Merge branch 'develop' into release-0.5.2

1 files changed, 1164 insertions, 0 deletions

diff --git a/app/snappy/snappy_unittest.cc b/app/snappy/snappy_unittest.cc
new file mode 100644
index 00000000..59c108f4
--- /dev/null
+++ b/app/snappy/snappy_unittest.cc
@@ -0,0 +1,1164 @@
+// Copyright 2005 and onwards Google Inc.
+//
+// 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 <math.h>
+#include <stdlib.h>
+
+
+#include <algorithm>
+#include <string>
+#include <vector>
+
+#include "snappy.h"
+#include "snappy-internal.h"
+#include "snappy-test.h"
+#include "snappy-sinksource.h"
+
+DEFINE_int32(start_len, -1,
+             "Starting prefix size for testing (-1: just full file contents)");
+DEFINE_int32(end_len, -1,
+             "Starting prefix size for testing (-1: just full file contents)");
+DEFINE_int32(bytes, 10485760,
+             "How many bytes to compress/uncompress per file for timing");
+
+DEFINE_bool(zlib, false,
+            "Run zlib compression (http://www.zlib.net)");
+DEFINE_bool(lzo, false,
+            "Run LZO compression (http://www.oberhumer.com/opensource/lzo/)");
+DEFINE_bool(quicklz, false,
+            "Run quickLZ compression (http://www.quicklz.com/)");
+DEFINE_bool(liblzf, false,
+            "Run libLZF compression "
+            "(http://www.goof.com/pcg/marc/liblzf.html)");
+DEFINE_bool(fastlz, false,
+            "Run FastLZ compression (http://www.fastlz.org/");
+DEFINE_bool(snappy, true, "Run snappy compression");
+
+
+DEFINE_bool(write_compressed, false,
+            "Write compressed versions of each file to <file>.comp");
+DEFINE_bool(write_uncompressed, false,
+            "Write uncompressed versions of each file to <file>.uncomp");
+
+namespace snappy {
+
+
+#ifdef HAVE_FUNC_MMAP
+
+// To test against code that reads beyond its input, this class copies a
+// string to a newly allocated group of pages, the last of which
+// is made unreadable via mprotect. Note that we need to allocate the
+// memory with mmap(), as POSIX allows mprotect() only on memory allocated
+// with mmap(), and some malloc/posix_memalign implementations expect to
+// be able to read previously allocated memory while doing heap allocations.
+class DataEndingAtUnreadablePage {
+ public:
+  explicit DataEndingAtUnreadablePage(const string& s) {
+    const size_t page_size = getpagesize();
+    const size_t size = s.size();
+    // Round up space for string to a multiple of page_size.
+    size_t space_for_string = (size + page_size - 1) & ~(page_size - 1);
+    alloc_size_ = space_for_string + page_size;
+    mem_ = mmap(NULL, alloc_size_,
+                PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
+    CHECK_NE(MAP_FAILED, mem_);
+    protected_page_ = reinterpret_cast<char*>(mem_) + space_for_string;
+    char* dst = protected_page_ - size;
+    memcpy(dst, s.data(), size);
+    data_ = dst;
+    size_ = size;
+    // Make guard page unreadable.
+    CHECK_EQ(0, mprotect(protected_page_, page_size, PROT_NONE));
+  }
+
+  ~DataEndingAtUnreadablePage() {
+    // Undo the mprotect.
+    CHECK_EQ(0, mprotect(protected_page_, getpagesize(), PROT_READ|PROT_WRITE));
+    CHECK_EQ(0, munmap(mem_, alloc_size_));
+  }
+
+  const char* data() const { return data_; }
+  size_t size() const { return size_; }
+
+ private:
+  size_t alloc_size_;
+  void* mem_;
+  char* protected_page_;
+  const char* data_;
+  size_t size_;
+};
+
+#else  // HAVE_FUNC_MMAP
+
+// Fallback for systems without mmap.
+typedef string DataEndingAtUnreadablePage;
+
+#endif
+
+enum CompressorType {
+  ZLIB, LZO, LIBLZF, QUICKLZ, FASTLZ, SNAPPY
+};
+
+const char* names[] = {
+  "ZLIB", "LZO", "LIBLZF", "QUICKLZ", "FASTLZ", "SNAPPY"
+};
+
+static size_t MinimumRequiredOutputSpace(size_t input_size,
+                                         CompressorType comp) {
+  switch (comp) {
+#ifdef ZLIB_VERSION
+    case ZLIB:
+      return ZLib::MinCompressbufSize(input_size);
+#endif  // ZLIB_VERSION
+
+#ifdef LZO_VERSION
+    case LZO:
+      return input_size + input_size/64 + 16 + 3;
+#endif  // LZO_VERSION
+
+#ifdef LZF_VERSION
+    case LIBLZF:
+      return input_size;
+#endif  // LZF_VERSION
+
+#ifdef QLZ_VERSION_MAJOR
+    case QUICKLZ:
+      return input_size + 36000;  // 36000 is used for scratch.
+#endif  // QLZ_VERSION_MAJOR
+
+#ifdef FASTLZ_VERSION
+    case FASTLZ:
+      return max(static_cast<int>(ceil(input_size * 1.05)), 66);
+#endif  // FASTLZ_VERSION
+
+    case SNAPPY:
+      return snappy::MaxCompressedLength(input_size);
+
+    default:
+      LOG(FATAL) << "Unknown compression type number " << comp;
+  }
+}
+
+// Returns true if we successfully compressed, false otherwise.
+//
+// If compressed_is_preallocated is set, do not resize the compressed buffer.
+// This is typically what you want for a benchmark, in order to not spend
+// time in the memory allocator. If you do set this flag, however,
+// "compressed" must be preinitialized to at least MinCompressbufSize(comp)
+// number of bytes, and may contain junk bytes at the end after return.
