Revert of Move prefix_set and parts of s_b_util into a new component safe_browsing_db.

chrome/browser/safe_browsing/prefix_set.cc

Index: chrome/browser/safe_browsing/prefix_set.cc
diff --git a/chrome/browser/safe_browsing/prefix_set.cc b/chrome/browser/safe_browsing/prefix_set.cc
new file mode 100644
index 0000000000000000000000000000000000000000..7cd69e99177d3a8d1512614690c541cf319869be
--- /dev/null
+++ b/chrome/browser/safe_browsing/prefix_set.cc
@@ -0,0 +1,448 @@
+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "chrome/browser/safe_browsing/prefix_set.h"
+
+#include <algorithm>
+
+#include "base/files/file_util.h"
+#include "base/files/scoped_file.h"
+#include "base/logging.h"
+#include "base/md5.h"
+#include "base/metrics/histogram.h"
+#include "base/metrics/sparse_histogram.h"
+
+namespace {
+
+// |kMagic| should be reasonably unique, and not match itself across
+// endianness changes.  I generated this value with:
+// md5 -qs chrome/browser/safe_browsing/prefix_set.cc | colrm 9
+static uint32 kMagic = 0x864088dd;
+
+// Version history:
+// Version 1: b6cb7cfe/r74487 by shess@chromium.org on 2011-02-10
+// Version 2: 2b59b0a6/r253924 by shess@chromium.org on 2014-02-27
+// Version 3: dd07faf5/r268145 by shess@chromium.org on 2014-05-05
+
+// Version 2 layout is identical to version 1.  The sort order of |index_|
+// changed from |int32| to |uint32| to match the change of |SBPrefix|.
+// Version 3 adds storage for full hashes.
+static uint32 kVersion = 3;
+static uint32 kDeprecatedVersion = 2;  // And lower.
+
+typedef struct {
+  uint32 magic;
+  uint32 version;
+  uint32 index_size;
+  uint32 deltas_size;
+  uint32 full_hashes_size;
+} FileHeader;
+
+// Common std::vector<> implementations add capacity by multiplying from the
+// current size (usually either by 2 or 1.5) to satisfy push_back() running in
+// amortized constant time.  This is not necessary for insert() at end(), but
+// AFAICT it seems true for some implementations.  SBPrefix values should
+// uniformly cover the 32-bit space, so the final size can be estimated given a
+// subset of the input.
+//
+// |kEstimateThreshold| is when estimates start converging.  Results are strong
+// starting around 1<<27.  1<<30 is chosen to prevent the degenerate case of
+// resizing capacity from >50% to 100%.
+//
+// TODO(shess): I'm sure there is math in the world to describe good settings
+// for estimating the size of a uniformly-distributed set of integers from a
+// sorted subset.  I do not have such math in me, so I assumed that my current
+// organic database of prefixes was scale-free, and wrote a script to see how
+// often given slop values would always suffice for given strides.  At 1<<30,
+// .5% slop was sufficient to cover all cases (though the code below uses 1%).
+//
+// TODO(shess): A smaller threshold uses less transient space in reallocation.
+// 1<<30 uses between 125% and 150%, 1<<29 between 112% and 125%, etc.  The cost
+// is that a smaller threshold needs more slop (locked down for the long term).
+// 1<<29 worked well with 1%, 1<<27 worked well with 2%.
+const SBPrefix kEstimateThreshold = 1 << 30;
+size_t EstimateFinalCount(SBPrefix current_prefix, size_t current_count) {
+  // estimated_count / current_count == estimated_max / current_prefix
+  // For large input sets, estimated_max of 2^32 is close enough.
+  const size_t estimated_prefix_count = static_cast<size_t>(
+      (static_cast<uint64>(current_count) << 32) / current_prefix);
+
+  // The estimate has an error bar, if the final total is below the estimate, no
+  // harm, but if it is above a capacity resize will happen at nearly 100%.  Add
+  // some slop to make sure all cases are covered.
+  return estimated_prefix_count + estimated_prefix_count / 100;
+}
+
+}  // namespace
+
+namespace safe_browsing {
+
+// For |std::upper_bound()| to find a prefix w/in a vector of pairs.
