Fix line endings. WHAMMY.

1 files changed, 1025 insertions, 1025 deletions

diff --git a/mp/src/tier1/snappy.cpp b/mp/src/tier1/snappy.cpp
index d633ca3e..b617049e 100644
--- a/mp/src/tier1/snappy.cpp
+++ b/mp/src/tier1/snappy.cpp
@@ -1,1025 +1,1025 @@
-// Copyright 2005 Google Inc. All Rights Reserved.

-//

-// Redistribution and use in source and binary forms, with or without

-// modification, are permitted provided that the following conditions are

-// met:

-//

-//     * Redistributions of source code must retain the above copyright

-// notice, this list of conditions and the following disclaimer.

-//     * Redistributions in binary form must reproduce the above

-// copyright notice, this list of conditions and the following disclaimer

-// in the documentation and/or other materials provided with the

-// distribution.

-//     * Neither the name of Google Inc. nor the names of its

-// contributors may be used to endorse or promote products derived from

-// this software without specific prior written permission.

-//

-// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

-// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT

-// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR

-// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT

-// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,

-// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT

-// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,

-// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY

-// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

-// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE

-// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

-

-#include "snappy.h"

-#include "snappy-internal.h"

-#include "snappy-sinksource.h"

-

-#include <stdio.h>

-

-#include <algorithm>

-#include <string>

-#include <vector>

-

-#ifdef _WIN32

-#pragma warning(disable:4018) // warning C4018: '<' : signed/unsigned mismatch

-#pragma warning(disable:4389) // warning C4389: '==' : signed/unsigned mismatch

-#endif //_WIN32

-

-namespace snappy {

-

-// Any hash function will produce a valid compressed bitstream, but a good

-// hash function reduces the number of collisions and thus yields better

-// compression for compressible input, and more speed for incompressible

-// input. Of course, it doesn't hurt if the hash function is reasonably fast

-// either, as it gets called a lot.

-static inline uint32 HashBytes(uint32 bytes, int shift) {

-  uint32 kMul = 0x1e35a7bd;

-  return (bytes * kMul) >> shift;

-}

-static inline uint32 Hash(const char* p, int shift) {

-  return HashBytes(UNALIGNED_LOAD32(p), shift);

-}

-

-size_t MaxCompressedLength(size_t source_len) {

-  // Compressed data can be defined as:

-  //    compressed := item* literal*

-  //    item       := literal* copy

-  //

-  // The trailing literal sequence has a space blowup of at most 62/60

-  // since a literal of length 60 needs one tag byte + one extra byte

-  // for length information.

-  //

-  // Item blowup is trickier to measure.  Suppose the "copy" op copies

-  // 4 bytes of data.  Because of a special check in the encoding code,

-  // we produce a 4-byte copy only if the offset is < 65536.  Therefore

-  // the copy op takes 3 bytes to encode, and this type of item leads

-  // to at most the 62/60 blowup for representing literals.

-  //

-  // Suppose the "copy" op copies 5 bytes of data.  If the offset is big

-  // enough, it will take 5 bytes to encode the copy op.  Therefore the

-  // worst case here is a one-byte literal followed by a five-byte copy.

-  // I.e., 6 bytes of input turn into 7 bytes of "compressed" data.

-  //

-  // This last factor dominates the blowup, so the final estimate is:

-  return 32 + source_len + source_len/6;

-}

-

-enum {

-  LITERAL = 0,

-  COPY_1_BYTE_OFFSET = 1,  // 3 bit length + 3 bits of offset in opcode

-  COPY_2_BYTE_OFFSET = 2,

-  COPY_4_BYTE_OFFSET = 3

-};

-

-// Copy "len" bytes from "src" to "op", one byte at a time.  Used for

-// handling COPY operations where the input and output regions may

-// overlap.  For example, suppose:

-//    src    == "ab"

-//    op     == src + 2

-//    len    == 20

-// After IncrementalCopy(src, op, len), the result will have

-// eleven copies of "ab"

-//    ababababababababababab

-// Note that this does not match the semantics of either memcpy()

-// or memmove().

-static inline void IncrementalCopy(const char* src, char* op, int len) {

-  DCHECK_GT(len, 0);

-  do {

-    *op++ = *src++;

-  } while (--len > 0);

-}

-

-// Equivalent to IncrementalCopy except that it can write up to ten extra

-// bytes after the end of the copy, and that it is faster.

-//

-// The main part of this loop is a simple copy of eight bytes at a time until

-// we've copied (at least) the requested amount of bytes.  However, if op and

-// src are less than eight bytes apart (indicating a repeating pattern of

-// length < 8), we first need to expand the pattern in order to get the correct

-// results. For instance, if the buffer looks like this, with the eight-byte

-// <src> and <op> patterns marked as intervals:

-//

-//    abxxxxxxxxxxxx

-//    [------]           src

-//      [------]         op

-//

-// a single eight-byte copy from <src> to <op> will repeat the pattern once,

-// after which we can move <op> two bytes without moving <src>:

-//

-//    ababxxxxxxxxxx

-//    [------]           src

-//        [------]       op

-//

-// and repeat the exercise until the two no longer overlap.

-//

-// This allows us to do very well in the special case of one single byte

-// repeated many times, without taking a big hit for more general cases.

-//

-// The worst case of extra writing past the end of the match occurs when

-// op - src == 1 and len == 1; the last copy will read from byte positions

-// [0..7] and write to [4..11], whereas it was only supposed to write to

-// position 1. Thus, ten excess bytes.

-

-namespace {

-

-const int kMaxIncrementCopyOverflow = 10;

-

-}  // namespace

-

-static inline void IncrementalCopyFastPath(const char* src, char* op, int len) {

-  while (op - src < 8) {

-    UNALIGNED_STORE64(op, UNALIGNED_LOAD64(src));

-    len -= op - src;

-    op += op - src;

-  }

-  while (len > 0) {

-    UNALIGNED_STORE64(op, UNALIGNED_LOAD64(src));

-    src += 8;

-    op += 8;

-    len -= 8;

-  }

-}

-

-static inline char* EmitLiteral(char* op,

-                                const char* literal,

-                                int len,

-                                bool allow_fast_path) {

-  int n = len - 1;      // Zero-length literals are disallowed

-  if (n < 60) {

-    // Fits in tag byte

-    *op++ = LITERAL | (n << 2);

-

-    // The vast majority of copies are below 16 bytes, for which a

-    // call to memcpy is overkill. This fast path can sometimes

-    // copy up to 15 bytes too much, but that is okay in the

-    // main loop, since we have a bit to go on for both sides:

-    //

-    //   - The input will always have kInputMarginBytes = 15 extra

-    //     available bytes, as long as we're in the main loop, and

-    //     if not, allow_fast_path = false.

-    //   - The output will always have 32 spare bytes (see

-    //     MaxCompressedLength).

-    if (allow_fast_path && len <= 16) {

-      UNALIGNED_STORE64(op, UNALIGNED_LOAD64(literal));

-      UNALIGNED_STORE64(op + 8, UNALIGNED_LOAD64(literal + 8));

-      return op + len;

-    }

-  } else {

-    // Encode in upcoming bytes

-    char* base = op;

-    int count = 0;

-    op++;

-    while (n > 0) {

-      *op++ = n & 0xff;

-      n >>= 8;

-      count++;

-    }

-    assert(count >= 1);

-    assert(count <= 4);

-    *base = LITERAL | ((59+count) << 2);

-  }

-  memcpy(op, literal, len);

-  return op + len;

-}

-

-static inline char* EmitCopyLessThan64(char* op, int offset, int len) {

-  DCHECK_LE(len, 64);

-  DCHECK_GE(len, 4);

-  DCHECK_LT(offset, 65536);

-

-  if ((len < 12) && (offset < 2048)) {

-    int len_minus_4 = len - 4;

-    assert(len_minus_4 < 8);            // Must fit in 3 bits

-    *op++ = COPY_1_BYTE_OFFSET | ((len_minus_4) << 2) | ((offset >> 8) << 5);

-    *op++ = offset & 0xff;

-  } else {

-    *op++ = COPY_2_BYTE_OFFSET | ((len-1) << 2);

-    LittleEndian::Store16(op, offset);

-    op += 2;

-  }

-  return op;

-}

-

-static inline char* EmitCopy(char* op, int offset, int len) {

-  // Emit 64 byte copies but make sure to keep at least four bytes reserved

-  while (len >= 68) {

-    op = EmitCopyLessThan64(op, offset, 64);

-    len -= 64;

-  }

-

-  // Emit an extra 60 byte copy if have too much data to fit in one copy

-  if (len > 64) {

-    op = EmitCopyLessThan64(op, offset, 60);

-    len -= 60;

-  }

-

-  // Emit remainder

-  op = EmitCopyLessThan64(op, offset, len);

-  return op;

-}

-

-

-bool GetUncompressedLength(const char* start, size_t n, size_t* result) {

-  uint32 v = 0;

-  const char* limit = start + n;

-  if (Varint::Parse32WithLimit(start, limit, &v) != NULL) {

-    *result = v;

-    return true;

-  } else {

-    return false;

-  }

-}

-

-namespace internal {

-uint16* WorkingMemory::GetHashTable(size_t input_size, int* table_size) {

-  // Use smaller hash table when input.size() is smaller, since we

-  // fill the table, incurring O(hash table size) overhead for

-  // compression, and if the input is short, we won't need that

-  // many hash table entries anyway.

