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#pragma once
#include "coding/diff_patch_common.hpp"
#include "base/assert.hpp"
#include "base/base.hpp"
#include "std/algorithm.hpp"
#include "std/unordered_map.hpp"
#include "std/utility.hpp"
#include "std/vector.hpp"
namespace diff
{
template <class PatchWriterT, typename SizeT = uint64_t> class PatchCoder
{
public:
typedef SizeT size_type;
explicit PatchCoder(PatchWriterT & patchWriter)
: m_LastOperation(COPY), m_LastOpCode(0), m_PatchWriter(patchWriter)
{
}
void Delete(size_type n)
{
if (n != 0)
Op(DELETE, n);
}
void Copy(size_type n)
{
if (n != 0)
Op(COPY, n);
}
template <typename TIter> void Insert(TIter it, size_type n)
{
if (n != 0)
{
Op(INSERT, n);
m_PatchWriter.WriteData(it, n);
}
}
void Finalize()
{
WriteLasOp();
}
private:
void Op(Operation op, size_type n)
{
if (m_LastOperation == op)
{
m_LastOpCode += (n << 1);
return;
}
WriteLasOp();
m_LastOpCode = (n << 1) | ((m_LastOperation + 1) % 3 == op ? 0 : 1);
m_LastOperation = op;
}
void WriteLasOp()
{
if (m_LastOpCode != 0)
m_PatchWriter.WriteOperation(m_LastOpCode);
else
CHECK_EQUAL(m_LastOperation, COPY, ()); // "We were just initialized."
}
Operation m_LastOperation;
size_type m_LastOpCode;
PatchWriterT & m_PatchWriter;
};
// Find minimal patch, with no more than maxPatchSize edited values, that transforms A into B.
// Returns the length of the minimal patch, or -1 if no such patch found.
// Intermediate information is saved into tmpSink and can be used later to restore
// the resulting patch.
template <
typename TSignedWord, // Signed word, capable of storing position in text.
class TSrcVector, // Source data (A).
class TDstVector, // Destination data (B).
class TTmpFileSink // Sink to store temporary information.
>
TSignedWord DiffMyersSimple(TSrcVector const & A,
TDstVector const & B,
TSignedWord maxPatchSize,
TTmpFileSink & tmpSink)
{
ASSERT_GREATER(maxPatchSize, 0, ());
vector<TSignedWord> V(2 * maxPatchSize + 1);
for (TSignedWord d = 0; d <= maxPatchSize; ++d)
{
for (TSignedWord k = -d; k <= d; k += 2)
{
TSignedWord x;
if (k == -d || (k != d && V[maxPatchSize + k - 1] < V[maxPatchSize + k + 1]))
x = V[maxPatchSize + k + 1];
else
x = V[maxPatchSize + k - 1] + 1;
while (x < static_cast<TSignedWord>(A.size()) &&
x - k < static_cast<TSignedWord>(B.size()) &&
A[x] == B[x - k])
++x;
V[maxPatchSize + k] = x;
if (x == static_cast<TSignedWord>(A.size()) && x - k == static_cast<TSignedWord>(B.size()))
return d;
}
tmpSink.Write(&V[maxPatchSize - d], (2 * d + 1) * sizeof(TSignedWord));
}
return -1;
}
// Differ that just replaces old with new, with the only optimization of skipping equal values
// at the beginning and at the end.
class SimpleReplaceDiffer
{
public:
template <typename SrcIterT, typename DstIterT, class PatchCoderT>
void Diff(SrcIterT srcBeg, SrcIterT srcEnd,
DstIterT dstBeg, DstIterT dstEnd,
PatchCoderT & patchCoder)
{
typename PatchCoderT::size_type begCopy = 0;
for (; srcBeg != srcEnd && dstBeg != dstEnd && *srcBeg == *dstBeg; ++srcBeg, ++dstBeg)
++begCopy;
patchCoder.Copy(begCopy);
typename PatchCoderT::size_type endCopy = 0;
for (; srcBeg != srcEnd && dstBeg != dstEnd && *(srcEnd-1) == *(dstEnd-1); --srcEnd, --dstEnd)
++endCopy;
patchCoder.Delete(srcEnd - srcBeg);
patchCoder.Insert(dstBeg, dstEnd - dstBeg);
patchCoder.Copy(endCopy);
}
};
// Given FineGrainedDiff and rolling Hasher, DiffWithRollingHash splits the source sequence
// into chunks of size m_BlockSize, finds equal chunks in the destination sequence, using rolling
// hash to find good candidates, writes info about equal chunks into patchCoder and for everything
// between equal chunks, calls FineGrainedDiff::Diff().
