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      1 /*
      2  * Copyright (c) 1999-2000 Image Power, Inc. and the University of
      3  *   British Columbia.
      4  * Copyright (c) 2001-2003 Michael David Adams.
      5  * All rights reserved.
      6  */
      7 
      8 /* __START_OF_JASPER_LICENSE__
      9  *
     10  * JasPer License Version 2.0
     11  *
     12  * Copyright (c) 2001-2006 Michael David Adams
     13  * Copyright (c) 1999-2000 Image Power, Inc.
     14  * Copyright (c) 1999-2000 The University of British Columbia
     15  *
     16  * All rights reserved.
     17  *
     18  * Permission is hereby granted, free of charge, to any person (the
     19  * "User") obtaining a copy of this software and associated documentation
     20  * files (the "Software"), to deal in the Software without restriction,
     21  * including without limitation the rights to use, copy, modify, merge,
     22  * publish, distribute, and/or sell copies of the Software, and to permit
     23  * persons to whom the Software is furnished to do so, subject to the
     24  * following conditions:
     25  *
     26  * 1.  The above copyright notices and this permission notice (which
     27  * includes the disclaimer below) shall be included in all copies or
     28  * substantial portions of the Software.
     29  *
     30  * 2.  The name of a copyright holder shall not be used to endorse or
     31  * promote products derived from the Software without specific prior
     32  * written permission.
     33  *
     34  * THIS DISCLAIMER OF WARRANTY CONSTITUTES AN ESSENTIAL PART OF THIS
     35  * LICENSE.  NO USE OF THE SOFTWARE IS AUTHORIZED HEREUNDER EXCEPT UNDER
     36  * THIS DISCLAIMER.  THE SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS
     37  * "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING
     38  * BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
     39  * PARTICULAR PURPOSE AND NONINFRINGEMENT OF THIRD PARTY RIGHTS.  IN NO
     40  * EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, OR ANY SPECIAL
     41  * INDIRECT OR CONSEQUENTIAL DAMAGES, OR ANY DAMAGES WHATSOEVER RESULTING
     42  * FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
     43  * NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION
     44  * WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.  NO ASSURANCES ARE
     45  * PROVIDED BY THE COPYRIGHT HOLDERS THAT THE SOFTWARE DOES NOT INFRINGE
     46  * THE PATENT OR OTHER INTELLECTUAL PROPERTY RIGHTS OF ANY OTHER ENTITY.
     47  * EACH COPYRIGHT HOLDER DISCLAIMS ANY LIABILITY TO THE USER FOR CLAIMS
     48  * BROUGHT BY ANY OTHER ENTITY BASED ON INFRINGEMENT OF INTELLECTUAL
     49  * PROPERTY RIGHTS OR OTHERWISE.  AS A CONDITION TO EXERCISING THE RIGHTS
     50  * GRANTED HEREUNDER, EACH USER HEREBY ASSUMES SOLE RESPONSIBILITY TO SECURE
     51  * ANY OTHER INTELLECTUAL PROPERTY RIGHTS NEEDED, IF ANY.  THE SOFTWARE
     52  * IS NOT FAULT-TOLERANT AND IS NOT INTENDED FOR USE IN MISSION-CRITICAL
     53  * SYSTEMS, SUCH AS THOSE USED IN THE OPERATION OF NUCLEAR FACILITIES,
     54  * AIRCRAFT NAVIGATION OR COMMUNICATION SYSTEMS, AIR TRAFFIC CONTROL
     55  * SYSTEMS, DIRECT LIFE SUPPORT MACHINES, OR WEAPONS SYSTEMS, IN WHICH
     56  * THE FAILURE OF THE SOFTWARE OR SYSTEM COULD LEAD DIRECTLY TO DEATH,
     57  * PERSONAL INJURY, OR SEVERE PHYSICAL OR ENVIRONMENTAL DAMAGE ("HIGH
     58  * RISK ACTIVITIES").  THE COPYRIGHT HOLDERS SPECIFICALLY DISCLAIM ANY
     59  * EXPRESS OR IMPLIED WARRANTY OF FITNESS FOR HIGH RISK ACTIVITIES.