-  assert(kMaxHashTableSize >= 256);

-  int htsize = 256;

-  while (htsize < kMaxHashTableSize && htsize < input_size) {

-    htsize <<= 1;

-  }

-  CHECK_EQ(0, htsize & (htsize - 1)) << ": must be power of two";

-  CHECK_LE(htsize, kMaxHashTableSize) << ": hash table too large";

-

-  uint16* table;

-  if (htsize <= ARRAYSIZE(small_table_)) {

-    table = small_table_;

-  } else {

-    if (large_table_ == NULL) {

-      large_table_ = new uint16[kMaxHashTableSize];

-    }

-    table = large_table_;

-  }

-

-  *table_size = htsize;

-  memset(table, 0, htsize * sizeof(*table));

-  return table;

-}

-}  // end namespace internal

-

-// For 0 <= offset <= 4, GetUint32AtOffset(UNALIGNED_LOAD64(p), offset) will

-// equal UNALIGNED_LOAD32(p + offset).  Motivation: On x86-64 hardware we have

-// empirically found that overlapping loads such as

-//  UNALIGNED_LOAD32(p) ... UNALIGNED_LOAD32(p+1) ... UNALIGNED_LOAD32(p+2)

-// are slower than UNALIGNED_LOAD64(p) followed by shifts and casts to uint32.

-static inline uint32 GetUint32AtOffset(uint64 v, int offset) {

-  DCHECK(0 <= offset && offset <= 4) << offset;

-  return v >> (LittleEndian::IsLittleEndian() ? 8 * offset : 32 - 8 * offset);

-}

-

-// 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* const input,

-                       const size_t input_size,

-                       char* op,

-                       uint16* table,

-                       const int table_size) {

-  // "ip" is the input pointer, and "op" is the output pointer.

-  const char* ip = input;

-  CHECK_LE(input_size, kBlockSize);

-  CHECK_EQ(table_size & (table_size - 1), 0) << ": table must be power of two";

-  const int shift = 32 - Bits::Log2Floor(table_size);

-  DCHECK_EQ(kuint32max >> shift, table_size - 1);

-  const char* ip_end = input + input_size;

-  const char* base_ip = ip;

-  // 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;

-

-  const int kInputMarginBytes = 15;

-  if (PREDICT_TRUE(input_size >= kInputMarginBytes)) {

-    const char* ip_limit = input + input_size - kInputMarginBytes;

-

-    for (uint32 next_hash = Hash(++ip, shift); ; ) {

-      DCHECK_LT(next_emit, 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, 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 skip = 32;

-

-      const char* next_ip = ip;

-      const char* candidate;

-      do {

-        ip = next_ip;

-        uint32 hash = next_hash;

-        DCHECK_EQ(hash, Hash(ip, shift));

-        uint32 bytes_between_hash_lookups = skip++ >> 5;

-        next_ip = ip + bytes_between_hash_lookups;

-        if (PREDICT_FALSE(next_ip > ip_limit)) {

-          goto emit_remainder;

-        }

-        next_hash = Hash(next_ip, shift);

-        candidate = base_ip + table[hash];

-        DCHECK_GE(candidate, base_ip);

-        DCHECK_LT(candidate, ip);

-

-        table[hash] = ip - base_ip;

-      } while (PREDICT_TRUE(UNALIGNED_LOAD32(ip) !=

-                            UNALIGNED_LOAD32(candidate)));

-

-      // 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."

-      DCHECK_LE(next_emit + 16, ip_end);

-      op = EmitLiteral(op, next_emit, ip - next_emit, true);

-

-      // 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.

-      uint64 input_bytes = 0;

-      uint32 candidate_bytes = 0;

-

-      do {

-        // We have a 4-byte match at ip, and no need to emit any

-        // "literal bytes" prior to ip.

-        const char* base = ip;

-        int matched = 4 + FindMatchLength(candidate + 4, ip + 4, ip_end);

-        ip += matched;

-        int offset = base - candidate;

-        DCHECK_EQ(0, memcmp(base, candidate, matched));

-        op = EmitCopy(op, offset, matched);

-        // We could immediately start working at ip now, but to improve

-        // compression we first update table[Hash(ip - 1, ...)].

-        const char* insert_tail = ip - 1;

-        next_emit = ip;

-        if (PREDICT_FALSE(ip >= ip_limit)) {

-          goto emit_remainder;

-        }

-        input_bytes = UNALIGNED_LOAD64(insert_tail);

-        uint32 prev_hash = HashBytes(GetUint32AtOffset(input_bytes, 0), shift);

-        table[prev_hash] = ip - base_ip - 1;

-        uint32 cur_hash = HashBytes(GetUint32AtOffset(input_bytes, 1), shift);

-        candidate = base_ip + table[cur_hash];

-        candidate_bytes = UNALIGNED_LOAD32(candidate);

-        table[cur_hash] = ip - base_ip;

-      } while (GetUint32AtOffset(input_bytes, 1) == candidate_bytes);

-

-      next_hash = HashBytes(GetUint32AtOffset(input_bytes, 2), shift);

-      ++ip;

-    }

-  }

-

- emit_remainder:

-  // Emit the remaining bytes as a literal

-  if (next_emit < ip_end) {

-    op = EmitLiteral(op, next_emit, ip_end - next_emit, false);

-  }

-

-  return op;

-}

-}  // end namespace internal

-

-// 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);

-//

-//   // Called after decompression

-//   bool CheckLength() const;

-//

-//   // Called repeatedly during decompression

-//   bool Append(const char* ip, uint32 length, bool allow_fast_path);

-//   bool AppendFromSelf(uint32 offset, uint32 length);

-// };

-//

-// "allow_fast_path" is a parameter that says if there is at least 16

-// readable bytes in "ip". It is currently only used by SnappyArrayWriter.

-

-// -----------------------------------------------------------------------

-// Lookup table for decompression code.  Generated by ComputeTable() below.

-// -----------------------------------------------------------------------

-

-// Mapping from i in range [0,4] to a mask to extract the bottom 8*i bits

-static const uint32 wordmask[] = {

-  0u, 0xffu, 0xffffu, 0xffffffu, 0xffffffffu

-};

-

-// Data stored per entry in lookup table:

-//      Range   Bits-used       Description

-//      ------------------------------------

-//      1..64   0..7            Literal/copy length encoded in opcode byte

-//      0..7    8..10           Copy offset encoded in opcode byte / 256

-//      0..4    11..13          Extra bytes after opcode

-//

-// We use eight bits for the length even though 7 would have sufficed

-// because of efficiency reasons:

