov_remaining_;
|
|
while (offset > 0) {
|
|
if (from_iov_offset >= offset) {
|
|
from_iov_offset -= offset;
|
|
break;
|
|
}
|
|
|
|
offset -= from_iov_offset;
|
|
--from_iov;
|
|
#if !defined(NDEBUG)
|
|
assert(from_iov >= output_iov_);
|
|
#endif // !defined(NDEBUG)
|
|
from_iov_offset = from_iov->iov_len;
|
|
}
|
|
|
|
// Copy <len> bytes starting from the iovec pointed to by from_iov_index to
|
|
// the current iovec.
|
|
while (len > 0) {
|
|
assert(from_iov <= curr_iov_);
|
|
if (from_iov != curr_iov_) {
|
|
const size_t to_copy =
|
|
std::min(from_iov->iov_len - from_iov_offset, len);
|
|
AppendNoCheck(GetIOVecPointer(from_iov, from_iov_offset), to_copy);
|
|
len -= to_copy;
|
|
if (len > 0) {
|
|
++from_iov;
|
|
from_iov_offset = 0;
|
|
}
|
|
} else {
|
|
size_t to_copy = curr_iov_remaining_;
|
|
if (to_copy == 0) {
|
|
// This iovec is full. Go to the next one.
|
|
if (curr_iov_ + 1 >= output_iov_end_) {
|
|
return false;
|
|
}
|
|
++curr_iov_;
|
|
curr_iov_output_ = reinterpret_cast<char*>(curr_iov_->iov_base);
|
|
curr_iov_remaining_ = curr_iov_->iov_len;
|
|
continue;
|
|
}
|
|
if (to_copy > len) {
|
|
to_copy = len;
|
|
}
|
|
|
|
IncrementalCopy(GetIOVecPointer(from_iov, from_iov_offset),
|
|
curr_iov_output_, curr_iov_output_ + to_copy,
|
|
curr_iov_output_ + curr_iov_remaining_);
|
|
curr_iov_output_ += to_copy;
|
|
curr_iov_remaining_ -= to_copy;
|
|
from_iov_offset += to_copy;
|
|
total_written_ += to_copy;
|
|
len -= to_copy;
|
|
}
|
|
}
|
|
|
|
return true;
|
|
}
|
|
|
|
inline void Flush() {}
|
|
};
|
|
|
|
bool RawUncompressToIOVec(const char* compressed, size_t compressed_length,
|
|
const struct iovec* iov, size_t iov_cnt) {
|
|
ByteArraySource reader(compressed, compressed_length);
|
|
return RawUncompressToIOVec(&reader, iov, iov_cnt);
|
|
}
|
|
|
|
bool RawUncompressToIOVec(Source* compressed, const struct iovec* iov,
|
|
size_t iov_cnt) {
|
|
SnappyIOVecWriter output(iov, iov_cnt);
|
|
return InternalUncompress(compressed, &output);
|
|
}
|
|
|
|
// -----------------------------------------------------------------------
|
|
// Flat array interfaces
|
|
// -----------------------------------------------------------------------
|
|
|
|
// A type that writes to a flat array.
|
|
// Note that this is not a "ByteSink", but a type that matches the
|
|
// Writer template argument to SnappyDecompressor::DecompressAllTags().
|
|
class SnappyArrayWriter {
|
|
private:
|
|
char* base_;
|
|
char* op_;
|
|
char* op_limit_;
|
|
// If op < op_limit_min_slop_ then it's safe to unconditionally write
|
|
// kSlopBytes starting at op.
|
|
char* op_limit_min_slop_;
|
|
|
|
public:
|
|
inline explicit SnappyArrayWriter(char* dst)
|
|
: base_(dst),
|
|
op_(dst),
|
|
op_limit_(dst),
|
|
op_limit_min_slop_(dst) {} // Safe default see invariant.
|
|
|
|
inline void SetExpectedLength(size_t len) {
|
|
op_limit_ = op_ + len;
|
|
// Prevent pointer from being past the buffer.
