# CCITTFaxDecoderStream.java

    /*
     * Copyright (c) 2012, Harald Kuhr
     * All rights reserved.
     *
     * Redistribution and use in source and binary forms, with or without
     * modification, are permitted provided that the following conditions are met:
     *
     * * Redistributions of source code must retain the above copyright notice, this
     *   list of conditions and the following disclaimer.
     *
     * * Redistributions in binary form must reproduce the above copyright notice,
     *   this list of conditions and the following disclaimer in the documentation
     *   and/or other materials provided with the distribution.
     *
     * * Neither the name of the copyright holder nor the names of its
     *   contributors may be used to endorse or promote products derived from
     *   this software without specific prior written permission.
     *
     * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
     * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
     * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
     * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
     * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
     * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
     * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     */
    package org.apache.pdfbox.filter;

    import java.io.EOFException;
    import java.io.FilterInputStream;
    import java.io.IOException;
    import java.io.InputStream;
    import java.util.Arrays;

    /**
     * CCITT Modified Huffman RLE, Group 3 (T4) and Group 4 (T6) fax compression.
     *
     * @author <a href="mailto:harald.kuhr@gmail.com">Harald Kuhr</a>
     * @author <a href="https://github.com/Schmidor">Oliver Schmidtmer</a>
     * @author last modified by $Author: haraldk$
     * @version $Id: CCITTFaxDecoderStream.java,v 1.0 23.05.12 15:55 haraldk Exp$
     *
     * Taken from commit 24c6682236e5a02151359486aa4075ddc5ab1534 of 18.08.2018 from twelvemonkeys/imageio/plugins/tiff/CCITTFaxDecoderStream.java
     *
     * Initial changes for PDFBox, discussed in PDFBOX-3338:
     * - removed Validate() usages
     * - catch VALUE_EOL in decode1D()
     */
    final class CCITTFaxDecoderStream extends FilterInputStream {
        // See TIFF 6.0 Specification, Section 10: "Modified Huffman Compression", page 43.

        private final int columns;
        private final byte[] decodedRow;

        private final boolean optionG32D;
        // Leading zeros for aligning EOL
        private final boolean optionG3Fill;
        private final boolean optionUncompressed;
        private final boolean optionByteAligned;

        private final int type;

        private int decodedLength;
        private int decodedPos;

        private int[] changesReferenceRow;
        private int[] changesCurrentRow;
        private int changesReferenceRowCount;
        private int changesCurrentRowCount;

        private int lastChangingElement = 0;

        /**
         * Creates a CCITTFaxDecoderStream.
         * This constructor may be used for CCITT streams embedded in PDF files,
         * which use EncodedByteAlign.
         *
         * @param stream the compressed CCITT stream.
         * @param columns the number of columns in the stream.
         * @param type the type of stream, must be one of {@code COMPRESSION_CCITT_MODIFIED_HUFFMAN_RLE},
         *             {@code COMPRESSION_CCITT_T4} or {@code COMPRESSION_CCITT_T6}.
         * @param options CCITT T.4 or T.6 options.
         * @param byteAligned enable byte alignment used in PDF files (EncodedByteAlign).
         */
        public CCITTFaxDecoderStream(final InputStream stream, final int columns, final int type,
                                     final long options, final boolean byteAligned) {
            super(stream);

            this.columns = columns;
            this.type = type;

            // We know this is only used for b/w (1 bit)
            decodedRow = new byte[(columns + 7) / 8];
            changesReferenceRow = new int[columns + 2];
            changesCurrentRow = new int[columns + 2];

