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-// Copyright 2018, 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.
-
-//
-// Internal helper functions for finding optimal edit transformations
-// between strings.
-
-#include "gtest/gtest.h"
-
-#include <functional>
-#include <list>
-#include <ostream> // NOLINT
-#include <queue>
-#include <vector>
-
-namespace testing {
-namespace internal {
-namespace {
-
-// The following implement data structures and code for a Dijkstra-search
-// based implementation of optimal edit distance.
-
-// Posible states a node can be in. Either a node is unsettled (it hasn't been
-// drawn from the priority queue yet), or it is settled and a back-link to its
-// parent node is fixed.
-enum EditSearchState {
- kUnsettled,
- kMatchParent,
- kAddParent,
- kRemoveParent,
- kReplaceParent
-};
-
-// Custom container for search states. This is smaller and faster than a hash
-// map, because the used states are dense along diagonals.
-// Specifically, each state requires only 1 byte, whereas a hash_map would
-// require storing the key, which would come to at least 8 bytes. std::map has
-// an extra 32 bytes per node (3 pointers + 1 byte, padded), so even though
-// there are circumstances where this class can have kBlockSize overhead per
-// state, on average it does better than 40 bytes of overhead per state.
-// In addition, in unopt builds (the usual way tests are run) the fewer
-// allocations + better locality has this method running 10-50x faster than
-// std::map for inputs that are large enough to measure.
-class EditSearchMap {
- public:
- EditSearchMap(size_t left_size, size_t right_size)
- : left_size_(left_size), right_size_(right_size) {
- GTEST_CHECK_(left_size_ == left_size && right_size_ == right_size)
- << "Overflow in size: Arguments too large";
- }
-
- // Gets a mutable reference to a state - this is actually of type
- // EditSearchState - inserting if it does not exist.
- unsigned char& insert(UInt32 left, UInt32 right) {
- std::vector<UInt32>* vec;
- size_t index1;
- size_t index2;
- if (left > right) {
- vec = &left_nodes_;
- index1 = left - right - 1;
- index2 = right;
- } else {
- vec = &right_nodes_;
- index1 = right - left;
- index2 = left;
- }
- if (vec->size() <= index1) {
- GTEST_CHECK_(vec->size() == index1)
- << "Array diagonals should only grow by one " << vec->size() << " vs "
- << index1;
- vec->push_back(block_indices_.size());
- // Round up
- block_indices_.resize(
- block_indices_.size() +
- (DiagonalLength(left, right) + kBlockSize - 1) / kBlockSize,
- kUnallocatedBlock);
- }
- const size_t bucket = index2 / kBlockSize;
- const size_t pos_in_bucket = index2 % kBlockSize;
- UInt32& level2 = block_indices_[(*vec)[index1] + bucket];
- if (level2 == kUnallocatedBlock) {
- level2 = nodes_.size();
- size_t diagonal_length = DiagonalLength(left, right);
- GTEST_CHECK_(diagonal_length > index2)
- << diagonal_length << " " << index2;
- size_t block_size = kBlockSize;
- if (diagonal_length / kBlockSize == bucket) {
- // We can never get here if diagonal_length is a multiple of
- // kBlockSize, which is what we want, since this would evaluate to 0.
- block_size = diagonal_length % kBlockSize;
- }
- nodes_.resize(nodes_.size() + block_size);
- }
- return nodes_[level2 + pos_in_bucket];
- }
-
- size_t MemoryUsage() const {
- return nodes_.capacity() +
- sizeof(UInt32) * (left_nodes_.capacity() + right_nodes_.capacity() +
- block_indices_.capacity());
- }
-
- private:
- enum { kBlockSize = 1024, kUnallocatedBlock = 0xFFFFFFFFul };
-
- size_t DiagonalLength(UInt32 left, UInt32 right) const {
- return std::min(left_size_ - left, right_size_ - right) +
- (left < right ? left : right);
- }
-
- // The state space is conceptually a left_size_ by right_size_ sparse matrix
- // of EditSearchStates. However, due to the access pattern of the search, it
- // is much better to store the nodes per diagonal rather than per row.
- UInt32 left_size_;
- UInt32 right_size_;
- // The nodes are stored by diagonals, split in two: Those to the left of the
- // main diagonal are in left_nodes_, and everything else is in right_nodes_.
- // The values are indices into block_indices_.
