/*
    Expand one page of fax data
    This file is part of viewfax - g3/g4 fax processing software.
    SPDX-FileCopyrightText: 1990, 1995  Frank D. Cringle.
    SPDX-License-Identifier: GPL-2.0-or-later
*/

#include "faxexpand.h"

#include <stdio.h>
#include <stdlib.h>

#include <QDebug>

#include "fax_debug.h"
// Uncomment this for verbose debug output
//#define DEBUG_FAX
#define verbose false

pagenode::pagenode()
{
}

/* Note that NeedBits() only works for n <= 16 */
#define NeedBits(n)                                                                                                                                                                                                                            \
    do {                                                                                                                                                                                                                                       \
        if (BitsAvail < (n)) {                                                                                                                                                                                                                 \
            BitAcc |= *sp++ << BitsAvail;                                                                                                                                                                                                      \
            BitsAvail += 16;                                                                                                                                                                                                                   \
        }                                                                                                                                                                                                                                      \
    } while (0)
#define GetBits(n) (BitAcc & ((1 << (n)) - 1))
#define ClrBits(n)                                                                                                                                                                                                                             \
    do {                                                                                                                                                                                                                                       \
        BitAcc >>= (n);                                                                                                                                                                                                                        \
        BitsAvail -= (n);                                                                                                                                                                                                                      \
    } while (0)

#ifdef DEBUG_FAX
#define DEBUG_SHOW putchar(BitAcc &(1 << t) ? '1' : '0')
#define LOOKUP(wid, tab)                                                                                                                                                                                                                       \
    do {                                                                                                                                                                                                                                       \
        int t;                                                                                                                                                                                                                                 \
        NeedBits(wid);                                                                                                                                                                                                                         \
        TabEnt = tab + GetBits(wid);                                                                                                                                                                                                           \
        printf("%08lX/%d: %s%5d\t", BitAcc, BitsAvail, StateNames[TabEnt->State], TabEnt->Param);                                                                                                                                              \
        for (t = 0; t < TabEnt->Width; t++)                                                                                                                                                                                                    \
            DEBUG_SHOW;                                                                                                                                                                                                                        \
        putchar('\n');                                                                                                                                                                                                                         \
        fflush(stdout);                                                                                                                                                                                                                        \
        ClrBits(TabEnt->Width);                                                                                                                                                                                                                \
    } while (0)

#define SETVAL(x)                                                                                                                                                                                                                              \
    do {                                                                                                                                                                                                                                       \
        *pa++ = RunLength + (x);                                                                                                                                                                                                               \
        printf("SETVAL: %d\t%d\n", RunLength + (x), a0);                                                                                                                                                                                       \
        a0 += x;                                                                                                                                                                                                                               \
        RunLength = 0;                                                                                                                                                                                                                         \
    } while (0)

const char *StateNames[] = {
    "Null   ",
    "Pass   ",
    "Horiz  ",
    "V0     ",
    "VR     ",
    "VL     ",
    "Ext    ",
    "TermW  ",
    "TermB  ",
    "MakeUpW",
    "MakeUpB",
    "MakeUp ",
    "EOL    ",
};

#else
#define LOOKUP(wid, tab)                                                                                                                                                                                                                       \
    do {                                                                                                                                                                                                                                       \
        NeedBits(wid);                                                                                                                                                                                                                         \
        TabEnt = tab + GetBits(wid);                                                                                                                                                                                                           \
        ClrBits(TabEnt->Width);                                                                                                                                                                                                                \
    } while (0)

#define SETVAL(x)                                                                                                                                                                                                                              \
    do {                                                                                                                                                                                                                                       \
        *pa++ = RunLength + (x);                                                                                                                                                                                                               \
        a0 += x;                                                                                                                                                                                                                               \
        RunLength = 0;                                                                                                                                                                                                                         \
    } while (0)
#endif

#define dumpruns(runs)                                                                                                                                                                                                                         \
    do {                                                                                                                                                                                                                                       \
        printf("-------------------- %d\n", LineNum);                                                                                                                                                                                          \
        for (pa = runs, a0 = 0; a0 < lastx; a0 += *pa++)                                                                                                                                                                                       \
            printf("%4d %d\n", a0, *pa);                                                                                                                                                                                                       \
    } while (0)

#define EndOfData(pn) (sp >= pn->data + pn->length / sizeof(*pn->data))

