private CommonHFSExtentDescriptor getExtent(int extIndex, long startBlock) {
long curStartBlock = startBlock;
while (extIndex >= extentDescriptors.size()) {
/* Need to read the next overflow extent into
* extentDescriptors. */
if (overflowExtentsStore == null) {
throw new RuntimeIOException(
"No overflow extents store to " + "query for overflow extents.");
}
CommonHFSExtentLeafRecord extentRecord;
if (all_extents_mapped) {
extentRecord = null;
} else {
extentRecord = overflowExtentsStore.getExtentRecord(curStartBlock);
}
final CommonHFSExtentDescriptor[] descriptors = extentRecord.getRecordData();
for (int i = 0; i < descriptors.length; ++i) {
final CommonHFSExtentDescriptor curDescriptor = descriptors[i];
final long blockCount = curDescriptor.getBlockCount();
if (blockCount == 0) {
/* End-of-fork at first occurrence of block count 0. */
all_extents_mapped = true;
break;
}
extentDescriptors.add(curDescriptor);
curStartBlock += blockCount;
}
}
return extentDescriptors.get(extIndex);
}
/* @Override */
public int read(byte[] data, int pos, int len) {
// System.err.println("ForkFilter.read(" + data + ", " + pos + ", " + len);
long offset = Long.MAX_VALUE; // MAX_VALUE as a sentinel for seek
long bytesToSkip = logicalPosition;
long curLogicalBlock = 0;
int extIndex;
long currentExtentLength;
if (extentDescriptors.size() < 1 || logicalPosition > forkLength) {
return -1; // EOF
}
// Skip all extents whose range is located before the requested position (logicalPosition)
// System.out.println("ForkFilter.read: skipping extents (bytesToSkip=" +
// bytesToSkip + ")...");
for (extIndex = 0; ; ++extIndex) {
CommonHFSExtentDescriptor cur = getExtent(extIndex, curLogicalBlock);
if (cur == null) {
/* No such extent available. */
return -1;
}
long currentBlockCount = cur.getBlockCount();
currentExtentLength = currentBlockCount * allocationBlockSize;
if (bytesToSkip >= currentExtentLength) {
bytesToSkip -= currentExtentLength;
curLogicalBlock += currentBlockCount;
} else {
offset =
fsOffset
+ firstBlockByteOffset
+ (cur.getStartBlock() * allocationBlockSize)
+ bytesToSkip;
break;
}
}
// System.out.println("done. skipped " + extIndex + " extents.");
if (logicalPosition != lastLogicalPos) {
// System.out.print("ForkFilter.read: (1)seeking to " + offset + "...");
sourceFile.seek(offset); // Seek to the correct position
// System.out.println("done.");
} else if (sourceFile.getFilePointer() != lastPhysicalPos) {
// System.out.print("ForkFilter.read: (2)seeking to " + offset + "...");
sourceFile.seek(lastPhysicalPos);
// System.out.println("done.");
}
long bytesLeftInStream = forkLength - logicalPosition;
// System.err.println("bytesLeftInStream: " + bytesLeftInStream + " len: " + len);
int totalBytesToRead = bytesLeftInStream < len ? (int) bytesLeftInStream : len;
int bytesLeftToRead = totalBytesToRead;
// System.err.println("bytesLeftToRead: " + bytesLeftToRead);
// Start reading. Extent by extent if needed.
for (; ; ++extIndex) {
// System.out.println("ForkFilter.read: reading extent " + extIndex + ".");
CommonHFSExtentDescriptor cur;
try {
cur = getExtent(extIndex, curLogicalBlock);
} catch (RuntimeException e) {
if (bytesLeftToRead == totalBytesToRead) {
throw e;
} else {
break;
}
}
sourceFile.seek(
fsOffset
+ firstBlockByteOffset
+ (cur.getStartBlock() * allocationBlockSize)
+ bytesToSkip);
long blockCount = cur.getBlockCount();
long bytesInExtent = blockCount * allocationBlockSize - bytesToSkip;
int bytesToReadFromExtent =
(bytesInExtent < bytesLeftToRead) ? (int) bytesInExtent : bytesLeftToRead;
int bytesReadFromExtent = 0;
while (bytesReadFromExtent < bytesToReadFromExtent) {
int bytesToRead = bytesToReadFromExtent - bytesReadFromExtent;
int positionInArray = pos + (totalBytesToRead - bytesLeftToRead) + bytesReadFromExtent;
int bytesRead = sourceFile.read(data, positionInArray, bytesToRead);
if (bytesRead > 0) bytesReadFromExtent += bytesRead;
else {
// Update tracker variables before returning
lastPhysicalPos = sourceFile.getFilePointer();
int totalBytesRead = positionInArray - pos;
logicalPosition += totalBytesRead;
return totalBytesRead;
}
}
bytesLeftToRead -= bytesReadFromExtent;
bytesToSkip = 0;
curLogicalBlock += blockCount;
if (bytesLeftToRead == 0) break;
}
// Update tracker variables before returning
lastPhysicalPos = sourceFile.getFilePointer();
logicalPosition += totalBytesToRead - bytesLeftToRead;
if (bytesLeftToRead < totalBytesToRead) {
int bytesRead = totalBytesToRead - bytesLeftToRead;
// System.err.println("final bytesRead: " + bytesRead);
return bytesRead;
} else return -1;
}
