| // Copyright 2017 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/installer/zucchini/equivalence_map.h" |
| |
| #include <algorithm> |
| |
| #include "base/logging.h" |
| #include "chrome/installer/zucchini/encoded_view.h" |
| #include "chrome/installer/zucchini/suffix_array.h" |
| |
| namespace zucchini { |
| |
| /******** Utility Functions ********/ |
| |
| double GetTokenSimilarity( |
| const ImageIndex& old_image_index, |
| const ImageIndex& new_image_index, |
| const std::vector<TargetsAffinity>& targets_affinities, |
| offset_t src, |
| offset_t dst) { |
| DCHECK(old_image_index.IsToken(src)); |
| DCHECK(new_image_index.IsToken(dst)); |
| |
| TypeTag old_type = old_image_index.LookupType(src); |
| TypeTag new_type = new_image_index.LookupType(dst); |
| if (old_type != new_type) |
| return kMismatchFatal; |
| |
| // Raw comparison. |
| if (!old_image_index.IsReference(src) && !new_image_index.IsReference(dst)) { |
| return old_image_index.GetRawValue(src) == new_image_index.GetRawValue(dst) |
| ? 1.0 |
| : -1.5; |
| } |
| |
| const ReferenceSet& old_ref_set = old_image_index.refs(old_type); |
| const ReferenceSet& new_ref_set = new_image_index.refs(new_type); |
| IndirectReference old_reference = old_ref_set.at(src); |
| IndirectReference new_reference = new_ref_set.at(dst); |
| PoolTag pool_tag = old_ref_set.pool_tag(); |
| |
| double affinity = targets_affinities[pool_tag.value()].AffinityBetween( |
| old_reference.target_key, new_reference.target_key); |
| |
| // Both targets are not associated, which implies a weak match. |
| if (affinity == 0.0) |
| return 0.5 * old_ref_set.width(); |
| |
| // At least one target is associated, so values are compared. |
| return affinity > 0.0 ? old_ref_set.width() : -2.0; |
| } |
| |
| double GetEquivalenceSimilarity( |
| const ImageIndex& old_image_index, |
| const ImageIndex& new_image_index, |
| const std::vector<TargetsAffinity>& targets_affinities, |
| const Equivalence& equivalence) { |
| double similarity = 0.0; |
| for (offset_t k = 0; k < equivalence.length; ++k) { |
| // Non-tokens are joined with the nearest previous token: skip until we |
| // cover the unit. |
| if (!new_image_index.IsToken(equivalence.dst_offset + k)) |
| continue; |
| |
| similarity += GetTokenSimilarity( |
| old_image_index, new_image_index, targets_affinities, |
| equivalence.src_offset + k, equivalence.dst_offset + k); |
| if (similarity == kMismatchFatal) |
| return kMismatchFatal; |
| } |
| return similarity; |
| } |
| |
| EquivalenceCandidate ExtendEquivalenceForward( |
| const ImageIndex& old_image_index, |
| const ImageIndex& new_image_index, |
| const std::vector<TargetsAffinity>& targets_affinities, |
| const EquivalenceCandidate& candidate, |
| double min_similarity) { |
| Equivalence equivalence = candidate.eq; |
| offset_t best_k = equivalence.length; |
| double current_similarity = candidate.similarity; |
| double best_similarity = current_similarity; |
| double current_penalty = min_similarity; |
| for (offset_t k = best_k; |
| equivalence.src_offset + k < old_image_index.size() && |
| equivalence.dst_offset + k < new_image_index.size(); |
| ++k) { |
| // Mismatch in type, |candidate| cannot be extended further. |
| if (old_image_index.LookupType(equivalence.src_offset + k) != |
| new_image_index.LookupType(equivalence.dst_offset + k)) { |
| break; |
| } |
| |
| if (!new_image_index.IsToken(equivalence.dst_offset + k)) { |
| // Non-tokens are joined with the nearest previous token: skip until we |
| // cover the unit, and extend |best_k| if applicable. |
| if (best_k == k) |
| best_k = k + 1; |
| continue; |
| } |
| |
| double similarity = GetTokenSimilarity( |
| old_image_index, new_image_index, targets_affinities, |
| equivalence.src_offset + k, equivalence.dst_offset + k); |
| current_similarity += similarity; |
| current_penalty = std::max(0.0, current_penalty) - similarity; |
| |
| if (current_similarity < 0.0 || current_penalty >= min_similarity) |
| break; |
| if (current_similarity >= best_similarity) { |
| best_similarity = current_similarity; |
| best_k = k + 1; |
| } |
| } |
| equivalence.length = best_k; |
| return {equivalence, best_similarity}; |
| } |
| |
| EquivalenceCandidate ExtendEquivalenceBackward( |