/* This macro handles coding errors in G3 data.
   We redefine it below for the G4 case */
#define SKIP_EOL                                                                                                                                                                                                                               \
    do {                                                                                                                                                                                                                                       \
        while (!EndOfData(pn)) {                                                                                                                                                                                                               \
            NeedBits(11);                                                                                                                                                                                                                      \
            if (GetBits(11) == 0)                                                                                                                                                                                                              \
                break;                                                                                                                                                                                                                         \
            ClrBits(1);                                                                                                                                                                                                                        \
        }                                                                                                                                                                                                                                      \
        ClrBits(11);                                                                                                                                                                                                                           \
        goto EOL;                                                                                                                                                                                                                              \
    } while (0)
#define eol2lab                                                                                                                                                                                                                                \
    EOL2:

/* the line expanders are written as macros so that they can be reused
   (twice each) but still have direct access to the local variables of
   the "calling" function */
#define expand1d()                                                                                                                                                                                                                             \
    do {                                                                                                                                                                                                                                       \
        while (a0 < lastx) {                                                                                                                                                                                                                   \
            int done = 0;                                                                                                                                                                                                                      \
            while (!done) { /* white first */                                                                                                                                                                                                  \
                LOOKUP(12, WhiteTable);                                                                                                                                                                                                        \
                switch (TabEnt->State) {                                                                                                                                                                                                       \
                case S_EOL:                                                                                                                                                                                                                    \
                    EOLcnt = 1;                                                                                                                                                                                                                \
                    goto EOL;                                                                                                                                                                                                                  \
                case S_TermW:                                                                                                                                                                                                                  \
                    SETVAL(TabEnt->Param);                                                                                                                                                                                                     \
                    done = 1;                                                                                                                                                                                                                  \
                    break;                                                                                                                                                                                                                     \
                case S_MakeUpW:                                                                                                                                                                                                                \
                case S_MakeUp:                                                                                                                                                                                                                 \
                    a0 += TabEnt->Param;                                                                                                                                                                                                       \
                    RunLength += TabEnt->Param;                                                                                                                                                                                                \
                    break;                                                                                                                                                                                                                     \
                case S_Ext:                                                                                                                                                                                                                    \
                    unexpected("Extension code", LineNum);                                                                                                                                                                                     \
                    SKIP_EOL;                                                                                                                                                                                                                  \
                    break;                                                                                                                                                                                                                     \
                default:                                                                                                                                                                                                                       \
                    unexpected("WhiteTable", LineNum);                                                                                                                                                                                         \
                    SKIP_EOL;                                                                                                                                                                                                                  \
                    break;                                                                                                                                                                                                                     \
                }                                                                                                                                                                                                                              \
            }                                                                                                                                                                                                                                  \
            done = a0 >= lastx;                                                                                                                                                                                                                \
            while (!done) { /* then black */                                                                                                                                                                                                   \
                LOOKUP(13, BlackTable);                                                                                                                                                                                                        \
                switch (TabEnt->State) {                                                                                                                                                                                                       \
                case S_EOL:                                                                                                                                                                                                                    \
                    EOLcnt = 1;                                                                                                                                                                                                                \
                    goto EOL;                                                                                                                                                                                                                  \
                case S_TermB:                                                                                                                                                                                                                  \
                    SETVAL(TabEnt->Param);                                                                                                                                                                                                     \
                    done = 1;                                                                                                                                                                                                                  \
                    break;                                                                                                                                                                                                                     \
                case S_MakeUpB:                                                                                                                                                                                                                \
                case S_MakeUp:                                                                                                                                                                                                                 \
                    a0 += TabEnt->Param;                                                                                                                                                                                                       \
                    RunLength += TabEnt->Param;                                                                                                                                                                                                \
                    break;                                                                                                                                                                                                                     \
                case S_Ext:                                                                                                                                                                                                                    \
                    unexpected("Extension code", LineNum);                                                                                                                                                                                     \
                    SKIP_EOL;                                                                                                                                                                                                                  \
                    break;                                                                                                                                                                                                                     \
                default:                                                                                                                                                                                                                       \
                    unexpected("BlackTable", LineNum);                                                                                                                                                                                         \
                    SKIP_EOL;                                                                                                                                                                                                                  \
                    break;                                                                                                                                                                                                                     \
                }                                                                                                                                                                                                                              \
            }                                                                                                                                                                                                                                  \
        }                                                                                                                                                                                                                                      \
    EOL:;                                                                                                                                                                                                                                      \
    } while (0)