+static bool Compress(const char* input, size_t input_size, CompressorType comp,
+                     string* compressed, bool compressed_is_preallocated) {
+  if (!compressed_is_preallocated) {
+    compressed->resize(MinimumRequiredOutputSpace(input_size, comp));
+  }
+
+  switch (comp) {
+#ifdef ZLIB_VERSION
+    case ZLIB: {
+      ZLib zlib;
+      uLongf destlen = compressed->size();
+      int ret = zlib.Compress(
+          reinterpret_cast<Bytef*>(string_as_array(compressed)),
+          &destlen,
+          reinterpret_cast<const Bytef*>(input),
+          input_size);
+      CHECK_EQ(Z_OK, ret);
+      if (!compressed_is_preallocated) {
+        compressed->resize(destlen);
+      }
+      return true;
+    }
+#endif  // ZLIB_VERSION
+
+#ifdef LZO_VERSION
+    case LZO: {
+      unsigned char* mem = new unsigned char[LZO1X_1_15_MEM_COMPRESS];
+      lzo_uint destlen;
+      int ret = lzo1x_1_15_compress(
+          reinterpret_cast<const uint8*>(input),
+          input_size,
+          reinterpret_cast<uint8*>(string_as_array(compressed)),
+          &destlen,
+          mem);
+      CHECK_EQ(LZO_E_OK, ret);
+      delete[] mem;
+      if (!compressed_is_preallocated) {
+        compressed->resize(destlen);
+      }
+      break;
+    }
+#endif  // LZO_VERSION
+
+#ifdef LZF_VERSION
+    case LIBLZF: {
+      int destlen = lzf_compress(input,
+                                 input_size,
+                                 string_as_array(compressed),
+                                 input_size);
+      if (destlen == 0) {
+        // lzf *can* cause lots of blowup when compressing, so they
+        // recommend to limit outsize to insize, and just not compress
+        // if it's bigger.  Ideally, we'd just swap input and output.
+        compressed->assign(input, input_size);
+        destlen = input_size;
+      }
+      if (!compressed_is_preallocated) {
+        compressed->resize(destlen);
+      }
+      break;
+    }
+#endif  // LZF_VERSION
+
+#ifdef QLZ_VERSION_MAJOR
+    case QUICKLZ: {
+      qlz_state_compress *state_compress = new qlz_state_compress;
+      int destlen = qlz_compress(input,
+                                 string_as_array(compressed),
+                                 input_size,
+                                 state_compress);
+      delete state_compress;
+      CHECK_NE(0, destlen);
+      if (!compressed_is_preallocated) {
+        compressed->resize(destlen);
+      }
+      break;
+    }
+#endif  // QLZ_VERSION_MAJOR
+
+#ifdef FASTLZ_VERSION
+    case FASTLZ: {
+      // Use level 1 compression since we mostly care about speed.
+      int destlen = fastlz_compress_level(
+          1,
+          input,
+          input_size,
+          string_as_array(compressed));
+      if (!compressed_is_preallocated) {
+        compressed->resize(destlen);
+      }
+      CHECK_NE(destlen, 0);
+      break;
+    }
+#endif  // FASTLZ_VERSION
+
+    case SNAPPY: {
+      size_t destlen;
+      snappy::RawCompress(input, input_size,
+                          string_as_array(compressed),
+                          &destlen);
+      CHECK_LE(destlen, snappy::MaxCompressedLength(input_size));
+      if (!compressed_is_preallocated) {
+        compressed->resize(destlen);
+      }
+      break;
+    }
+
+
+    default: {
+      return false;     // the asked-for library wasn't compiled in
+    }
+  }
+  return true;
+}
+
+static bool Uncompress(const string& compressed, CompressorType comp,
+                       int size, string* output) {
+  switch (comp) {
+#ifdef ZLIB_VERSION
+    case ZLIB: {
+      output->resize(size);
+      ZLib zlib;
+      uLongf destlen = output->size();
+      int ret = zlib.Uncompress(
+          reinterpret_cast<Bytef*>(string_as_array(output)),
+          &destlen,
+          reinterpret_cast<const Bytef*>(compressed.data()),
+          compressed.size());
+      CHECK_EQ(Z_OK, ret);
+      CHECK_EQ(static_cast<uLongf>(size), destlen);
+      break;
+    }
+#endif  // ZLIB_VERSION
+
+#ifdef LZO_VERSION
+    case LZO: {
+      output->resize(size);
+      lzo_uint destlen;
+      int ret = lzo1x_decompress(
+          reinterpret_cast<const uint8*>(compressed.data()),
+          compressed.size(),
+          reinterpret_cast<uint8*>(string_as_array(output)),
+          &destlen,
+          NULL);
+      CHECK_EQ(LZO_E_OK, ret);
+      CHECK_EQ(static_cast<lzo_uint>(size), destlen);
+      break;
+    }
+#endif  // LZO_VERSION
+
+#ifdef LZF_VERSION
+    case LIBLZF: {
+      output->resize(size);
+      int destlen = lzf_decompress(compressed.data(),
+                                   compressed.size(),
+                                   string_as_array(output),
+                                   output->size());
+      if (destlen == 0) {
+        // This error probably means we had decided not to compress,
+        // and thus have stored input in output directly.
