Mercurial > projects > dwt-win
view dwt/internal/image/PngDecodingDataStream.d @ 341:f403c83322c3 default tip
fix: thx torhu
author | Frank Benoit <benoit@tionex.de> |
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date | Sun, 08 Nov 2009 20:58:32 +0100 |
parents | 36f5cb12e1a2 |
children |
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/******************************************************************************* * Copyright (c) 2000, 2006 IBM Corporation and others. * All rights reserved. This program and the accompanying materials * are made available under the terms of the Eclipse Public License v1.0 * which accompanies this distribution, and is available at * http://www.eclipse.org/legal/epl-v10.html * * Contributors: * IBM Corporation - initial API and implementation * Port to the D programming language: * Frank Benoit <benoit@tionex.de> *******************************************************************************/ module dwt.internal.image.PngDecodingDataStream; import dwt.dwthelper.InputStream; import dwt.DWT; import dwt.internal.image.PngLzBlockReader; public class PngDecodingDataStream : InputStream { alias InputStream.read read; InputStream stream; byte currentByte; int nextBitIndex; PngLzBlockReader lzBlockReader; int adlerValue; static final int PRIME = 65521; static final int MAX_BIT = 7; this(InputStream stream) { super(); this.stream = stream; nextBitIndex = MAX_BIT + 1; adlerValue = 1; lzBlockReader = new PngLzBlockReader(this); readCompressedDataHeader(); lzBlockReader.readNextBlockHeader(); } /** * This method should be called when the image decoder thinks * that all of the compressed image data has been read. This * method will ensure that the next data value is an end of * block marker. If there are more blocks after this one, * the method will read them and ensure that they are empty. */ void assertImageDataAtEnd() { lzBlockReader.assertCompressedDataAtEnd(); } public override void close() { assertImageDataAtEnd(); checkAdler(); } int getNextIdatBits(int length) { int value = 0; for (int i = 0; i < length; i++) { value |= (getNextIdatBit() << i); } return value; } int getNextIdatBit() { if (nextBitIndex > MAX_BIT) { currentByte = getNextIdatByte(); nextBitIndex = 0; } return (currentByte & (1 << nextBitIndex)) >> nextBitIndex++; } byte getNextIdatByte() { byte nextByte = cast(byte)stream.read(); nextBitIndex = MAX_BIT + 1; return nextByte; } void updateAdler(byte value) { int low = adlerValue & 0xFFFF; int high = (adlerValue >> 16) & 0xFFFF; int valueInt = value & 0xFF; low = (low + valueInt) % PRIME; high = (low + high) % PRIME; adlerValue = (high << 16) | low; } public override int read() { byte nextDecodedByte = lzBlockReader.getNextByte(); updateAdler(nextDecodedByte); return nextDecodedByte & 0xFF; } public override int read(byte[] buffer, int off, int len) { for (int i = 0; i < len; i++) { int b = read(); if (b is -1) return i; buffer[off + i] = cast(byte)b; } return len; } void error() { DWT.error(DWT.ERROR_INVALID_IMAGE); } private void readCompressedDataHeader() { byte headerByte1 = getNextIdatByte(); byte headerByte2 = getNextIdatByte(); int number = ((headerByte1 & 0xFF) << 8) | (headerByte2 & 0xFF); if (number % 31 !is 0) error(); int compressionMethod = headerByte1 & 0x0F; if (compressionMethod !is 8) error(); int windowSizeHint = (headerByte1 & 0xF0) >> 4; if (windowSizeHint > 7) error(); int windowSize = (1 << (windowSizeHint + 8)); lzBlockReader.setWindowSize(windowSize); int dictionary = (headerByte2 & (1 << 5)); if (dictionary !is 0) error(); // int compressionLevel = (headerByte2 & 0xC0) >> 6; } void checkAdler() { int storedAdler = 0; storedAdler |= ((getNextIdatByte() & 0xFF) << 24); storedAdler |= ((getNextIdatByte() & 0xFF) << 16); storedAdler |= ((getNextIdatByte() & 0xFF) << 8); storedAdler |= (getNextIdatByte() & 0xFF); if (storedAdler !is adlerValue) error(); } }