#define CHECK_b1                                                                                                                                                                                                                               \
    do {                                                                                                                                                                                                                                       \
        if (pa != thisrun)                                                                                                                                                                                                                     \
            while (b1 <= a0 && b1 < lastx) {                                                                                                                                                                                                   \
                b1 += pb[0] + pb[1];                                                                                                                                                                                                           \
                pb += 2;                                                                                                                                                                                                                       \
            }                                                                                                                                                                                                                                  \
    } while (0)

#define expand2d(eolab)                                                                                                                                                                                                                        \
    do {                                                                                                                                                                                                                                       \
        while (a0 < lastx) {                                                                                                                                                                                                                   \
            LOOKUP(7, MainTable);                                                                                                                                                                                                              \
            switch (TabEnt->State) {                                                                                                                                                                                                           \
            case S_Pass:                                                                                                                                                                                                                       \
                CHECK_b1;                                                                                                                                                                                                                      \
                b1 += *pb++;                                                                                                                                                                                                                   \
                RunLength += b1 - a0;                                                                                                                                                                                                          \
                a0 = b1;                                                                                                                                                                                                                       \
                b1 += *pb++;                                                                                                                                                                                                                   \
                break;                                                                                                                                                                                                                         \
            case S_Horiz:                                                                                                                                                                                                                      \
                if ((pa - run0) & 1) {                                                                                                                                                                                                         \
                    int done = 0;                                                                                                                                                                                                              \
                    while (!done) { /* black first */                                                                                                                                                                                          \
                        LOOKUP(13, BlackTable);                                                                                                                                                                                                \
                        switch (TabEnt->State) {                                                                                                                                                                                               \
                        case S_TermB:                                                                                                                                                                                                          \
                            SETVAL(TabEnt->Param);                                                                                                                                                                                             \
                            done = 1;                                                                                                                                                                                                          \
                            break;                                                                                                                                                                                                             \
                        case S_MakeUpB:                                                                                                                                                                                                        \
                        case S_MakeUp:                                                                                                                                                                                                         \
                            a0 += TabEnt->Param;                                                                                                                                                                                               \
                            RunLength += TabEnt->Param;                                                                                                                                                                                        \
                            break;                                                                                                                                                                                                             \
                        default:                                                                                                                                                                                                               \
                            unexpected("BlackTable", LineNum);                                                                                                                                                                                 \
                            SKIP_EOL;                                                                                                                                                                                                          \
                            break;                                                                                                                                                                                                             \
                        }                                                                                                                                                                                                                      \
                    }                                                                                                                                                                                                                          \
                    done = 0;                                                                                                                                                                                                                  \
                    while (!done) { /* then white */                                                                                                                                                                                           \
                        LOOKUP(12, WhiteTable);                                                                                                                                                                                                \
                        switch (TabEnt->State) {                                                                                                                                                                                               \
                        case S_TermW:                                                                                                                                                                                                          \
                            SETVAL(TabEnt->Param);                                                                                                                                                                                             \
                            done = 1;                                                                                                                                                                                                          \
                            break;                                                                                                                                                                                                             \
                        case S_MakeUpW:                                                                                                                                                                                                        \
                        case S_MakeUp:                                                                                                                                                                                                         \
                            a0 += TabEnt->Param;                                                                                                                                                                                               \
                            RunLength += TabEnt->Param;                                                                                                                                                                                        \
                            break;                                                                                                                                                                                                             \
                        default:                                                                                                                                                                                                               \
                            unexpected("WhiteTable", LineNum);                                                                                                                                                                                 \
                            SKIP_EOL;                                                                                                                                                                                                          \
                            break;                                                                                                                                                                                                             \
                        }                                                                                                                                                                                                                      \
                    }                                                                                                                                                                                                                          \
                } else {                                                                                                                                                                                                                       \
                    int done = 0;                                                                                                                                                                                                              \
                    while (!done) { /* white first */                                                                                                                                                                                          \
                        LOOKUP(12, WhiteTable);                                                                                                                                                                                                \
                        switch (TabEnt->State) {                                                                                                                                                                                               \
                        case S_TermW:                                                                                                                                                                                                          \
                            SETVAL(TabEnt->Param);                                                                                                                                                                                             \
                            done = 1;                                                                                                                                                                                                          \
                            break;                                                                                                                                                                                                             \
                        case S_MakeUpW:                                                                                                                                                                                                        \
                        case S_MakeUp:                                                                                                                                                                                                         \
                            a0 += TabEnt->Param;                                                                                                                                                                                               \
                            RunLength += TabEnt->Param;                                                                                                                                                                                        \
                            break;                                                                                                                                                                                                             \
                        default:                                                                                                                                                                                                               \
                            unexpected("WhiteTable", LineNum);                                                                                                                                                                                 \
