diff options
Diffstat (limited to 'thirdparty/harfbuzz/src/hb-machinery.hh')
| -rw-r--r-- | thirdparty/harfbuzz/src/hb-machinery.hh | 20 |
1 files changed, 14 insertions, 6 deletions
diff --git a/thirdparty/harfbuzz/src/hb-machinery.hh b/thirdparty/harfbuzz/src/hb-machinery.hh index ff2a99f5ed..b555739cfb 100644 --- a/thirdparty/harfbuzz/src/hb-machinery.hh +++ b/thirdparty/harfbuzz/src/hb-machinery.hh @@ -136,6 +136,13 @@ static inline Type& StructAfter(TObject &X) /* * Lazy loaders. + * + * The lazy-loaders are thread-safe pointer-like objects that create their + * instead on-demand. They also support access to a "data" object that is + * necessary for creating their instance. The data object, if specified, + * is accessed via pointer math, located at a location before the position + * of the loader itself. This avoids having to store a pointer to data + * for every lazy-loader. Multiple lazy-loaders can access the same data. */ template <typename Data, unsigned int WheresData> @@ -176,12 +183,12 @@ struct hb_lazy_loader_t : hb_data_wrapper_t<Data, WheresData> void init0 () {} /* Init, when memory is already set to 0. No-op for us. */ void init () { instance.set_relaxed (nullptr); } - void fini () { do_destroy (instance.get ()); init (); } + void fini () { do_destroy (instance.get_acquire ()); init (); } void free_instance () { retry: - Stored *p = instance.get (); + Stored *p = instance.get_acquire (); if (unlikely (p && !cmpexch (p, nullptr))) goto retry; do_destroy (p); @@ -203,7 +210,7 @@ struct hb_lazy_loader_t : hb_data_wrapper_t<Data, WheresData> Stored * get_stored () const { retry: - Stored *p = this->instance.get (); + Stored *p = this->instance.get_acquire (); if (unlikely (!p)) { if (unlikely (this->is_inert ())) @@ -228,7 +235,8 @@ struct hb_lazy_loader_t : hb_data_wrapper_t<Data, WheresData> bool cmpexch (Stored *current, Stored *value) const { - /* This *must* be called when there are no other threads accessing. */ + /* This function can only be safely called directly if no + * other thread is accessing. */ return this->instance.cmpexch (current, value); } @@ -261,7 +269,7 @@ struct hb_lazy_loader_t : hb_data_wrapper_t<Data, WheresData> hb_free (p); } -// private: + private: /* Must only have one pointer. */ hb_atomic_ptr_t<Stored *> instance; }; @@ -283,7 +291,7 @@ struct hb_table_lazy_loader_t : hb_lazy_loader_t<T, { auto c = hb_sanitize_context_t (); if (core) - c.set_num_glyphs (0); // So we don't recurse ad infinitum... + c.set_num_glyphs (0); // So we don't recurse ad infinitum, or doesn't need num_glyphs return c.reference_table<T> (face); } static void destroy (hb_blob_t *p) { hb_blob_destroy (p); } |