|
|
op_limit_min_slop_ = op_limit_ - std::min<size_t>(kSlopBytes - 1, len);
|
|
}
|
|
|
|
inline bool CheckLength() const { return op_ == op_limit_; }
|
|
|
|
char* GetOutputPtr() { return op_; }
|
|
void SetOutputPtr(char* op) { op_ = op; }
|
|
|
|
inline bool Append(const char* ip, size_t len, char** op_p) {
|
|
char* op = *op_p;
|
|
const size_t space_left = op_limit_ - op;
|
|
if (space_left < len) return false;
|
|
std::memcpy(op, ip, len);
|
|
*op_p = op + len;
|
|
return true;
|
|
}
|
|
|
|
inline bool TryFastAppend(const char* ip, size_t available, size_t len,
|
|
char** op_p) {
|
|
char* op = *op_p;
|
|
const size_t space_left = op_limit_ - op;
|
|
if (len <= 16 && available >= 16 + kMaximumTagLength && space_left >= 16) {
|
|
// Fast path, used for the majority (about 95%) of invocations.
|
|
UnalignedCopy128(ip, op);
|
|
*op_p = op + len;
|
|
return true;
|
|
} else {
|
|
return false;
|
|
}
|
|
}
|
|
|
|
SNAPPY_ATTRIBUTE_ALWAYS_INLINE
|
|
inline bool AppendFromSelf(size_t offset, size_t len, char** op_p) {
|
|
char* const op = *op_p;
|
|
assert(op >= base_);
|
|
char* const op_end = op + len;
|
|
|
|
// Check if we try to append from before the start of the buffer.
|
|
if (SNAPPY_PREDICT_FALSE(static_cast<size_t>(op - base_) < offset))
|
|
return false;
|
|
|
|
if (SNAPPY_PREDICT_FALSE((kSlopBytes < 64 && len > kSlopBytes) ||
|
|
op >= op_limit_min_slop_ || offset < len)) {
|
|
if (op_end > op_limit_ || offset == 0) return false;
|
|
*op_p = IncrementalCopy(op - offset, op, op_end, op_limit_);
|
|
return true;
|
|
}
|
|
std::memmove(op, op - offset, kSlopBytes);
|
|
*op_p = op_end;
|
|
return true;
|
|
}
|
|
inline size_t Produced() const {
|
|
assert(op_ >= base_);
|
|
return op_ - base_;
|
|
}
|
|
inline void Flush() {}
|
|
};
|
|
|
|
bool RawUncompress(const char* compressed, size_t compressed_length,
|
|
char* uncompressed) {
|
|
ByteArraySource reader(compressed, compressed_length);
|
|
return RawUncompress(&reader, uncompressed);
|
|
}
|
|
|
|
bool RawUncompress(Source* compressed, char* uncompressed) {
|
|
SnappyArrayWriter output(uncompressed);
|
|
return InternalUncompress(compressed, &output);
|
|
}
|
|
|
|
bool Uncompress(const char* compressed, size_t compressed_length,
|
|
std::string* uncompressed) {
|
|
size_t ulength;
|
|
if (!GetUncompressedLength(compressed, compressed_length, &ulength)) {
|
|
return false;
|
|
}
|
|
// On 32-bit builds: max_size() < kuint32max. Check for that instead
|
|
// of crashing (e.g., consider externally specified compressed data).
|
|
if (ulength > uncompressed->max_size()) {
|
|
return false;
|
|
}
|
|
STLStringResizeUninitialized(uncompressed, ulength);
|
|
return RawUncompress(compressed, compressed_length,
|
|
string_as_array(uncompressed));
|
|
}
|
|
|
|
// A Writer that drops everything on the floor and just does validation
|
|
class SnappyDecompressionValidator {
|
|
private:
|
|
size_t expected_;
|
|
size_t produced_;
|
|
|
|
public:
|
|
inline SnappyDecompressionValidator() : expected_(0), produced_(0) {}
|
|
inline void SetExpectedLength(size_t len) { expected_ = len; }
|
|
size_t GetOutputPtr() { return produced_; }
|
|
void SetOutputPtr(size_t op) { produced_ = op; }
|
|
inline bool CheckLength() const { return expected_ == produced_; }
|
|
inline bool Append(const char* ip, size_t len, size_t* produced) {
|
|
// TODO: Switch to [[maybe_unused]] when we can assume C++17.
|
|
(void)ip;
|
|
|
|
*produced += len;
|
|
return *produced <= expected_;
|
|
}
|
|
inline bool TryFastAppend(const char* ip, size_t available, size_t length,
|
|
size_t* produced) {
|
|
// TODO: Switch to [[maybe_unused]] when we can assume C++17.
