/**
* Extracts <code>len</code> bytes of data from the current or subsequent fragments.
*
* @param b the buffer into which the data is read.
* @param off the start offset of the data.
* @param len the number of bytes read.
* @return the total number of bytes read into the buffer (always whatever was asked for), or -1
* if there is no more data because the end of a frame has been reached.
* @exception IOException if an I/O error occurs.
*/
public final int read(byte b[], int off, int len) throws IOException {
// System.err.println("EncapsulatedInputStream.read(byte [],"+off+","+len+")");
// System.err.println("EncapsulatedInputStream.read() at start,
// fragmentRemaining="+fragmentRemaining);
// System.err.println("EncapsulatedInputStream.read() at start,
// endOfFrameEncountered="+endOfFrameEncountered);
// System.err.println("EncapsulatedInputStream.read() at start,
// currentFragmentContainsEndOfFrame="+currentFragmentContainsEndOfFrame);
if (endOfFrameEncountered) {
// System.err.println("EncapsulatedInputStream.read() returning -1 since
// endOfFrameEncountered");
return -1; // i.e., won't advance until nextFrame() is called to reset this state
}
int count = 0;
int remainingToDo = len;
while (remainingToDo > 0 && !sequenceDelimiterEncountered && !endOfFrameEncountered) {
// System.err.println("EncapsulatedInputStream.read() remainingToDo="+remainingToDo);
if (fragment == null) {
if (firstTime) {
// System.err.println("EncapsulatedInputStream.read() firstTime");
// first time ... skip offset table ...
long offsetTableLength = readItemTag();
if (sequenceDelimiterEncountered) {
throw new IOException("Expected offset table item tag; got sequence delimiter");
}
// System.err.println("EncapsulatedInputStream.read() skipping
// offsetTableLength="+offsetTableLength);
i.skipInsistently(offsetTableLength);
bytesRead += offsetTableLength;
firstTime = false;
}
// load a new fragment ...
// System.err.println("EncapsulatedInputStream.read() loading a new fragment");
long vl =
readItemTag(); // if sequenceDelimiterEncountered, vl will be zero and no more will be
// done
if (vl != 0) {
currentFragmentContainsEndOfFrame = false;
fragmentRemaining = fragmentSize = (int) vl;
fragment = new byte[fragmentSize];
i.readInsistently(fragment, 0, fragmentSize);
bytesRead += fragmentSize;
fragmentOffset = 0;
// System.err.println("EncapsulatedInputStream.read() fragmentRemaining
// initially="+fragmentRemaining);
// System.err.println("EncapsulatedInputStream.read() fragment =
// "+com.pixelmed.utils.HexDump.dump(fragment));
// Ignore everything between (the last) EOI marker and the end of the fragment
int positionOfEOI = fragmentRemaining - 1;
while (--positionOfEOI > 0) {
int firstMarkerByte = fragment[positionOfEOI] & 0xff;
int secondMarkerByte = fragment[positionOfEOI + 1] & 0xff;
// System.err.println("EncapsulatedInputStream.read() fragment
// fragment["+positionOfEOI+"] = 0x"+Integer.toHexString(firstMarkerByte));
// System.err.println("EncapsulatedInputStream.read() fragment
// fragment["+(positionOfEOI+1)+"] = 0x"+Integer.toHexString(secondMarkerByte));
if (firstMarkerByte == 0xff && secondMarkerByte == 0xd9) {
currentFragmentContainsEndOfFrame = true;
break;
}
}
// System.err.println("EncapsulatedInputStream.read() positionOfEOI="+positionOfEOI);
if (positionOfEOI > 0) { // will be zero if we did not find one
fragmentRemaining =
positionOfEOI + 2; // effectively skips all (hopefully padding) bytes after the EOI
}
// System.err.println("EncapsulatedInputStream.read() fragmentRemaining after removing
// trailing padding="+fragmentRemaining);
}
}
int amountToCopyFromThisFragment =
remainingToDo < fragmentRemaining ? remainingToDo : fragmentRemaining;
// System.err.println("EncapsulatedInputStream.read()
// amountToCopyFromThisFragment="+amountToCopyFromThisFragment);
if (amountToCopyFromThisFragment > 0) {
System.arraycopy(fragment, fragmentOffset, b, off, amountToCopyFromThisFragment);
off += amountToCopyFromThisFragment;
fragmentOffset += amountToCopyFromThisFragment;
fragmentRemaining -= amountToCopyFromThisFragment;
remainingToDo -= amountToCopyFromThisFragment;
count += amountToCopyFromThisFragment;
}
if (fragmentRemaining <= 0) {
fragment = null;
if (currentFragmentContainsEndOfFrame) {
endOfFrameEncountered =
true; // once EOI has been seen in a fragment, use the rest of the fragment including
// the EOI, but no further
}
}
}
// System.err.println("EncapsulatedInputStream.read() returning count="+count);
// System.err.println("EncapsulatedInputStream.read()
// returning="+com.pixelmed.utils.HexDump.dump(fragment,off,count));
return count == 0
? -1
: count; // always returns more than 0 unless end, which is signalled by -1
}
