From b318059c8df3616fdee35412814c6712070da4f9 Mon Sep 17 00:00:00 2001
From: "Sven M. Hallberg" <pesco@khjk.org>
Date: Tue, 26 Nov 2019 18:18:05 +0100
Subject: [PATCH] recognize cross-reference streams (no decode, yet)
---
pdf.c | 104 +++++++++++++++++++++++++++++++++++++++++++++++-----------
1 file changed, 84 insertions(+), 20 deletions(-)
diff --git a/pdf.c b/pdf.c
index f6dd414..e15b5b6 100644
--- a/pdf.c
+++ b/pdf.c
@@ -31,6 +31,26 @@ mapch(uint8_t c, uint8_t v)
return h_action(h_ch(c), act_mapch, (void *)(uintptr_t)v);
}
+/* a helper to look up a value in a dictionary */
+const HParsedToken *
+dictentry(const HCountedArray *dict, const char *key)
+{
+ HParsedToken *ent;
+ HBytes k;
+ size_t len;
+
+ len = strlen(key);
+ for (size_t i = 0; i < dict->used; i++) {
+ ent = dict->elements[i];
+ k = H_INDEX_BYTES(ent, 0);
+
+ if (k.len == len && strncmp(key, k.token, k.len) == 0)
+ return H_INDEX_TOKEN(ent, 1);
+ }
+
+ return NULL;
+}
+
/*
* semantic actions
@@ -158,6 +178,60 @@ act_octal(const HParseResult *p, void *u)
#define act_xrefs h_act_last
+/*
+ * validate the /Type field on a cross-reference stream.
+ *
+ * p = pnat nat (dict offs offs)
+ */
+bool
+validate_xrstm(HParseResult *p, void *u)
+{
+ const HCountedArray *tdict = H_FIELD_SEQ(2, 0);
+ const HParsedToken *v = dictentry(tdict, "Type");
+
+#if 0
+ if (v == NULL)
+ fprintf(stderr, "stream dict has not /Type\n");
+ else if (v->token_type != TT_BYTES)
+ fprintf(stderr, "stream /Type is no name object\n");
+ else if (v->bytes.len == 4 && strncmp("XRef", v->bytes.token, v->bytes.len) == 0)
+ return true;
+ return false;
+#endif
+
+ return (v != NULL && v->token_type == TT_BYTES && v->bytes.len == 4 &&
+ strncmp("XRef", v->bytes.token, v->bytes.len) == 0);
+}
+
+/*
+ * interpret a cross-reference stream and return it in the same form as other
+ * cross-reference sections:
+ *
+ * p = pnat nat (dict offs offs)
+ * result = (xrefs dict)
+ */
+HParsedToken *
+act_xrstm(const HParseResult *p, void *u)
+{
+ HParsedToken *xrefs, *offs1, *offs2, *dict, *result;
+
+ dict = H_INDEX_TOKEN(p->ast, 2, 0);
+ offs1 = H_INDEX_TOKEN(p->ast, 2, 1);
+ offs2 = H_INDEX_TOKEN(p->ast, 2, 2);
+
+ // XXX decode XRefStm
+
+ xrefs = H_MAKE_SEQN(2);
+ xrefs->seq->elements[0] = offs1;
+ xrefs->seq->elements[1] = offs2;
+ xrefs->seq->used = 2;
+ result = H_MAKE_SEQN(2);
+ result->seq->elements[0] = xrefs;
+ result->seq->elements[1] = dict;
+ result->seq->used = 2;
+ return result;
+}
+
/*
* input grammar
@@ -316,7 +390,7 @@ init_parser(void)
H_RULE(xrhead, SEQ(xrnat, IGN(sp), xrnat, nl));
H_RULE(xrsub, SEQ(xrhead, h_many(xrent)));
H_ARULE(xrefs, SEQ(KW("xref"), nl, h_many(xrsub)));
- // XXX cross-reference streams
+ H_AVRULE(xrstm, SEQ(pnat, nat, KW("obj"), stream, KW("endobj")));
/* trailer */
H_RULE(startxr, SEQ(nl, KW("startxref"), nl,
@@ -324,7 +398,7 @@ init_parser(void)
LIT("%%EOF"), CHX(nl, end)));
// XXX should lws be allowed before EOF marker?
// NB: lws before xref offset is allowed, cf. p.48 (example 4)
- H_RULE(xr_td, SEQ(xrefs, KW("trailer"), dict));
+ H_RULE(xr_td, CHX(SEQ(xrefs, KW("trailer"), dict), xrstm));
H_RULE(tail, SEQ(body, h_optional(xr_td), startxr));
H_RULE(pdf, SEQ(header, h_many1(tail), end));
@@ -338,23 +412,10 @@ init_parser(void)
p_xref = xr_td;
}
-const HParsedToken *
-dictentry(const HCountedArray *dict, const char *key)
+HParsedToken *
+act_return(const HParseResult *p, void *u)
{
- HParsedToken *ent;
- HBytes k;
- size_t len;
-
- len = strlen(key);
- for (size_t i = 0; i < dict->used; i++) {
- ent = dict->elements[i];
- k = H_INDEX_BYTES(ent, 0);
-
- if (k.len == len && strncmp(key, k.token, k.len) == 0)
- return H_INDEX_TOKEN(ent, 1);
- }
-
- return NULL;
+ return u;
}
/*
@@ -365,7 +426,8 @@ dictentry(const HCountedArray *dict, const char *key)
HParser *
kstream(HAllocator *mm__, const HParsedToken *x, void *env)
{
- const HCountedArray *dict = H_INDEX_SEQ(x, 0);
+ const HParsedToken *dict_t = H_INDEX_TOKEN(x, 0);
+ const HCountedArray *dict = H_CAST_SEQ(dict_t);
const HParsedToken *v = NULL;
size_t sz;
@@ -379,7 +441,9 @@ kstream(HAllocator *mm__, const HParsedToken *x, void *env)
//fprintf(stderr, "parsing stream object, length %zu.\n", sz); // XXX debug
HParser *tell = h_tell__m(mm__);
HParser *skip = h_skip__m(mm__, sz * 8);
- return h_sequence__m(mm__, tell, skip, tell, NULL);
+ HParser *eps = h_epsilon_p__m(mm__);
+ HParser *ret = h_action__m(mm__, eps, act_return, (void *)dict_t);
+ return h_sequence__m(mm__, ret, tell, skip, tell, NULL);
fail:
#if 0
if (v == NULL)
--
GitLab