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; }