            switch (type) {
                case TIFFExtension.COMPRESSION_CCITT_MODIFIED_HUFFMAN_RLE:
                    optionByteAligned = byteAligned;
                    optionG32D = false;
                    optionG3Fill = false;
                    optionUncompressed = false;
                    break;
                case TIFFExtension.COMPRESSION_CCITT_T4:
                    optionByteAligned = byteAligned;
                    optionG32D = (options & TIFFExtension.GROUP3OPT_2DENCODING) != 0;
                    optionG3Fill = (options & TIFFExtension.GROUP3OPT_FILLBITS) != 0;
                    optionUncompressed = (options & TIFFExtension.GROUP3OPT_UNCOMPRESSED) != 0;
                    break;
                case TIFFExtension.COMPRESSION_CCITT_T6:
                    optionByteAligned = byteAligned;
                    optionG32D = false;
                    optionG3Fill = false;
                    optionUncompressed = (options & TIFFExtension.GROUP4OPT_UNCOMPRESSED) != 0;
                    break;
                default:
                    throw new IllegalArgumentException("Illegal parameter: " + type);
            }

        }

        private void fetch() throws IOException {
            if (decodedPos >= decodedLength) {
                decodedLength = 0;

                try {
                    decodeRow();
                }
                catch (ArrayIndexOutOfBoundsException e) {
                    // Mask the AIOOBE as an IOException
                    throw new IOException("Malformed CCITT stream", e);
                }
                catch (EOFException e) {
                    // TODO: Rewrite to avoid throw/catch for normal flow...
                    if (decodedLength != 0) {
                        throw e;
                    }

                    // ..otherwise, just let client code try to read past the
                    // end of stream
                    decodedLength = -1;
                }

                decodedPos = 0;
            }
        }

        private void decode1D() throws IOException {
            int index = 0;
            boolean white = true;
            changesCurrentRowCount = 0;

            do {
                int completeRun;

                if (white) {
                    completeRun = decodeRun(whiteRunTree);
                }
                else {
                    completeRun = decodeRun(blackRunTree);
                }

                index += completeRun;
                changesCurrentRow[changesCurrentRowCount++] = index;

                // Flip color for next run
                white = !white;
            } while (index < columns);
        }

        private void decode2D() throws IOException {
            changesReferenceRowCount = changesCurrentRowCount;
            int[] tmp = changesCurrentRow;
            changesCurrentRow = changesReferenceRow;
            changesReferenceRow = tmp;

            boolean white = true;
            int index = 0;
            changesCurrentRowCount = 0;

            mode: while (index < columns) {
                // read mode
                Node n = codeTree.root;

                while (true) {
                    n = n.walk(readBit());

                    if (n == null) {
                        continue mode;
                    }
                    else if (n.isLeaf) {
                        switch (n.value) {
                            case VALUE_HMODE:
                                int runLength;
                                runLength = decodeRun(white ? whiteRunTree : blackRunTree);
                                index += runLength;
                                changesCurrentRow[changesCurrentRowCount++] = index;

                                runLength = decodeRun(white ? blackRunTree : whiteRunTree);
                                index += runLength;
                                changesCurrentRow[changesCurrentRowCount++] = index;
                                break;

                            case VALUE_PASSMODE:
                                int pChangingElement = getNextChangingElement(index, white) + 1;

                                if (pChangingElement >= changesReferenceRowCount) {
                                    index = columns;
                                }
                                else {
                                    index = changesReferenceRow[pChangingElement];
                                }

                                break;

                            default:
                                // Vertical mode (-3 to 3)
                                int vChangingElement = getNextChangingElement(index, white);

                                if (vChangingElement >= changesReferenceRowCount || vChangingElement == -1) {
                                    index = columns + n.value;
                                }
                                else {
                                    index = changesReferenceRow[vChangingElement] + n.value;
                                }

                                changesCurrentRow[changesCurrentRowCount] = index;
                                changesCurrentRowCount++;
                                white = !white;

