/* Copyright (C) 2001-2023 Artifex Software, Inc.

   All Rights Reserved.

   This software is provided AS-IS with no warranty, either express or

   implied.

   This software is distributed under license and may not be copied,

   modified or distributed except as expressly authorized under the terms

   of the license contained in the file LICENSE in this distribution.

   Refer to licensing information at http://www.artifex.com or contact

   Artifex Software, Inc.,  39 Mesa Street, Suite 108A, San Francisco,

   CA 94129, USA, for further information.

*/

/*

    jbig2dec

*/

/* An implementation of MMR decoding. This is based on the

   implementation in Fitz, which in turn is based on the one

   in Ghostscript.

*/

#ifdef HAVE_CONFIG_H

#include "config.h"

#endif

#include "os_types.h"

#include <assert.h>

#include <stddef.h>

#include <stdio.h>

#include <string.h>

#include "jbig2.h"

#include "jbig2_priv.h"

#include "jbig2_arith.h"

#include "jbig2_generic.h"

#include "jbig2_image.h"

#include "jbig2_mmr.h"

#include "jbig2_segment.h"

typedef struct {

    uint32_t width;

    uint32_t height;

    const byte *data;

    size_t size;

    size_t consumed_bits;

    uint32_t data_index;

    uint32_t bit_index;

    uint32_t word;

} Jbig2MmrCtx;

#define MINUS1 UINT32_MAX

#define ERROR -1

#define ZEROES -2

#define UNCOMPRESSED -3

static void

jbig2_decode_mmr_init(Jbig2MmrCtx *mmr, int width, int height, const byte *data, size_t size)

{

    mmr->width = width;

    mmr->height = height;

    mmr->data = data;

    mmr->size = size;

    mmr->data_index = 0;

    mmr->bit_index = 32;

    mmr->word = 0;

    mmr->consumed_bits = 0;

    while (mmr->bit_index >= 8 && mmr->data_index < mmr->size) {

        mmr->bit_index -= 8;

        mmr->word |= (mmr->data[mmr->data_index] << mmr->bit_index);

        mmr->data_index++;

    }

}

static void

jbig2_decode_mmr_consume(Jbig2MmrCtx *mmr, int n_bits)

{

    mmr->consumed_bits += n_bits;

    if (mmr->consumed_bits > mmr->size * 8)

        mmr->consumed_bits = mmr->size * 8;

    mmr->word <<= n_bits;

    mmr->bit_index += n_bits;

    while (mmr->bit_index >= 8 && mmr->data_index < mmr->size) {

        mmr->bit_index -= 8;

        mmr->word |= (mmr->data[mmr->data_index] << mmr->bit_index);

        mmr->data_index++;

    }

}

/*

<raph> the first 2^(initialbits) entries map bit patterns to decodes

<raph> let's say initial_bits is 8 for the sake of example

<raph> and that the code is 1001

<raph> that means that entries 0x90 .. 0x9f have the entry { val, 4 }

<raph> because those are all the bytes that start with the code

<raph> and the 4 is the length of the code

... if (n_bits > initial_bits) ...

<raph> anyway, in that case, it basically points to a mini table

<raph> the n_bits is the maximum length of all codes beginning with that byte

<raph> so 2^(n_bits - initial_bits) is the size of the mini-table

<raph> peter came up with this, and it makes sense

*/

typedef struct {

    short val;

    short n_bits;

} mmr_table_node;