-//      (1) Extracting a byte is faster than a bit-field

-//      (2) It properly aligns copy offset so we do not need a <<8

-static const uint16 char_table[256] = {

-  0x0001, 0x0804, 0x1001, 0x2001, 0x0002, 0x0805, 0x1002, 0x2002,

-  0x0003, 0x0806, 0x1003, 0x2003, 0x0004, 0x0807, 0x1004, 0x2004,

-  0x0005, 0x0808, 0x1005, 0x2005, 0x0006, 0x0809, 0x1006, 0x2006,

-  0x0007, 0x080a, 0x1007, 0x2007, 0x0008, 0x080b, 0x1008, 0x2008,

-  0x0009, 0x0904, 0x1009, 0x2009, 0x000a, 0x0905, 0x100a, 0x200a,

-  0x000b, 0x0906, 0x100b, 0x200b, 0x000c, 0x0907, 0x100c, 0x200c,

-  0x000d, 0x0908, 0x100d, 0x200d, 0x000e, 0x0909, 0x100e, 0x200e,

-  0x000f, 0x090a, 0x100f, 0x200f, 0x0010, 0x090b, 0x1010, 0x2010,

-  0x0011, 0x0a04, 0x1011, 0x2011, 0x0012, 0x0a05, 0x1012, 0x2012,

-  0x0013, 0x0a06, 0x1013, 0x2013, 0x0014, 0x0a07, 0x1014, 0x2014,

-  0x0015, 0x0a08, 0x1015, 0x2015, 0x0016, 0x0a09, 0x1016, 0x2016,

-  0x0017, 0x0a0a, 0x1017, 0x2017, 0x0018, 0x0a0b, 0x1018, 0x2018,

-  0x0019, 0x0b04, 0x1019, 0x2019, 0x001a, 0x0b05, 0x101a, 0x201a,

-  0x001b, 0x0b06, 0x101b, 0x201b, 0x001c, 0x0b07, 0x101c, 0x201c,

-  0x001d, 0x0b08, 0x101d, 0x201d, 0x001e, 0x0b09, 0x101e, 0x201e,

-  0x001f, 0x0b0a, 0x101f, 0x201f, 0x0020, 0x0b0b, 0x1020, 0x2020,

-  0x0021, 0x0c04, 0x1021, 0x2021, 0x0022, 0x0c05, 0x1022, 0x2022,

-  0x0023, 0x0c06, 0x1023, 0x2023, 0x0024, 0x0c07, 0x1024, 0x2024,

-  0x0025, 0x0c08, 0x1025, 0x2025, 0x0026, 0x0c09, 0x1026, 0x2026,

-  0x0027, 0x0c0a, 0x1027, 0x2027, 0x0028, 0x0c0b, 0x1028, 0x2028,

-  0x0029, 0x0d04, 0x1029, 0x2029, 0x002a, 0x0d05, 0x102a, 0x202a,

-  0x002b, 0x0d06, 0x102b, 0x202b, 0x002c, 0x0d07, 0x102c, 0x202c,

-  0x002d, 0x0d08, 0x102d, 0x202d, 0x002e, 0x0d09, 0x102e, 0x202e,

-  0x002f, 0x0d0a, 0x102f, 0x202f, 0x0030, 0x0d0b, 0x1030, 0x2030,

-  0x0031, 0x0e04, 0x1031, 0x2031, 0x0032, 0x0e05, 0x1032, 0x2032,

-  0x0033, 0x0e06, 0x1033, 0x2033, 0x0034, 0x0e07, 0x1034, 0x2034,

-  0x0035, 0x0e08, 0x1035, 0x2035, 0x0036, 0x0e09, 0x1036, 0x2036,

-  0x0037, 0x0e0a, 0x1037, 0x2037, 0x0038, 0x0e0b, 0x1038, 0x2038,

-  0x0039, 0x0f04, 0x1039, 0x2039, 0x003a, 0x0f05, 0x103a, 0x203a,

-  0x003b, 0x0f06, 0x103b, 0x203b, 0x003c, 0x0f07, 0x103c, 0x203c,

-  0x0801, 0x0f08, 0x103d, 0x203d, 0x1001, 0x0f09, 0x103e, 0x203e,

-  0x1801, 0x0f0a, 0x103f, 0x203f, 0x2001, 0x0f0b, 0x1040, 0x2040

-};

-

-// In debug mode, allow optional computation of the table at startup.

-// Also, check that the decompression table is correct.

-#ifndef NDEBUG

-DEFINE_bool(snappy_dump_decompression_table, false,

-            "If true, we print the decompression table at startup.");

-

-static uint16 MakeEntry(unsigned int extra,

-                        unsigned int len,

-                        unsigned int copy_offset) {

-  // Check that all of the fields fit within the allocated space

-  DCHECK_EQ(extra,       extra & 0x7);          // At most 3 bits

-  DCHECK_EQ(copy_offset, copy_offset & 0x7);    // At most 3 bits

-  DCHECK_EQ(len,         len & 0x7f);           // At most 7 bits

-  return len | (copy_offset << 8) | (extra << 11);

-}

-

-static void ComputeTable() {

-  uint16 dst[256];

-

-  // Place invalid entries in all places to detect missing initialization

-  int assigned = 0;

-  for (int i = 0; i < 256; i++) {

-    dst[i] = 0xffff;

-  }

-

-  // Small LITERAL entries.  We store (len-1) in the top 6 bits.

-  for (unsigned int len = 1; len <= 60; len++) {

-    dst[LITERAL | ((len-1) << 2)] = MakeEntry(0, len, 0);

-    assigned++;

-  }

-

-  // Large LITERAL entries.  We use 60..63 in the high 6 bits to

-  // encode the number of bytes of length info that follow the opcode.

-  for (unsigned int extra_bytes = 1; extra_bytes <= 4; extra_bytes++) {

-    // We set the length field in the lookup table to 1 because extra

-    // bytes encode len-1.

-    dst[LITERAL | ((extra_bytes+59) << 2)] = MakeEntry(extra_bytes, 1, 0);

-    assigned++;

-  }

-

-  // COPY_1_BYTE_OFFSET.

-  //

-  // The tag byte in the compressed data stores len-4 in 3 bits, and

-  // offset/256 in 5 bits.  offset%256 is stored in the next byte.

-  //

-  // This format is used for length in range [4..11] and offset in

-  // range [0..2047]

-  for (unsigned int len = 4; len < 12; len++) {

-    for (unsigned int offset = 0; offset < 2048; offset += 256) {

-      dst[COPY_1_BYTE_OFFSET | ((len-4)<<2) | ((offset>>8)<<5)] =

-        MakeEntry(1, len, offset>>8);

-      assigned++;

-    }

-  }

-

-  // COPY_2_BYTE_OFFSET.

-  // Tag contains len-1 in top 6 bits, and offset in next two bytes.

-  for (unsigned int len = 1; len <= 64; len++) {

-    dst[COPY_2_BYTE_OFFSET | ((len-1)<<2)] = MakeEntry(2, len, 0);

-    assigned++;

-  }

-

-  // COPY_4_BYTE_OFFSET.

-  // Tag contents len-1 in top 6 bits, and offset in next four bytes.

-  for (unsigned int len = 1; len <= 64; len++) {

-    dst[COPY_4_BYTE_OFFSET | ((len-1)<<2)] = MakeEntry(4, len, 0);

-    assigned++;

-  }

-

-  // Check that each entry was initialized exactly once.

-  CHECK_EQ(assigned, 256);

-  for (int i = 0; i < 256; i++) {

-    CHECK_NE(dst[i], 0xffff);

-  }

-

-  if (FLAGS_snappy_dump_decompression_table) {

-    printf("static const uint16 char_table[256] = {\n  ");

-    for (int i = 0; i < 256; i++) {

-      printf("0x%04x%s",

-             dst[i],

-             ((i == 255) ? "\n" : (((i%8) == 7) ? ",\n  " : ", ")));

-    }

-    printf("};\n");

-  }

-

-  // Check that computed table matched recorded table

-  for (int i = 0; i < 256; i++) {

-    CHECK_EQ(dst[i], char_table[i]);

-  }

-}

-REGISTER_MODULE_INITIALIZER(snappy, ComputeTable());

-#endif /* !NDEBUG */

-

-// 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

-  uint32        peeked_;         // Bytes peeked from reader (need to skip)

-  bool          eof_;            // Hit end of input without an error?

-  char          scratch_[5];     // Temporary buffer for PeekFast() boundaries

-

-  // 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();

-

- 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 succcess, stores the length in *result and returns true.

-  // On failure, returns false.