template <class FineGrainedDiffT,
class HasherT,
class HashPosMultiMapT = unordered_multimap<typename HasherT::hash_type, uint64_t> >
class RollingHashDiffer
{
public:
explicit RollingHashDiffer(size_t blockSize,
FineGrainedDiffT const & fineGrainedDiff = FineGrainedDiffT())
: m_FineGrainedDiff(fineGrainedDiff), m_BlockSize(blockSize) {}
template <typename SrcIterT, typename DstIterT, class PatchCoderT>
void Diff(SrcIterT const srcBeg, SrcIterT const srcEnd,
DstIterT const dstBeg, DstIterT const dstEnd,
PatchCoderT & patchCoder)
{
if (srcEnd - srcBeg < m_BlockSize || dstEnd - dstBeg < m_BlockSize)
{
m_FineGrainedDiff.Diff(srcBeg, srcEnd, dstBeg, dstEnd, patchCoder);
return;
}
HasherT hasher;
HashPosMultiMapT srcHashes;
for (SrcIterT src = srcBeg; srcEnd - src >= m_BlockSize; src += m_BlockSize)
srcHashes.insert(HashPosMultiMapValue(hasher.Init(src, m_BlockSize), src - srcBeg));
SrcIterT srcLastDiff = srcBeg;
DstIterT dst = dstBeg, dstNext = dstBeg + m_BlockSize, dstLastDiff = dstBeg;
hash_type h = hasher.Init(dst, m_BlockSize);
while (dstNext != dstEnd)
{
pair<HashPosMultiMapIterator, HashPosMultiMapIterator> iters = srcHashes.equal_range(h);
if (iters.first != iters.second)
{
pos_type const srcLastDiffPos = srcLastDiff - srcBeg;
HashPosMultiMapIterator it = srcHashes.end();
for (HashPosMultiMapIterator i = iters.first; i != iters.second; ++i)
if (i->second >= srcLastDiffPos &&
(it == srcHashes.end() || i->second < it->second))
it = i;
if (it != srcHashes.end() &&
equal(srcBeg + it->second, srcBeg + it->second + m_BlockSize, dst))
{
pos_type srcBlockEqualPos = it->second;
m_FineGrainedDiff.Diff(srcLastDiff, srcBeg + srcBlockEqualPos,
dstLastDiff, dst, patchCoder);
patchCoder.Copy(m_BlockSize);
srcLastDiff = srcBeg + srcBlockEqualPos + m_BlockSize;
dst = dstLastDiff = dstNext;
if (dstEnd - dstNext < m_BlockSize)
break;
dstNext = dst + m_BlockSize;
h = hasher.Init(dst, m_BlockSize);
continue;
}
}
h = hasher.Scroll(*(dst++), *(dstNext++));
}
if (srcLastDiff != srcEnd || dstLastDiff != dstEnd)
m_FineGrainedDiff.Diff(srcLastDiff, srcEnd, dstLastDiff, dstEnd, patchCoder);
}
private:
typedef typename HasherT::hash_type hash_type;
typedef typename HashPosMultiMapT::value_type::second_type pos_type;
typedef typename HashPosMultiMapT::const_iterator HashPosMultiMapIterator;
typedef typename HashPosMultiMapT::value_type HashPosMultiMapValue;
FineGrainedDiffT m_FineGrainedDiff;
HasherT m_Hasher;
size_t m_BlockSize;
};
}
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