/* white decode table (runlength huffman codes) */

const mmr_table_node jbig2_mmr_white_decode[] = {

    {256, 12},

    {272, 12},

    {29, 8},

    {30, 8},

    {45, 8},

    {46, 8},

    {22, 7},

    {22, 7},

    {23, 7},

    {23, 7},

    {47, 8},

    {48, 8},

    {13, 6},

    {13, 6},

    {13, 6},

    {13, 6},

    {20, 7},

    {20, 7},

    {33, 8},

    {34, 8},

    {35, 8},

    {36, 8},

    {37, 8},

    {38, 8},

    {19, 7},

    {19, 7},

    {31, 8},

    {32, 8},

    {1, 6},

    {1, 6},

    {1, 6},

    {1, 6},

    {12, 6},

    {12, 6},

    {12, 6},

    {12, 6},

    {53, 8},

    {54, 8},

    {26, 7},

    {26, 7},

    {39, 8},

    {40, 8},

    {41, 8},

    {42, 8},

    {43, 8},

    {44, 8},

    {21, 7},

    {21, 7},

    {28, 7},

    {28, 7},

    {61, 8},

    {62, 8},

    {63, 8},

    {0, 8},

    {320, 8},

    {384, 8},

    {10, 5},

    {10, 5},

    {10, 5},

    {10, 5},

    {10, 5},

    {10, 5},

    {10, 5},

    {10, 5},

    {11, 5},

    {11, 5},

    {11, 5},

    {11, 5},

    {11, 5},

    {11, 5},

    {11, 5},

    {11, 5},

    {27, 7},

    {27, 7},

    {59, 8},

    {60, 8},

    {288, 9},

    {290, 9},

    {18, 7},

    {18, 7},

    {24, 7},

    {24, 7},

    {49, 8},

    {50, 8},

    {51, 8},

    {52, 8},

    {25, 7},

    {25, 7},

    {55, 8},

    {56, 8},

    {57, 8},

    {58, 8},

    {192, 6},

    {192, 6},

    {192, 6},

    {192, 6},

    {1664, 6},

    {1664, 6},

    {1664, 6},

    {1664, 6},

    {448, 8},

    {512, 8},

    {292, 9},

    {640, 8},

    {576, 8},

    {294, 9},

    {296, 9},

    {298, 9},

    {300, 9},

    {302, 9},

    {256, 7},

    {256, 7},

    {2, 4},

    {2, 4},

    {2, 4},

    {2, 4},

    {2, 4},

    {2, 4},

    {2, 4},

    {2, 4},

    {2, 4},

    {2, 4},

    {2, 4},

    {2, 4},

    {2, 4},

    {2, 4},

    {2, 4},

    {2, 4},

    {3, 4},

    {3, 4},

    {3, 4},

    {3, 4},

    {3, 4},

    {3, 4},

    {3, 4},

    {3, 4},

    {3, 4},

    {3, 4},

    {3, 4},

    {3, 4},

    {3, 4},

    {3, 4},

    {3, 4},

    {3, 4},

    {128, 5},

    {128, 5},

    {128, 5},

    {128, 5},

    {128, 5},

    {128, 5},

    {128, 5},

    {128, 5},

    {8, 5},

    {8, 5},

    {8, 5},

    {8, 5},

    {8, 5},

    {8, 5},

    {8, 5},

    {8, 5},

    {9, 5},

    {9, 5},

    {9, 5},

    {9, 5},

    {9, 5},

    {9, 5},

    {9, 5},

    {9, 5},

    {16, 6},

    {16, 6},

    {16, 6},

    {16, 6},

    {17, 6},

    {17, 6},

    {17, 6},

    {17, 6},

    {4, 4},

    {4, 4},

    {4, 4},

    {4, 4},

    {4, 4},

    {4, 4},

    {4, 4},

    {4, 4},

    {4, 4},

    {4, 4},

    {4, 4},

    {4, 4},

    {4, 4},

    {4, 4},

    {4, 4},

    {4, 4},

    {5, 4},

    {5, 4},

    {5, 4},

    {5, 4},

    {5, 4},

    {5, 4},

    {5, 4},

    {5, 4},

    {5, 4},

    {5, 4},

    {5, 4},

    {5, 4},

    {5, 4},

    {5, 4},

    {5, 4},

    {5, 4},

    {14, 6},

    {14, 6},

    {14, 6},

    {14, 6},

    {15, 6},

    {15, 6},

    {15, 6},

    {15, 6},

    {64, 5},

    {64, 5},

    {64, 5},

    {64, 5},

    {64, 5},

    {64, 5},

    {64, 5},

    {64, 5},

    {6, 4},

    {6, 4},

    {6, 4},

    {6, 4},

    {6, 4},

    {6, 4},

    {6, 4},

    {6, 4},

    {6, 4},

    {6, 4},

    {6, 4},

    {6, 4},

    {6, 4},

    {6, 4},

    {6, 4},

    {6, 4},

    {7, 4},

    {7, 4},

    {7, 4},

    {7, 4},

    {7, 4},

    {7, 4},

    {7, 4},

    {7, 4},

    {7, 4},

    {7, 4},

    {7, 4},

    {7, 4},

    {7, 4},

    {7, 4},

    {7, 4},

    {7, 4},

    {-2, 3},

    {-2, 3},

    {-1, 0},

    {-1, 0},

    {-1, 0},

    {-1, 0},

    {-1, 0},

    {-1, 0},

    {-1, 0},

    {-1, 0},

    {-1, 0},

    {-1, 0},

    {-1, 0},

    {-1, 0},

    {-1, 0},

    {-3, 4},

    {1792, 3},

    {1792, 3},

    {1984, 4},

    {2048, 4},

    {2112, 4},

    {2176, 4},

    {2240, 4},

    {2304, 4},

    {1856, 3},

    {1856, 3},

    {1920, 3},

    {1920, 3},

    {2368, 4},

    {2432, 4},

    {2496, 4},

    {2560, 4},

    {1472, 1},

    {1536, 1},

    {1600, 1},

    {1728, 1},

    {704, 1},

    {768, 1},

    {832, 1},

    {896, 1},

    {960, 1},

    {1024, 1},

    {1088, 1},

    {1152, 1},

    {1216, 1},

    {1280, 1},

    {1344, 1},

    {1408, 1}

};

