path: root/base/scfe.c

/* 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.
*/


/* CCITTFax encoding filter */
#include "stdio_.h"		/* includes std.h */
#include "memory_.h"
#include "gdebug.h"
#include "strimpl.h"
#include "scf.h"
#include "scfx.h"

/* ------ Macros and support routines ------ */

/* Statistics */
/* #define COLLECT_STATS_SCFE */

#ifdef COLLECT_STATS_SCFE
typedef struct stats_runs_s {
    ulong termination[64];
    ulong make_up[41];
} stats_runs_t;
static stats_runs_t stats_white_runs, stats_black_runs;

#define COUNT_RUN(tab, i) (tab)[i]++;

static void
print_run_stats(const gs_memory_t *mem, const stats_runs_t * stats)
{
    int i;
    ulong total;

    for (i = 0, total = 0; i < 41; i++)
        dmprintf1(mem, " %lu", stats->make_up[i]),
            total += stats->make_up[i];
    dmprintf1(mem, " total=%lu\n\t", total);
    for (i = 0, total = 0; i < 64; i++)
        dmprintf1(mem, " %lu", stats->termination[i]),
            total += stats->termination[i];
    dmprintf1(mem, " total=%lu\n", total);
}

#else /* !defined(COLLECT_STATS_SCFE) */

#define COUNT_RUN(cnt, i) DO_NOTHING

#endif /* DEBUG */

/* Put a run onto the output stream. */
/* Free variables: q, bits, bits_left. */

#define CF_PUT_RUN(ss, lenv, rt, stats)\
BEGIN\
    cfe_run rr;\
\
    if ( lenv >= 64 ) {\
        hce_store_state();\
        q = cf_put_long_run(ss, q, lenv, &rt);\
        hce_load_state();\
        lenv &= 63;\
    }\
    rr = rt.termination[lenv];\
    COUNT_RUN(stats.termination, lenv);\
    hc_put_value(ss, q, rr.code, rr.code_length);\
END

static byte *
cf_put_long_run(stream_CFE_state * ss, byte * q, int lenv, const cf_runs * prt)
{
    hce_declare_state;
    cfe_run rr;

#ifdef COLLECT_STATS_SCFE
    stats_runs_t *pstats =
    (prt == &cf_white_runs ? &stats_white_runs : &stats_black_runs);
#endif

    hce_load_state();
    while (lenv >= 2560 + 64) {
        rr = prt->make_up[40];
        COUNT_RUN(pstats->make_up, 40);
        hc_put_value(ss, q, rr.code, rr.code_length);
        lenv -= 2560;
    }
    rr = prt->make_up[lenv >> 6];
    COUNT_RUN(pstats->make_up, lenv >> 6);
    hc_put_value(ss, q, rr.code, rr.code_length);
    hce_store_state();
    return q;
}

#define CF_PUT_WHITE_RUN(ss, lenv)\
  CF_PUT_RUN(ss, lenv, cf_white_runs, stats_white_runs)

#define CF_PUT_BLACK_RUN(ss, lenv)\
  CF_PUT_RUN(ss, lenv, cf_black_runs, stats_black_runs)

/* ------ CCITTFaxEncode ------ */

private_st_CFE_state();

static void s_CFE_release(stream_state *);

/* Set default parameter values. */
static void
s_CFE_set_defaults(register stream_state * st)
{
    stream_CFE_state *const ss = (stream_CFE_state *) st;

    s_CFE_set_defaults_inline(ss);
}

/* Initialize CCITTFaxEncode filter */
static int
s_CFE_init(register stream_state * st)
{
    stream_CFE_state *const ss = (stream_CFE_state *) st;
    int columns = ss->Columns;

