/*
* Copyright 2001 Sun Microsystems, Inc. All Rights Reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Sun designates this
* particular file as subject to the "Classpath" exception as provided
* by Sun in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
* CA 95054 USA or visit www.sun.com if you need additional information or
* have any questions.
*/
package com.sun.imageio.plugins.jpeg;
import javax.imageio.stream.ImageInputStream;
import javax.imageio.IIOException;
import java.io.IOException;
/**
* A class wrapping a buffer and its state. For efficiency,
* the members are made visible to other classes in this package.
*/
class JPEGBuffer {
private boolean debug = false;
/**
* The size of the buffer. This is large enough to hold all
* known marker segments (other than thumbnails and icc profiles)
*/
final int BUFFER_SIZE = 4096;
/**
* The actual buffer.
*/
byte [] buf;
/**
* The number of bytes available for reading from the buffer.
* Anytime data is read from the buffer, this should be updated.
*/
int bufAvail;
/**
* A pointer to the next available byte in the buffer. This is
* used to read data from the buffer and must be updated to
* move through the buffer.
*/
int bufPtr;
/**
* The ImageInputStream buffered.
*/
ImageInputStream iis;
JPEGBuffer (ImageInputStream iis) {
buf = new byte[BUFFER_SIZE];
bufAvail = 0;
bufPtr = 0;
this.iis = iis;
}
/**
* Ensures that there are at least <code>count</code> bytes available
* in the buffer, loading more data and moving any remaining
* bytes to the front. A count of 0 means to just fill the buffer.
* If the count is larger than the buffer size, just fills the buffer.
* If the end of the stream is encountered before a non-0 count can
* be satisfied, an <code>IIOException</code> is thrown with the
* message "Image Format Error".
*/
void loadBuf(int count) throws IOException {
if (debug) {
System.out.print("loadbuf called with ");
System.out.print("count " + count + ", ");
System.out.println("bufAvail " + bufAvail + ", ");
}
if (count != 0) {
if (bufAvail >= count) { // have enough
return;
}
} else {
if (bufAvail == BUFFER_SIZE) { // already full
return;
}
}
// First copy any remaining bytes down to the beginning
if ((bufAvail > 0) && (bufAvail < BUFFER_SIZE)) {
System.arraycopy(buf, bufPtr, buf, 0, bufAvail);
}
// Now fill the rest of the buffer
int ret = iis.read(buf, bufAvail, buf.length - bufAvail);
if (debug) {
System.out.println("iis.read returned " + ret);
}
if (ret != -1) {
bufAvail += ret;
}
bufPtr = 0;
int minimum = Math.min(BUFFER_SIZE, count);
if (bufAvail < minimum) {
throw new IIOException ("Image Format Error");
}
}
/**
* Fills the data array from the stream, starting with
* the buffer and then reading directly from the stream
* if necessary. The buffer is left in an appropriate
* state. If the end of the stream is encountered, an
* <code>IIOException</code> is thrown with the
* message "Image Format Error".
*/
void readData(byte [] data) throws IOException {
int count = data.length;
// First see what's left in the buffer.
if (bufAvail >= count) { // It's enough
System.arraycopy(buf, bufPtr, data, 0, count);
bufAvail -= count;
bufPtr += count;
return;
}
int offset = 0;
if (bufAvail > 0) { // Some there, but not enough
System.arraycopy(buf, bufPtr, data, 0, bufAvail);
offset = bufAvail;
count -= bufAvail;
bufAvail = 0;
bufPtr = 0;
}
// Now read the rest directly from the stream
if (iis.read(data, offset, count) != count) {
throw new IIOException ("Image format Error");
}
}
/**
* Skips <code>count</code> bytes, leaving the buffer
* in an appropriate state. If the end of the stream is
* encountered, an <code>IIOException</code> is thrown with the
* message "Image Format Error".
*/
void skipData(int count) throws IOException {
// First see what's left in the buffer.
if (bufAvail >= count) { // It's enough
bufAvail -= count;
bufPtr += count;
return;
}
if (bufAvail > 0) { // Some there, but not enough
count -= bufAvail;
bufAvail = 0;
bufPtr = 0;
}
// Now read the rest directly from the stream
if (iis.skipBytes(count) != count) {
throw new IIOException ("Image format Error");
}
}
/**
* Push back the remaining contents of the buffer by
* repositioning the input stream.
*/
void pushBack() throws IOException {
iis.seek(iis.getStreamPosition()-bufAvail);
bufAvail = 0;
bufPtr = 0;
}
/**
* Return the stream position corresponding to the next
* available byte in the buffer.
*/
long getStreamPosition() throws IOException {
return (iis.getStreamPosition()-bufAvail);
}
/**
* Scan the buffer until the next 0xff byte, reloading
* the buffer as necessary. The buffer position is left
* pointing to the first non-0xff byte after a run of
* 0xff bytes. If the end of the stream is encountered,
* an EOI marker is inserted into the buffer and <code>true</code>
* is returned. Otherwise returns <code>false</code>.
*/
boolean scanForFF(JPEGImageReader reader) throws IOException {
boolean retval = false;
boolean foundFF = false;
while (foundFF == false) {
while (bufAvail > 0) {
if ((buf[bufPtr++] & 0xff) == 0xff) {
bufAvail--;
foundFF = true;
break; // out of inner while
}
bufAvail--;
}
// Reload the buffer and keep going
loadBuf(0);
// Skip any remaining pad bytes
if (foundFF == true) {
while ((bufAvail > 0) && (buf[bufPtr] & 0xff) == 0xff) {
bufPtr++; // Only if it still is 0xff
bufAvail--;
}
}
if (bufAvail == 0) { // Premature EOF
// send out a warning, but treat it as EOI
//reader.warningOccurred(JPEGImageReader.WARNING_NO_EOI);
retval = true;
buf[0] = (byte)JPEG.EOI;
bufAvail = 1;
bufPtr = 0;
foundFF = true;
}
}
return retval;
}
/**
* Prints the contents of the buffer, in hex.
* @param count the number of bytes to print,
* starting at the current available byte.
*/
void print(int count) {
System.out.print("buffer has ");
System.out.print(bufAvail);
System.out.println(" bytes available");
if (bufAvail < count) {
count = bufAvail;
}
for (int ptr = bufPtr; count > 0; count--) {
int val = (int)buf[ptr++] & 0xff;
System.out.print(" " + Integer.toHexString(val));
}
System.out.println();
}
}