/* black decode table (runlength huffman codes) */

const mmr_table_node jbig2_mmr_black_decode[] = {

    {128, 12},

    {160, 13},

    {224, 12},

    {256, 12},

    {10, 7},

    {11, 7},

    {288, 12},

    {12, 7},

    {9, 6},

    {9, 6},

    {8, 6},

    {8, 6},

    {7, 5},

    {7, 5},

    {7, 5},

    {7, 5},

    {6, 4},

    {6, 4},

    {6, 4},

    {6, 4},

    {6, 4},

    {6, 4},

    {6, 4},

    {6, 4},

    {5, 4},

    {5, 4},

    {5, 4},

    {5, 4},

    {5, 4},

    {5, 4},

    {5, 4},

    {5, 4},

    {1, 3},

    {1, 3},

    {1, 3},

    {1, 3},

    {1, 3},

    {1, 3},

    {1, 3},

    {1, 3},

    {1, 3},

    {1, 3},

    {1, 3},

    {1, 3},

    {1, 3},

    {1, 3},

    {1, 3},

    {1, 3},

    {4, 3},

    {4, 3},

    {4, 3},

    {4, 3},

    {4, 3},

    {4, 3},

    {4, 3},

    {4, 3},

    {4, 3},

    {4, 3},

    {4, 3},

    {4, 3},

    {4, 3},

    {4, 3},

    {4, 3},

    {4, 3},

    {3, 2},

    {3, 2},

    {3, 2},

    {3, 2},

    {3, 2},

    {3, 2},

    {3, 2},

    {3, 2},

    {3, 2},

    {3, 2},

    {3, 2},

    {3, 2},

    {3, 2},

    {3, 2},

    {3, 2},

    {3, 2},

    {3, 2},

    {3, 2},

    {3, 2},

    {3, 2},

    {3, 2},

    {3, 2},

    {3, 2},

    {3, 2},

    {3, 2},

    {3, 2},

    {3, 2},

    {3, 2},

    {3, 2},

    {3, 2},

    {3, 2},

    {3, 2},

    {2, 2},

    {2, 2},

    {2, 2},

    {2, 2},

    {2, 2},

    {2, 2},

    {2, 2},

    {2, 2},

    {2, 2},

    {2, 2},

    {2, 2},

    {2, 2},

    {2, 2},

    {2, 2},

    {2, 2},

    {2, 2},

    {2, 2},

    {2, 2},

    {2, 2},

    {2, 2},

    {2, 2},

    {2, 2},

    {2, 2},

    {2, 2},

    {2, 2},

    {2, 2},

    {2, 2},

    {2, 2},

    {2, 2},

    {2, 2},

    {2, 2},

    {2, 2},

    {-2, 4},

    {-2, 4},

    {-1, 0},

    {-1, 0},

    {-1, 0},

    {-1, 0},

    {-1, 0},

    {-1, 0},

    {-1, 0},

    {-1, 0},

    {-1, 0},

    {-1, 0},

    {-1, 0},

    {-1, 0},

    {-1, 0},

    {-3, 5},

    {1792, 4},

    {1792, 4},

    {1984, 5},

    {2048, 5},

    {2112, 5},

    {2176, 5},

    {2240, 5},

    {2304, 5},

    {1856, 4},

    {1856, 4},

    {1920, 4},

    {1920, 4},

    {2368, 5},

    {2432, 5},

    {2496, 5},

    {2560, 5},

    {18, 3},

    {18, 3},

    {18, 3},

    {18, 3},

    {18, 3},

    {18, 3},

    {18, 3},

    {18, 3},

    {52, 5},

    {52, 5},