    /*
     * The worst case for encoding is alternating white and black pixels.
     * For 1-D encoding, the worst case is 9 bits per 2 pixels; for 2-D
     * (horizontal), 12 bits per 2 pixels. However, for 2D vertical encoding
     * an offset 3 vertically encoded requires 7 bits of encoding. So we need
     * to allow 14 bits for this, not 12 (see bug 696413). To fill out a scan line,
     * we may add up to 6 12-bit EOL codes.
     */
    int code_bytes =
    (((columns * (ss->K == 0 ? 9 : 14)) + 15) >> 4) + 20;	/* add slop */
    int raster = ss->raster =
        ROUND_UP((columns + 7) >> 3, ss->DecodedByteAlign);

    s_hce_init_inline(ss);
    ss->lbuf = ss->lprev = ss->lcode = 0;	/* in case we have to release */
    if (columns > cfe_max_width)
        return ERRC;
/****** WRONG ******/
    /* Because skip_white_pixels can look as many as 4 bytes ahead, */
    /* we need to allow 4 extra bytes at the end of the row buffers. */
    ss->lbufstart = gs_alloc_bytes(st->memory, raster + 8, "CFE lbuf");
    ss->lcode = gs_alloc_bytes(st->memory, code_bytes, "CFE lcode");
    if (ss->lbufstart == 0 || ss->lcode == 0) {
        s_CFE_release(st);
        return ERRC;
/****** WRONG ******/
    }
    ss->lbuf = ss->lbufstart + 4;
    memset(ss->lbuf + raster, 0, 4); /* to pacify Valgrind */
    if (ss->K != 0) {
        ss->lprevstart = gs_alloc_bytes(st->memory, raster + 8, "CFE lprev");
        if (ss->lprevstart == 0) {
            s_CFE_release(st);
            return ERRC;
/****** WRONG ******/
        }
        ss->lprev = ss->lprevstart + 4;
        /* Clear the initial reference line for 2-D encoding. */
        /* Make sure it is terminated properly. */
        memset(ss->lprev, (ss->BlackIs1 ? 0 : 0xff), raster + 4); /* +4 to pacify Valgrind */
        if (columns & 7)
            ss->lprev[raster - 1] ^= 0x80 >> (columns & 7);
        else
            ss->lprev[raster] = ~ss->lprev[0];
    }
    ss->read_count = raster;
    ss->write_count = 0;
    ss->k_left = (ss->K > 0 ? 1 : ss->K);
    ss->max_code_bytes = code_bytes;
    return 0;
}

/* Release the filter. */
static void
s_CFE_release(stream_state * st)
{
    stream_CFE_state *const ss = (stream_CFE_state *) st;

    gs_free_object(st->memory, ss->lprevstart, "CFE lprev(close)");
    gs_free_object(st->memory, ss->lcode, "CFE lcode(close)");
    gs_free_object(st->memory, ss->lbufstart, "CFE lbuf(close)");
}

/* Flush the buffer */
static void cf_encode_1d(stream_CFE_state *, const byte *,
                          stream_cursor_write *);
static void cf_encode_2d(stream_CFE_state *, const byte *,
                          stream_cursor_write *, const byte *);
static int
s_CFE_process(stream_state * st, stream_cursor_read * pr,
              stream_cursor_write * pw, bool last)
{
    stream_CFE_state *const ss = (stream_CFE_state *) st;
    const byte *rlimit = pr->limit;
    byte *wlimit = pw->limit;
    int raster = ss->raster;
    byte end_mask = 1 << (-ss->Columns & 7);
    int status = 0;

    /* Update the pointers we actually use, in case GC moved the buffer */
    ss->lbuf = ss->lbufstart + 4;
    ss->lprev = ss->lprevstart + 4;

    for (;;) {
        stream_cursor_write w;

        if_debug2m('w', ss->memory, "[w]CFE: read_count = %d, write_count=%d,\n",
                   ss->read_count, ss->write_count);
        if_debug6m('w', ss->memory, "    pr = "PRI_INTPTR"(%d)"PRI_INTPTR", pw = "PRI_INTPTR"(%d)"PRI_INTPTR"\n",
                   (intptr_t) pr->ptr, (int)(rlimit - pr->ptr), (intptr_t) rlimit,
                   (intptr_t) pw->ptr, (int)(wlimit - pw->ptr), (intptr_t) wlimit);
        if (ss->write_count) {
            /* Copy more of an encoded line to the caller. */
            int wcount = wlimit - pw->ptr;
            int ccount = min(wcount, ss->write_count);