|
|
(void)ip;
|
|
(void)available;
|
|
(void)length;
|
|
(void)produced;
|
|
|
|
return false;
|
|
}
|
|
inline bool AppendFromSelf(size_t offset, size_t len, size_t* produced) {
|
|
// See SnappyArrayWriter::AppendFromSelf for an explanation of
|
|
// the "offset - 1u" trick.
|
|
if (*produced <= offset - 1u) return false;
|
|
*produced += len;
|
|
return *produced <= expected_;
|
|
}
|
|
inline void Flush() {}
|
|
};
|
|
|
|
bool IsValidCompressedBuffer(const char* compressed, size_t compressed_length) {
|
|
ByteArraySource reader(compressed, compressed_length);
|
|
SnappyDecompressionValidator writer;
|
|
return InternalUncompress(&reader, &writer);
|
|
}
|
|
|
|
bool IsValidCompressed(Source* compressed) {
|
|
SnappyDecompressionValidator writer;
|
|
return InternalUncompress(compressed, &writer);
|
|
}
|
|
|
|
void RawCompress(const char* input, size_t input_length, char* compressed,
|
|
size_t* compressed_length) {
|
|
ByteArraySource reader(input, input_length);
|
|
UncheckedByteArraySink writer(compressed);
|
|
Compress(&reader, &writer);
|
|
|
|
// Compute how many bytes were added
|
|
*compressed_length = (writer.CurrentDestination() - compressed);
|
|
}
|
|
|
|
size_t Compress(const char* input, size_t input_length,
|
|
std::string* compressed) {
|
|
// Pre-grow the buffer to the max length of the compressed output
|
|
STLStringResizeUninitialized(compressed, MaxCompressedLength(input_length));
|
|
|
|
size_t compressed_length;
|
|
RawCompress(input, input_length, string_as_array(compressed),
|
|
&compressed_length);
|
|
compressed->resize(compressed_length);
|
|
return compressed_length;
|
|
}
|
|
|
|
// -----------------------------------------------------------------------
|
|
// Sink interface
|
|
// -----------------------------------------------------------------------
|
|
|
|
// A type that decompresses into a Sink. The template parameter
|
|
// Allocator must export one method "char* Allocate(int size);", which
|
|
// allocates a buffer of "size" and appends that to the destination.
|
|
template <typename Allocator>
|
|
class SnappyScatteredWriter {
|
|
Allocator allocator_;
|
|
|
|
// We need random access into the data generated so far. Therefore
|
|
// we keep track of all of the generated data as an array of blocks.
|
|
// All of the blocks except the last have length kBlockSize.
|
|
std::vector<char*> blocks_;
|
|
size_t expected_;
|
|
|
|
// Total size of all fully generated blocks so far
|
|
size_t full_size_;
|
|
|
|
// Pointer into current output block
|
|
char* op_base_; // Base of output block
|
|
char* op_ptr_; // Pointer to next unfilled byte in block
|
|
char* op_limit_; // Pointer just past block
|
|
// If op < op_limit_min_slop_ then it's safe to unconditionally write
|
|
// kSlopBytes starting at op.
|
|
char* op_limit_min_slop_;
|
|
|
|
inline size_t Size() const { return full_size_ + (op_ptr_ - op_base_); }
|
|
|
|
bool SlowAppend(const char* ip, size_t len);
|
|
bool SlowAppendFromSelf(size_t offset, size_t len);
|
|
|
|
public:
|
|
inline explicit SnappyScatteredWriter(const Allocator& allocator)
|
|
: allocator_(allocator),
|
|
full_size_(0),
|
|
op_base_(NULL),
|
|
op_ptr_(NULL),
|
|
op_limit_(NULL),
|
|
op_limit_min_slop_(NULL) {}
|
|
char* GetOutputPtr() { return op_ptr_; }
|
|
void SetOutputPtr(char* op) { op_ptr_ = op; }
|
|
|
|
inline void SetExpectedLength(size_t len) {
|
|
assert(blocks_.empty());
|
|
expected_ = len;
|
|
}
|
|
|
|
inline bool CheckLength() const { return Size() == expected_; }
|
|
|
|
// Return the number of bytes actually uncompressed so far
|
|
inline size_t Produced() const { return Size(); }
|
|
|
|
inline bool Append(const char* ip, size_t len, char** op_p) {
|
|
char* op = *op_p;
|
|
size_t avail = op_limit_ - op;
|
|
if (len <= avail) {
|
|
// Fast path
|
|
std::memcpy(op, ip, len);
|
|
*op_p = op + len;
|
|
return true;
|
|
} else {
|
|
op_ptr_ = op;
|
|
bool res = SlowAppend(ip, len);
|
|
*op_p = op_ptr_;
|
|
return res;
|
|
}
|
|
}
|
|
|
|
inline bool TryFastAppend(const char* ip, size_t available, size_t length,
|
|
char** op_p) {
|
|
char* op = *op_p;
|
|
const int space_left = op_limit_ - op;
|
|
if (length <= 16 && available >= 16 + kMaximumTagLength &&
|
|
space_left >= 16) {
|
|
// Fast path, used for the majority (about 95%) of invocations.