| const ImageIndex& old_image_index, |
| const ImageIndex& new_image_index, |
| const std::vector<TargetsAffinity>& targets_affinities, |
| const EquivalenceCandidate& candidate, |
| double min_similarity) { |
| Equivalence equivalence = candidate.eq; |
| offset_t best_k = 0; |
| double current_similarity = candidate.similarity; |
| double best_similarity = current_similarity; |
| double current_penalty = 0.0; |
| for (offset_t k = 1; |
| k <= equivalence.dst_offset && k <= equivalence.src_offset; ++k) { |
| // Mismatch in type, |candidate| cannot be extended further. |
| if (old_image_index.LookupType(equivalence.src_offset - k) != |
| new_image_index.LookupType(equivalence.dst_offset - k)) { |
| break; |
| } |
| |
| // Non-tokens are joined with the nearest previous token: skip until we |
| // reach the next token. |
| if (!new_image_index.IsToken(equivalence.dst_offset - k)) |
| continue; |
| |
| DCHECK_EQ(old_image_index.LookupType(equivalence.src_offset - k), |
| new_image_index.LookupType(equivalence.dst_offset - |
| k)); // Sanity check. |
| double similarity = GetTokenSimilarity( |
| old_image_index, new_image_index, targets_affinities, |
| equivalence.src_offset - k, equivalence.dst_offset - k); |
| |
| current_similarity += similarity; |
| current_penalty = std::max(0.0, current_penalty) - similarity; |
| |
| if (current_similarity < 0.0 || current_penalty >= min_similarity) |
| break; |
| if (current_similarity >= best_similarity) { |
| best_similarity = current_similarity; |
| best_k = k; |
| } |
| } |
| |
| equivalence.dst_offset -= best_k; |
| equivalence.src_offset -= best_k; |
| equivalence.length += best_k; |
| return {equivalence, best_similarity}; |
| } |
| |
| EquivalenceCandidate VisitEquivalenceSeed( |
| const ImageIndex& old_image_index, |
| const ImageIndex& new_image_index, |
| const std::vector<TargetsAffinity>& targets_affinities, |
| offset_t src, |
| offset_t dst, |
| double min_similarity) { |
| EquivalenceCandidate candidate{{src, dst, 0}, 0.0}; // Empty. |
| if (!old_image_index.IsToken(src)) |
| return candidate; |
| candidate = |
| ExtendEquivalenceForward(old_image_index, new_image_index, |
| targets_affinities, candidate, min_similarity); |
| if (candidate.similarity < min_similarity) |
| return candidate; // Not worth exploring any more. |
| return ExtendEquivalenceBackward(old_image_index, new_image_index, |
| targets_affinities, candidate, |
| min_similarity); |
| } |
| |
| /******** EquivalenceMap ********/ |
| |
| EquivalenceMap::EquivalenceMap() = default; |
| |
| EquivalenceMap::EquivalenceMap( |
| const std::vector<EquivalenceCandidate>& equivalences) |
| : candidates_(equivalences) { |
| SortByDestination(); |
| } |
| |
| EquivalenceMap::EquivalenceMap(EquivalenceMap&&) = default; |
| |
| EquivalenceMap::~EquivalenceMap() = default; |
| |
| void EquivalenceMap::Build( |
| const std::vector<offset_t>& old_sa, |
| const EncodedView& old_view, |
| const EncodedView& new_view, |
| const std::vector<TargetsAffinity>& targets_affinities, |
| double min_similarity) { |
| DCHECK_EQ(old_sa.size(), old_view.size()); |
| |
| CreateCandidates(old_sa, old_view, new_view, targets_affinities, |
| min_similarity); |
| SortByDestination(); |
| Prune(old_view, new_view, targets_affinities, min_similarity); |
| |
| offset_t coverage = 0; |
| offset_t current_offset = 0; |
| for (auto candidate : candidates_) { |
| DCHECK_GE(candidate.eq.dst_offset, current_offset); |
| coverage += candidate.eq.length; |
| current_offset = candidate.eq.dst_end(); |
| } |
| LOG(INFO) << "Equivalence Count: " << size(); |
| LOG(INFO) << "Coverage / Extra / Total: " << coverage << " / " |
| << new_view.size() - coverage << " / " << new_view.size(); |
| } |
| |
| std::vector<Equivalence> EquivalenceMap::MakeForwardEquivalences() const { |
| std::vector<Equivalence> equivalences(size()); |
| std::transform(begin(), end(), equivalences.begin(), |
| [](const EquivalenceCandidate& c) { return c.eq; }); |
| std::sort(equivalences.begin(), equivalences.end(), |
| [](const Equivalence& a, const Equivalence& b) { |
| return a.src_offset < b.src_offset; |
| }); |
| return equivalences; |
| } |
| |
| void EquivalenceMap::CreateCandidates( |