                            SKIP_EOL;                                                                                                                                                                                                          \
                            break;                                                                                                                                                                                                             \
                        }                                                                                                                                                                                                                      \
                    }                                                                                                                                                                                                                          \
                    done = 0;                                                                                                                                                                                                                  \
                    while (!done) { /* then black */                                                                                                                                                                                           \
                        LOOKUP(13, BlackTable);                                                                                                                                                                                                \
                        switch (TabEnt->State) {                                                                                                                                                                                               \
                        case S_TermB:                                                                                                                                                                                                          \
                            SETVAL(TabEnt->Param);                                                                                                                                                                                             \
                            done = 1;                                                                                                                                                                                                          \
                            break;                                                                                                                                                                                                             \
                        case S_MakeUpB:                                                                                                                                                                                                        \
                        case S_MakeUp:                                                                                                                                                                                                         \
                            a0 += TabEnt->Param;                                                                                                                                                                                               \
                            RunLength += TabEnt->Param;                                                                                                                                                                                        \
                            break;                                                                                                                                                                                                             \
                        default:                                                                                                                                                                                                               \
                            unexpected("BlackTable", LineNum);                                                                                                                                                                                 \
                            SKIP_EOL;                                                                                                                                                                                                          \
                            break;                                                                                                                                                                                                             \
                        }                                                                                                                                                                                                                      \
                    }                                                                                                                                                                                                                          \
                }                                                                                                                                                                                                                              \
                CHECK_b1;                                                                                                                                                                                                                      \
                break;                                                                                                                                                                                                                         \
            case S_V0:                                                                                                                                                                                                                         \
                CHECK_b1;                                                                                                                                                                                                                      \
                SETVAL(b1 - a0);                                                                                                                                                                                                               \
                b1 += *pb++;                                                                                                                                                                                                                   \
                break;                                                                                                                                                                                                                         \
            case S_VR:                                                                                                                                                                                                                         \
                CHECK_b1;                                                                                                                                                                                                                      \
                SETVAL(b1 - a0 + TabEnt->Param);                                                                                                                                                                                               \
                b1 += *pb++;                                                                                                                                                                                                                   \
                break;                                                                                                                                                                                                                         \
            case S_VL:                                                                                                                                                                                                                         \
                CHECK_b1;                                                                                                                                                                                                                      \
                SETVAL(b1 - a0 - TabEnt->Param);                                                                                                                                                                                               \
                b1 -= *--pb;                                                                                                                                                                                                                   \
                break;                                                                                                                                                                                                                         \
            case S_Ext:                                                                                                                                                                                                                        \
                *pa++ = lastx - a0;                                                                                                                                                                                                            \
                if (verbose)                                                                                                                                                                                                                   \
                    qCDebug(FAX_LOG) << "Line " << LineNum << ": extension code\n";                                                                                                                                                            \
                SKIP_EOL;                                                                                                                                                                                                                      \
                break;                                                                                                                                                                                                                         \
            case S_EOL:                                                                                                                                                                                                                        \
                *pa++ = lastx - a0;                                                                                                                                                                                                            \
                NeedBits(4);                                                                                                                                                                                                                   \
                if (GetBits(4) && verbose) /* already seen 7 zeros */                                                                                                                                                                          \
                    qCDebug(FAX_LOG) << "Line " << LineNum << ": Bad EOL\n";                                                                                                                                                                   \
                ClrBits(4);                                                                                                                                                                                                                    \
                EOLcnt = 1;                                                                                                                                                                                                                    \
                goto eolab;                                                                                                                                                                                                                    \
                break;                                                                                                                                                                                                                         \
            default:                                                                                                                                                                                                                           \
                unexpected("MainTable", LineNum);                                                                                                                                                                                              \
                SKIP_EOL;                                                                                                                                                                                                                      \
                break;                                                                                                                                                                                                                         \
            }                                                                                                                                                                                                                                  \
        }                                                                                                                                                                                                                                      \
        if (RunLength) {                                                                                                                                                                                                                       \
            if (RunLength + a0 < lastx) {                                                                                                                                                                                                      \
                /* expect a final V0 */                                                                                                                                                                                                        \
                NeedBits(1);                                                                                                                                                                                                                   \
                if (!GetBits(1)) {                                                                                                                                                                                                             \
                    unexpected("MainTable", LineNum);                                                                                                                                                                                          \
                    SKIP_EOL;                                                                                                                                                                                                                  \
                }                                                                                                                                                                                                                              \
                ClrBits(1);                                                                                                                                                                                                                    \
            }                                                                                                                                                                                                                                  \
            SETVAL(0);                                                                                                                                                                                                                         \
        }                                                                                                                                                                                                                                      \
        eol2lab;                                                                                                                                                                                                                               \
    } while (0)