                                break;
                        }

                        continue mode;
                    }
                }
            }
        }

        private int getNextChangingElement(final int a0, final boolean white) {
            int start = (lastChangingElement & 0xFFFF_FFFE) + (white ? 0 : 1);
            if (start > 2) {
                start -= 2;
            }

            if (a0 == 0) {
                return start;
            }

            for (int i = start; i < changesReferenceRowCount; i += 2) {
                if (a0 < changesReferenceRow[i]) {
                    lastChangingElement = i;
                    return i;
                }
            }

            return -1;
        }

        private void decodeRowType2() throws IOException {
            if (optionByteAligned) {
                resetBuffer();
            }
            decode1D();
        }

        private void decodeRowType4() throws IOException {
            if (optionByteAligned) {
                resetBuffer();
            }
            eof: while (true) {
                // read till next EOL code
                Node n = eolOnlyTree.root;

                while (true) {
                    n = n.walk(readBit());

                    if (n == null) {
                        continue eof;
                    }

                    if (n.isLeaf) {
                        break eof;
                    }
                }
            }

            if (!optionG32D || readBit()) {
                decode1D();
            }
            else {
                decode2D();
            }
        }

        private void decodeRowType6() throws IOException {
            if (optionByteAligned) {
                resetBuffer();
            }
            decode2D();
        }

        private void decodeRow() throws IOException {
            switch (type) {
                case TIFFExtension.COMPRESSION_CCITT_MODIFIED_HUFFMAN_RLE:
                    decodeRowType2();
                    break;
                case TIFFExtension.COMPRESSION_CCITT_T4:
                    decodeRowType4();
                    break;
                case TIFFExtension.COMPRESSION_CCITT_T6:
                    decodeRowType6();
                    break;
                default:
                    throw new IllegalArgumentException("Illegal parameter: " + type);
            }

            int index = 0;
            boolean white = true;

            lastChangingElement = 0;
            for (int i = 0; i <= changesCurrentRowCount; i++) {
                int nextChange = columns;

                if (i != changesCurrentRowCount) {
                    nextChange = changesCurrentRow[i];
                }

                if (nextChange > columns) {
                    nextChange = columns;
                }

                int byteIndex = index / 8;

                while (index % 8 != 0 && (nextChange - index) > 0) {
                    decodedRow[byteIndex] |= (white ? 0 : 1 << (7 - ((index) % 8)));
                    index++;
                }

                if (index % 8 == 0) {
                    byteIndex = index / 8;
                    final byte value = (byte) (white ? 0x00 : 0xff);

                    while ((nextChange - index) > 7) {
                        decodedRow[byteIndex] = value;
                        index += 8;
                        ++byteIndex;
                    }
                }

                while ((nextChange - index) > 0) {
                    if (index % 8 == 0) {
                        decodedRow[byteIndex] = 0;
                    }

                    decodedRow[byteIndex] |= (white ? 0 : 1 << (7 - ((index) % 8)));
                    index++;
                }

                white = !white;
            }

            if (index != columns) {
                throw new IOException("Sum of run-lengths does not equal scan line width: " + index + " > " + columns);
            }

            decodedLength = (index + 7) / 8;
        }

        private int decodeRun(final Tree tree) throws IOException {
            int total = 0;

            Node n = tree.root;

            while (true) {
                boolean bit = readBit();
                n = n.walk(bit);

                if (n == null) {
                    throw new IOException("Unknown code in Huffman RLE stream");
                }

                if (n.isLeaf) {
                    total += n.value;
                    if (n.value >= 64) {
                        n = tree.root;
                    }
                    else if (n.value >= 0) {
                        return total;
                    }
                    else {
                        return columns;
                    }
                }
            }
        }

        private void resetBuffer() {
            bufferPos = -1;
        }

        int buffer = -1;
        int bufferPos = -1;

        private boolean readBit() throws IOException {
            if (bufferPos < 0 || bufferPos > 7) {
                buffer = in.read();

                if (buffer == -1) {
                    throw new EOFException("Unexpected end of Huffman RLE stream");
                }

                bufferPos = 0;
            }

            boolean isSet = (buffer & 0x80) != 0;
            buffer <<= 1;
            bufferPos++;

            return isSet;
        }

        @Override
        public int read() throws IOException {
            if (decodedLength < 0) {
                return 0x0;
            }

            if (decodedPos >= decodedLength) {
                fetch();