+        output->assign(compressed.data(), compressed.size());
+        destlen = compressed.size();
+      }
+      CHECK_EQ(destlen, size);
+      break;
+    }
+#endif  // LZF_VERSION
+
+#ifdef QLZ_VERSION_MAJOR
+    case QUICKLZ: {
+      output->resize(size);
+      qlz_state_decompress *state_decompress = new qlz_state_decompress;
+      int destlen = qlz_decompress(compressed.data(),
+                                   string_as_array(output),
+                                   state_decompress);
+      delete state_decompress;
+      CHECK_EQ(destlen, size);
+      break;
+    }
+#endif  // QLZ_VERSION_MAJOR
+
+#ifdef FASTLZ_VERSION
+    case FASTLZ: {
+      output->resize(size);
+      int destlen = fastlz_decompress(compressed.data(),
+                                      compressed.length(),
+                                      string_as_array(output),
+                                      size);
+      CHECK_EQ(destlen, size);
+      break;
+    }
+#endif  // FASTLZ_VERSION
+
+    case SNAPPY: {
+      snappy::RawUncompress(compressed.data(), compressed.size(),
+                            string_as_array(output));
+      break;
+    }
+
+
+    default: {
+      return false;     // the asked-for library wasn't compiled in
+    }
+  }
+  return true;
+}
+
+static void Measure(const char* data,
+                    size_t length,
+                    CompressorType comp,
+                    int repeats,
+                    int block_size) {
+  // Run tests a few time and pick median running times
+  static const int kRuns = 5;
+  double ctime[kRuns];
+  double utime[kRuns];
+  int compressed_size = 0;
+
+  {
+    // Chop the input into blocks
+    int num_blocks = (length + block_size - 1) / block_size;
+    vector<const char*> input(num_blocks);
+    vector<size_t> input_length(num_blocks);
+    vector<string> compressed(num_blocks);
+    vector<string> output(num_blocks);
+    for (int b = 0; b < num_blocks; b++) {
+      int input_start = b * block_size;
+      int input_limit = min<int>((b+1)*block_size, length);
+      input[b] = data+input_start;
+      input_length[b] = input_limit-input_start;
+
+      // Pre-grow the output buffer so we don't measure string append time.
+      compressed[b].resize(MinimumRequiredOutputSpace(block_size, comp));
+    }
+
+    // First, try one trial compression to make sure the code is compiled in
+    if (!Compress(input[0], input_length[0], comp, &compressed[0], true)) {
+      LOG(WARNING) << "Skipping " << names[comp] << ": "
+                   << "library not compiled in";
+      return;
+    }
+
+    for (int run = 0; run < kRuns; run++) {
+      CycleTimer ctimer, utimer;
+
+      for (int b = 0; b < num_blocks; b++) {
+        // Pre-grow the output buffer so we don't measure string append time.
+        compressed[b].resize(MinimumRequiredOutputSpace(block_size, comp));
+      }
+
+      ctimer.Start();
+      for (int b = 0; b < num_blocks; b++)
+        for (int i = 0; i < repeats; i++)
+          Compress(input[b], input_length[b], comp, &compressed[b], true);
+      ctimer.Stop();
+
+      // Compress once more, with resizing, so we don't leave junk
+      // at the end that will confuse the decompressor.
+      for (int b = 0; b < num_blocks; b++) {
+        Compress(input[b], input_length[b], comp, &compressed[b], false);
+      }
+
+      for (int b = 0; b < num_blocks; b++) {
+        output[b].resize(input_length[b]);
+      }
+
+      utimer.Start();
+      for (int i = 0; i < repeats; i++)
+        for (int b = 0; b < num_blocks; b++)
+          Uncompress(compressed[b], comp, input_length[b], &output[b]);
+      utimer.Stop();
+
+      ctime[run] = ctimer.Get();
+      utime[run] = utimer.Get();
+    }
+
+    compressed_size = 0;
+    for (int i = 0; i < compressed.size(); i++) {
+      compressed_size += compressed[i].size();
+    }
+  }
+
+  sort(ctime, ctime + kRuns);
+  sort(utime, utime + kRuns);
+  const int med = kRuns/2;
+
+  float comp_rate = (length / ctime[med]) * repeats / 1048576.0;
+  float uncomp_rate = (length / utime[med]) * repeats / 1048576.0;
+  string x = names[comp];
+  x += ":";
+  string urate = (uncomp_rate >= 0)
+                 ? StringPrintf("%.1f", uncomp_rate)
+                 : string("?");
+  printf("%-7s [b %dM] bytes %6d -> %6d %4.1f%%  "
+         "comp %5.1f MB/s  uncomp %5s MB/s\n",
+         x.c_str(),
+         block_size/(1<<20),
+         static_cast<int>(length), static_cast<uint32>(compressed_size),
+         (compressed_size * 100.0) / max<int>(1, length),
+         comp_rate,
+         urate.c_str());
+}
+
+
+static int VerifyString(const string& input) {
+  string compressed;
+  DataEndingAtUnreadablePage i(input);
+  const size_t written = snappy::Compress(i.data(), i.size(), &compressed);
+  CHECK_EQ(written, compressed.size());
+  CHECK_LE(compressed.size(),
+           snappy::MaxCompressedLength(input.size()));
+  CHECK(snappy::IsValidCompressedBuffer(compressed.data(), compressed.size()));
+
+  string uncompressed;
+  DataEndingAtUnreadablePage c(compressed);
+  CHECK(snappy::Uncompress(c.data(), c.size(), &uncompressed));
+  CHECK_EQ(uncompressed, input);
+  return uncompressed.size();
+}
+
+
+// Test that data compressed by a compressor that does not
+// obey block sizes is uncompressed properly.
+static void VerifyNonBlockedCompression(const string& input) {
+  if (input.length() > snappy::kBlockSize) {
+    // We cannot test larger blocks than the maximum block size, obviously.