static void unexpected(const char *what, int LineNum)
{
    if (verbose)
        qCCritical(FAX_LOG) << "Line " << LineNum << ": Unexpected state in " << what << endl;
}

/* Expand tiff modified huffman data (g3-1d without EOLs) */
void MHexpand(pagenode *pn, drawfunc df)
{
    int a0;         /* reference element */
    int lastx;      /* copy line width to register */
    t32bits BitAcc; /* bit accumulator */
    int BitsAvail;  /* # valid bits in BitAcc */
    int RunLength;  /* Length of current run */
    t16bits *sp;    /* pointer into compressed data */
    pixnum *pa;     /* pointer into new line */
    int EOLcnt;     /* number of consecutive EOLs */
    int LineNum;    /* line number */
    pixnum *runs;   /* list of run lengths */
    struct tabent *TabEnt;

    sp = pn->data;
    BitAcc = 0;
    BitsAvail = 0;
    lastx = pn->size.width();
    runs = (pixnum *)malloc(lastx * sizeof(pixnum));
    for (LineNum = 0; LineNum < pn->rowsperstrip;) {
#ifdef DEBUG_FAX
        printf("\nBitAcc=%08lX, BitsAvail = %d\n", BitAcc, BitsAvail);
        printf("-------------------- %d\n", LineNum);
        fflush(stdout);
#endif
        RunLength = 0;
        pa = runs;
        a0 = 0;
        EOLcnt = 0;
        if (BitsAvail & 7) /* skip to byte boundary */
            ClrBits(BitsAvail & 7);
        expand1d();
        if (RunLength)
            SETVAL(0);
        if (a0 != lastx) {
            if (verbose)
                qCWarning(FAX_LOG) << "Line " << LineNum << ": length is " << a0 << " (expected " << lastx << ")\n";
            while (a0 > lastx)
                a0 -= *--pa;
            if (a0 < lastx) {
                if ((pa - runs) & 1)
                    SETVAL(0);
                SETVAL(lastx - a0);
            }
        }
        (*df)(runs, LineNum++, pn);
    }
    free(runs);
    (void)EOLcnt; // make gcc happy
}

/* Expand group-3 1-dimensional data */
void g31expand(pagenode *pn, drawfunc df)
{
    int a0;         /* reference element */
    int lastx;      /* copy line width to register */
    t32bits BitAcc; /* bit accumulator */
    int BitsAvail;  /* # valid bits in BitAcc */
    int RunLength;  /* Length of current run */
    t16bits *sp;    /* pointer into compressed data */
    pixnum *pa;     /* pointer into new line */
    int EOLcnt;     /* number of consecutive EOLs */
    int LineNum;    /* line number */
    pixnum *runs;   /* list of run lengths */
    struct tabent *TabEnt;

