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Find best match between two bounds found by Paul Heckel's diff algorithm

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The best match is computed by Eugene W. Myers' O(ND) edit distance algorithm.
This commit is contained in:
Fangrui Song 2018-01-14 01:33:12 -08:00
parent eec5c77d6a
commit a47115208b
2 changed files with 79 additions and 121 deletions
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178
src/working_files.cc
View File

@ -6,10 +6,13 @@
#include <doctest/doctest.h>
#include <loguru.hpp>
#include <algorithm>
#include <climits>
namespace {
constexpr int kMaxDiff = 9;
lsPosition GetPositionForOffset(const std::string& content, int offset) {
if (offset >= content.size())
offset = (int)content.size() - 1;
@ -28,6 +31,39 @@ lsPosition GetPositionForOffset(const std::string& content, int offset) {
return result;
}
int MyersDiff(const char *a, int la, const char *b, int lb, int threshold) {
assert(threshold <= kMaxDiff);
static int v_static[kMaxDiff + 2];
const char *ea = a + la, *eb = b + lb;
// Strip prefix
for (; a < ea && b < eb && *a == *b; a++, b++) {}
// Strip suffix
for (; a < ea && b < eb && ea[-1] == eb[-1]; ea--, eb--) {}
la = ea - a;
lb = eb - b;
int* v = v_static + lb;
v[1] = 0;
for (int di = 0; di <= threshold; di++) {
int low = -di + 2 * std::max(0, di - lb), high = di - 2 * std::max(0, di - la);
for (int i = low; i <= high; i += 2) {
int x = i == -di || (i != di && v[i-1] < v[i+1]) ? v[i+1] : v[i-1] + 1,
y = x - i;
while (x < la && y < lb && a[x] == b[y])
x++, y++;
v[i] = x;
if (x == la && y == lb)
return di;
}
}
return threshold + 1;
}
int MyersDiff(const std::string& a, const std::string& b, int threshold) {
return MyersDiff(a.data(), a.size(), b.data(), b.size(), threshold);
}
} // namespace
std::vector<CXUnsavedFile> WorkingFiles::Snapshot::AsUnsavedFiles() const {
@ -57,20 +93,6 @@ void WorkingFile::SetIndexContent(const std::string& index_content) {
index_to_buffer.clear();
buffer_to_index.clear();
// TODO Remove
// Build lookup buffer.
index_lines_lookup.clear();
index_lines_lookup.reserve(index_lines.size());
for (int i = 0; i < index_lines.size(); ++i) {
std::string index_line = Trim(index_lines[i]);
auto it = index_lines_lookup.find(index_line);
if (it == index_lines_lookup.end())
index_lines_lookup[index_line] = {i + 1};
else
it->second.push_back(i + 1);
}
}
void WorkingFile::OnBufferContentUpdated() {
@ -79,20 +101,6 @@ void WorkingFile::OnBufferContentUpdated() {
index_to_buffer.clear();
buffer_to_index.clear();
// TODO Remove
// Build lookup buffer.
all_buffer_lines_lookup.clear();
all_buffer_lines_lookup.reserve(all_buffer_lines.size());
for (int i = 0; i < all_buffer_lines.size(); ++i) {
const std::string& buffer_line = all_buffer_lines[i];
auto it = all_buffer_lines_lookup.find(buffer_line);
if (it == all_buffer_lines_lookup.end())
all_buffer_lines_lookup[buffer_line] = {i + 1};
else
it->second.push_back(i + 1);
}
}
// Variant of Paul Heckel's diff algorithm
@ -141,7 +149,8 @@ void WorkingFile::ComputeLineMapping() {
for (auto h : index_hashes) {
if (from_index[i] >= 0) {
auto it = hash_to_unique.find(h);
if (it != hash_to_unique.end() && it->second >= 0) {
if (it != hash_to_unique.end() && it->second >= 0 &&
from_buffer[it->second] >= 0) {
from_index[i] = it->second;
from_buffer[it->second] = i;
} else
@ -150,6 +159,7 @@ void WorkingFile::ComputeLineMapping() {
i++;
}
std::fill(from_buffer.begin(), from_buffer.end(), -1);
for (i = 0; i < (int)index_hashes.size() - 1; i++) {
int j = from_index[i];
if (0 <= j && j + 1 < buffer_hashes.size() &&
@ -188,53 +198,29 @@ optional<int> WorkingFile::GetBufferLineFromIndexLine(int index_line) {
return nullopt;
}
// TODO Remove all_buffer_lines_lookup and only use diff
// Find the line in the cached index file. We'll try to find the most similar
// line in the buffer and return the index for that.
std::string index = Trim(index_lines[index_line - 1]);
auto buffer_it = all_buffer_lines_lookup.find(index);
if (buffer_it == all_buffer_lines_lookup.end()) {
if (index_to_buffer.empty())
ComputeLineMapping();
index_line--;
int up = index_line, down = index_line + 1;
while (up >= 0 && index_to_buffer[up] < 0)
up--;
while (down < int(index_to_buffer.size()) && index_to_buffer[down] < 0)
down++;
int ret;
if (up >= 0) {
if (down == int(index_to_buffer.size()) ||
index_line - up < down - index_line)