+    return;
+  }
+
+  string prefix;
+  Varint::Append32(&prefix, input.size());
+
+  // Setup compression table
+  snappy::internal::WorkingMemory wmem;
+  int table_size;
+  uint16* table = wmem.GetHashTable(input.size(), &table_size);
+
+  // Compress entire input in one shot
+  string compressed;
+  compressed += prefix;
+  compressed.resize(prefix.size()+snappy::MaxCompressedLength(input.size()));
+  char* dest = string_as_array(&compressed) + prefix.size();
+  char* end = snappy::internal::CompressFragment(input.data(), input.size(),
+                                                dest, table, table_size);
+  compressed.resize(end - compressed.data());
+
+  // Uncompress into string
+  string uncomp_str;
+  CHECK(snappy::Uncompress(compressed.data(), compressed.size(), &uncomp_str));
+  CHECK_EQ(uncomp_str, input);
+
+}
+
+// Expand the input so that it is at least K times as big as block size
+static string Expand(const string& input) {
+  static const int K = 3;
+  string data = input;
+  while (data.size() < K * snappy::kBlockSize) {
+    data += input;
+  }
+  return data;
+}
+
+static int Verify(const string& input) {
+  VLOG(1) << "Verifying input of size " << input.size();
+
+  // Compress using string based routines
+  const int result = VerifyString(input);
+
+
+  VerifyNonBlockedCompression(input);
+  if (!input.empty()) {
+    VerifyNonBlockedCompression(Expand(input));
+  }
+
+
+  return result;
+}
+
+// This test checks to ensure that snappy doesn't coredump if it gets
+// corrupted data.
+
+static bool IsValidCompressedBuffer(const string& c) {
+  return snappy::IsValidCompressedBuffer(c.data(), c.size());
+}
+static bool Uncompress(const string& c, string* u) {
+  return snappy::Uncompress(c.data(), c.size(), u);
+}
+
+TYPED_TEST(CorruptedTest, VerifyCorrupted) {
+  string source = "making sure we don't crash with corrupted input";
+  VLOG(1) << source;
+  string dest;
+  TypeParam uncmp;
+  snappy::Compress(source.data(), source.size(), &dest);
+
+  // Mess around with the data. It's hard to simulate all possible
+  // corruptions; this is just one example ...
+  CHECK_GT(dest.size(), 3);
+  dest[1]--;
+  dest[3]++;
+  // this really ought to fail.
+  CHECK(!IsValidCompressedBuffer(TypeParam(dest)));
+  CHECK(!Uncompress(TypeParam(dest), &uncmp));
+
+  // This is testing for a security bug - a buffer that decompresses to 100k
+  // but we lie in the snappy header and only reserve 0 bytes of memory :)
+  source.resize(100000);
+  for (int i = 0; i < source.length(); ++i) {
+    source[i] = 'A';
+  }
+  snappy::Compress(source.data(), source.size(), &dest);
+  dest[0] = dest[1] = dest[2] = dest[3] = 0;
+  CHECK(!IsValidCompressedBuffer(TypeParam(dest)));
+  CHECK(!Uncompress(TypeParam(dest), &uncmp));
+
+  if (sizeof(void *) == 4) {
+    // Another security check; check a crazy big length can't DoS us with an
+    // over-allocation.
+    // Currently this is done only for 32-bit builds.  On 64-bit builds,
+    // where 3 GB might be an acceptable allocation size, Uncompress()
+    // attempts to decompress, and sometimes causes the test to run out of
+    // memory.
+    dest[0] = dest[1] = dest[2] = dest[3] = 0xff;
+    // This decodes to a really large size, i.e., about 3 GB.
+    dest[4] = 'k';
+    CHECK(!IsValidCompressedBuffer(TypeParam(dest)));
+    CHECK(!Uncompress(TypeParam(dest), &uncmp));
+  } else {
+    LOG(WARNING) << "Crazy decompression lengths not checked on 64-bit build";
+  }
+
+  // This decodes to about 2 MB; much smaller, but should still fail.
+  dest[0] = dest[1] = dest[2] = 0xff;
+  dest[3] = 0x00;
+  CHECK(!IsValidCompressedBuffer(TypeParam(dest)));
+  CHECK(!Uncompress(TypeParam(dest), &uncmp));
+
+  // try reading stuff in from a bad file.
+  for (int i = 1; i <= 3; ++i) {
+    string data = ReadTestDataFile(StringPrintf("baddata%d.snappy", i).c_str(),
+                                   0);
+    string uncmp;
+    // check that we don't return a crazy length
+    size_t ulen;
+    CHECK(!snappy::GetUncompressedLength(data.data(), data.size(), &ulen)
+          || (ulen < (1<<20)));
+    uint32 ulen2;
+    snappy::ByteArraySource source(data.data(), data.size());
+    CHECK(!snappy::GetUncompressedLength(&source, &ulen2) ||
+          (ulen2 < (1<<20)));
+    CHECK(!IsValidCompressedBuffer(TypeParam(data)));
+    CHECK(!Uncompress(TypeParam(data), &uncmp));
+  }
+}
+
+// Helper routines to construct arbitrary compressed strings.
+// These mirror the compression code in snappy.cc, but are copied
+// here so that we can bypass some limitations in the how snappy.cc
+// invokes these routines.
