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DiffEngine.h
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DiffEngine.h
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/**
* GPL blah blah, see below for history
*/
#ifndef DIFFENGINE_H
#define DIFFENGINE_H
//#define USE_JUDY
#include <vector>
#include <map>
#include <set>
#include <utility>
#include <algorithm>
#include <cassert>
#include <string>
#include <numeric>
#ifdef USE_JUDY
#include "JudyHS.h"
#endif
#include "Wikidiff2.h"
#include "Word.h"
#include "textutil.h"
#ifdef HHVM_BUILD_DSO
#include "hphp/runtime/base/ini-setting.h"
#endif //HHVM_BUILD_DSO
#define WIKIDIFF2_CHANGE_THRESHOLD_DEFAULT "0.2"
#define WIKIDIFF2_MOVED_LINE_THRESHOLD_DEFAULT "0.4"
#ifdef DEBUG_MOVED_LINES
inline void debugLog(const char *fmt, ...) {
static FILE *f = nullptr;
char ch[2048];
va_list ap;
va_start(ap, fmt);
vsnprintf(ch, sizeof(ch), fmt, ap);
va_end(ap);
if(!f) f = fopen("/tmp/wd2-debug-log.log", "a");
if(!f) throw std::runtime_error("failed to open debug log...");
fwrite(ch, 1, strlen(ch), f);
fflush(f);
};
#else
#define debugLog(...)
#endif
struct WordDiffStats
{
int charsTotal = 0;
int opCharCount[4] = { 0 };
double charSimilarity;
WordDiffStats(TextUtil::WordVector& words1, TextUtil::WordVector& words2, long long bailoutComplexity);
};
/**
* Diff operation
*
* from and to are vectors containing pointers to the objects passed in from_lines and to_lines
*
* op is one of the following
* copy: A sequence of lines (in from and to) which are the same in both files.
* del: A sequence of lines (in from) which were in the first file but not the second.
* add: A sequence of lines (in to) which were in the second file but not the first.
* change: A sequence of lines which are different between the two files. Lines from the
* first file are in from, lines from the second are in to. The two vectors need
* not be the same length.
*/
template<typename T>
class DiffOp
{
public:
typedef std::vector<const T*, WD2_ALLOCATOR<const T*> > PointerVector;
DiffOp(int op_, const PointerVector & from_, const PointerVector & to_)
: op(op_), from(from_), to(to_) {}
enum {copy, del, add, change};
int op;
PointerVector from;
PointerVector to;
};
/**
* Basic diff template class. After construction, edits will contain a vector of DiffOpTemplate
* objects representing the diff
*/
template<typename T>
class Diff
{
public:
typedef std::vector<T, WD2_ALLOCATOR<T> > ValueVector;
typedef std::vector<DiffOp<T>, WD2_ALLOCATOR<T> > DiffOpVector;
Diff(const ValueVector & from_lines, const ValueVector & to_lines,
long long bailoutComplexity = 0);
virtual void add_edit(const DiffOp<T> & edit) {
edits.push_back(edit);
}
unsigned size() { return edits.size(); }
DiffOp<T> & operator[](int i) {return edits[i];}
DiffOpVector edits;
};
/**
* Class used internally by Diff to actually compute the diffs.
*
* The algorithm used here is mostly lifted from the perl module
* Algorithm::Diff (version 1.06) by Ned Konz, which is available at:
* http://www.perl.com/CPAN/authors/id/N/NE/NEDKONZ/Algorithm-Diff-1.06.zip
*
* More ideas are taken from:
* http://www.ics.uci.edu/~eppstein/161/960229.html
*
* Some ideas are (and a bit of code) are from from analyze.c, from GNU
* diffutils-2.7, which can be found at:
* ftp://gnudist.gnu.org/pub/gnu/diffutils/diffutils-2.7.tar.gz
*
* This implementation is largely due to Geoffrey T. Dairiki, who wrote this
* diff engine for phpwiki 1-3.3. It was then adopted by MediaWiki.