     60  *
     61  * __END_OF_JASPER_LICENSE__
     62  */
     63 
     64 /*
     65  * Tier 2 Decoder
     66  *
     67  * $Id: jpc_t2dec.c,v 1.2 2008-05-26 09:40:52 vp153 Exp $
     68  */
     69 
     70 /******************************************************************************\
     71 * Includes.
     72 \******************************************************************************/
     73 
     74 #include <stdio.h>
     75 #include <stdlib.h>
     76 #include <assert.h>
     77 
     78 #include "jasper/jas_types.h"
     79 #include "jasper/jas_fix.h"
     80 #include "jasper/jas_malloc.h"
     81 #include "jasper/jas_math.h"
     82 #include "jasper/jas_stream.h"
     83 #include "jasper/jas_debug.h"
     84 
     85 #include "jpc_bs.h"
     86 #include "jpc_dec.h"
     87 #include "jpc_cs.h"
     88 #include "jpc_mqdec.h"
     89 #include "jpc_t2dec.h"
     90 #include "jpc_t1cod.h"
     91 #include "jpc_math.h"
     92 
     93 /******************************************************************************\
     94 *
     95 \******************************************************************************/
     96 
     97 long jpc_dec_lookahead(jas_stream_t *in);
     98 static int jpc_getcommacode(jpc_bitstream_t *in);
     99 static int jpc_getnumnewpasses(jpc_bitstream_t *in);
    100 static int jpc_dec_decodepkt(jpc_dec_t *dec, jas_stream_t *pkthdrstream, jas_stream_t *in, int compno, int lvlno,
    101   int prcno, int lyrno);
    102 
    103 /******************************************************************************\
    104 * Code.
    105 \******************************************************************************/
    106 
    107 static int jpc_getcommacode(jpc_bitstream_t *in)
    108 {
    109     int n;
    110     int v;
    111 
    112     n = 0;
    113     for (;;) {
    114         if ((v = jpc_bitstream_getbit(in)) < 0) {
    115             return -1;
    116         }
    117         if (jpc_bitstream_eof(in)) {
    118             return -1;
    119         }
    120         if (!v) {
    121             break;
    122         }
    123         ++n;
    124     }
    125 
    126     return n;
    127 }
    128 
    129 static int jpc_getnumnewpasses(jpc_bitstream_t *in)
    130 {
    131     int n;
    132 
    133     if ((n = jpc_bitstream_getbit(in)) > 0) {
    134         if ((n = jpc_bitstream_getbit(in)) > 0) {
    135             if ((n = jpc_bitstream_getbits(in, 2)) == 3) {
    136                 if ((n = jpc_bitstream_getbits(in, 5)) == 31) {
    137                     if ((n = jpc_bitstream_getbits(in, 7)) >= 0) {
    138                         n += 36 + 1;
    139                     }
    140                 } else if (n >= 0) {
    141                     n += 5 + 1;
    142                 }
    143             } else if (n >= 0) {
    144                 n += 2 + 1;
    145             }
    146         } else if (!n) {
    147             n += 2;
    148         }
    149     } else if (!n) {
    150         ++n;
    151     }
    152 
    153     return n;
    154 }
    155 
    156 static int jpc_dec_decodepkt(jpc_dec_t *dec, jas_stream_t *pkthdrstream, jas_stream_t *in, int compno, int rlvlno,
    157   int prcno, int lyrno)
    158 {
    159     jpc_bitstream_t *inb;
    160     jpc_dec_tcomp_t *tcomp;
    161     jpc_dec_rlvl_t *rlvl;
    162     jpc_dec_band_t *band;
    163     jpc_dec_cblk_t *cblk;
    164     int n;
    165     int m;
    166     int i;
    167     jpc_tagtreenode_t *leaf;
    168     int included;
    169     int ret;
    170     int numnewpasses;
    171     jpc_dec_seg_t *seg;
    172     int len;
    173     int present;
    174     int savenumnewpasses;
    175     int mycounter;
    176     jpc_ms_t *ms;
    177     jpc_dec_tile_t *tile;
    178     jpc_dec_ccp_t *ccp;
    179     jpc_dec_cp_t *cp;
    180     int bandno;
    181     jpc_dec_prc_t *prc;
    182     int usedcblkcnt;
    183     int cblkno;
    184     uint_fast32_t bodylen;
    185     bool discard;
    186     int passno;
    187     int maxpasses;
    188     int hdrlen;
    189     int hdroffstart;
    190     int hdroffend;
    191 
    192     /* Avoid compiler warning about possible use of uninitialized
    193       variable. */
    194     bodylen = 0;
    195 
    196     discard = (lyrno >= dec->maxlyrs);
    197 
    198     tile = dec->curtile;
    199     cp = tile->cp;
    200     ccp = &cp->ccps[compno];
    201 
    202     /*
    203      * Decode the packet header.