+static void AppendLiteral(string* dst, const string& literal) {
+  if (literal.empty()) return;
+  int n = literal.size() - 1;
+  if (n < 60) {
+    // Fit length in tag byte
+    dst->push_back(0 | (n << 2));
+  } else {
+    // Encode in upcoming bytes
+    char number[4];
+    int count = 0;
+    while (n > 0) {
+      number[count++] = n & 0xff;
+      n >>= 8;
+    }
+    dst->push_back(0 | ((59+count) << 2));
+    *dst += string(number, count);
+  }
+  *dst += literal;
+}
+
+static void AppendCopy(string* dst, int offset, int length) {
+  while (length > 0) {
+    // Figure out how much to copy in one shot
+    int to_copy;
+    if (length >= 68) {
+      to_copy = 64;
+    } else if (length > 64) {
+      to_copy = 60;
+    } else {
+      to_copy = length;
+    }
+    length -= to_copy;
+
+    if ((to_copy < 12) && (offset < 2048)) {
+      assert(to_copy-4 < 8);            // Must fit in 3 bits
+      dst->push_back(1 | ((to_copy-4) << 2) | ((offset >> 8) << 5));
+      dst->push_back(offset & 0xff);
+    } else if (offset < 65536) {
+      dst->push_back(2 | ((to_copy-1) << 2));
+      dst->push_back(offset & 0xff);
+      dst->push_back(offset >> 8);
+    } else {
+      dst->push_back(3 | ((to_copy-1) << 2));
+      dst->push_back(offset & 0xff);
+      dst->push_back((offset >> 8) & 0xff);
+      dst->push_back((offset >> 16) & 0xff);
+      dst->push_back((offset >> 24) & 0xff);
+    }
+  }
+}
+
+TEST(Snappy, SimpleTests) {
+  Verify("");
+  Verify("a");
+  Verify("ab");
+  Verify("abc");
+
+  Verify("aaaaaaa" + string(16, 'b') + string("aaaaa") + "abc");
+  Verify("aaaaaaa" + string(256, 'b') + string("aaaaa") + "abc");
+  Verify("aaaaaaa" + string(2047, 'b') + string("aaaaa") + "abc");
+  Verify("aaaaaaa" + string(65536, 'b') + string("aaaaa") + "abc");
+  Verify("abcaaaaaaa" + string(65536, 'b') + string("aaaaa") + "abc");
+}
+
+// Verify max blowup (lots of four-byte copies)
+TEST(Snappy, MaxBlowup) {
+  string input;
+  for (int i = 0; i < 20000; i++) {
+    ACMRandom rnd(i);
+    uint32 bytes = static_cast<uint32>(rnd.Next());
+    input.append(reinterpret_cast<char*>(&bytes), sizeof(bytes));
+  }
+  for (int i = 19999; i >= 0; i--) {
+    ACMRandom rnd(i);
+    uint32 bytes = static_cast<uint32>(rnd.Next());
+    input.append(reinterpret_cast<char*>(&bytes), sizeof(bytes));
+  }
+  Verify(input);
+}
+
+TEST(Snappy, RandomData) {
+  ACMRandom rnd(FLAGS_test_random_seed);
+
+  const int num_ops = 20000;
+  for (int i = 0; i < num_ops; i++) {
+    if ((i % 1000) == 0) {
+      VLOG(0) << "Random op " << i << " of " << num_ops;
+    }
+
+    string x;
+    int len = rnd.Uniform(4096);
+    if (i < 100) {
+      len = 65536 + rnd.Uniform(65536);
+    }
+    while (x.size() < len) {
+      int run_len = 1;
+      if (rnd.OneIn(10)) {
+        run_len = rnd.Skewed(8);
+      }
+      char c = (i < 100) ? rnd.Uniform(256) : rnd.Skewed(3);
+      while (run_len-- > 0 && x.size() < len) {
+        x += c;
+      }
+    }
+
+    Verify(x);
+  }
+}
+
+TEST(Snappy, FourByteOffset) {
+  // The new compressor cannot generate four-byte offsets since
+  // it chops up the input into 32KB pieces.  So we hand-emit the
+  // copy manually.
+
+  // The two fragments that make up the input string.
+  string fragment1 = "012345689abcdefghijklmnopqrstuvwxyz";
+  string fragment2 = "some other string";
+
+  // How many times each fragment is emitted.
+  const int n1 = 2;
+  const int n2 = 100000 / fragment2.size();
+  const int length = n1 * fragment1.size() + n2 * fragment2.size();
+
+  string compressed;
+  Varint::Append32(&compressed, length);
+
+  AppendLiteral(&compressed, fragment1);
+  string src = fragment1;
+  for (int i = 0; i < n2; i++) {
+    AppendLiteral(&compressed, fragment2);
+    src += fragment2;
+  }
+  AppendCopy(&compressed, src.size(), fragment1.size());
+  src += fragment1;
+  CHECK_EQ(length, src.size());
+
+  string uncompressed;
+  CHECK(snappy::IsValidCompressedBuffer(compressed.data(), compressed.size()));
+  CHECK(snappy::Uncompress(compressed.data(), compressed.size(),
+                           &uncompressed));
+  CHECK_EQ(uncompressed, src);
+}
+
+
+static bool CheckUncompressedLength(const string& compressed,
+                                    size_t* ulength) {
+  const bool result1 = snappy::GetUncompressedLength(compressed.data(),
+                                                     compressed.size(),
+                                                     ulength);
+
+  snappy::ByteArraySource source(compressed.data(), compressed.size());
+  uint32 length;
+  const bool result2 = snappy::GetUncompressedLength(&source, &length);
+  CHECK_EQ(result1, result2);
+  return result1;
+}
+
+TEST(SnappyCorruption, TruncatedVarint) {
+  string compressed, uncompressed;
+  size_t ulength;
+  compressed.push_back('\xf0');
+  CHECK(!CheckUncompressedLength(compressed, &ulength));
+  CHECK(!snappy::IsValidCompressedBuffer(compressed.data(), compressed.size()));
+  CHECK(!snappy::Uncompress(compressed.data(), compressed.size(),
+                            &uncompressed));
+}
+
+TEST(SnappyCorruption, UnterminatedVarint) {
+  string compressed, uncompressed;
+  size_t ulength;
+  compressed.push_back(128);
+  compressed.push_back(128);
+  compressed.push_back(128);
+  compressed.push_back(128);
+  compressed.push_back(128);
+  compressed.push_back(10);
+  CHECK(!CheckUncompressedLength(compressed, &ulength));
+  CHECK(!snappy::IsValidCompressedBuffer(compressed.data(), compressed.size()));
+  CHECK(!snappy::Uncompress(compressed.data(), compressed.size(),
+                            &uncompressed));
+}
+
+TEST(Snappy, ReadPastEndOfBuffer) {
+  // Check that we do not read past end of input
+
+  // Make a compressed string that ends with a single-byte literal
+  string compressed;
+  Varint::Append32(&compressed, 1);
+  AppendLiteral(&compressed, "x");
+
+  string uncompressed;
+  DataEndingAtUnreadablePage c(compressed);
+  CHECK(snappy::Uncompress(c.data(), c.size(), &uncompressed));
+  CHECK_EQ(uncompressed, string("x"));
+}
+
+// Check for an infinite loop caused by a copy with offset==0
+TEST(Snappy, ZeroOffsetCopy) {
+  const char* compressed = "\x40\x12\x00\x00";
+  //  \x40              Length (must be > kMaxIncrementCopyOverflow)
+  //  \x12\x00\x00      Copy with offset==0, length==5
+  char uncompressed[100];
+  EXPECT_FALSE(snappy::RawUncompress(compressed, 4, uncompressed));
+}
+
+TEST(Snappy, ZeroOffsetCopyValidation) {
+  const char* compressed = "\x05\x12\x00\x00";
+  //  \x05              Length
+  //  \x12\x00\x00      Copy with offset==0, length==5
+  EXPECT_FALSE(snappy::IsValidCompressedBuffer(compressed, 4));
+}
+
+
+namespace {
+
+int TestFindMatchLength(const char* s1, const char *s2, unsigned length) {
+  return snappy::internal::FindMatchLength(s1, s2, s2 + length);
+}
+
+}  // namespace
+
+TEST(Snappy, FindMatchLength) {
+  // Exercise all different code paths through the function.
