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ByteVector::replace performance improvements

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This commit is contained in:
Mathias Panzenböck 2011-08-01 04:13:55 +02:00
parent fb2decb7de
commit ad7645f8e9
1 changed files with 50 additions and 20 deletions
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70
taglib/toolkit/tbytevector.cpp
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@ -431,29 +431,59 @@ ByteVector &ByteVector::replace(const ByteVector &pattern, const ByteVector &wit
if(pattern.size() == 0 || pattern.size() > size())
return *this;
const int patternSize = pattern.size();
const int withSize = with.size();
const uint withSize = with.size();
const uint patternSize = pattern.size();
int offset = 0;
int offset = find(pattern);
while(offset >= 0) {
const int originalSize = size();
if(withSize > patternSize)
resize(originalSize + withSize - patternSize);
if(patternSize != withSize)
::memcpy(data() + offset + withSize, mid(offset + patternSize).data(), originalSize - offset - patternSize);
if(withSize < patternSize)
resize(originalSize + withSize - patternSize);
::memcpy(data() + offset, with.data(), withSize);
offset = find(pattern, offset + withSize);
if(withSize == patternSize) {
// I think this case might be common enough to optimize it
offset = find(pattern);
while(offset >= 0) {
::memcpy(data() + offset, with.data(), withSize);
offset = find(pattern, offset + withSize);
}
return *this;
}
// calculate new size:
uint newSize = 0;
for(;;) {
int next = find(pattern, offset);
if(next < 0) {
newSize += size() - offset;
break;
}
newSize += (next - offset) + withSize;
offset = next + patternSize;
}
// new private data of appropriate size:
ByteVectorPrivate *newData = new ByteVectorPrivate(newSize, 0);
char *target = &newData->data[0];
const char *source = data();
// copy modified data into new private data:
offset = 0;
for(;;) {
int next = find(pattern, offset);
if(next < 0) {
::memcpy(target, source + offset, size() - offset);
break;
}
int chunkSize = next - offset;
::memcpy(target, source + offset, chunkSize);
target += chunkSize;
::memcpy(target, with.data(), withSize);
target += withSize;
offset += chunkSize + patternSize;
}
// replace private data:
if(d->deref())
delete d;
d = newData;
return *this;
}