- std::vector<UInt32> left_nodes_;
- std::vector<UInt32> right_nodes_;
- // Every entry here is an offset into the beginning of a kBlockSize-sized
- // block in nodes_. An entire diagonal is allocated together here; for a
- // diagonal of length <= kBlockSize, that's just a single entry, but for
- // longer diagonals multiple contiguous index entries will be reserved at
- // once. Unused entries will be assigned kUnallocatedBlock; this
- // double-indirect scheme is used to save memory in the cases when an entire
- // diagonal isn't needed.
- std::vector<UInt32> block_indices_;
- // This stores the actual EditSearchState data, pointed to by block_indices_.
- std::vector<unsigned char> nodes_;
-};
-
-struct EditHeapEntry {
- EditHeapEntry(UInt32 l, UInt32 r, UInt64 c, EditSearchState s)
- : left(l), right(r), cost(c), state(s) {}
-
- UInt32 left;
- UInt32 right;
- UInt64 cost : 61;
- // The state that the node will get when this entry is settled. Therefore,
- // this can never be kUnsettled.
- UInt64 state : 3;
-
- bool operator>(const EditHeapEntry& other) const { return cost > other.cost; }
-};
-
-// Need a min-queue, so invert the comparator.
-typedef std::priority_queue<EditHeapEntry, std::vector<EditHeapEntry>,
- std::greater<EditHeapEntry>>
- EditHeap;
-
-} // namespace
-
-std::vector<EditType> CalculateOptimalEdits(const std::vector<size_t>& left,
- const std::vector<size_t>& right,
- size_t* memory_usage) {
- const UInt64 kBaseCost = 100000;
- // We make replace a little more expensive than add/remove to lower
- // their priority.
- const UInt64 kReplaceCost = 100001;
- // In the common case where the vectors are the same (or almost the same)
- // size, we know that an add will have to be followed by some later remove
- // (or vice versa) in order to get the lengths to balance. We "borrow" some
- // of the cost of the later operation and bring it forward into the earlier
- // operation, to increase the cost of exploring (usually fruitlessly) around
- // the beginning of the graph.
- // However, there is a trade-off: This cheapens the cost of exploring around
- // the beginning of the graph (in one direction) when the vectors are
- // unequal in length. So we don't steal *all* the cost.
- // You can view this as a form of A*, using an admissable heuristic that has
- // been re-cast as a cost function that can be used in Dijkstra.
- const UInt64 kTowardsGoalCost = 50003;
- const UInt64 kAwayFromGoalCost = 2 * kBaseCost - kTowardsGoalCost;
-
- EditSearchMap node_map(left.size() + 1, right.size() + 1);
- EditHeap heap;
- heap.push(EditHeapEntry(0, 0, 0, kReplaceParent));
-
- while (!heap.empty()) {
- const EditHeapEntry current_entry = heap.top();
- heap.pop();
-
- UInt32 left_pos = current_entry.left;
- UInt32 right_pos = current_entry.right;
- unsigned char& current_state = node_map.insert(left_pos, right_pos);
- if (current_state != kUnsettled) {
- // Node was already settled by a previous entry in the priority queue,
- // this is a suboptimal path that should be ignored.
- continue;
- }
- current_state = current_entry.state;
-
- if (left_pos == left.size() && right_pos == right.size()) {
- // This is the normal exit point; if we terminate due to the heap being
- // empty, we'll fail a check later.
- break;
- }
-
- // Special case: Since the cost of a match is zero, we can immediately
- // settle the new node without putting it in the queue, since nothing can
- // have a smaller cost than it. Furthermore, we don't need to relax the
- // other two edges, since we know we don't need them: Any path from this
- // node that would use them has an path via the match that is at least as
- // cheap. Together, this means we can loop here until we stop matching.
- while (left_pos < left.size() && right_pos < right.size() &&
- left[left_pos] == right[right_pos]) {
- left_pos++;
- right_pos++;
- unsigned char& fast_forward_state = node_map.insert(left_pos, right_pos);
- if (fast_forward_state != kUnsettled) {
- // The search reached around and settled this node before settling the
- // base node. This means we're completely done with this iteration;
- // abort to the outer loop.
- goto outer_loop_bottom;
- // Otherwise, when can settle this node, even if it was created from
- // another state - we know the cost of settling it now is optimal.