-  bool ReadUncompressedLength(uint32* result) {

-    DCHECK(ip_ == NULL);       // Must not have read anything yet

-    // Length is encoded in 1..5 bytes

-    *result = 0;

-    uint32 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);

-      *result |= static_cast<uint32>(c & 0x7f) << 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>

-  void DecompressAllTags(Writer* writer) {

-    const char* ip = ip_;

-    for ( ;; ) {

-      if (ip_limit_ - ip < 5) {

-        ip_ = ip;

-        if (!RefillTag()) return;

-        ip = ip_;

-      }

-

-      const unsigned char c = *(reinterpret_cast<const unsigned char*>(ip++));

-      const uint32 entry = char_table[c];

-      const uint32 trailer = LittleEndian::Load32(ip) & wordmask[entry >> 11];

-      ip += entry >> 11;

-      const uint32 length = entry & 0xff;

-

-      if ((c & 0x3) == LITERAL) {

-        uint32 literal_length = length + trailer;

-        uint32 avail = ip_limit_ - ip;

-        while (avail < literal_length) {

-          bool allow_fast_path = (avail >= 16);

-          if (!writer->Append(ip, avail, allow_fast_path)) return;

-          literal_length -= avail;

-          reader_->Skip(peeked_);

-          size_t n;

-          ip = reader_->Peek(&n);

-          avail = (uint32)n;

-          peeked_ = avail;

-          if (avail == 0) return;  // Premature end of input

-          ip_limit_ = ip + avail;

-        }

-        bool allow_fast_path = (avail >= 16);

-        if (!writer->Append(ip, literal_length, allow_fast_path)) {

-          return;

-        }

-        ip += literal_length;

-      } else {

-        // 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 copy_offset = entry & 0x700;

-        if (!writer->AppendFromSelf(copy_offset + trailer, length)) {

-          return;

-        }

-      }

-    }

-  }

-};

-

-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_ = (uint32)n;

-    if (n == 0) {

-      eof_ = true;

-      return false;

-    }

-    ip_limit_ = ip + n;

-  }

-

-  // Read the tag character

-  DCHECK_LT(ip, ip_limit_);

-  const unsigned char c = *(reinterpret_cast<const unsigned char*>(ip));

-  const uint32 entry = char_table[c];

-  const uint32 needed = (entry >> 11) + 1;  // +1 byte for 'c'

-  DCHECK_LE(needed, sizeof(scratch_));

-

-  // Read more bytes from reader if needed

-  uint32 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.

-    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 to_add = min<uint32>(needed - nbuf, (uint32)length);

-      memcpy(scratch_ + nbuf, src, to_add);

-      nbuf += to_add;

-      reader_->Skip(to_add);

-    }

-    DCHECK_EQ(nbuf, needed);

-    ip_ = scratch_;

-    ip_limit_ = scratch_ + needed;

-  } else if (nbuf < 5) {

-    // Have enough bytes, but move into scratch_ so that we do not

-    // read past end of input

-    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,

-                               uint32 max_len) {

-  // Read the uncompressed length from the front of the compressed input

-  SnappyDecompressor decompressor(r);

-  uint32 uncompressed_len = 0;

-  if (!decompressor.ReadUncompressedLength(&uncompressed_len)) return false;

-  // Protect against possible DoS attack

-  if (static_cast<uint64>(uncompressed_len) > max_len) {

-    return false;

-  }

-

-  writer->SetExpectedLength(uncompressed_len);

-

-  // Process the entire input

-  decompressor.DecompressAllTags(writer);

-  return (decompressor.eof() && writer->CheckLength());

-}

-

-bool GetUncompressedLength(Source* source, uint32* result) {

-  SnappyDecompressor decompressor(source);

-  return decompressor.ReadUncompressedLength(result);

-}

-

-size_t Compress(Source* reader, Sink* writer) {

-  size_t written = 0;

-  int N = (int)reader->Available();

-  char ulength[Varint::kMax32];

-  char* p = Varint::Encode32(ulength, N);

-  writer->Append(ulength, p-ulength);

-  written += (p - ulength);

-

-  internal::WorkingMemory wmem;

-  char* scratch = NULL;

-  char* scratch_output = NULL;

-

-  while (N > 0) {

-    // Get next block to compress (without copying if possible)

-    size_t fragment_size;

-    const char* fragment = reader->Peek(&fragment_size);

-    DCHECK_NE(fragment_size, 0) << ": premature end of input";

-    const int num_to_read = min(N, kBlockSize);

-    size_t bytes_read = fragment_size;

-

-    int 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 {

-      // Read into scratch buffer

-      if (scratch == NULL) {

-        // If this is the last iteration, we want to allocate N bytes

-        // of space, otherwise the max possible kBlockSize space.

-        // num_to_read contains exactly the correct value

-        scratch = new char[num_to_read];

-      }

-      memcpy(scratch, fragment, bytes_read);

-      reader->Skip(bytes_read);

-

-      while (bytes_read < num_to_read) {

-        fragment = reader->Peek(&fragment_size);

-        size_t n = min<size_t>(fragment_size, num_to_read - bytes_read);

-        memcpy(scratch + bytes_read, fragment, n);

-        bytes_read += n;

-        reader->Skip(n);

-      }

-      DCHECK_EQ(bytes_read, num_to_read);

-      fragment = scratch;

-      fragment_size = num_to_read;

-    }

-    DCHECK_EQ(fragment_size, num_to_read);

-

-    // Get encoding table for compression

-    int table_size;

-    uint16* table = wmem.GetHashTable(num_to_read, &table_size);

-

-    // Compress input_fragment and append to dest

-    const size_t 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.

-    if (scratch_output == NULL) {

-      scratch_output = new char[max_output];

-    } else {

-      // 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, scratch_output);

-    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);

-  }

-

-  delete[] scratch;

-  delete[] scratch_output;

-

-  return written;

-}

-

-// -----------------------------------------------------------------------

-// 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_;

-

- public:

-  inline explicit SnappyArrayWriter(char* dst)

-      : base_(dst),

-        op_(dst) {

-  }

-

-  inline void SetExpectedLength(size_t len) {

-    op_limit_ = op_ + len;

-  }

-

-  inline bool CheckLength() const {

-    return op_ == op_limit_;

-  }

-

-  inline bool Append(const char* ip, uint32 len, bool allow_fast_path) {

-    char* op = op_;

-    const int space_left = op_limit_ - op;

-    if (allow_fast_path && len <= 16 && space_left >= 16) {

-      // Fast path, used for the majority (about 90%) of dynamic invocations.

-      UNALIGNED_STORE64(op, UNALIGNED_LOAD64(ip));

-      UNALIGNED_STORE64(op + 8, UNALIGNED_LOAD64(ip + 8));

-    } else {

-      if (space_left < len) {

-        return false;

-      }

-      memcpy(op, ip, len);

-    }

-    op_ = op + len;

-    return true;

-  }

-

-  inline bool AppendFromSelf(uint32 offset, uint32 len) {

-    char* op = op_;

-    const int space_left = op_limit_ - op;

-

-    if (op - base_ <= offset - 1u) {  // -1u catches offset==0

-      return false;

-    }

-    if (len <= 16 && offset >= 8 && space_left >= 16) {

-      // Fast path, used for the majority (70-80%) of dynamic invocations.

-      UNALIGNED_STORE64(op, UNALIGNED_LOAD64(op - offset));

-      UNALIGNED_STORE64(op + 8, UNALIGNED_LOAD64(op - offset + 8));

-    } else {

-      if (space_left >= len + kMaxIncrementCopyOverflow) {

-        IncrementalCopyFastPath(op - offset, op, len);

-      } else {

-        if (space_left < len) {

-          return false;

-        }

-        IncrementalCopy(op - offset, op, len);

-      }

-    }

-

-    op_ = op + len;

-    return true;

-  }

-};

-

-bool RawUncompress(const char* compressed, size_t n, char* uncompressed) {

-  ByteArraySource reader(compressed, n);

-  return RawUncompress(&reader, uncompressed);

-}

-

-bool RawUncompress(Source* compressed, char* uncompressed) {

-  SnappyArrayWriter output(uncompressed);

-  return InternalUncompress(compressed, &output, kuint32max);

-}

-

-bool Uncompress(const char* compressed, size_t n, string* uncompressed) {

-  size_t ulength;

-  if (!GetUncompressedLength(compressed, n, &ulength)) {

-    return false;

-  }

-  // Protect against possible DoS attack

-  if ((static_cast<uint64>(ulength) + uncompressed->size()) >

-      uncompressed->max_size()) {

-    return false;

-  }

-  STLStringResizeUninitialized(uncompressed, ulength);

-  return RawUncompress(compressed, n, 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() : produced_(0) { }

-  inline void SetExpectedLength(size_t len) {

-    expected_ = len;

-  }

-  inline bool CheckLength() const {

-    return expected_ == produced_;

-  }

-  inline bool Append(const char* ip, uint32 len, bool allow_fast_path) {

-    produced_ += len;

-    return produced_ <= expected_;

-  }

-  inline bool AppendFromSelf(uint32 offset, uint32 len) {

-    if (produced_ <= offset - 1u) return false;  // -1u catches offset==0

-    produced_ += len;

-    return produced_ <= expected_;

-  }

-};

-

-bool IsValidCompressedBuffer(const char* compressed, size_t n) {

-  ByteArraySource reader(compressed, n);