            memcpy(pw->ptr + 1, ss->lcode + ss->code_bytes - ss->write_count,
                   ccount);
            pw->ptr += ccount;
            if ((ss->write_count -= ccount) > 0) {
                status = 1;
                break;
            }
        }
        if (ss->read_count) {
            /* Copy more of an unencoded line from the caller. */
            int rcount = rlimit - pr->ptr;
            int ccount = min(rcount, ss->read_count);

            if (rcount == 0 && last)
                break;
            memcpy(ss->lbuf + raster - ss->read_count,
                   pr->ptr + 1, ccount);
            pr->ptr += ccount;
            if ((ss->read_count -= ccount) != 0)
                break;
        }
        /*
         * We have a full scan line in lbuf.  Ensure that it ends with
         * two polarity changes.
         */
        {
            byte *end = ss->lbuf + raster - 1;
            byte end_bit = *end & end_mask;
            byte not_bit = end_bit ^ end_mask;

            *end &= -end_mask;
            if (end_mask == 1)
                end[1] = (end_bit ? 0x40 : 0x80);
            else if (end_mask == 2)
                *end |= not_bit >> 1, end[1] = end_bit << 7;
            else
                *end |= (not_bit >> 1) | (end_bit >> 2);
        }
        /*
         * Write the output directly to the caller's buffer if it's large
         * enough, otherwise to our own buffer.
         */
        if (wlimit - pw->ptr >= ss->max_code_bytes) {
            w = *pw;
        } else {
            w.ptr = ss->lcode - 1;
            w.limit = w.ptr + ss->max_code_bytes;
        }
#ifdef DEBUG
        if (ss->K > 0) {
            if_debug2m('w', ss->memory, "[w2]new %d-D row, k_left=%d\n",
                       (ss->k_left == 1 ? 1 : 2), ss->k_left);
        } else {
            if_debug1m('w', ss->memory, "[w%d]new row\n", (ss->K < 0 ? 2 : 1));
        }
#endif
        /*
         * Write an EOL (actually a "beginning of line") if requested.
         */
        if (ss->EndOfLine) {
            const cfe_run *rp =
            (ss->K <= 0 ? &cf_run_eol :
             ss->k_left > 1 ? &cf2_run_eol_2d :
             &cf2_run_eol_1d);
            cfe_run run;

            hce_declare_state;

            hce_load_state();
            if (ss->EncodedByteAlign) {
                run = *rp;
                /* Pad the run on the left */
                /* so it winds up byte-aligned. */
                run.code_length +=
                    (bits_left - run_eol_code_length) & 7;
                if (run.code_length > 16)	/* <= 23 */
                    bits_left -= run.code_length & 7,
                        run.code_length = 16;
                rp = &run;
            }
            hc_put_code(ss, w.ptr, rp);
            hce_store_state();
        } else if (ss->EncodedByteAlign)
            ss->bits_left &= ~7;
        /* Encode the line. */
        if (ss->K == 0)
            cf_encode_1d(ss, ss->lbuf, &w);	/* pure 1-D */
        else if (ss->K < 0)
            cf_encode_2d(ss, ss->lbuf, &w, ss->lprev);	/* pure 2-D */
        else if (--(ss->k_left))	/* mixed, use 2-D */
            cf_encode_2d(ss, ss->lbuf, &w, ss->lprev);
        else {			/* mixed, use 1-D */
            cf_encode_1d(ss, ss->lbuf, &w);
            ss->k_left = ss->K;
        }
        /*
         * If we didn't write directly to the client's buffer, schedule
         * the output data to be written.
         */
        if (w.limit == wlimit)
            pw->ptr = w.ptr;
        else
            ss->write_count = ss->code_bytes = w.ptr - (ss->lcode - 1);
        if (ss->K != 0) {
            /* In 2-D modes, swap the current and previous scan lines. */
            byte *temp = ss->lbuf;
            byte *temp1 = ss->lbufstart;