- }
- fast_forward_state = kMatchParent;
- }
-
- // Relax adjacent nodes. We have no way to find or lower the cost of
- // existing entries in the heap, so we just push new entries and throw
- // them out at the top if the node is already settled. We *could* check to
- // see if they're already settled before pushing, but it turns out to be
- // ~not any faster, and more complicated to do so.
- //
- // If we're at an edge, there's only one node to relax.
- if (left_pos >= left.size()) {
- if (right_pos >= right.size()) {
- break; // Can happen due to the fast-path loop above.
- }
- heap.push(EditHeapEntry(left_pos, right_pos + 1,
- current_entry.cost + kTowardsGoalCost,
- kAddParent));
- continue;
- }
- if (right_pos >= right.size()) {
- heap.push(EditHeapEntry(left_pos + 1, right_pos,
- current_entry.cost + kTowardsGoalCost,
- kRemoveParent));
- continue;
- }
- // General case: Relax 3 edges.
- heap.push(EditHeapEntry(
- left_pos, right_pos + 1,
- current_entry.cost + (right.size() + left_pos > right_pos + left.size()
- ? kTowardsGoalCost
- : kAwayFromGoalCost),
- kAddParent));
- heap.push(EditHeapEntry(
- left_pos + 1, right_pos,
- current_entry.cost + (right.size() + left_pos < right_pos + left.size()
- ? kTowardsGoalCost
- : kAwayFromGoalCost),
- kRemoveParent));
- heap.push(EditHeapEntry(left_pos + 1, right_pos + 1,
- current_entry.cost + kReplaceCost, kReplaceParent));
- outer_loop_bottom : {} // Need the curlies to form a statement.
- }
-
- // Reconstruct the best path. We do it in reverse order.
- std::vector<EditType> best_path;
- UInt32 left_pos = left.size();
- UInt32 right_pos = right.size();
- while (left_pos != 0 || right_pos != 0) {
- GTEST_CHECK_(left_pos <= left.size() && right_pos <= right.size());
- // The node must already exist, but if it somehow doesn't, it will be
- // added as kUnsettled, which will crash below.
- const unsigned char state = node_map.insert(left_pos, right_pos);
- switch (state) {
- case kAddParent:
- right_pos--;
- break;
- case kRemoveParent:
- left_pos--;
- break;
- case kMatchParent:
- case kReplaceParent:
- left_pos--;
- right_pos--;
- break;
- default:
- GTEST_LOG_(FATAL) << "Unsettled node at " << left_pos << ","
- << right_pos;
- }
- best_path.push_back(static_cast<EditType>(state - 1));
- }
- std::reverse(best_path.begin(), best_path.end());
- if (memory_usage != NULL) {
- *memory_usage = node_map.MemoryUsage();
- }
- return best_path;
-}
-
-namespace {
-
-// Helper class to convert string into ids with deduplication.
-class InternalStrings {
- public:
- size_t GetId(const std::string* str) {
- IdMap::iterator it = ids_.find(str);
- if (it != ids_.end()) return it->second;
- size_t id = ids_.size();
- return ids_[str] = id;
- }
-
- private:
- struct IdMapCmp {
- bool operator()(const std::string* first, const std::string* second) const {
- return *first < *second;
- }
- };
- typedef std::map<const std::string*, size_t, IdMapCmp> IdMap;
- IdMap ids_;
-};
-
-} // namespace
-
-std::vector<EditType> CalculateOptimalEdits(
- const std::vector<std::string>& left,
- const std::vector<std::string>& right) {
- std::vector<size_t> left_ids, right_ids;
- {
- InternalStrings intern_table;
- for (size_t i = 0; i < left.size(); ++i) {
- left_ids.push_back(intern_table.GetId(&left[i]));
- }
- for (size_t i = 0; i < right.size(); ++i) {
- right_ids.push_back(intern_table.GetId(&right[i]));
- }
- }
- return CalculateOptimalEdits(left_ids, right_ids);
-}
-
-namespace {
-
-// Helper class that holds the state for one hunk and prints it out to the
-// stream.
-// It reorders adds/removes when possible to group all removes before all
-// adds. It also adds the hunk header before printing into the stream.