+  // 64-bit version:
+
+  // Hit s1_limit in 64-bit loop, hit s1_limit in single-character loop.
+  EXPECT_EQ(6, TestFindMatchLength("012345", "012345", 6));
+  EXPECT_EQ(11, TestFindMatchLength("01234567abc", "01234567abc", 11));
+
+  // Hit s1_limit in 64-bit loop, find a non-match in single-character loop.
+  EXPECT_EQ(9, TestFindMatchLength("01234567abc", "01234567axc", 9));
+
+  // Same, but edge cases.
+  EXPECT_EQ(11, TestFindMatchLength("01234567abc!", "01234567abc!", 11));
+  EXPECT_EQ(11, TestFindMatchLength("01234567abc!", "01234567abc?", 11));
+
+  // Find non-match at once in first loop.
+  EXPECT_EQ(0, TestFindMatchLength("01234567xxxxxxxx", "?1234567xxxxxxxx", 16));
+  EXPECT_EQ(1, TestFindMatchLength("01234567xxxxxxxx", "0?234567xxxxxxxx", 16));
+  EXPECT_EQ(4, TestFindMatchLength("01234567xxxxxxxx", "01237654xxxxxxxx", 16));
+  EXPECT_EQ(7, TestFindMatchLength("01234567xxxxxxxx", "0123456?xxxxxxxx", 16));
+
+  // Find non-match in first loop after one block.
+  EXPECT_EQ(8, TestFindMatchLength("abcdefgh01234567xxxxxxxx",
+                                   "abcdefgh?1234567xxxxxxxx", 24));
+  EXPECT_EQ(9, TestFindMatchLength("abcdefgh01234567xxxxxxxx",
+                                   "abcdefgh0?234567xxxxxxxx", 24));
+  EXPECT_EQ(12, TestFindMatchLength("abcdefgh01234567xxxxxxxx",
+                                    "abcdefgh01237654xxxxxxxx", 24));
+  EXPECT_EQ(15, TestFindMatchLength("abcdefgh01234567xxxxxxxx",
+                                    "abcdefgh0123456?xxxxxxxx", 24));
+
+  // 32-bit version:
+
+  // Short matches.
+  EXPECT_EQ(0, TestFindMatchLength("01234567", "?1234567", 8));
+  EXPECT_EQ(1, TestFindMatchLength("01234567", "0?234567", 8));
+  EXPECT_EQ(2, TestFindMatchLength("01234567", "01?34567", 8));
+  EXPECT_EQ(3, TestFindMatchLength("01234567", "012?4567", 8));
+  EXPECT_EQ(4, TestFindMatchLength("01234567", "0123?567", 8));
+  EXPECT_EQ(5, TestFindMatchLength("01234567", "01234?67", 8));
+  EXPECT_EQ(6, TestFindMatchLength("01234567", "012345?7", 8));
+  EXPECT_EQ(7, TestFindMatchLength("01234567", "0123456?", 8));
+  EXPECT_EQ(7, TestFindMatchLength("01234567", "0123456?", 7));
+  EXPECT_EQ(7, TestFindMatchLength("01234567!", "0123456??", 7));
+
+  // Hit s1_limit in 32-bit loop, hit s1_limit in single-character loop.
+  EXPECT_EQ(10, TestFindMatchLength("xxxxxxabcd", "xxxxxxabcd", 10));
+  EXPECT_EQ(10, TestFindMatchLength("xxxxxxabcd?", "xxxxxxabcd?", 10));
+  EXPECT_EQ(13, TestFindMatchLength("xxxxxxabcdef", "xxxxxxabcdef", 13));
+
+  // Same, but edge cases.
+  EXPECT_EQ(12, TestFindMatchLength("xxxxxx0123abc!", "xxxxxx0123abc!", 12));
+  EXPECT_EQ(12, TestFindMatchLength("xxxxxx0123abc!", "xxxxxx0123abc?", 12));
+
+  // Hit s1_limit in 32-bit loop, find a non-match in single-character loop.
+  EXPECT_EQ(11, TestFindMatchLength("xxxxxx0123abc", "xxxxxx0123axc", 13));
+
+  // Find non-match at once in first loop.