    204      */
    205 
    206     /* Decode the SOP marker segment if present. */
    207     if (cp->csty & JPC_COD_SOP) {
    208         if (jpc_dec_lookahead(in) == JPC_MS_SOP) {
    209             if (!(ms = jpc_getms(in, dec->cstate))) {
    210                 return -1;
    211             }
    212             if (jpc_ms_gettype(ms) != JPC_MS_SOP) {
    213                 jpc_ms_destroy(ms);
    214                 jas_eprintf("missing SOP marker segment\n");
    215                 return -1;
    216             }
    217             jpc_ms_destroy(ms);
    218         }
    219     }
    220 
    221 hdroffstart = jas_stream_getrwcount(pkthdrstream);
    222 
    223     if (!(inb = jpc_bitstream_sopen(pkthdrstream, "r"))) {
    224         return -1;
    225     }
    226 
    227     if ((present = jpc_bitstream_getbit(inb)) < 0) {
    228         return 1;
    229     }
    230     JAS_DBGLOG(10, ("\n", present));
    231     JAS_DBGLOG(10, ("present=%d ", present));
    232 
    233     /* Is the packet non-empty? */
    234     if (present) {
    235         /* The packet is non-empty. */
    236         tcomp = &tile->tcomps[compno];
    237         rlvl = &tcomp->rlvls[rlvlno];
    238         bodylen = 0;
    239         for (bandno = 0, band = rlvl->bands; bandno < rlvl->numbands;
    240           ++bandno, ++band) {
    241             if (!band->data) {
    242                 continue;
    243             }
    244             prc = &band->prcs[prcno];
    245             if (!prc->cblks) {
    246                 continue;
    247             }
    248             usedcblkcnt = 0;
    249             for (cblkno = 0, cblk = prc->cblks; cblkno < prc->numcblks;
    250               ++cblkno, ++cblk) {
    251                 ++usedcblkcnt;
    252                 if (!cblk->numpasses) {
    253                     leaf = jpc_tagtree_getleaf(prc->incltagtree, usedcblkcnt - 1);
    254                     if ((included = jpc_tagtree_decode(prc->incltagtree, leaf, lyrno + 1, inb)) < 0) {
    255                         return -1;
    256                     }
    257                 } else {
    258                     if ((included = jpc_bitstream_getbit(inb)) < 0) {
    259                         return -1;
    260                     }
    261                 }
    262                 JAS_DBGLOG(10, ("\n"));
    263                 JAS_DBGLOG(10, ("included=%d ", included));
    264                 if (!included) {
    265                     continue;
    266                 }
    267                 if (!cblk->numpasses) {
    268                     i = 1;
    269                     leaf = jpc_tagtree_getleaf(prc->numimsbstagtree, usedcblkcnt - 1);
    270                     for (;;) {
    271                         if ((ret = jpc_tagtree_decode(prc->numimsbstagtree, leaf, i, inb)) < 0) {
    272                             return -1;
    273                         }
    274                         if (ret) {
    275                             break;
    276                         }
    277                         ++i;
    278                     }
    279                     cblk->numimsbs = i - 1;
    280                     cblk->firstpassno = cblk->numimsbs * 3;
    281                 }
    282                 if ((numnewpasses = jpc_getnumnewpasses(inb)) < 0) {
    283                     return -1;
    284                 }
    285                 JAS_DBGLOG(10, ("numnewpasses=%d ", numnewpasses));
    286                 seg = cblk->curseg;
    287                 savenumnewpasses = numnewpasses;
    288                 mycounter = 0;
    289                 if (numnewpasses > 0) {
    290                     if ((m = jpc_getcommacode(inb)) < 0) {
    291                         return -1;
    292                     }
    293                     cblk->numlenbits += m;
    294                     JAS_DBGLOG(10, ("increment=%d ", m));