                if (decodedLength < 0) {
                    return 0x0;
                }
            }

            return decodedRow[decodedPos++] & 0xff;
        }

        @Override
        public int read(byte[] b, int off, int len) throws IOException {
            if (decodedLength < 0) {
                Arrays.fill(b, off, off + len, (byte) 0x0);
                return len;
            }

            if (decodedPos >= decodedLength) {
                fetch();

                if (decodedLength < 0) {
                    Arrays.fill(b, off, off + len, (byte) 0x0);
                    return len;
                }
            }

            int read = Math.min(decodedLength - decodedPos, len);
            System.arraycopy(decodedRow, decodedPos, b, off, read);
            decodedPos += read;

            return read;
        }

        @Override
        public long skip(long n) throws IOException {
            if (decodedLength < 0) {
                return -1;
            }

            if (decodedPos >= decodedLength) {
                fetch();

                if (decodedLength < 0) {
                    return -1;
                }
            }

            int skipped = (int) Math.min(decodedLength - decodedPos, n);
            decodedPos += skipped;

            return skipped;
        }

        @Override
        public boolean markSupported() {
            return false;
        }

        @Override
        public synchronized void reset() throws IOException {
            throw new IOException("mark/reset not supported");
        }

        private static final class Node {
            Node left;
            Node right;

            int value; // > 63 non term.

            boolean canBeFill = false;
            boolean isLeaf = false;

            void set(final boolean next, final Node node) {
                if (!next) {
                    left = node;
                }
                else {
                    right = node;
                }
            }

            Node walk(final boolean next) {
                return next ? right : left;
            }

            @Override
            public String toString() {
                return "[leaf=" + isLeaf + ", value=" + value + ", canBeFill=" + canBeFill + "]";
            }
        }

        private static final class Tree {
            final Node root = new Node();

            void fill(final int depth, final int path, final int value) throws IOException {
                Node current = root;

                for (int i = 0; i < depth; i++) {
                    int bitPos = depth - 1 - i;
                    boolean isSet = ((path >> bitPos) & 1) == 1;
                    Node next = current.walk(isSet);

                    if (next == null) {
                        next = new Node();

                        if (i == depth - 1) {
                            next.value = value;
                            next.isLeaf = true;
                        }

                        if (path == 0) {
                            next.canBeFill = true;
                        }

                        current.set(isSet, next);
                    }
                    else {
                        if (next.isLeaf) {
                            throw new IOException("node is leaf, no other following");
                        }
                    }

                    current = next;
                }
            }

            void fill(final int depth, final int path, final Node node) throws IOException {
                Node current = root;

                for (int i = 0; i < depth; i++) {
                    int bitPos = depth - 1 - i;
                    boolean isSet = ((path >> bitPos) & 1) == 1;
                    Node next = current.walk(isSet);

                    if (next == null) {
                        if (i == depth - 1) {
                            next = node;
                        }
                        else {
                            next = new Node();
                        }

                        if (path == 0) {
                            next.canBeFill = true;
                        }

                        current.set(isSet, next);
                    }
                    else {
                        if (next.isLeaf) {
                            throw new IOException("node is leaf, no other following");
                        }
                    }

