package ar.com.hjg.pngj.chunks;
import java.io.OutputStream;
import ar.com.hjg.pngj.ImageInfo;
import ar.com.hjg.pngj.PngjExceptionInternal;
/**
* Represents a instance of a PNG chunk.
* <p>
* See <a href="http://www.libpng.org/pub/png/spec/1.2/PNG-Chunks.html">http://www
* .libpng.org/pub/png/spec/1.2/PNG-Chunks .html</a> </a>
* <p>
* Concrete classes should extend {@link PngChunkSingle} or {@link PngChunkMultiple}
* <p>
* Note that some methods/fields are type-specific (getOrderingConstraint(), allowsMultiple()),<br>
* some are 'almost' type-specific (id,crit,pub,safe; the exception is PngUKNOWN), <br>
* and the rest are instance-specific
*/
public abstract class PngChunk {
/**
* Chunk-id: 4 letters
*/
public final String id;
/**
* Autocomputed at creation time
*/
public final boolean crit, pub, safe;
protected final ImageInfo imgInfo;
protected ChunkRaw raw;
private boolean priority = false; // For writing. Queued chunks with high priority will be written
// as soon as
// possible
protected int chunkGroup = -1; // chunk group where it was read or writen
/**
* Possible ordering constraint for a PngChunk type -only relevant for ancillary chunks.
* Theoretically, there could be more general constraints, but these cover the constraints for
* standard chunks.
*/
public enum ChunkOrderingConstraint {
/**
* no ordering constraint
*/
NONE,
/**
* Must go before PLTE (and hence, also before IDAT)
*/
BEFORE_PLTE_AND_IDAT,
/**
* Must go after PLTE (if exists) but before IDAT
*/
AFTER_PLTE_BEFORE_IDAT,
/**
* Must go after PLTE (and it must exist) but before IDAT
*/
AFTER_PLTE_BEFORE_IDAT_PLTE_REQUIRED,
/**
* Must before IDAT (before or after PLTE)
*/
BEFORE_IDAT,
/**
* Does not apply
*/
NA;
public boolean mustGoBeforePLTE() {
return this == BEFORE_PLTE_AND_IDAT;
}
public boolean mustGoBeforeIDAT() {
return this == BEFORE_IDAT || this == BEFORE_PLTE_AND_IDAT || this == AFTER_PLTE_BEFORE_IDAT;
}
/**
* after pallete, if exists
*/
public boolean mustGoAfterPLTE() {
return this == AFTER_PLTE_BEFORE_IDAT || this == AFTER_PLTE_BEFORE_IDAT_PLTE_REQUIRED;
}
public boolean isOk(int currentChunkGroup, boolean hasplte) {
if (this == NONE)
return true;
else if (this == BEFORE_IDAT)
return currentChunkGroup < ChunksList.CHUNK_GROUP_4_IDAT;
else if (this == BEFORE_PLTE_AND_IDAT)
return currentChunkGroup < ChunksList.CHUNK_GROUP_2_PLTE;
else if (this == AFTER_PLTE_BEFORE_IDAT)
return hasplte ? currentChunkGroup < ChunksList.CHUNK_GROUP_4_IDAT
: (currentChunkGroup < ChunksList.CHUNK_GROUP_4_IDAT && currentChunkGroup > ChunksList.CHUNK_GROUP_2_PLTE);
return false;
}
}
public PngChunk(String id, ImageInfo imgInfo) {
this.id = id;
this.imgInfo = imgInfo;
this.crit = ChunkHelper.isCritical(id);
this.pub = ChunkHelper.isPublic(id);
this.safe = ChunkHelper.isSafeToCopy(id);
}
protected final ChunkRaw createEmptyChunk(int len, boolean alloc) {
ChunkRaw c = new ChunkRaw(len, ChunkHelper.toBytes(id), alloc);
return c;
}
/**
* In which "chunkGroup" (see {@link ChunksList}for definition) this chunks instance was read or
* written.
* <p>
* -1 if not read or written (eg, queued)
*/
final public int getChunkGroup() {
return chunkGroup;
}
/**
* @see #getChunkGroup()
*/
final void setChunkGroup(int chunkGroup) {
this.chunkGroup = chunkGroup;
}
public boolean hasPriority() {
return priority;
}
public void setPriority(boolean priority) {
this.priority = priority;
}
final void write(OutputStream os) {
if (raw == null || raw.data == null)
raw = createRawChunk();
if (raw == null)
throw new PngjExceptionInternal("null chunk ! creation failed for " + this);
raw.writeChunk(os);
}
/**
* Creates the physical chunk. This is used when writing (serialization). Each particular chunk
* class implements its own logic.
*
* @return A newly allocated and filled raw chunk
*/
protected abstract ChunkRaw createRawChunk();
/**
* Parses raw chunk and fill inside data. This is used when reading (deserialization). Each
* particular chunk class implements its own logic.
*/
protected abstract void parseFromRaw(ChunkRaw c);
/**
* See {@link PngChunkMultiple} and {@link PngChunkSingle}
*
* @return true if PNG accepts multiple chunks of this class
*/
protected abstract boolean allowsMultiple();
public ChunkRaw getRaw() {
return raw;
}
void setRaw(ChunkRaw raw) {
this.raw = raw;
}
/**
* @see ChunkRaw#len
*/
public int getLen() {
return raw != null ? raw.len : -1;
}
/**
* @see ChunkRaw#getOffset()
*/
public long getOffset() {
return raw != null ? raw.getOffset() : -1;
}
/**
* This signals that the raw chunk (serialized data) as invalid, so that it's regenerated on
* write. This should be called for the (infrequent) case of chunks that were copied from a
* PngReader and we want to manually modify it.
*/
public void invalidateRawData() {
raw = null;
}
/**
* see {@link ChunkOrderingConstraint}
*/
public abstract ChunkOrderingConstraint getOrderingConstraint();
@Override
public String toString() {
return "chunk id= " + id + " (len=" + getLen() + " offset=" + getOffset() + ")";
}
}