    {640, 6},

    {704, 6},

    {768, 6},

    {832, 6},

    {55, 5},

    {55, 5},

    {56, 5},

    {56, 5},

    {1280, 6},

    {1344, 6},

    {1408, 6},

    {1472, 6},

    {59, 5},

    {59, 5},

    {60, 5},

    {60, 5},

    {1536, 6},

    {1600, 6},

    {24, 4},

    {24, 4},

    {24, 4},

    {24, 4},

    {25, 4},

    {25, 4},

    {25, 4},

    {25, 4},

    {1664, 6},

    {1728, 6},

    {320, 5},

    {320, 5},

    {384, 5},

    {384, 5},

    {448, 5},

    {448, 5},

    {512, 6},

    {576, 6},

    {53, 5},

    {53, 5},

    {54, 5},

    {54, 5},

    {896, 6},

    {960, 6},

    {1024, 6},

    {1088, 6},

    {1152, 6},

    {1216, 6},

    {64, 3},

    {64, 3},

    {64, 3},

    {64, 3},

    {64, 3},

    {64, 3},

    {64, 3},

    {64, 3},

    {13, 1},

    {13, 1},

    {13, 1},

    {13, 1},

    {13, 1},

    {13, 1},

    {13, 1},

    {13, 1},

    {13, 1},

    {13, 1},

    {13, 1},

    {13, 1},

    {13, 1},

    {13, 1},

    {13, 1},

    {13, 1},

    {23, 4},

    {23, 4},

    {50, 5},

    {51, 5},

    {44, 5},

    {45, 5},

    {46, 5},

    {47, 5},

    {57, 5},

    {58, 5},

    {61, 5},

    {256, 5},

    {16, 3},

    {16, 3},

    {16, 3},

    {16, 3},

    {17, 3},

    {17, 3},

    {17, 3},

    {17, 3},

    {48, 5},

    {49, 5},

    {62, 5},

    {63, 5},

    {30, 5},

    {31, 5},

    {32, 5},

    {33, 5},

    {40, 5},

    {41, 5},

    {22, 4},

    {22, 4},

    {14, 1},

    {14, 1},

    {14, 1},

    {14, 1},

    {14, 1},

    {14, 1},

    {14, 1},

    {14, 1},

    {14, 1},

    {14, 1},

    {14, 1},

    {14, 1},

    {14, 1},

    {14, 1},

    {14, 1},

    {14, 1},

    {15, 2},

    {15, 2},

    {15, 2},

    {15, 2},

    {15, 2},

    {15, 2},

    {15, 2},

    {15, 2},

    {128, 5},

    {192, 5},

    {26, 5},

    {27, 5},

    {28, 5},

    {29, 5},

    {19, 4},

    {19, 4},

    {20, 4},

    {20, 4},

    {34, 5},

    {35, 5},

    {36, 5},

    {37, 5},

    {38, 5},

    {39, 5},

    {21, 4},

    {21, 4},

    {42, 5},

    {43, 5},

    {0, 3},

    {0, 3},

    {0, 3},

    {0, 3}

};

#define getbit(buf, x) ( ( buf[x >> 3] >> ( 7 - (x & 7) ) ) & 1 )

/* On platforms that enforce aligned memory accesses, we can't just

 * cast the byte * to the type of object we are accessing, we have

 * unpack the requisite number of bytes, and deal with it that way.

