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package com.googlecode.mp4parser.boxes.mp4.objectdescriptors;
import java.nio.ByteBuffer;
public class BitWriterBuffer {
private ByteBuffer buffer;
int initialPos;
int position = 0;
public BitWriterBuffer(ByteBuffer buffer) {
this.buffer = buffer;
this.initialPos = buffer.position();
}
public void writeBits(int i, int numBits) {
assert i <= ((1 << numBits)-1): String.format("Trying to write a value bigger (%s) than the number bits (%s) allows. " +
"Please mask the value before writing it and make your code is really working as intended.", i, (1<<numBits)-1);
int left = 8 - position % 8;
if (numBits <= left) {
int current = (buffer.get(initialPos + position / 8));
current = current < 0 ? current + 256 : current;
current += i << (left - numBits);
buffer.put(initialPos + position / 8, (byte) (current > 127 ? current - 256 : current));
position += numBits;
} else {
int bitsSecondWrite = numBits - left;
writeBits(i >> bitsSecondWrite, left);
writeBits(i & (1 << bitsSecondWrite) - 1, bitsSecondWrite);
}
buffer.position(initialPos + position / 8 + ((position % 8 > 0) ? 1 : 0));
}
}
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