/*
* Assume that the window is properly positioned. Try to fill the read
* buffer with data from this file handle, starting at the location
* indicated by the starting offset field. If this file contains more
* data, return true. If this file doesn't contain more data, return
* false.
*
* In all cases, leave the the read buffer pointing at the target
* offset and in a state that's ready to support reads, even if there
* is nothing in the buffer. Note that the target offset, which may not
* be the same as starting offset.
* @return true if more data was read, false if not.
*/
protected boolean fillFromFile(FileHandle fileHandle, long targetOffset)
throws DatabaseException {
boolean foundData = false;
readBuffer.clear();
if (fileManager.readFromFile(
fileHandle.getFile(),
readBuffer,
startOffset,
fileHandle.getFileNum(),
false /* dataKnownToBeInFile */)) {
foundData = true;
nReadOperations += 1;
/*
* Ensure that fileNum and logVersion are in sync. setFileNum
* handles changes in the file number. But we must also update
* the logVersion here to handle the first read after we
* initialize fileNum and logVersion is unknown.
*/
logVersion = fileHandle.getLogVersion();
}
/*
* In all cases, setup read buffer for valid reading. If the buffer
* has no data, it will be positioned at the beginning, and will be
* able to correctly return the fact that there is no data present.
*/
endOffset = startOffset + threadSafeBufferPosition(readBuffer);
threadSafeBufferFlip(readBuffer);
threadSafeBufferPosition(readBuffer, (int) (targetOffset - startOffset));
return foundData;
}