            ss->lbuf = ss->lprev;
            ss->lbufstart = ss->lprevstart;
            ss->lprev = temp;
            ss->lprevstart = temp1;
        }
        /* Note that the input buffer needs refilling. */
        ss->read_count = raster;
    }
    /*
     * When we exit from the loop, we know that write_count = 0, and
     * there is no line waiting to be processed in the input buffer.
     */
    if (last && status == 0) {
        const cfe_run *rp =
        (ss->K > 0 ? &cf2_run_eol_1d : &cf_run_eol);
        int i = (!ss->EndOfBlock ? 0 : ss->K < 0 ? 2 : 6);
        uint bits_to_write =
        hc_bits_size - ss->bits_left + i * rp->code_length;
        byte *q = pw->ptr;

        hce_declare_state;

        if (wlimit - q < (bits_to_write + 7) >> 3) {
            status = 1;
            goto out;
        }
        hce_load_state();
        if (ss->EncodedByteAlign)
            bits_left &= ~7;
        while (--i >= 0)
            hc_put_code(ss, q, rp);
        /* Force out the last byte or bytes. */
        pw->ptr = hc_put_last_bits((stream_hc_state *) ss, q);
    }
  out:
    if_debug9m('w', ss->memory, "[w]CFE exit %d: read_count = %d, write_count = %d,\n"
               "     pr = "PRI_INTPTR"(%d)"PRI_INTPTR"; pw = "PRI_INTPTR"(%d)"PRI_INTPTR"\n",
               status, ss->read_count, ss->write_count,
               (intptr_t) pr->ptr, (int)(rlimit - pr->ptr), (intptr_t) rlimit,
               (intptr_t) pw->ptr, (int)(wlimit - pw->ptr), (intptr_t) wlimit);
#ifdef DEBUG
    if (pr->ptr > rlimit || pw->ptr > wlimit) {
        lprintf("Pointer overrun!\n");
        status = ERRC;
    }
#ifdef COLLECT_STATS_SCFE
    if (gs_debug_c('w') && status == 1) {
        dmlputs(ss->memory, "[w]white runs:");
        print_run_stats(ss->memory, &stats_white_runs);
        dmlputs(ss->memory, "[w]black runs:");
        print_run_stats(ss->memory, &stats_black_runs);
    }
#endif
#endif
    return status;
}

/* Encode a 1-D scan line. */
/* Attempt to stop coverity thinking skip_white_pixels() taints lbuf:*/
/* coverity[ -tainted_data_return ] */
/* coverity[ -tainted_data_argument arg-2 ] */
static void
cf_encode_1d(stream_CFE_state * ss, const byte * lbuf, stream_cursor_write * pw)
{
    uint count = ss->raster << 3;
    byte *q = pw->ptr;
    int end_count = -ss->Columns & 7;
    int rlen;

    hce_declare_state;
    const byte *p = lbuf;
    byte invert = (ss->BlackIs1 ? 0 : 0xff);

    /* Invariant: data = p[-1] ^ invert. */
    uint data = *p++ ^ invert;

    hce_load_state();
    while (count != end_count) {
        /* Parse a white run. */
        skip_white_pixels(data, p, count, invert, rlen);
        CF_PUT_WHITE_RUN(ss, rlen);
        if (count == end_count)
            break;
        /* Parse a black run. */
        skip_black_pixels(data, p, count, invert, rlen);
        CF_PUT_BLACK_RUN(ss, rlen);
    }
    hce_store_state();
    pw->ptr = q;
}