|
|
UnalignedCopy128(ip, op);
|
|
*op_p = op + length;
|
|
return true;
|
|
} else {
|
|
return false;
|
|
}
|
|
}
|
|
|
|
inline bool AppendFromSelf(size_t offset, size_t len, char** op_p) {
|
|
char* op = *op_p;
|
|
assert(op >= op_base_);
|
|
// Check if we try to append from before the start of the buffer.
|
|
if (SNAPPY_PREDICT_FALSE((kSlopBytes < 64 && len > kSlopBytes) ||
|
|
static_cast<size_t>(op - op_base_) < offset ||
|
|
op >= op_limit_min_slop_ || offset < len)) {
|
|
if (offset == 0) return false;
|
|
if (SNAPPY_PREDICT_FALSE(static_cast<size_t>(op - op_base_) < offset ||
|
|
op + len > op_limit_)) {
|
|
op_ptr_ = op;
|
|
bool res = SlowAppendFromSelf(offset, len);
|
|
*op_p = op_ptr_;
|
|
return res;
|
|
}
|
|
*op_p = IncrementalCopy(op - offset, op, op + len, op_limit_);
|
|
return true;
|
|
}
|
|
// Fast path
|
|
char* const op_end = op + len;
|
|
std::memmove(op, op - offset, kSlopBytes);
|
|
*op_p = op_end;
|
|
return true;
|
|
}
|
|
|
|
// Called at the end of the decompress. We ask the allocator
|
|
// write all blocks to the sink.
|
|
inline void Flush() { allocator_.Flush(Produced()); }
|
|
};
|
|
|
|
template <typename Allocator>
|
|
bool SnappyScatteredWriter<Allocator>::SlowAppend(const char* ip, size_t len) {
|
|
size_t avail = op_limit_ - op_ptr_;
|
|
while (len > avail) {
|
|
// Completely fill this block
|
|
std::memcpy(op_ptr_, ip, avail);
|
|
op_ptr_ += avail;
|
|
assert(op_limit_ - op_ptr_ == 0);
|
|
full_size_ += (op_ptr_ - op_base_);
|
|
len -= avail;
|
|
ip += avail;
|
|
|
|
// Bounds check
|
|
if (full_size_ + len > expected_) return false;
|
|
|
|
// Make new block
|
|
size_t bsize = std::min<size_t>(kBlockSize, expected_ - full_size_);
|
|
op_base_ = allocator_.Allocate(bsize);
|
|
op_ptr_ = op_base_;
|
|
op_limit_ = op_base_ + bsize;
|
|
op_limit_min_slop_ = op_limit_ - std::min<size_t>(kSlopBytes - 1, bsize);
|
|
|
|
blocks_.push_back(op_base_);
|
|
avail = bsize;
|
|
}
|
|
|
|
std::memcpy(op_ptr_, ip, len);
|
|
op_ptr_ += len;
|
|
return true;
|
|
}
|
|
|
|
template <typename Allocator>
|
|
bool SnappyScatteredWriter<Allocator>::SlowAppendFromSelf(size_t offset,
|
|
size_t len) {
|
|
// Overflow check
|
|
// See SnappyArrayWriter::AppendFromSelf for an explanation of
|
|
// the "offset - 1u" trick.
|
|
const size_t cur = Size();
|
|
if (offset - 1u >= cur) return false;
|
|
if (expected_ - cur < len) return false;
|
|
|
|
// Currently we shouldn't ever hit this path because Compress() chops the
|
|
// input into blocks and does not create cross-block copies. However, it is
|
|
// nice if we do not rely on that, since we can get better compression if we
|
|
// allow cross-block copies and thus might want to change the compressor in
|
|
// the future.
