ref: 17128cefa8384e9433de8a725686b4e544a83308
dir: pdffs/pdf.c
#include <u.h>
#include <libc.h>
#include <bio.h>
#include <ctype.h>
#include "pdf.h"
int Tfmt(Fmt *f);
int ⊗fmt(Fmt *f);
/*
* pre-1.5 xref section reader
* PDF>=1.5 may have BOTH (or either) old xref format and xref streams
*/
static int
xrefread(Pdf *pdf, int xref0, int nxref)
{
int i, j, sz, n, newnxref;
Xref xref;
char *s, *e;
Xref *x;
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 = Bread(pdf->bio, s+i, sz-i)) < 1)
goto err;
}
/* store non-free objects only */
newnxref = pdf->nxref;
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);
/* FIXME xref.gen */
xref.type = Xusual;
/* 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 int
trailerread(Pdf *pdf)
{
Object *o;
if((o = pdfobj(pdf, pdf->bio)) == nil)
goto err;
if(o->type != Odict){
werrstr("isn't a dictionary");
goto err;
}
pdf->root = pdfref(dictget(o, "Root"));
pdf->info = pdfref(dictget(o, "Info"));
pdfobjfree(o);
return 0;
err:
pdfobjfree(o);
return -1;
}
static int
getint(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 */
static int
xrefstreamread(Pdf *pdf)
{
Object *o;
Stream *s;
Xref *x;
uchar buf[32];
int w[8], nw, i, c, n, nxref, newnxref, prev, extra;
s = nil;
if((o = pdfobj(pdf, pdf->bio)) == nil){
werrstr("xref stream obj: %r");
goto err;
}
if((prev = dictint(o, "Prev")) > 0){
if(Bseek(pdf->bio, prev, 0) != prev){
werrstr("xref stream prev seek failed");
goto err;
}
if(xrefstreamread(pdf) != 0){
pdfobjfree(o);
return -1;
}
}
if((s = streamopen(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 = streamsize(s)/n) < 1){
werrstr("no xref elements in the stream");
goto err;
}
extra = streamsize(s) % (nxref*n);
if(extra != 0)
fprint(2, "extra %d bytes in xref stream", extra);
newnxref = pdf->nxref + nxref;
if((x = realloc(pdf->xref, newnxref*sizeof(Xref))) == nil)
goto err;
pdf->xref = x;
x += pdf->nxref;
while(Bread(s->bio, buf, n) == n){ /* stop on short read or error */
c = getint(buf, w[0], 1); /* default type is 1 */
if(c == 1){ /* not compressed */
x->off = getint(buf+w[0], w[1], 0);
x->gen = getint(buf+w[0]+w[1], w[2], 0);
x->type = Xuncompressed;
pdf->nxref++;
fprint(2, "xref %⊗\n", *x);
x++;
}else if(c == 2){ /* compressed */
x->objnum = getint(buf+w[0], w[1], 0);
x->id = getint(buf+w[0]+w[1], w[2], 0);
x->type = Xcompressed;
pdf->nxref++;
fprint(2, "xref %⊗\n", *x);
x++;
}
}
streamclose(s);
pdf->root = pdfref(dictget(o, "Root"));
pdf->info = pdfref(dictget(o, "Info"));
pdfobjfree(o);
return 0;
err:
streamclose(s);
pdfobjfree(o);
return -1;
}
Pdf *
pdfopen(Biobuf *b)
{
Pdf *pdf;
Object *o;
char tmp[64], *s, *x;
int xref0; /* 7.5.4 xref subsection first object number */
int nxref; /* 7.5.4 xref subsection number of objects */
int xreftb; /* 7.5.4 xref table offset from the beginning of the file */
int i, n, off;
fmtinstall('T', Tfmt);
fmtinstall(L'⊗', ⊗fmt);
o = nil;
if((pdf = calloc(1, sizeof(*pdf))) == nil)
goto err;
pdf->bio = b;
/* check header */
if(Bread(b, tmp, 8) != 8 ||
strncmp(tmp, "%PDF-", 5) != 0 || !isdigit(tmp[5]) || tmp[6] != '.' || !isdigit(tmp[7])){
werrstr("not a pdf");
goto err;
}
/* 7.5.4, 7.5.8 xref table */
/* read a block of data */
n = sizeof(tmp)-1;
Bseek(b, -n, 2);
if(Bread(b, tmp, n) != n){
badtrailer:
werrstr("invalid trailer");
goto err;
}
tmp[n] = 0;
/* search for a valid string that the block ends with */
for(i = n-1, s = &tmp[i]; i > 0 && *s != 0; i--, s--);
s++;
/* find "startxref" */
if((x = strrchr(s, 'f')) == nil || !isws(x[1]) || x-8 < s+1 || memcmp(x-8, "startxref", 9) != 0)
goto badtrailer;
x++;
if((xreftb = strtol(x, nil, 10)) < 1)
goto badtrailer;
/* read xref */
if(Bseek(b, xreftb, 0) != xreftb){
werrstr("xref position out of range");
goto err;
}
morexref:
off = Boffset(b);
n = sizeof(tmp)-1;
if((n = Bread(b, tmp, n)) < 16){
badxref:
werrstr("invalid xref: %r");
goto err;
}
tmp[n] = 0;
if(memcmp(tmp, "xref", 4) == 0){
/* 7.5.4 xref */
x = tmp+4;
xref0 = strtol(x, &x, 10);
nxref = strtol(x, &x, 10);
/* skip whitespace and move to the first subsection */
for(; isws(*x) && x < tmp+n; x++);
n = x-tmp+off;
if(Bseek(b, n, 0) != n)
goto badxref;
if(xref0 >= 0 && nxref > 0 && xrefread(pdf, xref0, nxref) != 0)
goto badxref;
goto morexref; /* there could be more updates, try it */
}else if(memcmp(tmp, "trailer", 7) == 0){ /* 7.5.5 file trailer */
/* move to the trailer dictionary */
n = off + 8;
if(Bseek(b, n, 0) != n || trailerread(pdf) != 0){
werrstr("invalid trailer: %r");
goto err;
}
}else if(isdigit(tmp[0])){ /* could be 7.5.8 xref stream (since PDF 1.5) */
if(Bseek(b, xreftb, 0) != xreftb)
goto badxref;
if(xrefstreamread(pdf) != 0)
goto err;
}
/* root is required, info is optional */
if(pdf->root == &null){
werrstr("no root");
goto err;
}
return pdf;
err:
werrstr("pdfopen: %r [at %p]", (void*)Boffset(b));
pdfclose(pdf);
pdfobjfree(o);
return nil;
}
void
pdfclose(Pdf *pdf)
{
if(pdf == nil)
return;
if(pdf->bio != nil)
Bterm(pdf->bio);
free(pdf->xref);
free(pdf);
}