+// static
+bool PrefixSet::PrefixLess(const IndexPair& a, const IndexPair& b) {
+  return a.first < b.first;
+}
+
+PrefixSet::PrefixSet() {
+}
+
+PrefixSet::PrefixSet(IndexVector* index,
+                     std::vector<uint16>* deltas,
+                     std::vector<SBFullHash>* full_hashes) {
+  DCHECK(index && deltas && full_hashes);
+  index_.swap(*index);
+  deltas_.swap(*deltas);
+  full_hashes_.swap(*full_hashes);
+}
+
+PrefixSet::~PrefixSet() {}
+
+bool PrefixSet::PrefixExists(SBPrefix prefix) const {
+  if (index_.empty())
+    return false;
+
+  // Find the first position after |prefix| in |index_|.
+  IndexVector::const_iterator iter =
+      std::upper_bound(index_.begin(), index_.end(),
+                       IndexPair(prefix, 0), PrefixLess);
+
+  // |prefix| comes before anything that's in the set.
+  if (iter == index_.begin())
+    return false;
+
+  // Capture the upper bound of our target entry's deltas.
+  const size_t bound = (iter == index_.end() ? deltas_.size() : iter->second);
+
+  // Back up to the entry our target is in.
+  --iter;
+
+  // All prefixes in |index_| are in the set.
+  SBPrefix current = iter->first;
+  if (current == prefix)
+    return true;
+
+  // Scan forward accumulating deltas while a match is possible.
+  for (size_t di = iter->second; di < bound && current < prefix; ++di) {
+    current += deltas_[di];
+  }
+
+  return current == prefix;
+}
+
+bool PrefixSet::Exists(const SBFullHash& hash) const {
+  if (std::binary_search(full_hashes_.begin(), full_hashes_.end(),
+                         hash, SBFullHashLess)) {
+    return true;
+  }
+  return PrefixExists(hash.prefix);
+}
+
+void PrefixSet::GetPrefixes(std::vector<SBPrefix>* prefixes) const {
+  prefixes->reserve(index_.size() + deltas_.size());
+
+  for (size_t ii = 0; ii < index_.size(); ++ii) {
+    // The deltas for this |index_| entry run to the next index entry,
+    // or the end of the deltas.
+    const size_t deltas_end =
+        (ii + 1 < index_.size()) ? index_[ii + 1].second : deltas_.size();
+
+    SBPrefix current = index_[ii].first;
+    prefixes->push_back(current);
+    for (size_t di = index_[ii].second; di < deltas_end; ++di) {
+      current += deltas_[di];
+      prefixes->push_back(current);
+    }
+  }
+}
+
+// static
+scoped_ptr<const PrefixSet> PrefixSet::LoadFile(
+    const base::FilePath& filter_name) {
+  int64 size_64;
+  if (!base::GetFileSize(filter_name, &size_64))
+    return nullptr;
+  using base::MD5Digest;
+  if (size_64 < static_cast<int64>(sizeof(FileHeader) + sizeof(MD5Digest)))
+    return nullptr;
+
+  base::ScopedFILE file(base::OpenFile(filter_name, "rb"));
+  if (!file.get())
+    return nullptr;
+
+  FileHeader header;
+  size_t read = fread(&header, sizeof(header), 1, file.get());
+  if (read != 1)
+    return nullptr;
+
+  // The file looks valid, start building the digest.
+  base::MD5Context context;
+  base::MD5Init(&context);
+  base::MD5Update(&context, base::StringPiece(reinterpret_cast<char*>(&header),
+                                              sizeof(header)));
+
+  if (header.magic != kMagic)
+    return nullptr;
+
+  // Track version read to inform removal of support for older versions.
+  UMA_HISTOGRAM_SPARSE_SLOWLY("SB2.PrefixSetVersionRead", header.version);
+
+  if (header.version <= kDeprecatedVersion) {
+    return nullptr;
+  } else if (header.version != kVersion) {
+    return nullptr;
+  }
+
+  IndexVector index;
+  const size_t index_bytes = sizeof(index[0]) * header.index_size;
+
+  std::vector<uint16> deltas;
+  const size_t deltas_bytes = sizeof(deltas[0]) * header.deltas_size;
+
+  std::vector<SBFullHash> full_hashes;
+  const size_t full_hashes_bytes =
+      sizeof(full_hashes[0]) * header.full_hashes_size;
+
+  // Check for bogus sizes before allocating any space.
+  const size_t expected_bytes = sizeof(header) +
+      index_bytes + deltas_bytes + full_hashes_bytes + sizeof(MD5Digest);
+  if (static_cast<int64>(expected_bytes) != size_64)
+    return nullptr;
+
+  // Read the index vector.  Herb Sutter indicates that vectors are
+  // guaranteed to be contiuguous, so reading to where element 0 lives
+  // is valid.