    sp = pn->data;
    BitAcc = 0;
    BitsAvail = 0;
    lastx = pn->size.width();
    runs = (pixnum *)malloc(lastx * sizeof(pixnum));
    EOLcnt = 0;
    for (LineNum = 0; LineNum < pn->rowsperstrip;) {
#ifdef DEBUG_FAX
        fprintf(stderr, "\nBitAcc=%08lX, BitsAvail = %d\n", BitAcc, BitsAvail);
        fprintf(stderr, "-------------------- %d\n", LineNum);
        fflush(stderr);
#endif
        if (EOLcnt == 0)
            while (!EndOfData(pn)) {
                /* skip over garbage after a coding error */
                NeedBits(11);
                if (GetBits(11) == 0)
                    break;
                ClrBits(1);
            }
        for (EOLcnt = 1; !EndOfData(pn); EOLcnt++) {
            /* we have seen 11 zeros, which implies EOL,
               skip possible fill bits too */
            while (true) {
                NeedBits(8);
                if (GetBits(8))
                    break;
                ClrBits(8);
            }
            while (GetBits(1) == 0)
                ClrBits(1);
            ClrBits(1); /* the eol flag */
            NeedBits(11);
            if (GetBits(11))
                break;
            ClrBits(11);
        }
        if (EOLcnt > 1 && EOLcnt != 6 && verbose) {
            qCCritical(FAX_LOG) << "Line " << LineNum << ": bad RTC (" << EOLcnt << " EOLs)\n";
        }
        if (EOLcnt >= 6 || EndOfData(pn)) {
            free(runs);
            return;
        }
        RunLength = 0;
        pa = runs;
        a0 = 0;
        EOLcnt = 0;
        expand1d();
        if (RunLength)
            SETVAL(0);
        if (a0 != lastx) {
            if (verbose)
                qCWarning(FAX_LOG) << "Line " << LineNum << ": length is " << a0 << " (expected " << lastx << ")\n";
            while (a0 > lastx)
                a0 -= *--pa;
            if (a0 < lastx) {
                if ((pa - runs) & 1)
                    SETVAL(0);
                SETVAL(lastx - a0);
            }
        }
        (*df)(runs, LineNum++, pn);
    }
    free(runs);
}

/* Expand group-3 2-dimensional data */
void g32expand(pagenode *pn, drawfunc df)
{
    int RunLength;                /* Length of current run */
    int a0;                       /* reference element */
    int b1;                       /* next change on previous line */
    int lastx = pn->size.width(); /* copy line width to register */
    pixnum *run0, *run1;          /* run length arrays */
    pixnum *thisrun, *pa, *pb;    /* pointers into runs */
    t16bits *sp;                  /* pointer into compressed data */
    t32bits BitAcc;               /* bit accumulator */
    int BitsAvail;                /* # valid bits in BitAcc */
    int EOLcnt;                   /* number of consecutive EOLs */
    int refline = 0;              /* 1D encoded reference line */
    int LineNum;                  /* line number */
    struct tabent *TabEnt;

    sp = pn->data;
    BitAcc = 0;
    BitsAvail = 0;
    /* allocate space for 2 runlength arrays */
    run0 = (pixnum *)malloc(2 * ((lastx + 5) & ~1) * sizeof(pixnum));
    run1 = run0 + ((lastx + 5) & ~1);
    run1[0] = lastx;
    run1[1] = 0;
    EOLcnt = 0;
    for (LineNum = 0; LineNum < pn->rowsperstrip;) {
#ifdef DEBUG_FAX
        printf("\nBitAcc=%08lX, BitsAvail = %d\n", BitAcc, BitsAvail);
        printf("-------------------- %d\n", LineNum);
        fflush(stdout);
#endif
        if (EOLcnt == 0)
            while (!EndOfData(pn)) {
                /* skip over garbage after a coding error */
                NeedBits(11);
                if (GetBits(11) == 0)
                    break;
                ClrBits(1);
            }
        for (EOLcnt = 1; !EndOfData(pn); EOLcnt++) {
            /* we have seen 11 zeros, which implies EOL,
               skip possible fill bits too */
            while (true) {
                NeedBits(8);
                if (GetBits(8))
                    break;
                ClrBits(8);
            }
            while (GetBits(1) == 0)
                ClrBits(1);
            ClrBits(1); /* the eol flag */
            NeedBits(12);
            refline = GetBits(1); /* 1D / 2D flag */
            ClrBits(1);
            if (GetBits(11))
                break;
            ClrBits(11);
        }
        if (EOLcnt > 1 && EOLcnt != 6 && verbose)
            qCCritical(FAX_LOG) << "Line " << LineNum << ": bad RTC (" << EOLcnt << " EOLs)\n";
        if (EOLcnt >= 6 || EndOfData(pn)) {
            free(run0);
            return;
        }
        if (LineNum == 0 && refline == 0 && verbose)
            qCDebug(FAX_LOG) << "First line is 2-D encoded\n";
        RunLength = 0;
        if (LineNum & 1) {
            pa = run1;
            pb = run0;
        } else {
            pa = run0;
            pb = run1;
        }
        thisrun = pa;
        EOLcnt = 0;
        a0 = 0;
        b1 = *pb++;

        if (refline) {
            expand1d();
        } else {
            expand2d(EOL2);
        }
        if (RunLength)
            SETVAL(0);
        if (a0 != lastx) {
            if (verbose)
                qCWarning(FAX_LOG) << "Line " << LineNum << ": length is " << a0 << " (expected " << lastx << ")\n";
            while (a0 > lastx)
                a0 -= *--pa;
            if (a0 < lastx) {
                if ((pa - run0) & 1)
                    SETVAL(0);
                SETVAL(lastx - a0);
            }
        }
        SETVAL(0); /* imaginary change at end of line for reference */
        (*df)(thisrun, LineNum++, pn);
    }
    free(run0);
}