*
* Finally, it was ported to C++ by Tim Starling in February 2006
*
* @access private
*/
template<typename T>
class DiffEngine
{
public:
// Vectors
typedef std::vector<bool> BoolVector; // skip the allocator here to get the specialisation
typedef std::vector<const T*, WD2_ALLOCATOR<const T*> > PointerVector;
typedef std::vector<T, WD2_ALLOCATOR<T> > ValueVector;
typedef std::vector<int, WD2_ALLOCATOR<int> > IntVector;
typedef std::vector<std::pair<int, int>, WD2_ALLOCATOR<std::pair<int, int> > > IntPairVector;
// Maps
#ifdef USE_JUDY
typedef JudyHS<IntVector> MatchesMap;
#else
typedef std::map<T, IntVector, std::less<T>, WD2_ALLOCATOR<IntVector> > MatchesMap;
#endif
// Sets
typedef std::set<int, std::less<int>, WD2_ALLOCATOR<int> > IntSet;
#ifdef USE_JUDY
typedef JudySet ValueSet;
#else
typedef std::set<T, std::less<T>, WD2_ALLOCATOR<T> > ValueSet;
#endif
DiffEngine() : done(false) {}
void clear();
void diff (const ValueVector & from_lines,
const ValueVector & to_lines, Diff<T> & diff,
long long bailoutComplexity = 0);
int lcs_pos (int ypos);
void compareseq (int xoff, int xlim, int yoff, int ylim);
void shift_boundaries (const ValueVector & lines, BoolVector & changed,
const BoolVector & other_changed);
protected:
int diag (int xoff, int xlim, int yoff, int ylim, int nchunks,
IntPairVector & seps);
BoolVector xchanged, ychanged;
PointerVector xv, yv;
IntVector xind, yind;
IntVector seq;
IntSet in_seq;
int lcs;
bool done;
enum {MAX_CHUNKS=8};
void detectDissimilarChanges(PointerVector& del, PointerVector& add, Diff<T>& diff, long long bailoutComplexity);
bool looksLikeChange(const T& del, const T& add, long long bailoutComplexity);
void writeChange(Diff<T>& diff, PointerVector& del, PointerVector& add, const PointerVector& empty);
};
//-----------------------------------------------------------------------------
// DiffEngine implementation
//-----------------------------------------------------------------------------
template<typename T>
void DiffEngine<T>::clear()
{
xchanged.clear();
ychanged.clear();
xv.clear();
yv.clear();
xind.clear();
yind.clear();
seq.clear();
in_seq.clear();
done = false;
}
inline double characterSimilarityThreshold()
{
#ifdef HHVM_BUILD_DSO
// HHVM module
HPHP::Variant value(WIKIDIFF2_CHANGE_THRESHOLD_DEFAULT);
HPHP::IniSetting::Get(std::string("wikidiff2.change_threshold"), value);
return value.toDouble();
#else
// Zend module
double ret = INI_FLT("wikidiff2.change_threshold");
return ret;
#endif //HHVM_BUILD_DSO
}
inline double movedLineThreshold()
{
#ifdef HHVM_BUILD_DSO
// HHVM module
HPHP::Variant value(WIKIDIFF2_MOVED_LINE_THRESHOLD_DEFAULT);
HPHP::IniSetting::Get(std::string("wikidiff2.moved_line_threshold"), value);
return value.toDouble();
#else
// Zend module
double ret = INI_FLT("wikidiff2.moved_line_threshold");
return ret;
#endif //HHVM_BUILD_DSO
}
// for a DiffOp::change, decide whether it should be treated as a successive add and delete based on similarity.
template<typename T>
inline bool DiffEngine<T>::looksLikeChange(const T& del, const T& add, long long bailoutComplexity)
{
TextUtil::WordVector words1, words2;
TextUtil::explodeWords(del, words1);
TextUtil::explodeWords(add, words2);
WordDiffStats ds(words1, words2, bailoutComplexity);
return ds.charSimilarity > characterSimilarityThreshold();
}
// go through list of changed lines. if they are too dissimilar, convert to del+add.