+  EXPECT_EQ(6, TestFindMatchLength("xxxxxx0123xxxxxxxx",
+                                   "xxxxxx?123xxxxxxxx", 18));
+  EXPECT_EQ(7, TestFindMatchLength("xxxxxx0123xxxxxxxx",
+                                   "xxxxxx0?23xxxxxxxx", 18));
+  EXPECT_EQ(8, TestFindMatchLength("xxxxxx0123xxxxxxxx",
+                                   "xxxxxx0132xxxxxxxx", 18));
+  EXPECT_EQ(9, TestFindMatchLength("xxxxxx0123xxxxxxxx",
+                                   "xxxxxx012?xxxxxxxx", 18));
+
+  // Same, but edge cases.
+  EXPECT_EQ(6, TestFindMatchLength("xxxxxx0123", "xxxxxx?123", 10));
+  EXPECT_EQ(7, TestFindMatchLength("xxxxxx0123", "xxxxxx0?23", 10));
+  EXPECT_EQ(8, TestFindMatchLength("xxxxxx0123", "xxxxxx0132", 10));
+  EXPECT_EQ(9, TestFindMatchLength("xxxxxx0123", "xxxxxx012?", 10));
+
+  // Find non-match in first loop after one block.
+  EXPECT_EQ(10, TestFindMatchLength("xxxxxxabcd0123xx",
+                                    "xxxxxxabcd?123xx", 16));
+  EXPECT_EQ(11, TestFindMatchLength("xxxxxxabcd0123xx",
+                                    "xxxxxxabcd0?23xx", 16));
+  EXPECT_EQ(12, TestFindMatchLength("xxxxxxabcd0123xx",
+                                    "xxxxxxabcd0132xx", 16));
+  EXPECT_EQ(13, TestFindMatchLength("xxxxxxabcd0123xx",
+                                    "xxxxxxabcd012?xx", 16));
+
+  // Same, but edge cases.
+  EXPECT_EQ(10, TestFindMatchLength("xxxxxxabcd0123", "xxxxxxabcd?123", 14));
+  EXPECT_EQ(11, TestFindMatchLength("xxxxxxabcd0123", "xxxxxxabcd0?23", 14));
+  EXPECT_EQ(12, TestFindMatchLength("xxxxxxabcd0123", "xxxxxxabcd0132", 14));
+  EXPECT_EQ(13, TestFindMatchLength("xxxxxxabcd0123", "xxxxxxabcd012?", 14));
+}
+
+TEST(Snappy, FindMatchLengthRandom) {
+  const int kNumTrials = 10000;
+  const int kTypicalLength = 10;
+  ACMRandom rnd(FLAGS_test_random_seed);
+
+  for (int i = 0; i < kNumTrials; i++) {
+    string s, t;
+    char a = rnd.Rand8();
+    char b = rnd.Rand8();
+    while (!rnd.OneIn(kTypicalLength)) {
+      s.push_back(rnd.OneIn(2) ? a : b);
+      t.push_back(rnd.OneIn(2) ? a : b);
+    }
+    DataEndingAtUnreadablePage u(s);
+    DataEndingAtUnreadablePage v(t);
+    int matched = snappy::internal::FindMatchLength(
+        u.data(), v.data(), v.data() + t.size());
+    if (matched == t.size()) {
+      EXPECT_EQ(s, t);
+    } else {
+      EXPECT_NE(s[matched], t[matched]);
+      for (int j = 0; j < matched; j++) {
+        EXPECT_EQ(s[j], t[j]);
+      }
+    }
+  }
+}
+
+
+static void CompressFile(const char* fname) {
+  string fullinput;
+  file::GetContents(fname, &fullinput, file::Defaults()).CheckSuccess();
+
+  string compressed;
+  Compress(fullinput.data(), fullinput.size(), SNAPPY, &compressed, false);
+
+  file::SetContents(string(fname).append(".comp"), compressed, file::Defaults())
+      .CheckSuccess();
+}
+
+static void UncompressFile(const char* fname) {
+  string fullinput;
+  file::GetContents(fname, &fullinput, file::Defaults()).CheckSuccess();
+
+  size_t uncompLength;
+  CHECK(CheckUncompressedLength(fullinput, &uncompLength));
+
+  string uncompressed;
+  uncompressed.resize(uncompLength);
+  CHECK(snappy::Uncompress(fullinput.data(), fullinput.size(), &uncompressed));
+
+  file::SetContents(string(fname).append(".uncomp"), uncompressed,
+                    file::Defaults()).CheckSuccess();
+}
+
+static void MeasureFile(const char* fname) {
+  string fullinput;
+  file::GetContents(fname, &fullinput, file::Defaults()).CheckSuccess();
+  printf("%-40s :\n", fname);
+
+  int start_len = (FLAGS_start_len < 0) ? fullinput.size() : FLAGS_start_len;
+  int end_len = fullinput.size();
+  if (FLAGS_end_len >= 0) {
+    end_len = min<int>(fullinput.size(), FLAGS_end_len);
+  }
+  for (int len = start_len; len <= end_len; len++) {
+    const char* const input = fullinput.data();
+    int repeats = (FLAGS_bytes + len) / (len + 1);
+    if (FLAGS_zlib)     Measure(input, len, ZLIB, repeats, 1024<<10);
+    if (FLAGS_lzo)      Measure(input, len, LZO, repeats, 1024<<10);
+    if (FLAGS_liblzf)   Measure(input, len, LIBLZF, repeats, 1024<<10);
+    if (FLAGS_quicklz)  Measure(input, len, QUICKLZ, repeats, 1024<<10);
+    if (FLAGS_fastlz)   Measure(input, len, FASTLZ, repeats, 1024<<10);
+    if (FLAGS_snappy)    Measure(input, len, SNAPPY, repeats, 4096<<10);
+
+    // For block-size based measurements