/* Redefine the "skip to eol" macro.  We cannot recover from coding
   errors in G4 data */
#undef SKIP_EOL
#undef eol2lab
#define SKIP_EOL                                                                                                                                                                                                                               \
    do {                                                                                                                                                                                                                                       \
        if (verbose)                                                                                                                                                                                                                           \
            qCCritical(FAX_LOG) << "Line " << LineNum << ": G4 coding error\n";                                                                                                                                                                \
        free(run0);                                                                                                                                                                                                                            \
        return;                                                                                                                                                                                                                                \
    } while (0)
#define eol2lab

/* Expand group-4 data */
void g4expand(pagenode *pn, drawfunc df)
{
    int RunLength;                /* Length of current run */
    int a0;                       /* reference element */
    int b1;                       /* next change on previous line */
    int lastx = pn->size.width(); /* copy line width to register */
    pixnum *run0, *run1;          /* run length arrays */
    pixnum *thisrun, *pa, *pb;    /* pointers into runs */
    t16bits *sp;                  /* pointer into compressed data */
    t32bits BitAcc;               /* bit accumulator */
    int BitsAvail;                /* # valid bits in BitAcc */
    int LineNum;                  /* line number */
    int EOLcnt;
    struct tabent *TabEnt;

    sp = pn->data;
    BitAcc = 0;
    BitsAvail = 0;
    /* allocate space for 2 runlength arrays */
    run0 = (pixnum *)malloc(2 * ((lastx + 5) & ~1) * sizeof(pixnum));
    run1 = run0 + ((lastx + 5) & ~1);
    run1[0] = lastx; /* initial reference line */
    run1[1] = 0;

    for (LineNum = 0; LineNum < pn->rowsperstrip;) {
#ifdef DEBUG_FAX
        printf("\nBitAcc=%08lX, BitsAvail = %d\n", BitAcc, BitsAvail);
        printf("-------------------- %d\n", LineNum);
        fflush(stdout);
#endif
        RunLength = 0;
        if (LineNum & 1) {
            pa = run1;
            pb = run0;
        } else {
            pa = run0;
            pb = run1;
        }
        thisrun = pa;
        a0 = 0;
        b1 = *pb++;
        expand2d(EOFB);
        if (a0 < lastx) {
            if ((pa - run0) & 1)
                SETVAL(0);
            SETVAL(lastx - a0);
        }
        SETVAL(0); /* imaginary change at end of line for reference */
        (*df)(thisrun, LineNum++, pn);
        continue;
    EOFB:
        NeedBits(13);
        if (GetBits(13) != 0x1001 && verbose)
            qCCritical(FAX_LOG) << "Bad RTC\n";
        break;
    }
    free(run0);
    (void)EOLcnt; // make gcc happy
}

