static int jpc_enc_encodemainhdr(jpc_enc_t *enc)
{
	jpc_siz_t *siz;
	jpc_cod_t *cod;
	jpc_qcd_t *qcd;
	int i;
long startoff;
long mainhdrlen;
	jpc_enc_cp_t *cp;
	jpc_qcc_t *qcc;
	jpc_enc_tccp_t *tccp;
	uint_fast16_t cmptno;
	jpc_tsfb_band_t bandinfos[JPC_MAXBANDS];
	jpc_fix_t mctsynweight;
	jpc_enc_tcp_t *tcp;
	jpc_tsfb_t *tsfb;
	jpc_tsfb_band_t *bandinfo;
	uint_fast16_t numbands;
	uint_fast16_t bandno;
	uint_fast16_t rlvlno;
	uint_fast16_t analgain;
	jpc_fix_t absstepsize;
	char buf[1024];
	jpc_com_t *com;

	cp = enc->cp;

startoff = jas_stream_getrwcount(enc->out);

	/* Write SOC marker segment. */
	if (!(enc->mrk = jpc_ms_create(JPC_MS_SOC))) {
		return -1;
	}
	if (jpc_putms(enc->out, enc->cstate, enc->mrk)) {
		jas_eprintf("cannot write SOC marker\n");
		return -1;
	}
	jpc_ms_destroy(enc->mrk);
	enc->mrk = 0;

	/* Write SIZ marker segment. */
	if (!(enc->mrk = jpc_ms_create(JPC_MS_SIZ))) {
		return -1;
	}
	siz = &enc->mrk->parms.siz;
	siz->caps = 0;
	siz->xoff = cp->imgareatlx;
	siz->yoff = cp->imgareatly;
	siz->width = cp->refgrdwidth;
	siz->height = cp->refgrdheight;
	siz->tilexoff = cp->tilegrdoffx;
	siz->tileyoff = cp->tilegrdoffy;
	siz->tilewidth = cp->tilewidth;
	siz->tileheight = cp->tileheight;
	siz->numcomps = cp->numcmpts;
	siz->comps = jas_alloc2(siz->numcomps, sizeof(jpc_sizcomp_t));
	assert(siz->comps);
	for (i = 0; i < JAS_CAST(int, cp->numcmpts); ++i) {
		siz->comps[i].prec = cp->ccps[i].prec;
		siz->comps[i].sgnd = cp->ccps[i].sgnd;
		siz->comps[i].hsamp = cp->ccps[i].sampgrdstepx;
		siz->comps[i].vsamp = cp->ccps[i].sampgrdstepy;
	}
	if (jpc_putms(enc->out, enc->cstate, enc->mrk)) {
		jas_eprintf("cannot write SIZ marker\n");
		return -1;
	}
	jpc_ms_destroy(enc->mrk);
	enc->mrk = 0;

	if (!(enc->mrk = jpc_ms_create(JPC_MS_COM))) {
		return -1;
	}
	sprintf(buf, "Creator: JasPer Version %s", jas_getversion());
 	com = &enc->mrk->parms.com;
 	com->len = JAS_CAST(uint_fast16_t, strlen(buf));
 	com->regid = JPC_COM_LATIN;
	if (!(com->data = JAS_CAST(jas_uchar *, jas_strdup(buf)))) {
 		abort();
 	}
 	if (jpc_putms(enc->out, enc->cstate, enc->mrk)) {
		jas_eprintf("cannot write COM marker\n");
		return -1;
	}
	jpc_ms_destroy(enc->mrk);
	enc->mrk = 0;

#if 0
	if (!(enc->mrk = jpc_ms_create(JPC_MS_CRG))) {
		return -1;
	}
	crg = &enc->mrk->parms.crg;
	crg->comps = jas_alloc2(crg->numcomps, sizeof(jpc_crgcomp_t));
	if (jpc_putms(enc->out, enc->cstate, enc->mrk)) {
		jas_eprintf("cannot write CRG marker\n");
		return -1;
	}
	jpc_ms_destroy(enc->mrk);
	enc->mrk = 0;
#endif

	tcp = &cp->tcp;
	tccp = &cp->tccp;
	for (cmptno = 0; cmptno < cp->numcmpts; ++cmptno) {
		tsfb = jpc_cod_gettsfb(tccp->qmfbid, tccp->maxrlvls - 1);
		jpc_tsfb_getbands(tsfb, 0, 0, 1 << tccp->maxrlvls, 1 << tccp->maxrlvls,
		  bandinfos);
		jpc_tsfb_destroy(tsfb);
		mctsynweight = jpc_mct_getsynweight(tcp->mctid, cmptno);
		numbands = 3 * tccp->maxrlvls - 2;
		for (bandno = 0, bandinfo = bandinfos; bandno < numbands;
		  ++bandno, ++bandinfo) {
			rlvlno = (bandno) ? ((bandno - 1) / 3 + 1) : 0;
			analgain = JPC_NOMINALGAIN(tccp->qmfbid, tccp->maxrlvls,
			  rlvlno, bandinfo->orient);
			if (!tcp->intmode) {
				absstepsize = jpc_fix_div(jpc_inttofix(1 <<
				  (analgain + 1)), bandinfo->synenergywt);
			} else {
				absstepsize = jpc_inttofix(1);
			}	
			cp->ccps[cmptno].stepsizes[bandno] =
			  jpc_abstorelstepsize(absstepsize,
			  cp->ccps[cmptno].prec + analgain);
		}
		cp->ccps[cmptno].numstepsizes = numbands;
	}

