Rework pdf_lexbuf to allow for dynamic parsing buffers.

Currently pdf_lexbufs use a static scratch buffer for parsing. In
the main case this is 64K in size, but in other cases it can be
just 256 bytes; this causes problems when parsing long strings.

Even the 64K limit is an implementation limit of Acrobat, not an
architectural limit of PDF.

Change here to allow dynamic buffers. This means a slightly more
complex setup and destruction for each buffer, but more importantly
requires correct cleanup on errors. To avoid having to insert
lots more try/catch clauses this commit includes various changes to
the code so we reuse pdf_lexbufs where possible. This keeps the
speed up.

1 files changed, 55 insertions, 14 deletions

diff --git a/pdf/pdf_lex.c b/pdf/pdf_lex.c
index c6ab6604..967b6dcc 100644
--- a/pdf/pdf_lex.c
+++ b/pdf/pdf_lex.c
@@ -231,16 +231,21 @@ end:
 }
 
 static int
-lex_string(fz_stream *f, char *buf, int n)
+lex_string(fz_stream *f, pdf_lexbuf *lb)
 {
-	char *s = buf;
-	char *e = buf + n;
+	char *s = lb->scratch;
+	char *e = s + lb->size;
 	int bal = 1;
 	int oct;
 	int c;
 
-	while (s < e)
+	while (1)
 	{
+		if (s == e)
+		{
+			s += pdf_lexbuf_grow(lb);
+			e = lb->scratch + lb->size;
+		}
 		c = fz_read_byte(f);
 		switch (c)
 		{
@@ -319,19 +324,25 @@ lex_string(fz_stream *f, char *buf, int n)
 		}
 	}
 end:
-	return s - buf;
+	lb->len = s - lb->scratch;
+	return PDF_TOK_STRING;
 }
 
 static int
-lex_hex_string(fz_stream *f, char *buf, int n)
+lex_hex_string(fz_stream *f, pdf_lexbuf *lb)
 {
-	char *s = buf;
-	char *e = buf + n;
+	char *s = lb->scratch;
+	char *e = s + lb->size;
 	int a = 0, x = 0;
 	int c;
 
-	while (s < e)
+	while (1)
 	{
+		if (s == e)
+		{
+			s += pdf_lexbuf_grow(lb);
+			e = lb->scratch + lb->size;
+		}
 		c = fz_read_byte(f);
 		switch (c)
 		{
@@ -357,7 +368,8 @@ lex_hex_string(fz_stream *f, char *buf, int n)
 		}
 	}
 end:
-	return s - buf;
+	lb->len = s - lb->scratch;
+	return PDF_TOK_STRING;
 }
 
 static int
@@ -399,6 +411,37 @@ pdf_token_from_keyword(char *key)
 	return PDF_TOK_KEYWORD;
 }
 
+void pdf_lexbuf_init(fz_context *ctx, pdf_lexbuf *lb, int size)
+{
+	lb->size = lb->base_size = size;
+	lb->len = 0;
+	lb->ctx = ctx;
+	lb->scratch = &lb->buffer[0];
+}
+
+void pdf_lexbuf_fin(pdf_lexbuf *lb)
+{
+	if (lb && lb->size != lb->base_size)
+		fz_free(lb->ctx, lb->scratch);
+}
+
+ptrdiff_t pdf_lexbuf_grow(pdf_lexbuf *lb)
+{
+	char *old = lb->scratch;
+	int newsize = lb->size * 2;
+	if (lb->size == lb->base_size)
+	{
+		lb->scratch = fz_malloc(lb->ctx, newsize);
+		memcpy(lb->scratch, lb->buffer, lb->size);
+	}
+	else
+	{
+		lb->scratch = fz_resize_array(lb->ctx, lb->scratch, newsize, 1);
+	}
+	lb->size = newsize;
+	return lb->scratch - old;
+}
+
 int
 pdf_lex(fz_stream *f, pdf_lexbuf *buf)
 {
@@ -419,8 +462,7 @@ pdf_lex(fz_stream *f, pdf_lexbuf *buf)
 			lex_name(f, buf);
 			return PDF_TOK_NAME;
 		case '(':
-			buf->len = lex_string(f, buf->scratch, buf->size);
-			return PDF_TOK_STRING;
+			return lex_string(f, buf);
 		case ')':
 			fz_warn(f->ctx, "lexical error (unexpected ')')");
 			continue;
@@ -433,8 +475,7 @@ pdf_lex(fz_stream *f, pdf_lexbuf *buf)
 			else
 			{
 				fz_unread_byte(f);
-				buf->len = lex_hex_string(f, buf->scratch, buf->size);
-				return PDF_TOK_STRING;
+				return lex_hex_string(f, buf);
 			}
 		case '>':
 			c = fz_read_byte(f);