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, 4 insertions, 3 deletions

diff --git a/pdf/pdf_xobject.c b/pdf/pdf_xobject.c
index ffa86184..1de0b20e 100644
--- a/pdf/pdf_xobject.c
+++ b/pdf/pdf_xobject.c
@@ -23,7 +23,8 @@ pdf_free_xobject_imp(fz_context *ctx, fz_storable *xobj_)
 	if (xobj->resources)
 		pdf_drop_obj(xobj->resources);
 	if (xobj->contents)
-		fz_drop_buffer(ctx, xobj->contents);
+		//fz_drop_buffer(ctx, xobj->contents);
+		pdf_drop_obj(xobj->contents);
 	pdf_drop_obj(xobj->me);
 	fz_free(ctx, xobj);
 }
@@ -33,7 +34,7 @@ pdf_xobject_size(pdf_xobject *xobj)
 {
 	if (xobj == NULL)
 		return 0;
-	return sizeof(*xobj) + (xobj->colorspace ? xobj->colorspace->size : 0) + (xobj->contents ? xobj->contents->len : 0);
+	return sizeof(*xobj) + (xobj->colorspace ? xobj->colorspace->size : 0);
 }
 
 pdf_xobject *
@@ -98,7 +99,7 @@ pdf_load_xobject(pdf_document *xref, pdf_obj *dict)
 
 	fz_try(ctx)
 	{
-		form->contents = pdf_load_stream(xref, pdf_to_num(dict), pdf_to_gen(dict));
+		form->contents = pdf_keep_obj(dict);
 	}
 	fz_catch(ctx)
 	{