                    current = next;
                }
            }
        }

        static final short[][] BLACK_CODES = {
                { // 2 bits
                  0x2, 0x3,
                  },
                { // 3 bits
                  0x2, 0x3,
                  },
                { // 4 bits
                  0x2, 0x3,
                  },
                { // 5 bits
                  0x3,
                  },
                { // 6 bits
                  0x4, 0x5,
                  },
                { // 7 bits
                  0x4, 0x5, 0x7,
                  },
                { // 8 bits
                  0x4, 0x7,
                  },
                { // 9 bits
                  0x18,
                  },
                { // 10 bits
                  0x17, 0x18, 0x37, 0x8, 0xf,
                  },
                { // 11 bits
                  0x17, 0x18, 0x28, 0x37, 0x67, 0x68, 0x6c, 0x8, 0xc, 0xd,
                  },
                { // 12 bits
                  0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x1c, 0x1d, 0x1e, 0x1f, 0x24, 0x27, 0x28, 0x2b, 0x2c, 0x33,
                  0x34, 0x35, 0x37, 0x38, 0x52, 0x53, 0x54, 0x55, 0x56, 0x57, 0x58, 0x59, 0x5a, 0x5b, 0x64, 0x65,
                  0x66, 0x67, 0x68, 0x69, 0x6a, 0x6b, 0x6c, 0x6d, 0xc8, 0xc9, 0xca, 0xcb, 0xcc, 0xcd, 0xd2, 0xd3,
                  0xd4, 0xd5, 0xd6, 0xd7, 0xda, 0xdb,
                  },
                { // 13 bits
                  0x4a, 0x4b, 0x4c, 0x4d, 0x52, 0x53, 0x54, 0x55, 0x5a, 0x5b, 0x64, 0x65, 0x6c, 0x6d, 0x72, 0x73,
                  0x74, 0x75, 0x76, 0x77,
                  }
        };
        static final short[][] BLACK_RUN_LENGTHS = {
                { // 2 bits
                  3, 2,
                  },
                { // 3 bits
                  1, 4,
                  },
                { // 4 bits
                  6, 5,
                  },
                { // 5 bits
                  7,
                  },
                { // 6 bits
                  9, 8,
                  },
                { // 7 bits
                  10, 11, 12,
                  },
                { // 8 bits
                  13, 14,
                  },
                { // 9 bits
                  15,
                  },
                { // 10 bits
                  16, 17, 0, 18, 64,
                  },
                { // 11 bits
                  24, 25, 23, 22, 19, 20, 21, 1792, 1856, 1920,
                  },
                { // 12 bits
                  1984, 2048, 2112, 2176, 2240, 2304, 2368, 2432, 2496, 2560, 52, 55, 56, 59, 60, 320, 384, 448, 53,
                  54, 50, 51, 44, 45, 46, 47, 57, 58, 61, 256, 48, 49, 62, 63, 30, 31, 32, 33, 40, 41, 128, 192, 26,
                  27, 28, 29, 34, 35, 36, 37, 38, 39, 42, 43,
                  },
                { // 13 bits
                  640, 704, 768, 832, 1280, 1344, 1408, 1472, 1536, 1600, 1664, 1728, 512, 576, 896, 960, 1024, 1088,
                  1152, 1216,
                  }
        };

        public static final short[][] WHITE_CODES = {
                { // 4 bits
                  0x7, 0x8, 0xb, 0xc, 0xe, 0xf,
                  },
                { // 5 bits
                  0x12, 0x13, 0x14, 0x1b, 0x7, 0x8,
                  },
                { // 6 bits
                  0x17, 0x18, 0x2a, 0x2b, 0x3, 0x34, 0x35, 0x7, 0x8,
                  },
                { // 7 bits
                  0x13, 0x17, 0x18, 0x24, 0x27, 0x28, 0x2b, 0x3, 0x37, 0x4, 0x8, 0xc,
                  },
                { // 8 bits
                  0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x1a, 0x1b, 0x2, 0x24, 0x25, 0x28, 0x29, 0x2a, 0x2b, 0x2c, 0x2d,
                  0x3, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x4, 0x4a, 0x4b, 0x5, 0x52, 0x53, 0x54, 0x55, 0x58, 0x59,
                  0x5a, 0x5b, 0x64, 0x65, 0x67, 0x68, 0xa, 0xb,
                  },
                { // 9 bits
                  0x98, 0x99, 0x9a, 0x9b, 0xcc, 0xcd, 0xd2, 0xd3, 0xd4, 0xd5, 0xd6, 0xd7, 0xd8, 0xd9, 0xda, 0xdb,
                  },
                { // 10 bits
                },
                { // 11 bits
                  0x8, 0xc, 0xd,
                  },
                { // 12 bits
                  0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x1c, 0x1d, 0x1e, 0x1f,
                  }
        };

