#include <u.h>#include <libc.h>#include <ctype.h>#include "pdf.h" /* * 7.5.4 pre-1.5 xref section reader * PDF>=1.5 may have BOTH (or either) old xref format and xref streams */intxrefreadold(Pdf *pdf){	int xref0; /* 7.5.4 xref subsection first object number */	int nxref; /* 7.5.4 xref subsection number of objects */	int i, j, sz, n, newnxref;	Xref xref;	char *s, *e;	Xref *x; 	Sseek(pdf->s, 4, 1);		if(Sgeti(pdf->s, &xref0) != 1 || xref0 < 0){		werrstr("invalid xref0");		return -1;	}	if(Sgeti(pdf->s, &nxref) != 1 || nxref < 0){		werrstr("invalid nxref");		return -1;	}	if(nxref < 1)		return 0; 	/* skip whitespace and move to the first subsection */	do; while(isspace(Sgetc(pdf->s)));	Sungetc(pdf->s); 	s = nil;	if((x = realloc(pdf->xref, (pdf->nxref + nxref)*sizeof(Xref))) == nil)		goto err;	pdf->xref = x; 	/* read the entire thing at once */	sz = nxref*20;	if((s = malloc(sz)) == nil)		goto err;	for(i = 0; i < sz; i += n){		if((n = Sread(pdf->s, s+i, sz-i)) < 1)			goto err;	} 	/* store non-free objects only */	newnxref = pdf->nxref;	xref.objstm = 0;	for(e = s, i = 0; i < nxref; i++, e += 20){		if(!isspace(e[10]) || !isspace(e[18]) || !isspace(e[19])){			werrstr("invalid xref line (%d/%d)", i, nxref);			goto err;		}		xref.id = xref0 + i;		xref.off = strtoul(e, nil, 10);		xref.gen = strtoul(e+11, nil, 10); 		/* search in already existing xrefs, update if found */		for(j = 0; j < pdf->nxref; j++){			if(pdf->xref[j].id != xref.id)				continue;			if(e[17] == 'f') /* it was freed */				pdf->xref[j].id = 0;			else if(e[17] == 'n')				pdf->xref[j].off = xref.off;			break;		}		if(j >= pdf->nxref && e[17] == 'n') /* that's a new one, insert unless it's free */			pdf->xref[newnxref++] = xref;	}	free(s);	s = nil; 	/* scale down */	for(i = j = 0; i < newnxref; i++){		if(pdf->xref[i].id != 0)			pdf->xref[j++] = pdf->xref[i];	}	if((x = realloc(pdf->xref, j*sizeof(Xref))) == nil)		goto err;	pdf->xref = x;	pdf->nxref = j; 	return 0;err:	free(s);	return -1;} static intgetint(uchar *b, int sz, int dflt){	int x, i; 	if(sz == 0)		return dflt;	x = 0;	for(i = 0; i < sz; i++)		x = x<<8 | b[i]; 	return x;} /* 7.5.8.3 Cross-reference stream data */intxrefreadstream(Pdf *pdf){	Object *o, *p, *index;	Stream *s;	Xref *x;	uchar buf[32];	int w[8], nw, c, n, nxref, newnxref, prev, extra;	int i, ni, nsubsec, subsec; 	s = nil;	if((o = pdfobj(pdf, pdf->s, 0)) == nil){		werrstr("xref stream obj: %r");		goto err;	} 	index = dictget(o, "Index"); /* 7.5.8.2 subsection indexing */	nsubsec = arraylen(index) / 2; 	if((prev = dictint(o, "Prev")) > 0){ /* 7.5.8.2 previous xref stream */		if(Sseek(pdf->s, prev, 0) != prev){			werrstr("xref stream prev seek failed");			goto err;		}		if(xrefreadstream(pdf) != 0){			pdfobjfree(o);			return -1;		}	}	if((s = Sopen(o)) == nil){		werrstr("failed to stream xref: %r");		goto err;	}	if((nw = dictints(o, "W", w, nelem(w))) < 3 || nw >= nelem(w)){		werrstr("nW=%d", nw);		goto err;	} 	for(n = i = 0; i < nw; i++)		n += w[i]; /* size of each element. w[i] MAY be 0 */	if(n > sizeof(buf)){		werrstr("W is beyond imaginable: %d bytes", n);		goto err;	}	if((nxref = Ssize(s)/n) < 1){		werrstr("no xref elements in the stream");		goto err;	}	extra = Ssize(s) % (nxref*n);	if(extra != 0)		fprint(2, "extra %d bytes in xref stream\n", extra); 	newnxref = pdf->nxref + nxref;	if((x = realloc(pdf->xref, newnxref*sizeof(Xref))) == nil)		goto err;	pdf->xref = x;	x += pdf->nxref;	i = 0;	for(ni = subsec = 0; Sread(s, buf, n) == n; ni--, i++){ /* stop on short read or error */		if(ni == 0 && nsubsec > 0){			i = arrayint(index, subsec*2+0); /* index of the first object */			ni = arrayint(index, subsec*2+1); /* number of objects in the subsection */			subsec++;		} 		c = getint(buf, w[0], 1); /* default type is 1 */		if(c == 1){ /* uncompressed */			x->objstm = 0;			x->id = i;			x->off = getint(buf+w[0], w[1], 0);			x->gen = getint(buf+w[0]+w[1], w[2], 0);			pdf->nxref++;			x++;		}else if(c == 2){ /* compressed */			x->id = i;			x->objstm = getint(buf+w[0], w[1], 0);			x->index = getint(buf+w[0]+w[1], w[2], 0);			pdf->nxref++;			x++;		}	} 	Sclose(s);	if((p = dictget(o, "Root")) != &null)		pdf->root = pdfref(p);	if((p = dictget(o, "Info")) != &null)		pdf->info = pdfref(p);	pdf->top = o; 	return 0;err:	Sclose(s);	pdfobjfree(o);	return -1;}