template<typename T>
inline void DiffEngine<T>::detectDissimilarChanges(PointerVector& del, PointerVector& add, Diff<T>& diff, long long bailoutComplexity)
{
int i;
static PointerVector empty;
int lastChange = 0;
for (i = 0; i < del.size() && i < add.size(); ++i) {
if (!looksLikeChange(*del[i], *add[i], bailoutComplexity)) {
if(i > lastChange) {
// add the changed segment
PointerVector d, a;
int changeBegin = lastChange;
for(; lastChange < i; ++lastChange) {
d.push_back(del[lastChange]);
a.push_back(add[lastChange]);
}
diff.add_edit(DiffOp<T>(DiffOp<T>::change, d, a));
add.erase(add.begin() + changeBegin, add.begin() + i);
del.erase(del.begin() + changeBegin, del.begin() + i);
i -= (lastChange - changeBegin);
}
// convert dissimilar piece to delete + add
PointerVector d, a;
d.push_back(del[i]);
a.push_back(add[i]);
diff.add_edit(DiffOp<T>(DiffOp<T>::add, empty, a));
diff.add_edit(DiffOp<T>(DiffOp<T>::del, d, empty));
add.erase(add.begin() + i);
del.erase(del.begin() + i);
--i;
}
}
}
template<>
inline void DiffEngine<Word>::detectDissimilarChanges(PointerVector& del, PointerVector& add, Diff<Word>& diff, long long bailoutComplexity)
{
// compiles to no-op in Word specialization.
}
template<typename T>
void DiffEngine<T>::diff (const ValueVector & from_lines,
const ValueVector & to_lines, Diff<T> & diff,
long long bailoutComplexity /* = 0 */)
{
int n_from = (int)from_lines.size();
int n_to = (int)to_lines.size();
// If this diff engine has been used before for a diff, clear the member variables
if (done) {
clear();
}
xchanged.resize(n_from);
ychanged.resize(n_to);
seq.resize(std::max(n_from, n_to) + 1);
// Skip leading common lines.
int skip, endskip;
for (skip = 0; skip < n_from && skip < n_to; skip++) {
if (from_lines[skip] != to_lines[skip])
break;
xchanged[skip] = ychanged[skip] = false;
}
// Skip trailing common lines.
int xi = n_from, yi = n_to;
for (endskip = 0; --xi > skip && --yi > skip; endskip++) {
if (from_lines[xi] != to_lines[yi])
break;
xchanged[xi] = ychanged[yi] = false;
}
long long complexity = (long long)(n_from - skip - endskip)
* (n_to - skip - endskip);
// If too complex, just output "whole left side replaced with right"
if (bailoutComplexity > 0 && complexity > bailoutComplexity) {
PointerVector del;
PointerVector add;
for (xi = 0; xi < n_from; xi++) {
del.push_back(&from_lines[xi]);
}
for (yi = 0; yi < n_to; yi++) {
add.push_back(&to_lines[yi]);
}
diff.add_edit(DiffOp<T>(DiffOp<T>::change, del, add));
done = true;
return;
}
// Ignore lines which do not exist in both files.
ValueSet xhash, yhash;
for (xi = skip; xi < n_from - endskip; xi++) {
xhash.insert(from_lines[xi]);
}
for (yi = skip; yi < n_to - endskip; yi++) {
const T & line = to_lines[yi];
if ( (ychanged[yi] = (xhash.find(line) == xhash.end())) )
continue;
yhash.insert(line);
yv.push_back(&line);
yind.push_back(yi);
}
for (xi = skip; xi < n_from - endskip; xi++) {
const T & line = from_lines[xi];
if ( (xchanged[xi] = (yhash.find(line) == yhash.end())) )
continue;
xv.push_back(&line);
xind.push_back(xi);
}
// Find the LCS.
compareseq(0, xv.size(), 0, yv.size());
// Merge edits when possible
shift_boundaries(from_lines, xchanged, ychanged);
shift_boundaries(to_lines, ychanged, xchanged);
// Compute the edit operations.
xi = yi = 0;
while (xi < n_from || yi < n_to) {
assert(yi < n_to || xchanged[xi]);
assert(xi < n_from || ychanged[yi]);
// Skip matching "snake".