-class Hunk {
- public:
- Hunk(size_t left_start, size_t right_start)
- : left_start_(left_start),
- right_start_(right_start),
- adds_(),
- removes_(),
- common_() {}
-
- void PushLine(char edit, const char* line) {
- switch (edit) {
- case ' ':
- ++common_;
- FlushEdits();
- hunk_.push_back(std::make_pair(' ', line));
- break;
- case '-':
- ++removes_;
- hunk_removes_.push_back(std::make_pair('-', line));
- break;
- case '+':
- ++adds_;
- hunk_adds_.push_back(std::make_pair('+', line));
- break;
- }
- }
-
- void PrintTo(std::ostream* os) {
- PrintHeader(os);
- FlushEdits();
- for (std::list<std::pair<char, const char*> >::const_iterator it =
- hunk_.begin();
- it != hunk_.end(); ++it) {
- *os << it->first << it->second << "\n";
- }
- }
-
- bool has_edits() const { return adds_ || removes_; }
-
- private:
- void FlushEdits() {
- hunk_.splice(hunk_.end(), hunk_removes_);
- hunk_.splice(hunk_.end(), hunk_adds_);
- }
-
- // Print a unified diff header for one hunk.
- // The format is
- // "@@ -<left_start>,<left_length> +<right_start>,<right_length> @@"
- // where the left/right parts are omitted if unnecessary.
- void PrintHeader(std::ostream* ss) const {
- *ss << "@@ ";
- if (removes_) {
- *ss << "-" << left_start_ << "," << (removes_ + common_);
- }
- if (removes_ && adds_) {
- *ss << " ";
- }
- if (adds_) {
- *ss << "+" << right_start_ << "," << (adds_ + common_);
- }
- *ss << " @@\n";
- }
-
- size_t left_start_, right_start_;
- size_t adds_, removes_, common_;
- std::list<std::pair<char, const char*> > hunk_, hunk_adds_, hunk_removes_;
-};
-
-} // namespace
-
-// Create a list of diff hunks in Unified diff format.
-// Each hunk has a header generated by PrintHeader above plus a body with
-// lines prefixed with ' ' for no change, '-' for deletion and '+' for
-// addition.
-// 'context' represents the desired unchanged prefix/suffix around the diff.
-// If two hunks are close enough that their contexts overlap, then they are
-// joined into one hunk.
-std::string CreateUnifiedDiff(const std::vector<std::string>& left,
- const std::vector<std::string>& right,
- size_t context) {
- const std::vector<EditType> edits = CalculateOptimalEdits(left, right);
-
- size_t l_i = 0, r_i = 0, edit_i = 0;
- std::stringstream ss;
- while (edit_i < edits.size()) {
- // Find first edit.
- while (edit_i < edits.size() && edits[edit_i] == kEditMatch) {
- ++l_i;
- ++r_i;
- ++edit_i;
- }
-
- // Find the first line to include in the hunk.
- const size_t prefix_context = std::min(l_i, context);
- Hunk hunk(l_i - prefix_context + 1, r_i - prefix_context + 1);
- for (size_t i = prefix_context; i > 0; --i) {
- hunk.PushLine(' ', left[l_i - i].c_str());
- }
-
- // Iterate the edits until we found enough suffix for the hunk or the input
- // is over.
- size_t n_suffix = 0;
- for (; edit_i < edits.size(); ++edit_i) {
- if (n_suffix >= context) {
- // Continue only if the next hunk is very close.
- std::vector<EditType>::const_iterator it = edits.begin() + edit_i;
- while (it != edits.end() && *it == kEditMatch) ++it;
- if (it == edits.end() || (it - edits.begin()) - edit_i >= context) {
- // There is no next edit or it is too far away.
- break;
- }
- }
-
- EditType edit = edits[edit_i];
- // Reset count when a non match is found.
- n_suffix = edit == kEditMatch ? n_suffix + 1 : 0;
-
- if (edit == kEditMatch || edit == kEditRemove || edit == kEditReplace) {
- hunk.PushLine(edit == kEditMatch ? ' ' : '-', left[l_i].c_str());
- }
- if (edit == kEditAdd || edit == kEditReplace) {
- hunk.PushLine('+', right[r_i].c_str());
- }
-
- // Advance indices, depending on edit type.
- l_i += edit != kEditAdd;
- r_i += edit != kEditRemove;
- }
-
- if (!hunk.has_edits()) {
- // We are done. We don't want this hunk.
- break;
- }
-
- hunk.PrintTo(&ss);
- }
- return ss.str();
-}
-
-} // namespace internal
-} // namespace testing