-  SnappyDecompressionValidator writer;

-  return InternalUncompress(&reader, &writer, kuint32max);

-}

-

-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, string* compressed) {

-  // Pre-grow the buffer to the max length of the compressed output

-  compressed->resize(MaxCompressedLength(input_length));

-

-  size_t compressed_length;

-  RawCompress(input, input_length, string_as_array(compressed),

-              &compressed_length);

-  compressed->resize(compressed_length);

-  return compressed_length;

-}

-

-

-} // end namespace snappy

-

+// Copyright 2005 Google Inc. All Rights Reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include "snappy.h"
+#include "snappy-internal.h"
+#include "snappy-sinksource.h"
+
+#include <stdio.h>
+
+#include <algorithm>
+#include <string>
+#include <vector>
+
+#ifdef _WIN32
+#pragma warning(disable:4018) // warning C4018: '<' : signed/unsigned mismatch
+#pragma warning(disable:4389) // warning C4389: '==' : signed/unsigned mismatch
+#endif //_WIN32
+
+namespace snappy {
+
+// Any hash function will produce a valid compressed bitstream, but a good
+// hash function reduces the number of collisions and thus yields better
+// compression for compressible input, and more speed for incompressible
+// input. Of course, it doesn't hurt if the hash function is reasonably fast
+// either, as it gets called a lot.
+static inline uint32 HashBytes(uint32 bytes, int shift) {
+  uint32 kMul = 0x1e35a7bd;
+  return (bytes * kMul) >> shift;
+}
+static inline uint32 Hash(const char* p, int shift) {
+  return HashBytes(UNALIGNED_LOAD32(p), shift);
+}
+
+size_t MaxCompressedLength(size_t source_len) {
+  // Compressed data can be defined as:
+  //    compressed := item* literal*
+  //    item       := literal* copy
+  //
+  // The trailing literal sequence has a space blowup of at most 62/60
+  // since a literal of length 60 needs one tag byte + one extra byte
+  // for length information.
+  //
+  // Item blowup is trickier to measure.  Suppose the "copy" op copies
+  // 4 bytes of data.  Because of a special check in the encoding code,
+  // we produce a 4-byte copy only if the offset is < 65536.  Therefore
+  // the copy op takes 3 bytes to encode, and this type of item leads
+  // to at most the 62/60 blowup for representing literals.
+  //
+  // Suppose the "copy" op copies 5 bytes of data.  If the offset is big
+  // enough, it will take 5 bytes to encode the copy op.  Therefore the
+  // worst case here is a one-byte literal followed by a five-byte copy.
+  // I.e., 6 bytes of input turn into 7 bytes of "compressed" data.
+  //
+  // This last factor dominates the blowup, so the final estimate is:
+  return 32 + source_len + source_len/6;
+}
+
+enum {
+  LITERAL = 0,
+  COPY_1_BYTE_OFFSET = 1,  // 3 bit length + 3 bits of offset in opcode
+  COPY_2_BYTE_OFFSET = 2,
+  COPY_4_BYTE_OFFSET = 3
+};
+
+// Copy "len" bytes from "src" to "op", one byte at a time.  Used for
+// handling COPY operations where the input and output regions may
+// overlap.  For example, suppose:
+//    src    == "ab"
+//    op     == src + 2
+//    len    == 20
+// After IncrementalCopy(src, op, len), the result will have
+// eleven copies of "ab"
+//    ababababababababababab
+// Note that this does not match the semantics of either memcpy()
+// or memmove().
+static inline void IncrementalCopy(const char* src, char* op, int len) {
+  DCHECK_GT(len, 0);
+  do {
+    *op++ = *src++;
+  } while (--len > 0);
+}
+
+// Equivalent to IncrementalCopy except that it can write up to ten extra
+// bytes after the end of the copy, and that it is faster.
+//
+// The main part of this loop is a simple copy of eight bytes at a time until
+// we've copied (at least) the requested amount of bytes.  However, if op and
+// src are less than eight bytes apart (indicating a repeating pattern of
+// length < 8), we first need to expand the pattern in order to get the correct
+// results. For instance, if the buffer looks like this, with the eight-byte
+// <src> and <op> patterns marked as intervals:
+//
+//    abxxxxxxxxxxxx
+//    [------]           src
+//      [------]         op
+//
+// a single eight-byte copy from <src> to <op> will repeat the pattern once,
+// after which we can move <op> two bytes without moving <src>:
+//
+//    ababxxxxxxxxxx
+//    [------]           src
+//        [------]       op
+//
+// and repeat the exercise until the two no longer overlap.
+//
+// This allows us to do very well in the special case of one single byte
+// repeated many times, without taking a big hit for more general cases.
+//
+// The worst case of extra writing past the end of the match occurs when
+// op - src == 1 and len == 1; the last copy will read from byte positions
+// [0..7] and write to [4..11], whereas it was only supposed to write to
+// position 1. Thus, ten excess bytes.
+
+namespace {
+
+const int kMaxIncrementCopyOverflow = 10;
+
+}  // namespace
+
+static inline void IncrementalCopyFastPath(const char* src, char* op, int len) {
+  while (op - src < 8) {
+    UNALIGNED_STORE64(op, UNALIGNED_LOAD64(src));
+    len -= op - src;
+    op += op - src;
+  }
+  while (len > 0) {
+    UNALIGNED_STORE64(op, UNALIGNED_LOAD64(src));
+    src += 8;
+    op += 8;
+    len -= 8;
+  }
+}
+
+static inline char* EmitLiteral(char* op,
+                                const char* literal,
+                                int len,
+                                bool allow_fast_path) {
+  int n = len - 1;      // Zero-length literals are disallowed
+  if (n < 60) {
+    // Fits in tag byte
+    *op++ = LITERAL | (n << 2);
+
+    // The vast majority of copies are below 16 bytes, for which a
+    // call to memcpy is overkill. This fast path can sometimes
+    // copy up to 15 bytes too much, but that is okay in the
+    // main loop, since we have a bit to go on for both sides:
+    //
+    //   - The input will always have kInputMarginBytes = 15 extra
+    //     available bytes, as long as we're in the main loop, and
+    //     if not, allow_fast_path = false.
+    //   - The output will always have 32 spare bytes (see
+    //     MaxCompressedLength).
+    if (allow_fast_path && len <= 16) {
+      UNALIGNED_STORE64(op, UNALIGNED_LOAD64(literal));
+      UNALIGNED_STORE64(op + 8, UNALIGNED_LOAD64(literal + 8));
+      return op + len;
+    }
+  } else {
+    // Encode in upcoming bytes
+    char* base = op;
+    int count = 0;
+    op++;
+    while (n > 0) {
+      *op++ = n & 0xff;
+      n >>= 8;
+      count++;
+    }
+    assert(count >= 1);
+    assert(count <= 4);
+    *base = LITERAL | ((59+count) << 2);
+  }
+  memcpy(op, literal, len);
+  return op + len;
+}
+
+static inline char* EmitCopyLessThan64(char* op, int offset, int len) {
+  DCHECK_LE(len, 64);
+  DCHECK_GE(len, 4);
+  DCHECK_LT(offset, 65536);
+
+  if ((len < 12) && (offset < 2048)) {
+    int len_minus_4 = len - 4;
+    assert(len_minus_4 < 8);            // Must fit in 3 bits
+    *op++ = COPY_1_BYTE_OFFSET | ((len_minus_4) << 2) | ((offset >> 8) << 5);
+    *op++ = offset & 0xff;
+  } else {
+    *op++ = COPY_2_BYTE_OFFSET | ((len-1) << 2);
+    LittleEndian::Store16(op, offset);
+    op += 2;
+  }
+  return op;
+}
+
+static inline char* EmitCopy(char* op, int offset, int len) {
+  // Emit 64 byte copies but make sure to keep at least four bytes reserved
+  while (len >= 68) {
+    op = EmitCopyLessThan64(op, offset, 64);
+    len -= 64;
+  }
+