PointerVector del;
PointerVector add;
PointerVector empty;
while (xi < n_from && yi < n_to && !xchanged[xi] && !ychanged[yi]) {
del.push_back(&from_lines[xi]);
add.push_back(&to_lines[yi]);
++xi;
++yi;
}
if (del.size()) {
diff.add_edit(DiffOp<T>(DiffOp<T>::copy, del, add));
del.clear();
add.clear();
}
// Find deletes & adds.
while (xi < n_from && xchanged[xi])
del.push_back(&from_lines[xi++]);
while (yi < n_to && ychanged[yi])
add.push_back(&to_lines[yi++]);
detectDissimilarChanges(del, add, diff, bailoutComplexity);
if (del.size() && add.size()) {
writeChange(diff, del, add, empty);
} else if (del.size())
diff.add_edit(DiffOp<T>(DiffOp<T>::del, del, empty));
else if (add.size())
diff.add_edit(DiffOp<T>(DiffOp<T>::add, empty, add));
}
done = true;
}
template<class T>
inline void DiffEngine<T>::writeChange(Diff<T>& diff, PointerVector& del, PointerVector& add, const PointerVector& empty)
{
if ( del.size() == add.size() ) {
diff.add_edit(DiffOp<T>(DiffOp<T>::change, del, add));
} else {
// this is a change containing added and deleted lines; convert them to the right DiffOps so the
// moved paragraph detection code gets a chance to see them
size_t commonSize = std::min(del.size(), add.size());
PointerVector changeDel(del.begin(), del.begin() + commonSize);
PointerVector changeAdd(add.begin(), add.begin() + commonSize);
diff.add_edit(DiffOp<T>(DiffOp<T>::change, changeDel, changeAdd));
if (del.size() > commonSize)
diff.add_edit(DiffOp<T>(DiffOp<T>::del, PointerVector(del.begin() + commonSize, del.end()), empty));
if (add.size() > commonSize)
diff.add_edit(DiffOp<T>(DiffOp<T>::add, empty, PointerVector(add.begin() + commonSize, add.end())));
}
}
template<>
inline void DiffEngine<Word>::writeChange(Diff<Word>& diff, PointerVector& del, PointerVector& add, const PointerVector& empty)
{
diff.add_edit(DiffOp<Word>(DiffOp<Word>::change, del, add));
}
/* Divide the Largest Common Subsequence (LCS) of the sequences
* [XOFF, XLIM) and [YOFF, YLIM) into NCHUNKS approximately equally
* sized segments.
*
* Returns (LCS, SEPS). LCS is the length of the LCS. SEPS is an
* array of NCHUNKS+1 (X, Y) indexes giving the diving points between
* sub sequences. The first sub-sequence is contained in [X0, X1),
* [Y0, Y1), the second in [X1, X2), [Y1, Y2) and so on. Note
* that (X0, Y0) == (XOFF, YOFF) and
* (X[NCHUNKS], Y[NCHUNKS]) == (XLIM, YLIM).
*
* This function assumes that the first lines of the specified portions
* of the two files do not match, and likewise that the last lines do not
* match. The caller must trim matching lines from the beginning and end
* of the portions it is going to specify.
*/
template <typename T>
int DiffEngine<T>::diag (int xoff, int xlim, int yoff, int ylim, int nchunks,
IntPairVector & seps)
{
using std::swap;
using std::make_pair;
using std::copy;
bool flip = false;
MatchesMap ymatches;
if (xlim - xoff > ylim - yoff) {
// Things seems faster (I'm not sure I understand why)
// when the shortest sequence in X.
flip = true;
swap(xoff, yoff);
swap(xlim, ylim);
}
if (flip)
for (int i = ylim - 1; i >= yoff; i--)
ymatches[*xv[i]].push_back(i);
else
for (int i = ylim - 1; i >= yoff; i--)
ymatches[*yv[i]].push_back(i);
int nlines = ylim - yoff;
lcs = 0;
seq[0] = yoff - 1;
in_seq.clear();
// 2-d array, line major, chunk minor
IntVector ymids(nlines * nchunks);
int numer = xlim - xoff + nchunks - 1;
int x = xoff, x1, y1;
for (int chunk = 0; chunk < nchunks; chunk++) {
if (chunk > 0)
for (int i = 0; i <= lcs; i++)
ymids.at(i * nchunks + chunk-1) = seq[i];
x1 = xoff + (int)((numer + (xlim-xoff)*chunk) / nchunks);
for ( ; x < x1; x++) {
const T & line = flip ? *yv[x] : *xv[x];
#ifdef USE_JUDY
IntVector * pMatches = ymatches.Get(line);
if (!pMatches)
continue;
#else
typename MatchesMap::iterator iter = ymatches.find(line);
if (iter == ymatches.end())
continue;
IntVector * pMatches = &(iter->second);
#endif
IntVector::iterator y;
int k = 0;
for (y = pMatches->begin(); y != pMatches->end(); ++y) {
if (!in_seq.count(*y)) {
k = lcs_pos(*y);
assert(k > 0);
copy(ymids.begin() + (k-1) * nchunks, ymids.begin() + k * nchunks,
ymids.begin() + k * nchunks);
++y;
break;
}
}
for ( ; y != pMatches->end(); ++y) {
if (*y > seq[k-1]) {
assert(*y < seq[k]);
// Optimization: this is a common case:
// next match is just replacing previous match.