| const std::vector<offset_t>& old_sa, |
| const EncodedView& old_view, |
| const EncodedView& new_view, |
| const std::vector<TargetsAffinity>& targets_affinities, |
| double min_similarity) { |
| candidates_.clear(); |
| |
| // This is an heuristic to find 'good' equivalences on encoded views. |
| // Equivalences are found in ascending order of |new_image|. |
| offset_t dst_offset = 0; |
| |
| while (dst_offset < new_view.size()) { |
| if (!new_view.IsToken(dst_offset)) { |
| ++dst_offset; |
| continue; |
| } |
| auto match = |
| SuffixLowerBound(old_sa, old_view.begin(), |
| new_view.begin() + dst_offset, new_view.end()); |
| |
| offset_t next_dst_offset = dst_offset + 1; |
| // TODO(huangs): Clean up. |
| double best_similarity = min_similarity; |
| EquivalenceCandidate best_candidate = {{0, 0, 0}, 0.0}; |
| for (auto it = match; it != old_sa.end(); ++it) { |
| EquivalenceCandidate candidate = VisitEquivalenceSeed( |
| old_view.image_index(), new_view.image_index(), targets_affinities, |
| static_cast<offset_t>(*it), dst_offset, min_similarity); |
| if (candidate.similarity > best_similarity) { |
| best_candidate = candidate; |
| best_similarity = candidate.similarity; |
| next_dst_offset = candidate.eq.dst_end(); |
| } else { |
| break; |
| } |
| } |
| for (auto it = match; it != old_sa.begin(); --it) { |
| EquivalenceCandidate candidate = VisitEquivalenceSeed( |
| old_view.image_index(), new_view.image_index(), targets_affinities, |
| static_cast<offset_t>(it[-1]), dst_offset, min_similarity); |
| if (candidate.similarity > best_similarity) { |
| best_candidate = candidate; |
| best_similarity = candidate.similarity; |
| next_dst_offset = candidate.eq.dst_end(); |
| } else { |
| break; |
| } |
| } |
| if (best_candidate.similarity >= min_similarity) { |
| candidates_.push_back(best_candidate); |
| } |
| |
| dst_offset = next_dst_offset; |
| } |
| } |
| |
| void EquivalenceMap::SortByDestination() { |
| std::sort(candidates_.begin(), candidates_.end(), |
| [](const EquivalenceCandidate& a, const EquivalenceCandidate& b) { |
| return a.eq.dst_offset < b.eq.dst_offset; |
| }); |
| } |
| |
| void EquivalenceMap::Prune( |
| const EncodedView& old_view, |
| const EncodedView& new_view, |
| const std::vector<TargetsAffinity>& target_affinities, |
| double min_similarity) { |
| for (auto current = candidates_.begin(); current != candidates_.end(); |
| ++current) { |
| if (current->similarity < min_similarity) |
| continue; // This candidate will be discarded anyways. |
| |
| // Look ahead to resolve overlaps, until a better candidate is found. |
| for (auto next = current + 1; next != candidates_.end(); ++next) { |
| DCHECK_GE(next->eq.dst_offset, current->eq.dst_offset); |
| if (next->eq.dst_offset >= current->eq.dst_offset + current->eq.length) |
| break; // No more overlap. |
| |
| offset_t delta = current->eq.dst_end() - next->eq.dst_offset; |
| |
| // |next| is better, so |current| shrinks. |
| if (current->similarity < next->similarity) { |
| current->eq.length -= delta; |
| current->similarity = GetEquivalenceSimilarity( |
| old_view.image_index(), new_view.image_index(), target_affinities, |
| current->eq); |
| break; |
| } |
| } |
| |
| // Shrinks all overlapping candidates following and worse than |current|. |
| for (auto next = current + 1; next != candidates_.end(); ++next) { |
| if (next->eq.dst_offset >= current->eq.dst_offset + current->eq.length) |
| break; // No more overlap. |
| |
| offset_t delta = current->eq.dst_end() - next->eq.dst_offset; |
| next->eq.length = next->eq.length > delta ? next->eq.length - delta : 0; |
| next->eq.src_offset += delta; |
| next->eq.dst_offset += delta; |
| next->similarity = GetEquivalenceSimilarity(old_view.image_index(), |
| new_view.image_index(), |
| target_affinities, next->eq); |
| DCHECK_EQ(next->eq.dst_offset, current->eq.dst_end()); |
| } |
| } |
| |
| // Discard all candidates with similarity smaller than |min_similarity|. |
| candidates_.erase( |
| std::remove_if(candidates_.begin(), candidates_.end(), |
| [min_similarity](const EquivalenceCandidate& candidate) { |
| return candidate.similarity < min_similarity; |
| }), |
| candidates_.end()); |
| } |
| |
| } // namespace zucchini |