|
|
// TODO Replace this with a properly optimized path. This is not
|
|
// triggered right now. But this is so super slow, that it would regress
|
|
// performance unacceptably if triggered.
|
|
size_t src = cur - offset;
|
|
char* op = op_ptr_;
|
|
while (len-- > 0) {
|
|
char c = blocks_[src >> kBlockLog][src & (kBlockSize - 1)];
|
|
if (!Append(&c, 1, &op)) {
|
|
op_ptr_ = op;
|
|
return false;
|
|
}
|
|
src++;
|
|
}
|
|
op_ptr_ = op;
|
|
return true;
|
|
}
|
|
|
|
class SnappySinkAllocator {
|
|
public:
|
|
explicit SnappySinkAllocator(Sink* dest) : dest_(dest) {}
|
|
~SnappySinkAllocator() {}
|
|
|
|
char* Allocate(int size) {
|
|
Datablock block(new char[size], size);
|
|
blocks_.push_back(block);
|
|
return block.data;
|
|
}
|
|
|
|
// We flush only at the end, because the writer wants
|
|
// random access to the blocks and once we hand the
|
|
// block over to the sink, we can't access it anymore.
|
|
// Also we don't write more than has been actually written
|
|
// to the blocks.
|
|
void Flush(size_t size) {
|
|
size_t size_written = 0;
|
|
for (Datablock& block : blocks_) {
|
|
size_t block_size = std::min<size_t>(block.size, size - size_written);
|
|
dest_->AppendAndTakeOwnership(block.data, block_size,
|
|
&SnappySinkAllocator::Deleter, NULL);
|
|
size_written += block_size;
|
|
}
|
|
blocks_.clear();
|
|
}
|
|
|
|
private:
|
|
struct Datablock {
|
|
char* data;
|
|
size_t size;
|
|
Datablock(char* p, size_t s) : data(p), size(s) {}
|
|
};
|
|
|
|
static void Deleter(void* arg, const char* bytes, size_t size) {
|
|
// TODO: Switch to [[maybe_unused]] when we can assume C++17.
|
|
(void)arg;
|
|
(void)size;
|
|
|
|
delete[] bytes;
|
|
}
|
|
|
|
Sink* dest_;
|
|
std::vector<Datablock> blocks_;
|
|
|
|
// Note: copying this object is allowed
|
|
};
|
|
|
|
size_t UncompressAsMuchAsPossible(Source* compressed, Sink* uncompressed) {
|
|
SnappySinkAllocator allocator(uncompressed);
|
|
SnappyScatteredWriter<SnappySinkAllocator> writer(allocator);
|
|
InternalUncompress(compressed, &writer);
|
|
return writer.Produced();
|
|
}
|
|
|
|
bool Uncompress(Source* compressed, Sink* uncompressed) {
|
|
// Read the uncompressed length from the front of the compressed input
|
|
SnappyDecompressor decompressor(compressed);
|
|
uint32_t uncompressed_len = 0;
|
|
if (!decompressor.ReadUncompressedLength(&uncompressed_len)) {
|
|
return false;
|
|
}
|
|
|
|
char c;
|
|
size_t allocated_size;
|
|
char* buf = uncompressed->GetAppendBufferVariable(1, uncompressed_len, &c, 1,
|
|
&allocated_size);
|
|
|
|
const size_t compressed_len = compressed->Available();
|
|
// If we can get a flat buffer, then use it, otherwise do block by block
|
|
// uncompression
|
|
if (allocated_size >= uncompressed_len) {
|
|
SnappyArrayWriter writer(buf);
|
|
bool result = InternalUncompressAllTags(&decompressor, &writer,
|
|
compressed_len, uncompressed_len);
|
|
uncompressed->Append(buf, writer.Produced());
|
|
return result;
|
|
} else {
|
|
SnappySinkAllocator allocator(uncompressed);
|
|
SnappyScatteredWriter<SnappySinkAllocator> writer(allocator);
|
|
return InternalUncompressAllTags(&decompressor, &writer, compressed_len,
|
|
uncompressed_len);
|
|
}
|
|
}
|
|
|
|
} // namespace snappy
|