in_seq.erase(seq[k]);
seq[k] = *y;
in_seq.insert(*y);
} else if (!in_seq.count(*y)) {
k = lcs_pos(*y);
assert(k > 0);
copy(ymids.begin() + (k-1) * nchunks, ymids.begin() + k * nchunks,
ymids.begin() + k * nchunks);
}
}
}
}
seps.clear();
seps.resize(nchunks + 1);
seps[0] = flip ? make_pair(yoff, xoff) : make_pair(xoff, yoff);
IntVector::iterator ymid = ymids.begin() + lcs * nchunks;
for (int n = 0; n < nchunks - 1; n++) {
x1 = xoff + (numer + (xlim - xoff) * n) / nchunks;
y1 = ymid[n] + 1;
seps[n+1] = flip ? make_pair(y1, x1) : make_pair(x1, y1);
}
seps[nchunks] = flip ? make_pair(ylim, xlim) : make_pair(xlim, ylim);
return lcs;
}
template <typename T>
int DiffEngine<T>::lcs_pos (int ypos) {
int end = lcs;
if (end == 0 || ypos > seq[end]) {
seq[++lcs] = ypos;
in_seq.insert(ypos);
return lcs;
}
int beg = 1;
while (beg < end) {
int mid = (beg + end) / 2;
if ( ypos > seq[mid] )
beg = mid + 1;
else
end = mid;
}
assert(ypos != seq[end]);
in_seq.erase(seq[end]);
seq[end] = ypos;
in_seq.insert(ypos);
return end;
}
/* Find LCS of two sequences.
*
* The results are recorded in the vectors {x,y}changed[], by
* storing a 1 in the element for each line that is an insertion
* or deletion (ie. is not in the LCS).
*
* The subsequence of file 0 is [XOFF, XLIM) and likewise for file 1.
*
* Note that XLIM, YLIM are exclusive bounds.
* All line numbers are origin-0 and discarded lines are not counted.
*/
template <typename T>
void DiffEngine<T>::compareseq (int xoff, int xlim, int yoff, int ylim) {
using std::pair;
IntPairVector seps;
int lcs;
// Slide down the bottom initial diagonal.
while (xoff < xlim && yoff < ylim && *xv[xoff] == *yv[yoff]) {
++xoff;
++yoff;
}
// Slide up the top initial diagonal.
while (xlim > xoff && ylim > yoff && *xv[xlim - 1] == *yv[ylim - 1]) {
--xlim;
--ylim;
}
if (xoff == xlim || yoff == ylim)
lcs = 0;
else {
// This is ad hoc but seems to work well.
//nchunks = sqrt(min(xlim - xoff, ylim - yoff) / 2.5);
//nchunks = max(2,min(8,(int)nchunks));
int nchunks = std::min(MAX_CHUNKS-1, std::min(xlim - xoff, ylim - yoff)) + 1;
lcs = diag(xoff, xlim, yoff, ylim, nchunks, seps);
}
if (lcs == 0) {
// X and Y sequences have no common subsequence:
// mark all changed.
while (yoff < ylim)
ychanged[yind[yoff++]] = true;
while (xoff < xlim)
xchanged[xind[xoff++]] = true;
} else {
// Use the partitions to split this problem into subproblems.
IntPairVector::iterator pt1, pt2;
pt1 = pt2 = seps.begin();
while (++pt2 != seps.end()) {
compareseq (pt1->first, pt2->first, pt1->second, pt2->second);
pt1 = pt2;
}
}
}
/* Adjust inserts/deletes of identical lines to join changes
* as much as possible.
*
* We do something when a run of changed lines include a
* line at one end and has an excluded, identical line at the other.