    295                     while (numnewpasses > 0) {
    296                         passno = cblk->firstpassno + cblk->numpasses + mycounter;
    297     /* XXX - the maxpasses is not set precisely but this doesn't matter... */
    298                         maxpasses = JPC_SEGPASSCNT(passno, cblk->firstpassno, 10000, (ccp->cblkctx & JPC_COX_LAZY) != 0, (ccp->cblkctx & JPC_COX_TERMALL) != 0);
    299                         if (!discard && !seg) {
    300                             if (!(seg = jpc_seg_alloc())) {
    301                                 return -1;
    302                             }
    303                             jpc_seglist_insert(&cblk->segs, cblk->segs.tail, seg);
    304                             if (!cblk->curseg) {
    305                                 cblk->curseg = seg;
    306                             }
    307                             seg->passno = passno;
    308                             seg->type = JPC_SEGTYPE(seg->passno, cblk->firstpassno, (ccp->cblkctx & JPC_COX_LAZY) != 0);
    309                             seg->maxpasses = maxpasses;
    310                         }
    311                         n = JAS_MIN(numnewpasses, maxpasses);
    312                         mycounter += n;
    313                         numnewpasses -= n;
    314                         if ((len = jpc_bitstream_getbits(inb, cblk->numlenbits + jpc_floorlog2(n))) < 0) {
    315                             return -1;
    316                         }
    317                         JAS_DBGLOG(10, ("len=%d ", len));
    318                         if (!discard) {
    319                             seg->lyrno = lyrno;
    320                             seg->numpasses += n;
    321                             seg->cnt = len;
    322                             seg = seg->next;
    323                         }
    324                         bodylen += len;
    325                     }
    326                 }
    327                 cblk->numpasses += savenumnewpasses;
    328             }
    329         }
    330 
    331         jpc_bitstream_inalign(inb, 0, 0);
    332 
    333     } else {
    334         if (jpc_bitstream_inalign(inb, 0x7f, 0)) {
    335             jas_eprintf("alignment failed\n");
    336             return -1;
    337         }
    338     }
    339     jpc_bitstream_close(inb);
    340 
    341     hdroffend = jas_stream_getrwcount(pkthdrstream);
    342     hdrlen = hdroffend - hdroffstart;
    343     if (jas_getdbglevel() >= 5) {
    344         jas_eprintf("hdrlen=%lu bodylen=%lu \n", (unsigned long) hdrlen,
    345           (unsigned long) bodylen);
    346     }
    347 
    348     if (cp->csty & JPC_COD_EPH) {
    349         if (jpc_dec_lookahead(pkthdrstream) == JPC_MS_EPH) {
    350             if (!(ms = jpc_getms(pkthdrstream, dec->cstate))) {
    351                 jas_eprintf("cannot get (EPH) marker segment\n");
    352                 return -1;
    353             }
    354             if (jpc_ms_gettype(ms) != JPC_MS_EPH) {
    355                 jpc_ms_destroy(ms);
    356                 jas_eprintf("missing EPH marker segment\n");
    357                 return -1;
    358             }
    359             jpc_ms_destroy(ms);
    360         }
    361     }
    362 
    363     /* decode the packet body. */
    364 
    365     if (jas_getdbglevel() >= 1) {
    366         jas_eprintf("packet body offset=%06ld\n", (long) jas_stream_getrwcount(in));
    367     }
    368 
    369     if (!discard) {
    370         tcomp = &tile->tcomps[compno];
    371         rlvl = &tcomp->rlvls[rlvlno];
    372         for (bandno = 0, band = rlvl->bands; bandno < rlvl->numbands;
    373           ++bandno, ++band) {
    374             if (!band->data) {
    375                 continue;
    376             }
    377             prc = &band->prcs[prcno];