+  if (header.index_size) {
+    index.resize(header.index_size);
+    read = fread(&(index[0]), sizeof(index[0]), index.size(), file.get());
+    if (read != index.size())
+      return nullptr;
+    base::MD5Update(&context,
+                    base::StringPiece(reinterpret_cast<char*>(&(index[0])),
+                                      index_bytes));
+  }
+
+  // Read vector of deltas.
+  if (header.deltas_size) {
+    deltas.resize(header.deltas_size);
+    read = fread(&(deltas[0]), sizeof(deltas[0]), deltas.size(), file.get());
+    if (read != deltas.size())
+      return nullptr;
+    base::MD5Update(&context,
+                    base::StringPiece(reinterpret_cast<char*>(&(deltas[0])),
+                                      deltas_bytes));
+  }
+
+  // Read vector of full hashes.
+  if (header.full_hashes_size) {
+    full_hashes.resize(header.full_hashes_size);
+    read = fread(&(full_hashes[0]), sizeof(full_hashes[0]), full_hashes.size(),
+                 file.get());
+    if (read != full_hashes.size())
+      return nullptr;
+    base::MD5Update(&context,
+                    base::StringPiece(
+                        reinterpret_cast<char*>(&(full_hashes[0])),
+                        full_hashes_bytes));
+  }
+
+  base::MD5Digest calculated_digest;
+  base::MD5Final(&calculated_digest, &context);
+
+  base::MD5Digest file_digest;
+  read = fread(&file_digest, sizeof(file_digest), 1, file.get());
+  if (read != 1)
+    return nullptr;
+
+  if (0 != memcmp(&file_digest, &calculated_digest, sizeof(file_digest)))
+    return nullptr;
+
+  // Steals vector contents using swap().
+  return make_scoped_ptr(
+      new PrefixSet(&index, &deltas, &full_hashes));
+}
+
+bool PrefixSet::WriteFile(const base::FilePath& filter_name) const {
+  FileHeader header;
+  header.magic = kMagic;
+  header.version = kVersion;
+  header.index_size = static_cast<uint32>(index_.size());
+  header.deltas_size = static_cast<uint32>(deltas_.size());
+  header.full_hashes_size = static_cast<uint32>(full_hashes_.size());
+
+  // Sanity check that the 32-bit values never mess things up.
+  if (static_cast<size_t>(header.index_size) != index_.size() ||
+      static_cast<size_t>(header.deltas_size) != deltas_.size() ||
+      static_cast<size_t>(header.full_hashes_size) != full_hashes_.size()) {
+    NOTREACHED();
+    return false;
+  }
+
+  base::ScopedFILE file(base::OpenFile(filter_name, "wb"));
+  if (!file.get())
+    return false;
+
+  base::MD5Context context;
+  base::MD5Init(&context);
+
+  // TODO(shess): The I/O code in safe_browsing_store_file.cc would
+  // sure be useful about now.
+  size_t written = fwrite(&header, sizeof(header), 1, file.get());
+  if (written != 1)
+    return false;
+  base::MD5Update(&context, base::StringPiece(reinterpret_cast<char*>(&header),
+                                              sizeof(header)));
+
+  // As for reads, the standard guarantees the ability to access the
+  // contents of the vector by a pointer to an element.
+  if (index_.size()) {
+    const size_t index_bytes = sizeof(index_[0]) * index_.size();
+    written = fwrite(&(index_[0]), sizeof(index_[0]), index_.size(),
+                     file.get());
+    if (written != index_.size())
+      return false;
+    base::MD5Update(&context,
+                    base::StringPiece(
+                        reinterpret_cast<const char*>(&(index_[0])),
+                        index_bytes));
+  }
+
+  if (deltas_.size()) {
+    const size_t deltas_bytes = sizeof(deltas_[0]) * deltas_.size();
+    written = fwrite(&(deltas_[0]), sizeof(deltas_[0]), deltas_.size(),
+                     file.get());
+    if (written != deltas_.size())
+      return false;
+    base::MD5Update(&context,
+                    base::StringPiece(
+                        reinterpret_cast<const char*>(&(deltas_[0])),
+                        deltas_bytes));
+  }
+
+  if (full_hashes_.size()) {
+    const size_t elt_size = sizeof(full_hashes_[0]);
+    const size_t elts = full_hashes_.size();
+    const size_t full_hashes_bytes = elt_size * elts;
+    written = fwrite(&(full_hashes_[0]), elt_size, elts, file.get());
+    if (written != elts)
+      return false;
+    base::MD5Update(&context,
+                    base::StringPiece(
+                        reinterpret_cast<const char*>(&(full_hashes_[0])),
+                        full_hashes_bytes));
+  }
+
+  base::MD5Digest digest;
+  base::MD5Final(&digest, &context);
+  written = fwrite(&digest, sizeof(digest), 1, file.get());
+  if (written != 1)
+    return false;
+
+  // TODO(shess): Can this code check that the close was successful?
