long File::rfind(const ByteVector &pattern, long fromOffset, const ByteVector &before)
{
if(!d->stream || pattern.size() > d->bufferSize)
return -1;
// The position in the file that the current buffer starts at.
ByteVector buffer;
// These variables are used to keep track of a partial match that happens at
// the end of a buffer.
/*
int previousPartialMatch = -1;
int beforePreviousPartialMatch = -1;
*/
// Save the location of the current read pointer. We will restore the
// position using seek() before all returns.
long originalPosition = tell();
// Start the search at the offset.
long bufferOffset;
if(fromOffset == 0) {
seek(-1 * int(d->bufferSize), End);
bufferOffset = tell();
}
else {
seek(fromOffset + -1 * int(d->bufferSize), Beginning);
bufferOffset = tell();
}
// See the notes in find() for an explanation of this algorithm.
for(buffer = readBlock(d->bufferSize); buffer.size() > 0; buffer = readBlock(d->bufferSize)) {
// TODO: (1) previous partial match
// (2) pattern contained in current buffer
long location = buffer.rfind(pattern);
if(location >= 0) {
seek(originalPosition);
return bufferOffset + location;
}
if(!before.isNull() && buffer.find(before) >= 0) {
seek(originalPosition);
return -1;
}
// TODO: (3) partial match
bufferOffset -= d->bufferSize;
seek(bufferOffset);
}
// Since we hit the end of the file, reset the status before continuing.
clear();
seek(originalPosition);
return -1;
}
long File::rfind(const ByteVector &pattern, long fromOffset, const ByteVector &before)
{
if(!d->stream || pattern.size() > bufferSize())
return -1;
// The position in the file that the current buffer starts at.
ByteVector buffer;
// These variables are used to keep track of a partial match that happens at
// the end of a buffer.
/*
int previousPartialMatch = -1;
int beforePreviousPartialMatch = -1;
*/
// Save the location of the current read pointer. We will restore the
// position using seek() before all returns.
long originalPosition = tell();
// Start the search at the offset.
if(fromOffset == 0)
fromOffset = length();
long bufferLength = bufferSize();
long bufferOffset = fromOffset + pattern.size();
// See the notes in find() for an explanation of this algorithm.
while(true) {
if(bufferOffset > bufferLength) {
bufferOffset -= bufferLength;
}
else {
bufferLength = bufferOffset;
bufferOffset = 0;
}
seek(bufferOffset);
buffer = readBlock(bufferLength);
if(buffer.isEmpty())
break;
// TODO: (1) previous partial match
// (2) pattern contained in current buffer
const long location = buffer.rfind(pattern);
if(location >= 0) {
seek(originalPosition);
return bufferOffset + location;
}
if(!before.isEmpty() && buffer.find(before) >= 0) {
seek(originalPosition);
return -1;
}
// TODO: (3) partial match
}
// Since we hit the end of the file, reset the status before continuing.
clear();
seek(originalPosition);
return -1;
}