        public static final short[][] WHITE_RUN_LENGTHS = {
                { // 4 bits
                  2, 3, 4, 5, 6, 7,
                  },
                { // 5 bits
                  128, 8, 9, 64, 10, 11,
                  },
                { // 6 bits
                  192, 1664, 16, 17, 13, 14, 15, 1, 12,
                  },
                { // 7 bits
                  26, 21, 28, 27, 18, 24, 25, 22, 256, 23, 20, 19,
                  },
                { // 8 bits
                  33, 34, 35, 36, 37, 38, 31, 32, 29, 53, 54, 39, 40, 41, 42, 43, 44, 30, 61, 62, 63, 0, 320, 384, 45,
                  59, 60, 46, 49, 50, 51, 52, 55, 56, 57, 58, 448, 512, 640, 576, 47, 48,
                  },
                { // 9 bits
                  1472, 1536, 1600, 1728, 704, 768, 832, 896, 960, 1024, 1088, 1152, 1216, 1280, 1344, 1408,
                  },
                { // 10 bits
                },
                { // 11 bits
                  1792, 1856, 1920,
                  },
                { // 12 bits
                  1984, 2048, 2112, 2176, 2240, 2304, 2368, 2432, 2496, 2560,
                  }
        };

        final static Node EOL;
        final static Node FILL;
        final static Tree blackRunTree;
        final static Tree whiteRunTree;
        final static Tree eolOnlyTree;
        final static Tree codeTree;

        final static int VALUE_EOL = -2000;
        final static int VALUE_FILL = -1000;
        final static int VALUE_PASSMODE = -3000;
        final static int VALUE_HMODE = -4000;

        static {
            EOL = new Node();
            EOL.isLeaf = true;
            EOL.value = VALUE_EOL;
            FILL = new Node();
            FILL.value = VALUE_FILL;
            FILL.left = FILL;
            FILL.right = EOL;

            eolOnlyTree = new Tree();
            try {
                eolOnlyTree.fill(12, 0, FILL);
                eolOnlyTree.fill(12, 1, EOL);
            }
            catch (IOException e) {
                throw new AssertionError(e);
            }

            blackRunTree = new Tree();
            try {
                for (int i = 0; i < BLACK_CODES.length; i++) {
                    for (int j = 0; j < BLACK_CODES[i].length; j++) {
                        blackRunTree.fill(i + 2, BLACK_CODES[i][j], BLACK_RUN_LENGTHS[i][j]);
                    }
                }
                blackRunTree.fill(12, 0, FILL);
                blackRunTree.fill(12, 1, EOL);
            }
            catch (IOException e) {
                throw new AssertionError(e);
            }

            whiteRunTree = new Tree();
            try {
                for (int i = 0; i < WHITE_CODES.length; i++) {
                    for (int j = 0; j < WHITE_CODES[i].length; j++) {
                        whiteRunTree.fill(i + 4, WHITE_CODES[i][j], WHITE_RUN_LENGTHS[i][j]);
                    }
                }

                whiteRunTree.fill(12, 0, FILL);
                whiteRunTree.fill(12, 1, EOL);
            }
            catch (IOException e) {
                throw new AssertionError(e);
            }

            codeTree = new Tree();
            try {
                codeTree.fill(4, 1, VALUE_PASSMODE); // pass mode
                codeTree.fill(3, 1, VALUE_HMODE); // H mode
                codeTree.fill(1, 1, 0); // V(0)
                codeTree.fill(3, 3, 1); // V_R(1)
                codeTree.fill(6, 3, 2); // V_R(2)
                codeTree.fill(7, 3, 3); // V_R(3)
                codeTree.fill(3, 2, -1); // V_L(1)
                codeTree.fill(6, 2, -2); // V_L(2)
                codeTree.fill(7, 2, -3); // V_L(3)
            }
            catch (IOException e) {
                throw new AssertionError(e);
            }
        }
    }