 * Note that the comments below about being 16/32 bit boundaries

 * is referring to offsets into the byte stream, *not* memory

 * addresses.

 */

#define getword16(b)  ((uint16_t)(b[0] | (b[1] << 8)))

#define getword32(b)  ((uint32_t)(getword16(b) | (getword16((b + 2)) << 16)))

static uint32_t

jbig2_find_changing_element(const byte *line, uint32_t x, uint32_t w)

{

    int a;

    uint8_t     all8;

    uint16_t    all16;

    uint32_t    all32;

    if (line == NULL)

        return w;

    if (x == MINUS1) {

        a = 0;

        x = 0;

    } else if (x < w) {

        a = getbit(line, x);

        x++;

    } else {

        return x;

    }

    /* We will be looking for a uint8 or uint16 or uint32 that has at least one

    bit different from <a>, so prepare some useful values for comparison. */

    all8  = (a) ? 0xff : 0;

    all16 = (a) ? 0xffff : 0;

    all32 = (a) ? 0xffffffff : 0;

    /* Check individual bits up to next 8-bit boundary.

    [Would it be worth looking at top 4 bits, then at 2 bits then at 1 bit,

    instead of iterating over all 8 bits? */

    if ( ((uint8_t*) line)[ x / 8] == all8) {

        /* Don't bother checking individual bits if the enclosing uint8 equals

        all8 - just move to the next byte. */

        x = x / 8 * 8 + 8;

        if (x >= w) {

            x = w;

            goto end;

        }

    } else {

        for(;;) {

            if (x == w) {

                goto end;

            }

            if (x % 8 == 0) {

                break;

            }

            if (getbit(line, x) != a) {

                goto end;

            }

            x += 1;

        }

    }

    assert(x % 8 == 0);

    /* Check next uint8 if we are not on 16-bit boundary. */

    if (x % 16) {

        if (w - x < 8) {

            goto check1;

        }

        if ( ((uint8_t*) line)[ x / 8] != all8) {

            goto check1;

        }

        x += 8; /* This will make x a multiple of 16. */

    }

    assert(x % 16 == 0);

    /* Check next uint16 if we are not on 32-bit boundary. */

    if (x % 32) {

        if (w - x < 16) {

            goto check8;

        }

        if ( getword16((line + (x / 8))) != all16) {

            goto check8_no_eof;

        }

        x += 16; /* This will make x a multiple of 32. */

    }

    /* We are now on a 32-bit boundary. Check uint32's until we reach last

    sub-32-bit region. */

    assert(x % 32 == 0);

    for(;;) {

        if (w - x < 32) {

            /* We could still look at the uint32 here - if it equals all32, we

            know there is no match before <w> so could do {x = w; goto end;}.

            But for now we simply fall into the epilogue checking, which will

            look at the next uint16, then uint8, then last 8 bits. */

            goto check16;

        }

        if ( getword32((line + (x / 8))) != all32) {

            goto check16_no_eof;

        }

        x += 32;

    }

    /* Check next uint16. */

check16:

    assert(x % 16 == 0);

    if (w - x < 16) {

        goto check8;

    }

check16_no_eof:

    assert(w - x >= 16);

    if ( getword16((line + (x / 8))) != all16) {

        goto check8_no_eof;

    }

    x += 16;

    /* Check next uint8. */

check8:

    assert(x % 8 == 0);

    if (w - x < 8) {

        goto check1;

    }

check8_no_eof:

    assert(w - x >= 8);

    if ( ((uint8_t*) line)[x/8] != all8) {

        goto check1;

    }

    x += 8;

    /* Check up to the next 8 bits. */

check1:

    assert(x % 8 == 0);

    if ( ((uint8_t*) line)[ x / 8] == all8) {

        x = w;

        goto end;

    }

    {

        for(;;) {

            if (x == w) {

                goto end;

