From 31cc688591341718e1c1daedcc791bc4d25fc306 Mon Sep 17 00:00:00 2001
From: "Sven M. Hallberg" <pesco@khjk.org>
Date: Sun, 24 Nov 2019 20:16:49 +0100
Subject: [PATCH] try to parse xrefs before the rest of the document
---
pdf.c | 51 +++++++++++++++++++++++++++++++++++++++------------
1 file changed, 39 insertions(+), 12 deletions(-)
diff --git a/pdf.c b/pdf.c
index eff119b..b095f35 100644
--- a/pdf.c
+++ b/pdf.c
@@ -165,6 +165,8 @@ act_octal(const HParseResult *p, void *u)
HParser *p_pdf;
HParser *p_pdfdbg;
+HParser *p_startxref;
+HParser *p_xref;
/* continuation for h_bind() */
HParser *kstream(HAllocator *, const HParsedToken *, void *);
@@ -317,23 +319,23 @@ init_parser(void)
// XXX cross-reference streams
/* trailer */
- H_RULE(tdict, SEQ(KW("trailer"), dict, nl));
- H_RULE(startxr, SEQ(KW("startxref"), nl,
- lws, xrnat, nl));
- // NB: lws before xref offset is allowed, cf. p.48 (example 4)
- H_RULE(eofmark, SEQ(LIT("%%EOF"), CHX(nl, end)));
+ H_RULE(startxr, SEQ(nl, KW("startxref"), nl,
+ lws, xrnat, nl,
+ LIT("%%EOF"), CHX(nl, end)));
// XXX should lws be allowed before EOF marker?
- H_RULE(txrefs, SEQ(xrefs, tdict));
- H_RULE(trailer, SEQ(h_optional(txrefs), startxr, eofmark));
+ // NB: lws before xref offset is allowed, cf. p.48 (example 4)
+ H_RULE(xr_td, SEQ(xrefs, KW("trailer"), dict));
- H_RULE(tail, SEQ(body, trailer));
+ H_RULE(tail, SEQ(body, h_optional(xr_td), startxr));
H_RULE(pdf, SEQ(header, h_many1(tail), end));
/* debug parser to consume as much as possible */
- H_RULE(pdfdbg, SEQ(header, h_many(tail), body, OPT(trailer)));
+ H_RULE(pdfdbg, SEQ(header, h_many(tail), body, OPT(xr_td), OPT(startxr)));
p_pdf = pdf;
p_pdfdbg = pdfdbg;
+ p_startxref = startxr;
+ p_xref = xr_td;
}
/*
@@ -395,10 +397,10 @@ fail:
int main(int argc, char *argv[])
{
- HParseResult *res;
+ HParseResult *res = NULL;
const char *infile = NULL;
const uint8_t *input;
- size_t sz;
+ size_t sz, startxref;
int fd;
/* command line handling */
@@ -419,8 +421,33 @@ int main(int argc, char *argv[])
if (input == MAP_FAILED)
err(1, "mmap");
- /* build and run parser */
+ /* build parsers */
init_parser();
+
+ /* search for the "startxref" section from the back of the file */
+ HParser *p = h_left(p_startxref, h_end_p());
+ for (size_t i = 0; i < sz; i++) {
+ res = h_parse(p, input + sz - i, i);
+ if (res) break;
+ }
+ if (res == NULL) {
+ fprintf(stderr, "%s: startxref not found\n", infile);
+ return 1;
+ }
+ startxref = H_INDEX_UINT(res->ast, 0);
+
+ /* parse cross-references and trailer dictionary */
+ res = h_parse(p_xref, input + startxref, sz - startxref);
+ if (!res) {
+ fprintf(stderr, "%s: error parsing xref/trailer at "
+ "position %zu (0x%zx)\n", infile, startxref, startxref);
+ // continue anyway...
+ }
+ // XXX debug
+ //h_pprint(stderr, res->ast, 0, 2);
+ //return 0;
+
+ /* run the main parser */
res = h_parse(p_pdf, input, sz);
if (!res) {
fprintf(stderr, "%s: no parse\n", infile);
--
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