    378             if (!prc->cblks) {
    379                 continue;
    380             }
    381             for (cblkno = 0, cblk = prc->cblks; cblkno < prc->numcblks;
    382               ++cblkno, ++cblk) {
    383                 seg = cblk->curseg;
    384                 while (seg) {
    385                     if (!seg->stream) {
    386                         if (!(seg->stream = jas_stream_memopen(0, 0))) {
    387                             return -1;
    388                         }
    389                     }
    390 #if 0
    391 jas_eprintf("lyrno=%02d, compno=%02d, lvlno=%02d, prcno=%02d, bandno=%02d, cblkno=%02d, passno=%02d numpasses=%02d cnt=%d numbps=%d, numimsbs=%d\n", lyrno, compno, rlvlno, prcno, band - rlvl->bands, cblk - prc->cblks, seg->passno, seg->numpasses, seg->cnt, band->numbps, cblk->numimsbs);
    392 #endif
    393                     if (seg->cnt > 0) {
    394                         if (jpc_getdata(in, seg->stream, seg->cnt) < 0) {
    395                             return -1;
    396                         }
    397                         seg->cnt = 0;
    398                     }
    399                     if (seg->numpasses >= seg->maxpasses) {
    400                         cblk->curseg = seg->next;
    401                     }
    402                     seg = seg->next;
    403                 }
    404             }
    405         }
    406     } else {
    407         if (jas_stream_gobble(in, bodylen) != JAS_CAST(int, bodylen)) {
    408             return -1;
    409         }
    410     }
    411     return 0;
    412 }
    413 
    414 /********************************************************************************************/
    415 /********************************************************************************************/
    416 
    417 int jpc_dec_decodepkts(jpc_dec_t *dec, jas_stream_t *pkthdrstream, jas_stream_t *in)
    418 {
    419     jpc_dec_tile_t *tile;
    420     jpc_pi_t *pi;
    421     int ret;
    422 
    423     tile = dec->curtile;
    424     pi = tile->pi;
    425     for (;;) {
    426 if (!tile->pkthdrstream || jas_stream_peekc(tile->pkthdrstream) == EOF) {
    427         switch (jpc_dec_lookahead(in)) {
    428         case JPC_MS_EOC:
    429         case JPC_MS_SOT:
    430             return 0;
    431             break;
    432         case JPC_MS_SOP:
    433         case JPC_MS_EPH:
    434         case 0:
    435             break;
    436         default:
    437             return -1;
    438             break;
    439         }
    440 }
    441         if ((ret = jpc_pi_next(pi))) {
    442             return ret;
    443         }
    444 if (dec->maxpkts >= 0 && dec->numpkts >= dec->maxpkts) {
    445     jas_eprintf("warning: stopping decode prematurely as requested\n");
    446     return 0;
    447 }
    448         if (jas_getdbglevel() >= 1) {
    449             jas_eprintf("packet offset=%08ld prg=%d cmptno=%02d "
    450               "rlvlno=%02d prcno=%03d lyrno=%02d\n", (long)
    451               jas_stream_getrwcount(in), jpc_pi_prg(pi), jpc_pi_cmptno(pi),
    452               jpc_pi_rlvlno(pi), jpc_pi_prcno(pi), jpc_pi_lyrno(pi));
    453         }
    454         if (jpc_dec_decodepkt(dec, pkthdrstream, in, jpc_pi_cmptno(pi), jpc_pi_rlvlno(pi),
    455           jpc_pi_prcno(pi), jpc_pi_lyrno(pi))) {
    456             return -1;
    457         }
    458 ++dec->numpkts;
    459     }
    460 
    461     return 0;
    462 }
    463 
    464 jpc_pi_t *jpc_dec_pi_create(jpc_dec_t *dec, jpc_dec_tile_t *tile)
    465 {
    466     jpc_pi_t *pi;
    467     int compno;
    468     jpc_picomp_t *picomp;
    469     jpc_pirlvl_t *pirlvl;
    470     jpc_dec_tcomp_t *tcomp;
    471     int rlvlno;
    472     jpc_dec_rlvl_t *rlvl;
    473     int prcno;
    474     int *prclyrno;
    475     jpc_dec_cmpt_t *cmpt;
    476 
    477     if (!(pi = jpc_pi_create0())) {