+  // Emit an extra 60 byte copy if have too much data to fit in one copy
+  if (len > 64) {
+    op = EmitCopyLessThan64(op, offset, 60);
+    len -= 60;
+  }
+
+  // Emit remainder
+  op = EmitCopyLessThan64(op, offset, len);
+  return op;
+}
+
+
+bool GetUncompressedLength(const char* start, size_t n, size_t* result) {
+  uint32 v = 0;
+  const char* limit = start + n;
+  if (Varint::Parse32WithLimit(start, limit, &v) != NULL) {
+    *result = v;
+    return true;
+  } else {
+    return false;
+  }
+}
+
+namespace internal {
+uint16* WorkingMemory::GetHashTable(size_t input_size, int* table_size) {
+  // Use smaller hash table when input.size() is smaller, since we
+  // fill the table, incurring O(hash table size) overhead for
+  // compression, and if the input is short, we won't need that
+  // many hash table entries anyway.
+  assert(kMaxHashTableSize >= 256);
+  int htsize = 256;
+  while (htsize < kMaxHashTableSize && htsize < input_size) {
+    htsize <<= 1;
+  }
+  CHECK_EQ(0, htsize & (htsize - 1)) << ": must be power of two";
+  CHECK_LE(htsize, kMaxHashTableSize) << ": hash table too large";
+
+  uint16* table;
+  if (htsize <= ARRAYSIZE(small_table_)) {
+    table = small_table_;
+  } else {
+    if (large_table_ == NULL) {
+      large_table_ = new uint16[kMaxHashTableSize];
+    }
+    table = large_table_;
+  }
+
+  *table_size = htsize;
+  memset(table, 0, htsize * sizeof(*table));
+  return table;
+}
+}  // end namespace internal
+
+// For 0 <= offset <= 4, GetUint32AtOffset(UNALIGNED_LOAD64(p), offset) will
+// equal UNALIGNED_LOAD32(p + offset).  Motivation: On x86-64 hardware we have
+// empirically found that overlapping loads such as
+//  UNALIGNED_LOAD32(p) ... UNALIGNED_LOAD32(p+1) ... UNALIGNED_LOAD32(p+2)
+// are slower than UNALIGNED_LOAD64(p) followed by shifts and casts to uint32.
+static inline uint32 GetUint32AtOffset(uint64 v, int offset) {
+  DCHECK(0 <= offset && offset <= 4) << offset;
+  return v >> (LittleEndian::IsLittleEndian() ? 8 * offset : 32 - 8 * offset);
+}
+
+// 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* const input,
+                       const size_t input_size,
+                       char* op,
+                       uint16* table,
+                       const int table_size) {
+  // "ip" is the input pointer, and "op" is the output pointer.
+  const char* ip = input;
+  CHECK_LE(input_size, kBlockSize);
+  CHECK_EQ(table_size & (table_size - 1), 0) << ": table must be power of two";
+  const int shift = 32 - Bits::Log2Floor(table_size);
+  DCHECK_EQ(kuint32max >> shift, table_size - 1);
+  const char* ip_end = input + input_size;
+  const char* base_ip = ip;
+  // 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;
+
+  const int kInputMarginBytes = 15;
+  if (PREDICT_TRUE(input_size >= kInputMarginBytes)) {
+    const char* ip_limit = input + input_size - kInputMarginBytes;
+
+    for (uint32 next_hash = Hash(++ip, shift); ; ) {
+      DCHECK_LT(next_emit, 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, 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 skip = 32;
+
+      const char* next_ip = ip;
+      const char* candidate;
+      do {
+        ip = next_ip;
+        uint32 hash = next_hash;
+        DCHECK_EQ(hash, Hash(ip, shift));
+        uint32 bytes_between_hash_lookups = skip++ >> 5;
+        next_ip = ip + bytes_between_hash_lookups;
+        if (PREDICT_FALSE(next_ip > ip_limit)) {
+          goto emit_remainder;
+        }
+        next_hash = Hash(next_ip, shift);
+        candidate = base_ip + table[hash];
+        DCHECK_GE(candidate, base_ip);
+        DCHECK_LT(candidate, ip);
+
+        table[hash] = ip - base_ip;
+      } while (PREDICT_TRUE(UNALIGNED_LOAD32(ip) !=
+                            UNALIGNED_LOAD32(candidate)));
+
+      // 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."
+      DCHECK_LE(next_emit + 16, ip_end);
+      op = EmitLiteral(op, next_emit, ip - next_emit, true);
+
+      // 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.
+      uint64 input_bytes = 0;
+      uint32 candidate_bytes = 0;
+
+      do {
+        // We have a 4-byte match at ip, and no need to emit any
+        // "literal bytes" prior to ip.
+        const char* base = ip;
+        int matched = 4 + FindMatchLength(candidate + 4, ip + 4, ip_end);
+        ip += matched;
+        int offset = base - candidate;
+        DCHECK_EQ(0, memcmp(base, candidate, matched));
+        op = EmitCopy(op, offset, matched);
+        // We could immediately start working at ip now, but to improve
+        // compression we first update table[Hash(ip - 1, ...)].
+        const char* insert_tail = ip - 1;
+        next_emit = ip;
+        if (PREDICT_FALSE(ip >= ip_limit)) {
+          goto emit_remainder;
+        }
+        input_bytes = UNALIGNED_LOAD64(insert_tail);
+        uint32 prev_hash = HashBytes(GetUint32AtOffset(input_bytes, 0), shift);
+        table[prev_hash] = ip - base_ip - 1;
+        uint32 cur_hash = HashBytes(GetUint32AtOffset(input_bytes, 1), shift);
+        candidate = base_ip + table[cur_hash];
+        candidate_bytes = UNALIGNED_LOAD32(candidate);
+        table[cur_hash] = ip - base_ip;
+      } while (GetUint32AtOffset(input_bytes, 1) == candidate_bytes);
+
+      next_hash = HashBytes(GetUint32AtOffset(input_bytes, 2), shift);
+      ++ip;
+    }
+  }
+
+ emit_remainder:
+  // Emit the remaining bytes as a literal
+  if (next_emit < ip_end) {
+    op = EmitLiteral(op, next_emit, ip_end - next_emit, false);
+  }
+
+  return op;
+}
+}  // end namespace internal
+
+// 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);
+//
+//   // Called after decompression
+//   bool CheckLength() const;
+//
+//   // Called repeatedly during decompression
+//   bool Append(const char* ip, uint32 length, bool allow_fast_path);
+//   bool AppendFromSelf(uint32 offset, uint32 length);
+// };
+//
+// "allow_fast_path" is a parameter that says if there is at least 16
+// readable bytes in "ip". It is currently only used by SnappyArrayWriter.
+
+// -----------------------------------------------------------------------
+// Lookup table for decompression code.  Generated by ComputeTable() below.
+// -----------------------------------------------------------------------
+
+// Mapping from i in range [0,4] to a mask to extract the bottom 8*i bits
+static const uint32 wordmask[] = {
+  0u, 0xffu, 0xffffu, 0xffffffu, 0xffffffffu
+};
+
+// Data stored per entry in lookup table:
+//      Range   Bits-used       Description
+//      ------------------------------------
+//      1..64   0..7            Literal/copy length encoded in opcode byte
+//      0..7    8..10           Copy offset encoded in opcode byte / 256
+//      0..4    11..13          Extra bytes after opcode
+//
+// We use eight bits for the length even though 7 would have sufficed
+// because of efficiency reasons:
+//      (1) Extracting a byte is faster than a bit-field
+//      (2) It properly aligns copy offset so we do not need a <<8
+static const uint16 char_table[256] = {
+  0x0001, 0x0804, 0x1001, 0x2001, 0x0002, 0x0805, 0x1002, 0x2002,
+  0x0003, 0x0806, 0x1003, 0x2003, 0x0004, 0x0807, 0x1004, 0x2004,
+  0x0005, 0x0808, 0x1005, 0x2005, 0x0006, 0x0809, 0x1006, 0x2006,
+  0x0007, 0x080a, 0x1007, 0x2007, 0x0008, 0x080b, 0x1008, 0x2008,
+  0x0009, 0x0904, 0x1009, 0x2009, 0x000a, 0x0905, 0x100a, 0x200a,
+  0x000b, 0x0906, 0x100b, 0x200b, 0x000c, 0x0907, 0x100c, 0x200c,
