Switch to reading content streams on the fly during interpretation.

Previously, before interpreting a pages content stream we would
load it entirely into a buffer. Then we would interpret that
buffer. This has a cost in memory use.

Here, we update the code to read from a stream on the fly.

This has required changes in various different parts of the code.

Firstly, we have removed all use of the FILE lock - as stream
reads can now safely be interrupted by resource (or object) reads
from elsewhere in the file, the file lock becomes a very hard
thing to maintain, and doesn't actually benefit us at all. The
choices were to either use a recursive lock, or to remove it
entirely; I opted for the latter.

The file lock enum value remains as a placeholder for future use in
extendable data streams.

Secondly, we add a new 'concat' filter that concatenates a series of
streams together into one, optionally putting whitespace between each
stream (as the pdf parser requires this).

Finally, we change page/xobject/pattern content streams to work
on the fly, but we leave type3 glyphs using buffers (as presumably
these will be run repeatedly).

1 files changed, 2 insertions, 3 deletions

diff --git a/pdf/base_object.c b/pdf/base_object.c
index 97cb97cc..2a5e6d78 100644
--- a/pdf/base_object.c
+++ b/pdf/base_object.c
@@ -145,8 +145,8 @@ pdf_new_indirect(fz_context *ctx, int num, int gen, void *xref)
 pdf_obj *
 pdf_keep_obj(pdf_obj *obj)
 {
-	assert(obj);
-	obj->refs ++;
+	if (obj)
+		obj->refs ++;
 	return obj;
 }
 
@@ -159,7 +159,6 @@ int pdf_is_indirect(pdf_obj *obj)
 	do { \
 		if (obj && obj->kind == PDF_INDIRECT) \
 		{\
-			fz_assert_lock_not_held(obj->ctx, FZ_LOCK_FILE); \
 			obj = pdf_resolve_indirect(obj); \
 		} \
 	} while (0)