Multi-threading support for MuPDF

When we moved over to a context based system, we laid the foundation
for a thread-safe mupdf. This commit should complete that process.

Firstly, fz_clone_context is properly implemented so that it
makes a new context, but shares certain sections (currently
just the allocator, and the store).

Secondly, we add locking (to parts of the code that have
previously just had placeholder LOCK/UNLOCK comments). Functions
to lock and unlock a mutex are added to the allocator structure;
omit these (as is the case today) and no multithreading is
(safely) possible. The context will refuse to clone if these are
not provided.

Finally we flesh out the LOCK/UNLOCK comments to be real calls of
the functions - unfortunately this requires us to plumb fz_context
into the fz_keep_storable function (and all the fz_keep_xxx
functions that call it). This is the largest section of the patch.

No changes expected to any test files.

1 files changed, 6 insertions, 1 deletions

diff --git a/scripts/cmapdump.c b/scripts/cmapdump.c
index 2d318f14..a41533f7 100644
--- a/scripts/cmapdump.c
+++ b/scripts/cmapdump.c
@@ -176,7 +176,7 @@ void fz_free_aa_context(fz_context *ctx)
 {
 }
 
-void *fz_keep_storable(fz_storable *s)
+void *fz_keep_storable(fz_context *ctx, fz_storable *s)
 {
 	return s;
 }
@@ -193,6 +193,11 @@ void fz_free_store_context(fz_context *ctx)
 {
 }
 
+fz_store *fz_store_keep(fz_context *ctx)
+{
+	return NULL;
+}
+
 int fz_store_scavenge(fz_context *ctx, unsigned int size, int *phase)
 {
 	return 0;