+    if (0 && FLAGS_snappy) {
+      Measure(input, len, SNAPPY, repeats, 8<<10);
+      Measure(input, len, SNAPPY, repeats, 16<<10);
+      Measure(input, len, SNAPPY, repeats, 32<<10);
+      Measure(input, len, SNAPPY, repeats, 64<<10);
+      Measure(input, len, SNAPPY, repeats, 256<<10);
+      Measure(input, len, SNAPPY, repeats, 1024<<10);
+    }
+  }
+}
+
+static struct {
+  const char* label;
+  const char* filename;
+  size_t size_limit;
+} files[] = {
+  { "html", "html", 0 },
+  { "urls", "urls.10K", 0 },
+  { "jpg", "house.jpg", 0 },
+  { "jpg_200", "house.jpg", 200 },
+  { "pdf", "mapreduce-osdi-1.pdf", 0 },
+  { "html4", "html_x_4", 0 },
+  { "cp", "cp.html", 0 },
+  { "c", "fields.c", 0 },
+  { "lsp", "grammar.lsp", 0 },
+  { "xls", "kennedy.xls", 0 },
+  { "xls_200", "kennedy.xls", 200 },
+  { "txt1", "alice29.txt", 0 },
+  { "txt2", "asyoulik.txt", 0 },
+  { "txt3", "lcet10.txt", 0 },
+  { "txt4", "plrabn12.txt", 0 },
+  { "bin", "ptt5", 0 },
+  { "bin_200", "ptt5", 200 },
+  { "sum", "sum", 0 },
+  { "man", "xargs.1", 0 },
+  { "pb", "geo.protodata", 0 },
+  { "gaviota", "kppkn.gtb", 0 },
+};
+
+static void BM_UFlat(int iters, int arg) {
+  StopBenchmarkTiming();
+
+  // Pick file to process based on "arg"
+  CHECK_GE(arg, 0);
+  CHECK_LT(arg, ARRAYSIZE(files));
+  string contents = ReadTestDataFile(files[arg].filename,
+                                     files[arg].size_limit);
+
+  string zcontents;
+  snappy::Compress(contents.data(), contents.size(), &zcontents);
+  char* dst = new char[contents.size()];
+
+  SetBenchmarkBytesProcessed(static_cast<int64>(iters) *
+                             static_cast<int64>(contents.size()));
+  SetBenchmarkLabel(files[arg].label);
+  StartBenchmarkTiming();
+  while (iters-- > 0) {
+    CHECK(snappy::RawUncompress(zcontents.data(), zcontents.size(), dst));
+  }
+  StopBenchmarkTiming();
+
+  delete[] dst;
+}
+BENCHMARK(BM_UFlat)->DenseRange(0, ARRAYSIZE(files) - 1);
+
+static void BM_UValidate(int iters, int arg) {
+  StopBenchmarkTiming();
+
+  // Pick file to process based on "arg"
+  CHECK_GE(arg, 0);
+  CHECK_LT(arg, ARRAYSIZE(files));
+  string contents = ReadTestDataFile(files[arg].filename,
+                                     files[arg].size_limit);
+
+  string zcontents;
+  snappy::Compress(contents.data(), contents.size(), &zcontents);
+
+  SetBenchmarkBytesProcessed(static_cast<int64>(iters) *
+                             static_cast<int64>(contents.size()));
+  SetBenchmarkLabel(files[arg].label);
+  StartBenchmarkTiming();
+  while (iters-- > 0) {
+    CHECK(snappy::IsValidCompressedBuffer(zcontents.data(), zcontents.size()));
+  }
+  StopBenchmarkTiming();
+}
+BENCHMARK(BM_UValidate)->DenseRange(0, 4);
+
+
+static void BM_ZFlat(int iters, int arg) {
+  StopBenchmarkTiming();
+
+  // Pick file to process based on "arg"
+  CHECK_GE(arg, 0);
+  CHECK_LT(arg, ARRAYSIZE(files));
+  string contents = ReadTestDataFile(files[arg].filename,
+                                     files[arg].size_limit);
+
+  char* dst = new char[snappy::MaxCompressedLength(contents.size())];
+
+  SetBenchmarkBytesProcessed(static_cast<int64>(iters) *
+                             static_cast<int64>(contents.size()));
+  StartBenchmarkTiming();
+
+  size_t zsize = 0;
+  while (iters-- > 0) {
+    snappy::RawCompress(contents.data(), contents.size(), dst, &zsize);
+  }
+  StopBenchmarkTiming();
+  const double compression_ratio =
+      static_cast<double>(zsize) / std::max<size_t>(1, contents.size());
+  SetBenchmarkLabel(StringPrintf("%s (%.2f %%)",
+                                 files[arg].label, 100.0 * compression_ratio));
+  VLOG(0) << StringPrintf("compression for %s: %zd -> %zd bytes",
+                          files[arg].label, contents.size(), zsize);
+  delete[] dst;
+}
+BENCHMARK(BM_ZFlat)->DenseRange(0, ARRAYSIZE(files) - 1);
+
+
+}  // namespace snappy
+
+
+int main(int argc, char** argv) {
+  InitGoogle(argv[0], &argc, &argv, true);
+  File::Init();
+  RunSpecifiedBenchmarks();
+
+
+  if (argc >= 2) {
+    for (int arg = 1; arg < argc; arg++) {
+      if (FLAGS_write_compressed) {
+        CompressFile(argv[arg]);
+      } else if (FLAGS_write_uncompressed) {
+        UncompressFile(argv[arg]);
+      } else {
+        MeasureFile(argv[arg]);
+      }
+    }
+    return 0;
+  }
+
+  return RUN_ALL_TESTS();
+}