            }

            if (getbit(line, x) != a) {

                goto end;

            }

            x += 1;

        }

    }

end:

    return x;

}

#undef getword16

#undef getword32

static uint32_t

jbig2_find_changing_element_of_color(const byte *line, uint32_t x, uint32_t w, int color)

{

    if (line == NULL)

        return w;

    x = jbig2_find_changing_element(line, x, w);

    if (x < w && getbit(line, x) != color)

        x = jbig2_find_changing_element(line, x, w);

    return x;

}

static const byte lm[8] = { 0xFF, 0x7F, 0x3F, 0x1F, 0x0F, 0x07, 0x03, 0x01 };

static const byte rm[8] = { 0x00, 0x80, 0xC0, 0xE0, 0xF0, 0xF8, 0xFC, 0xFE };

static void

jbig2_set_bits(byte *line, uint32_t x0, uint32_t x1)

{

    uint32_t a0, a1, b0, b1, a;

    a0 = x0 >> 3;

    a1 = x1 >> 3;

    b0 = x0 & 7;

    b1 = x1 & 7;

    if (a0 == a1) {

        line[a0] |= lm[b0] & rm[b1];

    } else {

        line[a0] |= lm[b0];

        for (a = a0 + 1; a < a1; a++)

            line[a] = 0xFF;

        if (b1)

            line[a1] |= rm[b1];

    }

}

static int

jbig2_decode_get_code(Jbig2MmrCtx *mmr, const mmr_table_node *table, int initial_bits)

{

    uint32_t word = mmr->word;

    int table_ix = word >> (32 - initial_bits);

    int val = table[table_ix].val;

    int n_bits = table[table_ix].n_bits;

    if (n_bits > initial_bits) {

        int mask = (1 << (32 - initial_bits)) - 1;

        table_ix = val + ((word & mask) >> (32 - n_bits));

        val = table[table_ix].val;

        n_bits = initial_bits + table[table_ix].n_bits;

    }

    jbig2_decode_mmr_consume(mmr, n_bits);

    return val;

}

static int

jbig2_decode_get_run(Jbig2Ctx *ctx, Jbig2MmrCtx *mmr, const mmr_table_node *table, int initial_bits)

{

    int result = 0;

    int val;

    do {

        val = jbig2_decode_get_code(mmr, table, initial_bits);

        if (val == ERROR)

            return jbig2_error(ctx, JBIG2_SEVERITY_FATAL, JBIG2_UNKNOWN_SEGMENT_NUMBER, "invalid code detected in MMR-coded data");

        else if (val == UNCOMPRESSED)

            return jbig2_error(ctx, JBIG2_SEVERITY_FATAL, JBIG2_UNKNOWN_SEGMENT_NUMBER, "uncompressed code in MMR-coded data");

        else if (val == ZEROES)

            return jbig2_error(ctx, JBIG2_SEVERITY_FATAL, JBIG2_UNKNOWN_SEGMENT_NUMBER, "zeroes code in MMR-coded data");

        result += val;

    } while (val >= 64);

    return result;

}

static int

jbig2_decode_mmr_line(Jbig2Ctx *ctx, Jbig2MmrCtx *mmr, const byte *ref, byte *dst, int *eofb)

{

    uint32_t a0 = MINUS1;

    uint32_t a1, a2, b1, b2;

    int c = 0;                  /* 0 is white, black is 1 */

    while (1) {

        uint32_t word = mmr->word;

        /* printf ("%08x\n", word); */

        if (a0 != MINUS1 && a0 >= mmr->width)

            break;

        if ((word >> (32 - 3)) == 1) {

            int white_run, black_run;

            jbig2_decode_mmr_consume(mmr, 3);

            if (a0 == MINUS1)

                a0 = 0;

            if (c == 0) {

                white_run = jbig2_decode_get_run(ctx, mmr, jbig2_mmr_white_decode, 8);

                if (white_run < 0)

                    return jbig2_error(ctx, JBIG2_SEVERITY_WARNING, JBIG2_UNKNOWN_SEGMENT_NUMBER, "failed to decode white H run");

                black_run = jbig2_decode_get_run(ctx, mmr, jbig2_mmr_black_decode, 7);

                if (black_run < 0)

                    return jbig2_error(ctx, JBIG2_SEVERITY_WARNING, JBIG2_UNKNOWN_SEGMENT_NUMBER, "failed to decode black H run");