static const unsigned char zerotab[256] = {0x88, 0x07, 0x16, 0x06, 0x25, 0x05, 0x15, 0x05, 0x34, 0x04, 0x14, 0x04, 0x24, 0x04, 0x14, 0x04, 0x43, 0x03, 0x13, 0x03, 0x23, 0x03, 0x13, 0x03, 0x33, 0x03, 0x13, 0x03, 0x23, 0x03, 0x13, 0x03,
                                           0x52, 0x02, 0x12, 0x02, 0x22, 0x02, 0x12, 0x02, 0x32, 0x02, 0x12, 0x02, 0x22, 0x02, 0x12, 0x02, 0x42, 0x02, 0x12, 0x02, 0x22, 0x02, 0x12, 0x02, 0x32, 0x02, 0x12, 0x02, 0x22, 0x02, 0x12, 0x02,
                                           0x61, 0x01, 0x11, 0x01, 0x21, 0x01, 0x11, 0x01, 0x31, 0x01, 0x11, 0x01, 0x21, 0x01, 0x11, 0x01, 0x41, 0x01, 0x11, 0x01, 0x21, 0x01, 0x11, 0x01, 0x31, 0x01, 0x11, 0x01, 0x21, 0x01, 0x11, 0x01,
                                           0x51, 0x01, 0x11, 0x01, 0x21, 0x01, 0x11, 0x01, 0x31, 0x01, 0x11, 0x01, 0x21, 0x01, 0x11, 0x01, 0x41, 0x01, 0x11, 0x01, 0x21, 0x01, 0x11, 0x01, 0x31, 0x01, 0x11, 0x01, 0x21, 0x01, 0x11, 0x01,
                                           0x70, 0x00, 0x10, 0x00, 0x20, 0x00, 0x10, 0x00, 0x30, 0x00, 0x10, 0x00, 0x20, 0x00, 0x10, 0x00, 0x40, 0x00, 0x10, 0x00, 0x20, 0x00, 0x10, 0x00, 0x30, 0x00, 0x10, 0x00, 0x20, 0x00, 0x10, 0x00,
                                           0x50, 0x00, 0x10, 0x00, 0x20, 0x00, 0x10, 0x00, 0x30, 0x00, 0x10, 0x00, 0x20, 0x00, 0x10, 0x00, 0x40, 0x00, 0x10, 0x00, 0x20, 0x00, 0x10, 0x00, 0x30, 0x00, 0x10, 0x00, 0x20, 0x00, 0x10, 0x00,
                                           0x60, 0x00, 0x10, 0x00, 0x20, 0x00, 0x10, 0x00, 0x30, 0x00, 0x10, 0x00, 0x20, 0x00, 0x10, 0x00, 0x40, 0x00, 0x10, 0x00, 0x20, 0x00, 0x10, 0x00, 0x30, 0x00, 0x10, 0x00, 0x20, 0x00, 0x10, 0x00,
                                           0x50, 0x00, 0x10, 0x00, 0x20, 0x00, 0x10, 0x00, 0x30, 0x00, 0x10, 0x00, 0x20, 0x00, 0x10, 0x00, 0x40, 0x00, 0x10, 0x00, 0x20, 0x00, 0x10, 0x00, 0x30, 0x00, 0x10, 0x00, 0x20, 0x00, 0x10, 0x00};

#define check(v)                                                                                                                                                                                                                               \
    do {                                                                                                                                                                                                                                       \
        prezeros = zerotab[v];                                                                                                                                                                                                                 \
        postzeros = prezeros & 15;                                                                                                                                                                                                             \
        prezeros >>= 4;                                                                                                                                                                                                                        \
        if (prezeros == 8) {                                                                                                                                                                                                                   \
            zeros += 8;                                                                                                                                                                                                                        \
            break;                                                                                                                                                                                                                             \
        }                                                                                                                                                                                                                                      \
        if (zeros + prezeros < 11) {                                                                                                                                                                                                           \
            empty = 0;                                                                                                                                                                                                                         \
            zeros = postzeros;                                                                                                                                                                                                                 \
            break;                                                                                                                                                                                                                             \
        }                                                                                                                                                                                                                                      \
        zeros = postzeros;                                                                                                                                                                                                                     \
        if (empty)                                                                                                                                                                                                                             \
            EOLcnt++;                                                                                                                                                                                                                          \
        lines++;                                                                                                                                                                                                                               \
        empty = 1;                                                                                                                                                                                                                             \
    } while (false)

/* count fax lines */
int G3count(pagenode *pn, int twoD)
{
    t16bits *p = pn->data;
    t16bits *end = p + pn->length / sizeof(*p);
    int lines = 0;  /* lines seen so far */
    int zeros = 0;  /* number of consecutive zero bits seen */
    int EOLcnt = 0; /* number of consecutive EOLs seen */
    int empty = 1;  /* empty line */
    int prezeros, postzeros;

    while (p < end && EOLcnt < 6) {
        t16bits bits = *p++;
        check(bits & 255);
        if (twoD && (prezeros + postzeros == 7)) {
            if (postzeros || ((bits & 0x100) == 0))
                zeros--;
        }
        check(bits >> 8);
        if (twoD && (prezeros + postzeros == 7)) {
            if (postzeros || ((p < end) && ((*p & 1) == 0)))
                zeros--;
        }
    }
    return lines - EOLcnt; /* don't count trailing EOLs */
}