	if (!(enc->mrk = jpc_ms_create(JPC_MS_COD))) {
		return -1;
	}
	cod = &enc->mrk->parms.cod;
	cod->csty = cp->tccp.csty | cp->tcp.csty;
	cod->compparms.csty = cp->tccp.csty | cp->tcp.csty;
	cod->compparms.numdlvls = cp->tccp.maxrlvls - 1;
	cod->compparms.numrlvls = cp->tccp.maxrlvls;
	cod->prg = cp->tcp.prg;
	cod->numlyrs = cp->tcp.numlyrs;
	cod->compparms.cblkwidthval = JPC_COX_CBLKSIZEEXPN(cp->tccp.cblkwidthexpn);
	cod->compparms.cblkheightval = JPC_COX_CBLKSIZEEXPN(cp->tccp.cblkheightexpn);
	cod->compparms.cblksty = cp->tccp.cblksty;
	cod->compparms.qmfbid = cp->tccp.qmfbid;
	cod->mctrans = (cp->tcp.mctid != JPC_MCT_NONE);
	if (tccp->csty & JPC_COX_PRT) {
		for (rlvlno = 0; rlvlno < tccp->maxrlvls; ++rlvlno) {
			cod->compparms.rlvls[rlvlno].parwidthval = tccp->prcwidthexpns[rlvlno];
			cod->compparms.rlvls[rlvlno].parheightval = tccp->prcheightexpns[rlvlno];
		}
	}
	if (jpc_putms(enc->out, enc->cstate, enc->mrk)) {
		jas_eprintf("cannot write COD marker\n");
		return -1;
	}
	jpc_ms_destroy(enc->mrk);
	enc->mrk = 0;

	if (!(enc->mrk = jpc_ms_create(JPC_MS_QCD))) {
		return -1;
	}
	qcd = &enc->mrk->parms.qcd;
	qcd->compparms.qntsty = (tccp->qmfbid == JPC_COX_INS) ?
	  JPC_QCX_SEQNT : JPC_QCX_NOQNT;
	qcd->compparms.numstepsizes = cp->ccps[0].numstepsizes;
	qcd->compparms.numguard = cp->tccp.numgbits;
	qcd->compparms.stepsizes = cp->ccps[0].stepsizes;
	if (jpc_putms(enc->out, enc->cstate, enc->mrk)) {
		return -1;
	}
	/* We do not want the step size array to be freed! */
	qcd->compparms.stepsizes = 0;
	jpc_ms_destroy(enc->mrk);
	enc->mrk = 0;

	tccp = &cp->tccp;
	for (cmptno = 1; cmptno < cp->numcmpts; ++cmptno) {
		if (!(enc->mrk = jpc_ms_create(JPC_MS_QCC))) {
			return -1;
		}
		qcc = &enc->mrk->parms.qcc;
		qcc->compno = cmptno;
		qcc->compparms.qntsty = (tccp->qmfbid == JPC_COX_INS) ?
		  JPC_QCX_SEQNT : JPC_QCX_NOQNT;
		qcc->compparms.numstepsizes = cp->ccps[cmptno].numstepsizes;
		qcc->compparms.numguard = cp->tccp.numgbits;
		qcc->compparms.stepsizes = cp->ccps[cmptno].stepsizes;
		if (jpc_putms(enc->out, enc->cstate, enc->mrk)) {
			return -1;
		}
		/* We do not want the step size array to be freed! */
		qcc->compparms.stepsizes = 0;
		jpc_ms_destroy(enc->mrk);
		enc->mrk = 0;
	}

#define MAINTLRLEN	2
	mainhdrlen = jas_stream_getrwcount(enc->out) - startoff;
	enc->len += mainhdrlen;
	if (enc->cp->totalsize != UINT_FAST32_MAX) {
		uint_fast32_t overhead;
		overhead = mainhdrlen + MAINTLRLEN;
		enc->mainbodysize = (enc->cp->totalsize >= overhead) ?
		  (enc->cp->totalsize - overhead) : 0;
	} else {
		enc->mainbodysize = UINT_FAST32_MAX;
	}

	return 0;
}

The product performs a calculation that can produce an integer overflow or wraparound when the logic assumes that the resulting value will always be larger than the original value. This occurs when an integer value is incremented to a value that is too large to store in the associated representation. When this occurs, the value may become a very small or negative number.