    478         return 0;
    479     }
    480     pi->numcomps = dec->numcomps;
    481     if (!(pi->picomps = jas_alloc2(pi->numcomps, sizeof(jpc_picomp_t)))) {
    482         jpc_pi_destroy(pi);
    483         return 0;
    484     }
    485     for (compno = 0, picomp = pi->picomps; compno < pi->numcomps; ++compno,
    486       ++picomp) {
    487         picomp->pirlvls = 0;
    488     }
    489 
    490     for (compno = 0, tcomp = tile->tcomps, picomp = pi->picomps;
    491       compno < pi->numcomps; ++compno, ++tcomp, ++picomp) {
    492         picomp->numrlvls = tcomp->numrlvls;
    493         if (!(picomp->pirlvls = jas_alloc2(picomp->numrlvls,
    494           sizeof(jpc_pirlvl_t)))) {
    495             jpc_pi_destroy(pi);
    496             return 0;
    497         }
    498         for (rlvlno = 0, pirlvl = picomp->pirlvls; rlvlno <
    499           picomp->numrlvls; ++rlvlno, ++pirlvl) {
    500             pirlvl->prclyrnos = 0;
    501         }
    502         for (rlvlno = 0, pirlvl = picomp->pirlvls, rlvl = tcomp->rlvls;
    503           rlvlno < picomp->numrlvls; ++rlvlno, ++pirlvl, ++rlvl) {
    504 /* XXX sizeof(long) should be sizeof different type */
    505             pirlvl->numprcs = rlvl->numprcs;
    506             if (!(pirlvl->prclyrnos = jas_alloc2(pirlvl->numprcs,
    507               sizeof(long)))) {
    508                 jpc_pi_destroy(pi);
    509                 return 0;
    510             }
    511         }
    512     }
    513 
    514     pi->maxrlvls = 0;
    515     for (compno = 0, tcomp = tile->tcomps, picomp = pi->picomps, cmpt =
    516       dec->cmpts; compno < pi->numcomps; ++compno, ++tcomp, ++picomp,
    517       ++cmpt) {
    518         picomp->hsamp = cmpt->hstep;
    519         picomp->vsamp = cmpt->vstep;
    520         for (rlvlno = 0, pirlvl = picomp->pirlvls, rlvl = tcomp->rlvls;
    521           rlvlno < picomp->numrlvls; ++rlvlno, ++pirlvl, ++rlvl) {
    522             pirlvl->prcwidthexpn = rlvl->prcwidthexpn;
    523             pirlvl->prcheightexpn = rlvl->prcheightexpn;
    524             for (prcno = 0, prclyrno = pirlvl->prclyrnos;
    525               prcno < pirlvl->numprcs; ++prcno, ++prclyrno) {
    526                 *prclyrno = 0;
    527             }
    528             pirlvl->numhprcs = rlvl->numhprcs;
    529         }
    530         if (pi->maxrlvls < tcomp->numrlvls) {
    531             pi->maxrlvls = tcomp->numrlvls;
    532         }
    533     }
    534 
    535     pi->numlyrs = tile->cp->numlyrs;
    536     pi->xstart = tile->xstart;
    537     pi->ystart = tile->ystart;
    538     pi->xend = tile->xend;
    539     pi->yend = tile->yend;
    540 
    541     pi->picomp = 0;
    542     pi->pirlvl = 0;
    543     pi->x = 0;
    544     pi->y = 0;
    545     pi->compno = 0;
    546     pi->rlvlno = 0;
    547     pi->prcno = 0;
    548     pi->lyrno = 0;
    549     pi->xstep = 0;
    550     pi->ystep = 0;
    551 
    552     pi->pchgno = -1;
    553 
    554     pi->defaultpchg.prgord = tile->cp->prgord;
    555     pi->defaultpchg.compnostart = 0;
    556     pi->defaultpchg.compnoend = pi->numcomps;
    557     pi->defaultpchg.rlvlnostart = 0;
    558     pi->defaultpchg.rlvlnoend = pi->maxrlvls;
    559     pi->defaultpchg.lyrnoend = pi->numlyrs;
    560     pi->pchg = 0;
    561 
    562     pi->valid = 0;
    563 
    564     return pi;
    565 }
    566 
    567 long jpc_dec_lookahead(jas_stream_t *in)
    568 {
    569     uint_fast16_t x;
    570     if (jpc_getuint16(in, &x)) {
    571         return -1;
    572     }
    573     if (jas_stream_ungetc(in, x & 0xff) == EOF ||
    574       jas_stream_ungetc(in, x >> 8) == EOF) {
    575         return -1;
    576     }
    577     if (x >= JPC_MS_INMIN /*&& x <= JPC_MS_INMAX*/) {
    578         return x;
    579     }
    580     return 0;
    581 }
    582