/* Encode a 2-D scan line. */
/* coverity[ -tainted_data_argument : arg-1 ] */
static void
cf_encode_2d(stream_CFE_state * ss, const byte * lbuf, stream_cursor_write * pw,
             const byte * lprev)
{
    byte invert_white = (ss->BlackIs1 ? 0 : 0xff);
    byte invert = invert_white;
    uint count = ss->raster << 3;
    int end_count = -ss->Columns & 7;
    const byte *p = lbuf;
    byte *q = pw->ptr;
    uint data = *p++ ^ invert;

    hce_declare_state;
    /*
     * In order to handle the nominal 'changing white' at the beginning of
     * each scan line, we need to suppress the test for an initial black bit
     * in the reference line when we are at the very beginning of the scan
     * line.  To avoid an extra test, we use two different mask tables.
     */
    static const byte initial_count_bit[8] =
    {
        0, 1, 2, 4, 8, 0x10, 0x20, 0x40
    };
    static const byte further_count_bit[8] =
    {
        0x80, 1, 2, 4, 8, 0x10, 0x20, 0x40
    };
    const byte *count_bit = initial_count_bit;

    hce_load_state();
    while (count != end_count) {
        /*
         * If invert == invert_white, white and black have their
         * correct meanings; if invert == ~invert_white,
         * black and white are interchanged.
         */
        uint a0 = count;
        uint a1;

#define b1 (a1 - diff)		/* only for printing */
        int diff;
        uint prev_count = count;
        const byte *prev_p = p - lbuf + lprev;
        byte prev_data = prev_p[-1] ^ invert;
        int rlen;

        /* Find the a1 and b1 transitions. */
        skip_white_pixels(data, p, count, invert, rlen);
        a1 = count;
        if ((prev_data & count_bit[prev_count & 7])) {
            /* Look for changing white first. */
            skip_black_pixels(prev_data, prev_p, prev_count, invert, rlen);
        }
        count_bit = further_count_bit;	/* no longer at beginning */
      pass:
        if (prev_count != end_count)
            skip_white_pixels(prev_data, prev_p, prev_count, invert, rlen);
        diff = a1 - prev_count;	/* i.e., logical b1 - a1 */
        /* In all the comparisons below, remember that count */
        /* runs downward, not upward, so the comparisons are */
        /* reversed. */
        if (diff <= -2) {
            /* Could be a pass mode.  Find b2. */
            if (prev_count != end_count)
                skip_black_pixels(prev_data, prev_p,
                                  prev_count, invert, rlen);
            if (prev_count > a1) {
                /* Use pass mode. */
                if_debug4m('W', ss->memory, "[W]pass: count = %d, a1 = %d, b1 = %d, new count = %d\n",
                           a0, a1, b1, prev_count);
                hc_put_value(ss, q, cf2_run_pass_value, cf2_run_pass_length);
                a0 = prev_count;
                goto pass;
            }
        }
        /* Check for vertical coding. */
        if (diff <= 3 && diff >= -3) {
            /* Use vertical coding. */
            const cfe_run *cp = &cf2_run_vertical[diff + 3];

            if_debug5m('W', ss->memory, "[W]vertical %d: count = %d, a1 = %d, b1 = %d, new count = %d\n",
                       diff, a0, a1, b1, count);
            hc_put_code(ss, q, cp);
            invert = ~invert;	/* a1 polarity changes */
            data ^= 0xff;
            continue;
        }
        /* No luck, use horizontal coding. */
        if (count != end_count)
            skip_black_pixels(data, p, count, invert, rlen);	/* find a2 */
        hc_put_value(ss, q, cf2_run_horizontal_value,
                     cf2_run_horizontal_length);
        a0 -= a1;
        a1 -= count;
        if (invert == invert_white) {
            if_debug3m('W', ss->memory, "[W]horizontal: white = %d, black = %d, new count = %d\n",
                      a0, a1, count);
            CF_PUT_WHITE_RUN(ss, a0);
            CF_PUT_BLACK_RUN(ss, a1);
        } else {
            if_debug3m('W', ss->memory, "[W]horizontal: black = %d, white = %d, new count = %d\n",
                       a0, a1, count);
            CF_PUT_BLACK_RUN(ss, a0);
            CF_PUT_WHITE_RUN(ss, a1);
#undef b1
        }
    }
    hce_store_state();
    pw->ptr = q;
}

/* Stream template */
const stream_template s_CFE_template =
{
    &st_CFE_state, s_CFE_init, s_CFE_process, 1, 1,
    s_CFE_release, s_CFE_set_defaults
};