+  0x000d, 0x0908, 0x100d, 0x200d, 0x000e, 0x0909, 0x100e, 0x200e,
+  0x000f, 0x090a, 0x100f, 0x200f, 0x0010, 0x090b, 0x1010, 0x2010,
+  0x0011, 0x0a04, 0x1011, 0x2011, 0x0012, 0x0a05, 0x1012, 0x2012,
+  0x0013, 0x0a06, 0x1013, 0x2013, 0x0014, 0x0a07, 0x1014, 0x2014,
+  0x0015, 0x0a08, 0x1015, 0x2015, 0x0016, 0x0a09, 0x1016, 0x2016,
+  0x0017, 0x0a0a, 0x1017, 0x2017, 0x0018, 0x0a0b, 0x1018, 0x2018,
+  0x0019, 0x0b04, 0x1019, 0x2019, 0x001a, 0x0b05, 0x101a, 0x201a,
+  0x001b, 0x0b06, 0x101b, 0x201b, 0x001c, 0x0b07, 0x101c, 0x201c,
+  0x001d, 0x0b08, 0x101d, 0x201d, 0x001e, 0x0b09, 0x101e, 0x201e,
+  0x001f, 0x0b0a, 0x101f, 0x201f, 0x0020, 0x0b0b, 0x1020, 0x2020,
+  0x0021, 0x0c04, 0x1021, 0x2021, 0x0022, 0x0c05, 0x1022, 0x2022,
+  0x0023, 0x0c06, 0x1023, 0x2023, 0x0024, 0x0c07, 0x1024, 0x2024,
+  0x0025, 0x0c08, 0x1025, 0x2025, 0x0026, 0x0c09, 0x1026, 0x2026,
+  0x0027, 0x0c0a, 0x1027, 0x2027, 0x0028, 0x0c0b, 0x1028, 0x2028,
+  0x0029, 0x0d04, 0x1029, 0x2029, 0x002a, 0x0d05, 0x102a, 0x202a,
+  0x002b, 0x0d06, 0x102b, 0x202b, 0x002c, 0x0d07, 0x102c, 0x202c,
+  0x002d, 0x0d08, 0x102d, 0x202d, 0x002e, 0x0d09, 0x102e, 0x202e,
+  0x002f, 0x0d0a, 0x102f, 0x202f, 0x0030, 0x0d0b, 0x1030, 0x2030,
+  0x0031, 0x0e04, 0x1031, 0x2031, 0x0032, 0x0e05, 0x1032, 0x2032,
+  0x0033, 0x0e06, 0x1033, 0x2033, 0x0034, 0x0e07, 0x1034, 0x2034,
+  0x0035, 0x0e08, 0x1035, 0x2035, 0x0036, 0x0e09, 0x1036, 0x2036,
+  0x0037, 0x0e0a, 0x1037, 0x2037, 0x0038, 0x0e0b, 0x1038, 0x2038,
+  0x0039, 0x0f04, 0x1039, 0x2039, 0x003a, 0x0f05, 0x103a, 0x203a,
+  0x003b, 0x0f06, 0x103b, 0x203b, 0x003c, 0x0f07, 0x103c, 0x203c,
+  0x0801, 0x0f08, 0x103d, 0x203d, 0x1001, 0x0f09, 0x103e, 0x203e,
+  0x1801, 0x0f0a, 0x103f, 0x203f, 0x2001, 0x0f0b, 0x1040, 0x2040
+};
+
+// In debug mode, allow optional computation of the table at startup.
+// Also, check that the decompression table is correct.
+#ifndef NDEBUG
+DEFINE_bool(snappy_dump_decompression_table, false,
+            "If true, we print the decompression table at startup.");
+
+static uint16 MakeEntry(unsigned int extra,
+                        unsigned int len,
+                        unsigned int copy_offset) {
+  // Check that all of the fields fit within the allocated space
+  DCHECK_EQ(extra,       extra & 0x7);          // At most 3 bits
+  DCHECK_EQ(copy_offset, copy_offset & 0x7);    // At most 3 bits
+  DCHECK_EQ(len,         len & 0x7f);           // At most 7 bits
+  return len | (copy_offset << 8) | (extra << 11);
+}
+
+static void ComputeTable() {
+  uint16 dst[256];
+
+  // Place invalid entries in all places to detect missing initialization
+  int assigned = 0;
+  for (int i = 0; i < 256; i++) {
+    dst[i] = 0xffff;
+  }
+
+  // Small LITERAL entries.  We store (len-1) in the top 6 bits.
+  for (unsigned int len = 1; len <= 60; len++) {
+    dst[LITERAL | ((len-1) << 2)] = MakeEntry(0, len, 0);
+    assigned++;
+  }
+
+  // Large LITERAL entries.  We use 60..63 in the high 6 bits to
+  // encode the number of bytes of length info that follow the opcode.
+  for (unsigned int extra_bytes = 1; extra_bytes <= 4; extra_bytes++) {
+    // We set the length field in the lookup table to 1 because extra
+    // bytes encode len-1.
+    dst[LITERAL | ((extra_bytes+59) << 2)] = MakeEntry(extra_bytes, 1, 0);
+    assigned++;
+  }
+
+  // COPY_1_BYTE_OFFSET.
+  //
+  // The tag byte in the compressed data stores len-4 in 3 bits, and
+  // offset/256 in 5 bits.  offset%256 is stored in the next byte.
+  //
+  // This format is used for length in range [4..11] and offset in
+  // range [0..2047]
+  for (unsigned int len = 4; len < 12; len++) {
+    for (unsigned int offset = 0; offset < 2048; offset += 256) {
+      dst[COPY_1_BYTE_OFFSET | ((len-4)<<2) | ((offset>>8)<<5)] =
+        MakeEntry(1, len, offset>>8);
+      assigned++;
+    }
+  }
+
+  // COPY_2_BYTE_OFFSET.
+  // Tag contains len-1 in top 6 bits, and offset in next two bytes.
+  for (unsigned int len = 1; len <= 64; len++) {
+    dst[COPY_2_BYTE_OFFSET | ((len-1)<<2)] = MakeEntry(2, len, 0);
+    assigned++;
+  }
+
+  // COPY_4_BYTE_OFFSET.
+  // Tag contents len-1 in top 6 bits, and offset in next four bytes.
+  for (unsigned int len = 1; len <= 64; len++) {
+    dst[COPY_4_BYTE_OFFSET | ((len-1)<<2)] = MakeEntry(4, len, 0);
+    assigned++;
+  }
+
+  // Check that each entry was initialized exactly once.
+  CHECK_EQ(assigned, 256);
+  for (int i = 0; i < 256; i++) {
+    CHECK_NE(dst[i], 0xffff);
+  }
+
+  if (FLAGS_snappy_dump_decompression_table) {
+    printf("static const uint16 char_table[256] = {\n  ");
+    for (int i = 0; i < 256; i++) {
+      printf("0x%04x%s",
+             dst[i],
+             ((i == 255) ? "\n" : (((i%8) == 7) ? ",\n  " : ", ")));
+    }
+    printf("};\n");
+  }
+
+  // Check that computed table matched recorded table
+  for (int i = 0; i < 256; i++) {
+    CHECK_EQ(dst[i], char_table[i]);
+  }
+}
+REGISTER_MODULE_INITIALIZER(snappy, ComputeTable());
+#endif /* !NDEBUG */
+
+// 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
+  uint32        peeked_;         // Bytes peeked from reader (need to skip)
+  bool          eof_;            // Hit end of input without an error?
+  char          scratch_[5];     // Temporary buffer for PeekFast() boundaries
+
+  // 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();
+
+ 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 succcess, stores the length in *result and returns true.
+  // On failure, returns false.
+  bool ReadUncompressedLength(uint32* result) {
+    DCHECK(ip_ == NULL);       // Must not have read anything yet
+    // Length is encoded in 1..5 bytes
+    *result = 0;
+    uint32 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);
+      *result |= static_cast<uint32>(c & 0x7f) << 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>
+  void DecompressAllTags(Writer* writer) {
+    const char* ip = ip_;
+    for ( ;; ) {
+      if (ip_limit_ - ip < 5) {
+        ip_ = ip;
+        if (!RefillTag()) return;
+        ip = ip_;
+      }
+
+      const unsigned char c = *(reinterpret_cast<const unsigned char*>(ip++));
+      const uint32 entry = char_table[c];
+      const uint32 trailer = LittleEndian::Load32(ip) & wordmask[entry >> 11];
+      ip += entry >> 11;
+      const uint32 length = entry & 0xff;
+
+      if ((c & 0x3) == LITERAL) {
+        uint32 literal_length = length + trailer;
+        uint32 avail = ip_limit_ - ip;
+        while (avail < literal_length) {
+          bool allow_fast_path = (avail >= 16);
+          if (!writer->Append(ip, avail, allow_fast_path)) return;
+          literal_length -= avail;
+          reader_->Skip(peeked_);
+          size_t n;
+          ip = reader_->Peek(&n);
+          avail = (uint32)n;
+          peeked_ = avail;
+          if (avail == 0) return;  // Premature end of input
+          ip_limit_ = ip + avail;
+        }
+        bool allow_fast_path = (avail >= 16);
+        if (!writer->Append(ip, literal_length, allow_fast_path)) {
+          return;
+        }
+        ip += literal_length;
+      } else {
+        // 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 copy_offset = entry & 0x700;
+        if (!writer->AppendFromSelf(copy_offset + trailer, length)) {
+          return;
+        }
+      }
+    }
+  }
+};
+
+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_ = (uint32)n;
+    if (n == 0) {
+      eof_ = true;
+      return false;
+    }
+    ip_limit_ = ip + n;
+  }
+
+  // Read the tag character
+  DCHECK_LT(ip, ip_limit_);