ret = index_to_buffer[up] - up + index_line;
else
ret = index_to_buffer[down] - down + index_line;
} else if (down < int(index_to_buffer.size()))
ret = index_to_buffer[down] - down + index_line;
else
if (index_to_buffer[index_line] >= 0)
return index_to_buffer[index_line] + 1;
int up = index_line, down = index_line;
while (--up >= 0 && index_to_buffer[up] < 0) {}
while (++down < int(index_to_buffer.size()) && index_to_buffer[down] < 0) {}
up = up < 0 ? 0 : index_to_buffer[up];
down = down >= int(index_to_buffer.size()) ? buffer_to_index.size() - 1
: index_to_buffer[down];
if (up > down)
return nullopt;
ret = std::max(ret, 0);
ret = std::min(ret, int(buffer_to_index.size()) - 1);
return ret + 1;
}
// TODO: Use levenshtein distance to find the best match (but only to an
// extent)
// From all the identical lines, return the one which is closest to
// |index_line|. There will usually only be one identical line.
assert(!buffer_it->second.empty());
int closest_dist = INT_MAX;
int closest_buffer_line = INT_MIN;
for (int buffer_line : buffer_it->second) {
int dist = std::abs(buffer_line - index_line);
if (dist <= closest_dist) {
closest_dist = dist;
closest_buffer_line = buffer_line;
int best = up, best_dist = kMaxDiff + 1;
const std::string& needle = Trim(index_lines[index_line]);
for (int i = up; i <= down; i++) {
int dist = MyersDiff(needle, all_buffer_lines[i], kMaxDiff);
if (dist < best_dist) {
best_dist = dist;
best = i;
}
}
return closest_buffer_line;
return best + 1;
}
optional<int> WorkingFile::GetIndexLineFromBufferLine(int buffer_line) {
@ -250,49 +236,27 @@ optional<int> WorkingFile::GetIndexLineFromBufferLine(int buffer_line) {
return nullopt;
}
// Find the line in the index file. We'll try to find the most similar line
// in the index file and return the index for that.
std::string buffer = all_buffer_lines[buffer_line - 1];
auto index_it = index_lines_lookup.find(buffer);
if (index_it == index_lines_lookup.end()) {
if (buffer_to_index.empty())
ComputeLineMapping();
buffer_line--;
int up = buffer_line, down = buffer_line + 1;
while (up >= 0 && buffer_to_index[up] < 0)
up--;
while (down < int(buffer_to_index.size()) && buffer_to_index[down] < 0)
down++;
int ret;
if (up >= 0) {
if (down == int(buffer_to_index.size()) ||
buffer_line - up <= down - buffer_line)
ret = buffer_to_index[up] - up + buffer_line;
else
ret = buffer_to_index[down] - down + buffer_line;
} else if (down < int(buffer_to_index.size()))
ret = buffer_to_index[down] - down + buffer_line;
else
int up = buffer_line, down = buffer_line;
while (--up >= 0 && buffer_to_index[up] < 0) {}
while (++down < int(buffer_to_index.size()) && buffer_to_index[down] < 0) {}
up = up < 0 ? 0 : buffer_to_index[up];
down = down >= int(buffer_to_index.size()) ? index_to_buffer.size() - 1
: buffer_to_index[down];
if (up > down)
return nullopt;
ret = std::max(ret, 0);
ret = std::min(ret, int(index_to_buffer.size()) - 1);
return ret + 1;
}
// From all the identical lines, return the one which is closest to
// |index_line|. There will usually only be one identical line.
assert(!index_it->second.empty());
int closest_dist = INT_MAX;
int closest_index_line = INT_MIN;
for (int index_line : index_it->second) {
int dist = std::abs(buffer_line - index_line);
if (dist <= closest_dist) {
closest_dist = dist;
closest_index_line = index_line;
int best = up, best_dist = kMaxDiff + 1;
const std::string& needle = Trim(raw_buffer_lines[buffer_line]);
for (int i = up; i <= down; i++) {
int dist = MyersDiff(needle, index_lines[i], kMaxDiff);
if (dist < best_dist) {
best_dist = dist;
best = i;
}
}
return closest_index_line;
return best + 1;
}
optional<std::string> WorkingFile::GetBufferLineContentFromIndexLine(

6
src/working_files.h
View File

@ -21,12 +21,6 @@ struct WorkingFile {
std::vector<std::string> all_buffer_lines;
// Note: This assumes 0-based lines (1-based lines are normally assumed).
std::vector<std::string> raw_buffer_lines;
// This map goes from disk-line -> indicies+1 in index_lines.
// Note: The items in the value entry are 1-based lines.
std::unordered_map<std::string, std::vector<int>> index_lines_lookup;
// This map goes from buffer-line -> indices+1 in all_buffer_lines.
// Note: The items in the value entry are 1-based liness.
std::unordered_map<std::string, std::vector<int>> all_buffer_lines_lookup;
// Mappings between index line number and buffer line number.
// Empty indicates stale.
std::vector<int> index_to_buffer;