                /* printf ("H %d %d\n", white_run, black_run); */

                a1 = a0 + white_run;

                a2 = a1 + black_run;

                if (a1 > mmr->width)

                    a1 = mmr->width;

                if (a2 > mmr->width)

                    a2 = mmr->width;

                if (a2 < a1) {

                    jbig2_error(ctx, JBIG2_SEVERITY_WARNING, JBIG2_UNKNOWN_SEGMENT_NUMBER, "ignoring negative black H run");

                    a2 = a1;

                }

                if (a1 < mmr->width)

                    jbig2_set_bits(dst, a1, a2);

                a0 = a2;

            } else {

                black_run = jbig2_decode_get_run(ctx, mmr, jbig2_mmr_black_decode, 7);

                if (black_run < 0)

                    return jbig2_error(ctx, JBIG2_SEVERITY_WARNING, JBIG2_UNKNOWN_SEGMENT_NUMBER, "failed to decode black H run");

                white_run = jbig2_decode_get_run(ctx, mmr, jbig2_mmr_white_decode, 8);

                if (white_run < 0)

                    return jbig2_error(ctx, JBIG2_SEVERITY_WARNING, JBIG2_UNKNOWN_SEGMENT_NUMBER, "failed to decode white H run");

                /* printf ("H %d %d\n", black_run, white_run); */

                a1 = a0 + black_run;

                a2 = a1 + white_run;

                if (a1 > mmr->width)

                    a1 = mmr->width;

                if (a2 > mmr->width)

                    a2 = mmr->width;

                if (a1 < a0) {

                    jbig2_error(ctx, JBIG2_SEVERITY_WARNING, JBIG2_UNKNOWN_SEGMENT_NUMBER, "ignoring negative white H run");

                    a1 = a0;

                }

                if (a0 < mmr->width)

                    jbig2_set_bits(dst, a0, a1);

                a0 = a2;

            }

        }

        else if ((word >> (32 - 4)) == 1) {

            /* printf ("P\n"); */

            jbig2_decode_mmr_consume(mmr, 4);

            b1 = jbig2_find_changing_element_of_color(ref, a0, mmr->width, !c);

            b2 = jbig2_find_changing_element(ref, b1, mmr->width);

            if (c) {

                if (b2 < a0) {

                    jbig2_error(ctx, JBIG2_SEVERITY_WARNING, JBIG2_UNKNOWN_SEGMENT_NUMBER, "ignoring negative P run");

                    b2 = a0;

                }

                if (a0 < mmr->width)

                    jbig2_set_bits(dst, a0, b2);

            }

            a0 = b2;

        }

        else if ((word >> (32 - 1)) == 1) {

            /* printf ("V(0)\n"); */

            jbig2_decode_mmr_consume(mmr, 1);

            b1 = jbig2_find_changing_element_of_color(ref, a0, mmr->width, !c);

            if (c) {

                if (b1 < a0) {

                    jbig2_error(ctx, JBIG2_SEVERITY_WARNING, JBIG2_UNKNOWN_SEGMENT_NUMBER, "ignoring negative V(0) run");

                    b1 = a0;

                }

                if (a0 < mmr->width)

                    jbig2_set_bits(dst, a0, b1);

            }

            a0 = b1;

            c = !c;

        }

        else if ((word >> (32 - 3)) == 3) {

            /* printf ("VR(1)\n"); */

            jbig2_decode_mmr_consume(mmr, 3);

            b1 = jbig2_find_changing_element_of_color(ref, a0, mmr->width, !c);

            if (b1 + 1 <= mmr->width)

                b1 += 1;

            if (c) {

                if (b1 < a0) {

                    jbig2_error(ctx, JBIG2_SEVERITY_WARNING, JBIG2_UNKNOWN_SEGMENT_NUMBER, "ignoring negative VR(1) run");

                    b1 = a0;

                }