* We are free to choose which identical line is included.
* `compareseq' usually chooses the one at the beginning,
* but usually it is cleaner to consider the following identical line
* to be the "change".
*
* This is extracted verbatim from analyze.c (GNU diffutils-2.7).
*/
template <typename T>
void DiffEngine<T>::shift_boundaries (const ValueVector & lines, BoolVector & changed,
const BoolVector & other_changed)
{
int i = 0;
int j = 0;
int len = (int)lines.size();
int other_len = (int)other_changed.size();
while (1) {
/*
* Scan forwards to find beginning of another run of changes.
* Also keep track of the corresponding point in the other file.
*
* Throughout this code, i and j are adjusted together so that
* the first i elements of changed and the first j elements
* of other_changed both contain the same number of zeros
* (unchanged lines).
* Furthermore, j is always kept so that j == other_len or
* other_changed[j] == false.
*/
while (j < other_len && other_changed[j])
j++;
while (i < len && ! changed[i]) {
i++; j++;
while (j < other_len && other_changed[j])
j++;
}
if (i == len)
break;
int start = i, runlength, corresponding;
// Find the end of this run of changes.
while (++i < len && changed[i])
continue;
do {
/*
* Record the length of this run of changes, so that
* we can later determine whether the run has grown.
*/
runlength = i - start;
/*
* Move the changed region back, so long as the
* previous unchanged line matches the last changed one.
* This merges with previous changed regions.
*/
while (start > 0 && lines[start - 1] == lines[i - 1]) {
changed[--start] = true;
changed[--i] = false;
while (start > 0 && changed[start - 1])
start--;
while (other_changed[--j])
continue;
}
/*
* Set CORRESPONDING to the end of the changed run, at the last
* point where it corresponds to a changed run in the other file.
* CORRESPONDING == LEN means no such point has been found.
*/
corresponding = j < other_len ? i : len;
/*
* Move the changed region forward, so long as the
* first changed line matches the following unchanged one.
* This merges with following changed regions.
* Do this second, so that if there are no merges,
* the changed region is moved forward as far as possible.
*/
while (i < len && lines[start] == lines[i]) {
changed[start++] = false;
changed[i++] = true;
while (i < len && changed[i])
i++;
j++;
if (j < other_len && other_changed[j]) {
corresponding = i;
while (j < other_len && other_changed[j])
j++;
}
}
} while (runlength != i - start);
/*
* If possible, move the fully-merged run of changes
* back to a corresponding run in the other file.
*/
while (corresponding < i) {
changed[--start] = 1;
changed[--i] = 0;
while (other_changed[--j])
continue;
}
}
}
//-----------------------------------------------------------------------------
// Diff implementation
//-----------------------------------------------------------------------------
template<typename T>
Diff<T>::Diff(const ValueVector & from_lines, const ValueVector & to_lines,
long long bailoutComplexity)
{
DiffEngine<T> engine;
engine.diff(from_lines, to_lines, *this, bailoutComplexity);
}
inline WordDiffStats::WordDiffStats(TextUtil::WordVector& words1, TextUtil::WordVector& words2, long long bailoutComplexity)
{
auto countOpChars = [] (DiffEngine<Word>::PointerVector& p) {
return std::accumulate(p.begin(), p.end(), 0, [] (int a, const Word *b) {
return a + (b->suffixEnd - b->bodyStart);
});
};
Diff<Word> diff(words1, words2, bailoutComplexity);
for (int i = 0; i < diff.size(); ++i) {
int op = diff[i].op;
int charCount;
switch (op) {
case DiffOp<Word>::del:
case DiffOp<Word>::copy:
charCount = countOpChars(diff[i].from);
break;
case DiffOp<Word>::add:
charCount = countOpChars(diff[i].to);
break;
case DiffOp<Word>::change:
charCount = std::max(countOpChars(diff[i].from), countOpChars(diff[i].to));
break;
}
opCharCount[op] += charCount;
charsTotal += charCount;
}
if (opCharCount[DiffOp<Word>::copy] == 0) {
charSimilarity = 0.0;
} else {
if (charsTotal) {
charSimilarity = double(opCharCount[DiffOp<Word>::copy]) / charsTotal;
} else {
charSimilarity = 0.0;
}
}
}
#endif