+  const unsigned char c = *(reinterpret_cast<const unsigned char*>(ip));
+  const uint32 entry = char_table[c];
+  const uint32 needed = (entry >> 11) + 1;  // +1 byte for 'c'
+  DCHECK_LE(needed, sizeof(scratch_));
+
+  // Read more bytes from reader if needed
+  uint32 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.
+    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 to_add = min<uint32>(needed - nbuf, (uint32)length);
+      memcpy(scratch_ + nbuf, src, to_add);
+      nbuf += to_add;
+      reader_->Skip(to_add);
+    }
+    DCHECK_EQ(nbuf, needed);
+    ip_ = scratch_;
+    ip_limit_ = scratch_ + needed;
+  } else if (nbuf < 5) {
+    // Have enough bytes, but move into scratch_ so that we do not
+    // read past end of input
+    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,
+                               uint32 max_len) {
+  // Read the uncompressed length from the front of the compressed input
+  SnappyDecompressor decompressor(r);
+  uint32 uncompressed_len = 0;
+  if (!decompressor.ReadUncompressedLength(&uncompressed_len)) return false;
+  // Protect against possible DoS attack
+  if (static_cast<uint64>(uncompressed_len) > max_len) {
+    return false;
+  }
+
+  writer->SetExpectedLength(uncompressed_len);
+
+  // Process the entire input
+  decompressor.DecompressAllTags(writer);
+  return (decompressor.eof() && writer->CheckLength());
+}
+
+bool GetUncompressedLength(Source* source, uint32* result) {
+  SnappyDecompressor decompressor(source);
+  return decompressor.ReadUncompressedLength(result);
+}
+
+size_t Compress(Source* reader, Sink* writer) {
+  size_t written = 0;
+  int N = (int)reader->Available();
+  char ulength[Varint::kMax32];
+  char* p = Varint::Encode32(ulength, N);
+  writer->Append(ulength, p-ulength);
+  written += (p - ulength);
+
+  internal::WorkingMemory wmem;
+  char* scratch = NULL;
+  char* scratch_output = NULL;
+
+  while (N > 0) {
+    // Get next block to compress (without copying if possible)
+    size_t fragment_size;
+    const char* fragment = reader->Peek(&fragment_size);
+    DCHECK_NE(fragment_size, 0) << ": premature end of input";
+    const int num_to_read = min(N, kBlockSize);
+    size_t bytes_read = fragment_size;
+
+    int 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 {
+      // Read into scratch buffer
+      if (scratch == NULL) {
+        // If this is the last iteration, we want to allocate N bytes
+        // of space, otherwise the max possible kBlockSize space.
+        // num_to_read contains exactly the correct value
+        scratch = new char[num_to_read];
+      }
+      memcpy(scratch, fragment, bytes_read);
+      reader->Skip(bytes_read);
+
+      while (bytes_read < num_to_read) {
+        fragment = reader->Peek(&fragment_size);
+        size_t n = min<size_t>(fragment_size, num_to_read - bytes_read);
+        memcpy(scratch + bytes_read, fragment, n);
+        bytes_read += n;
+        reader->Skip(n);
+      }
+      DCHECK_EQ(bytes_read, num_to_read);
+      fragment = scratch;
+      fragment_size = num_to_read;
+    }
+    DCHECK_EQ(fragment_size, num_to_read);
+
+    // Get encoding table for compression
+    int table_size;
+    uint16* table = wmem.GetHashTable(num_to_read, &table_size);
+
+    // Compress input_fragment and append to dest
+    const size_t 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.
+    if (scratch_output == NULL) {
+      scratch_output = new char[max_output];
+    } else {
+      // 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, scratch_output);
+    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);
+  }
+
+  delete[] scratch;
+  delete[] scratch_output;
+
+  return written;
+}
+
+// -----------------------------------------------------------------------
+// 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_;
+
+ public:
+  inline explicit SnappyArrayWriter(char* dst)
+      : base_(dst),
+        op_(dst) {
+  }
+
+  inline void SetExpectedLength(size_t len) {
+    op_limit_ = op_ + len;
+  }
+
+  inline bool CheckLength() const {
+    return op_ == op_limit_;
+  }
+
+  inline bool Append(const char* ip, uint32 len, bool allow_fast_path) {
+    char* op = op_;
+    const int space_left = op_limit_ - op;
+    if (allow_fast_path && len <= 16 && space_left >= 16) {
+      // Fast path, used for the majority (about 90%) of dynamic invocations.
+      UNALIGNED_STORE64(op, UNALIGNED_LOAD64(ip));
+      UNALIGNED_STORE64(op + 8, UNALIGNED_LOAD64(ip + 8));
+    } else {
+      if (space_left < len) {
+        return false;
+      }
+      memcpy(op, ip, len);
+    }
+    op_ = op + len;
+    return true;
+  }
+
+  inline bool AppendFromSelf(uint32 offset, uint32 len) {
+    char* op = op_;
+    const int space_left = op_limit_ - op;
+
+    if (op - base_ <= offset - 1u) {  // -1u catches offset==0
+      return false;
+    }
+    if (len <= 16 && offset >= 8 && space_left >= 16) {
+      // Fast path, used for the majority (70-80%) of dynamic invocations.
+      UNALIGNED_STORE64(op, UNALIGNED_LOAD64(op - offset));
+      UNALIGNED_STORE64(op + 8, UNALIGNED_LOAD64(op - offset + 8));
+    } else {
+      if (space_left >= len + kMaxIncrementCopyOverflow) {
+        IncrementalCopyFastPath(op - offset, op, len);
+      } else {
+        if (space_left < len) {
+          return false;
+        }
+        IncrementalCopy(op - offset, op, len);
+      }
+    }
+
+    op_ = op + len;
+    return true;
+  }
+};
+
+bool RawUncompress(const char* compressed, size_t n, char* uncompressed) {
+  ByteArraySource reader(compressed, n);
+  return RawUncompress(&reader, uncompressed);
+}
+
+bool RawUncompress(Source* compressed, char* uncompressed) {
+  SnappyArrayWriter output(uncompressed);
+  return InternalUncompress(compressed, &output, kuint32max);
+}
+
+bool Uncompress(const char* compressed, size_t n, string* uncompressed) {
+  size_t ulength;
+  if (!GetUncompressedLength(compressed, n, &ulength)) {
+    return false;
+  }
+  // Protect against possible DoS attack
+  if ((static_cast<uint64>(ulength) + uncompressed->size()) >
+      uncompressed->max_size()) {
+    return false;
+  }
+  STLStringResizeUninitialized(uncompressed, ulength);
+  return RawUncompress(compressed, n, 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() : produced_(0) { }
+  inline void SetExpectedLength(size_t len) {
+    expected_ = len;
+  }
+  inline bool CheckLength() const {
+    return expected_ == produced_;
+  }
+  inline bool Append(const char* ip, uint32 len, bool allow_fast_path) {
+    produced_ += len;
+    return produced_ <= expected_;
+  }
+  inline bool AppendFromSelf(uint32 offset, uint32 len) {
+    if (produced_ <= offset - 1u) return false;  // -1u catches offset==0
+    produced_ += len;
+    return produced_ <= expected_;
+  }
+};
+
+bool IsValidCompressedBuffer(const char* compressed, size_t n) {
+  ByteArraySource reader(compressed, n);
+  SnappyDecompressionValidator writer;
+  return InternalUncompress(&reader, &writer, kuint32max);
+}
+
+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, string* compressed) {
+  // Pre-grow the buffer to the max length of the compressed output
+  compressed->resize(MaxCompressedLength(input_length));
+
+  size_t compressed_length;
+  RawCompress(input, input_length, string_as_array(compressed),
+              &compressed_length);
+  compressed->resize(compressed_length);
+  return compressed_length;
+}
+
+
+} // end namespace snappy
+