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package jogamp.opengl.util.pngj.chunks;
import java.io.ByteArrayInputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.zip.CRC32;
import jogamp.opengl.util.pngj.PngHelper;
import jogamp.opengl.util.pngj.PngjBadCrcException;
import jogamp.opengl.util.pngj.PngjOutputException;
/**
* Wraps the raw chunk data Short lived object, to be created while serialing/deserializing Do not reuse it for
* different chunks
*
* see http://www.libpng.org/pub/png/spec/1.2/PNG-Chunks.html
*/
public class ChunkRaw {
public final int len;
public final byte[] idbytes = new byte[4]; // 4 bytes
public byte[] data = null; // crc not included
private int crcval = 0;
// public int offset=-1; // only for read chunks - informational
public ChunkRaw(int len, byte[] idbytes, boolean alloc) {
this.len = len;
System.arraycopy(idbytes, 0, this.idbytes, 0, 4);
if (alloc)
allocData();
}
public void writeChunk(OutputStream os) {
if (idbytes.length != 4)
throw new PngjOutputException("bad chunkid [" + ChunkHelper.toString(idbytes) + "]");
computeCrc();
PngHelper.writeInt4(os, len);
PngHelper.writeBytes(os, idbytes);
if (len > 0)
PngHelper.writeBytes(os, data, 0, len);
// System.err.println("writing chunk " + this.toString() + "crc=" + crcval);
PngHelper.writeInt4(os, crcval);
}
/**
* called after setting data, before writing to os
*/
private void computeCrc() {
CRC32 crcengine = PngHelper.getCRC();
crcengine.reset();
crcengine.update(idbytes, 0, 4);
if (len > 0)
crcengine.update(data, 0, len); //
crcval = (int) crcengine.getValue();
}
public String toString() {
return "chunkid=" + ChunkHelper.toString(idbytes) + " len=" + len;
}
/**
* position before: just after chunk id. positon after: after crc Data should be already allocated. Checks CRC
* Return number of byte read.
*/
public int readChunkData(InputStream is) {
PngHelper.readBytes(is, data, 0, len);
int crcori = PngHelper.readInt4(is);
computeCrc();
if (crcori != crcval)
throw new PngjBadCrcException("crc invalid for chunk " + toString() + " calc=" + crcval + " read=" + crcori);
return len + 4;
}
public ByteArrayInputStream getAsByteStream() { // only the data
return new ByteArrayInputStream(data);
}
private void allocData() {
if (data == null || data.length < len)
data = new byte[len];
}
}
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