+  file.reset();
+
+  return true;
+}
+
+void PrefixSet::AddRun(SBPrefix index_prefix,
+                       const uint16* run_begin, const uint16* run_end) {
+  // Preempt organic capacity decisions for |delta_| once strong estimates can
+  // be made.
+  if (index_prefix > kEstimateThreshold &&
+      deltas_.capacity() < deltas_.size() + (run_end - run_begin)) {
+    deltas_.reserve(EstimateFinalCount(index_prefix, deltas_.size()));
+  }
+
+  index_.push_back(std::make_pair(index_prefix, deltas_.size()));
+  deltas_.insert(deltas_.end(), run_begin, run_end);
+}
+
+PrefixSetBuilder::PrefixSetBuilder()
+    : prefix_set_(new PrefixSet()) {
+}
+
+PrefixSetBuilder::PrefixSetBuilder(const std::vector<SBPrefix>& prefixes)
+    : prefix_set_(new PrefixSet()) {
+  for (size_t i = 0; i < prefixes.size(); ++i) {
+    AddPrefix(prefixes[i]);
+  }
+}
+
+PrefixSetBuilder::~PrefixSetBuilder() {
+}
+
+scoped_ptr<const PrefixSet> PrefixSetBuilder::GetPrefixSet(
+    const std::vector<SBFullHash>& hashes) {
+  DCHECK(prefix_set_.get());
+
+  // Flush runs until buffered data is gone.
+  while (!buffer_.empty()) {
+    EmitRun();
+  }
+
+  // Precisely size |index_| for read-only.  It's 50k-60k, so minor savings, but
+  // they're almost free.
+  PrefixSet::IndexVector(prefix_set_->index_).swap(prefix_set_->index_);
+
+  prefix_set_->full_hashes_ = hashes;
+  std::sort(prefix_set_->full_hashes_.begin(), prefix_set_->full_hashes_.end(),
+            SBFullHashLess);
+
+  return prefix_set_.Pass();
+}
+
+scoped_ptr<const PrefixSet> PrefixSetBuilder::GetPrefixSetNoHashes() {
+  return GetPrefixSet(std::vector<SBFullHash>()).Pass();
+}
+
+void PrefixSetBuilder::EmitRun() {
+  DCHECK(prefix_set_.get());
+
+  SBPrefix prev_prefix = buffer_[0];
+  uint16 run[PrefixSet::kMaxRun];
+  size_t run_pos = 0;
+
+  size_t i;
+  for (i = 1; i < buffer_.size() && run_pos < PrefixSet::kMaxRun; ++i) {
+    // Calculate the delta.  |unsigned| is mandatory, because the
+    // sorted_prefixes could be more than INT_MAX apart.
+    DCHECK_GT(buffer_[i], prev_prefix);
+    const unsigned delta = buffer_[i] - prev_prefix;
+    const uint16 delta16 = static_cast<uint16>(delta);
+
+    // Break the run if the delta doesn't fit.
+    if (delta != static_cast<unsigned>(delta16))
+      break;
+
+    // Continue the run of deltas.
+    run[run_pos++] = delta16;
+    DCHECK_EQ(static_cast<unsigned>(run[run_pos - 1]), delta);
+
+    prev_prefix = buffer_[i];
+  }
+  prefix_set_->AddRun(buffer_[0], run, run + run_pos);
+  buffer_.erase(buffer_.begin(), buffer_.begin() + i);
+}
+
+void PrefixSetBuilder::AddPrefix(SBPrefix prefix) {
+  DCHECK(prefix_set_.get());
+
+  if (buffer_.empty()) {
+    DCHECK(prefix_set_->index_.empty());
+    DCHECK(prefix_set_->deltas_.empty());
+  } else {
+    // Drop duplicates.
+    if (buffer_.back() == prefix)
+      return;
+
+    DCHECK_LT(buffer_.back(), prefix);
+  }
+  buffer_.push_back(prefix);
+
+  // Flush buffer when a run can be constructed.  +1 for the index item, and +1
+  // to leave at least one item in the buffer for dropping duplicates.
+  if (buffer_.size() > PrefixSet::kMaxRun + 2)
+    EmitRun();
+}
+
+}  // namespace safe_browsing