basic async mechanism

[vg.git] / vg_async.h

diff --git a/vg_async.h b/vg_async.h
new file mode 100644 (file)
index 0000000..366f448
--- /dev/null
+++ b/vg_async.h
@@ -0,0 +1,138 @@
+/* Copyright (C) 2021-2023 Harry Godden (hgn) - All Rights Reserved 
+ *
+ * primateves that you use when you need to run something from another thread 
+ * back in the main loop of vg, at the start of each frame
+ */
+
+#ifndef VG_ASYNC_H
+#define VG_ASYNC_H
+
+#include "vg/vg.h"
+
+typedef struct vg_async_item vg_async_item;
+
+struct vg_async_item{
+   vg_async_item *next;
+
+   void *payload;
+   u32 size;
+
+   void (*fn_runner)( void *payload, u32 size );
+};
+
+struct vg_async{
+   void *buffer;
+   
+   vg_async_item *start, *end;
+
+   SDL_sem *sem_wait_for_flush;
+   SDL_SpinLock sl_index;
+}
+static vg_async;
+
+/*
+ * Allocate an asynchronous call with a bit of memory
+ */
+VG_STATIC vg_async_item *vg_async_alloc( u32 size )
+{
+   SDL_AtomicLock( &vg_async.sl_index );
+
+   u32 total_allocation = vg_align8(size) + vg_align8(sizeof(vg_async_item)),
+       remaining        = vg_linear_remaining( vg_async.buffer ),
+       capacity         = vg_linear_get_capacity( vg_async.buffer );
+
+   if( total_allocation > capacity ){
+      SDL_AtomicUnlock( &vg_async.sl_index );
+      vg_error( "Requested: %umb. Buffer size: %umb\n",
+                  (total_allocation/1024)/1024,
+                  (capacity/1024)/1024 );
+      vg_fatal_exit_loop( "async alloc invalid size\n" );
+   }
+
+   if( total_allocation > remaining ){
+      SDL_AtomicUnlock( &vg_async.sl_index );
+      SDL_SemWait( vg_async.sem_wait_for_flush );
+      SDL_AtomicLock( &vg_async.sl_index );
+
+      remaining = vg_linear_remaining( vg_async.buffer );
+      capacity = vg_linear_get_capacity( vg_async.buffer );
+
+      assert( remaining == capacity );
+      assert( vg_async.start == NULL );
+      assert( vg_async.end   == NULL );
+   }
+
+   void *block = vg_linear_alloc( vg_async.buffer, total_allocation );
+
+   vg_async_item *entry = block;
+   entry->next = NULL;
+   entry->payload = ((u8*)block) + vg_align8(sizeof(vg_async_item)); 
+   entry->size = size;
+   entry->fn_runner = NULL;
+
+   if( vg_async.end ){
+      vg_async.end->next = entry;
+      vg_async.end = entry;
+   }else{
+      vg_async.start = entry;
+      vg_async.end = entry;
+   }
+
+   SDL_AtomicUnlock( &vg_async.sl_index );
+
+   return entry;
+}
+
+/*
+ * Mark the call as being filled and ready to go
+ */
+VG_STATIC void vg_async_dispatch( vg_async_item *item, 
+                                  void (*runner)( void *payload, u32 size ) )
+{
+   SDL_AtomicLock( &vg_async.sl_index );
+   item->fn_runner = runner;
+   SDL_AtomicUnlock( &vg_async.sl_index );
+}
+
+/*
+ * Run as much of the async buffer as possible
+ */
+VG_STATIC void vg_run_async_checked(void)
+{
+   SDL_AtomicLock( &vg_async.sl_index );
+
+   while( vg_async.start ){
+      vg_async_item *entry = vg_async.start;
+
+      if( entry->fn_runner ){
+         entry->fn_runner( entry->payload, entry->size );
+         vg_async.start = entry->next;
+
+         if( vg_async.start == NULL ){
+            vg_async.end = NULL;
+
+            vg_linear_clear( vg_async.buffer );
+
+            if( !SDL_SemValue( vg_async.sem_wait_for_flush ) ){
+               SDL_SemPost( vg_async.sem_wait_for_flush );
+            }
+         }
+      }
+      else{
+         break;
+      }
+
+      /* TODO: if exceed max frametime.... */
+   }
+
+   SDL_AtomicUnlock( &vg_async.sl_index );
+}
+
+VG_STATIC void vg_async_init(void)
+{
+   vg_async.sem_wait_for_flush = SDL_CreateSemaphore(0);
+   vg_async.buffer = vg_create_linear_allocator( NULL, 50*1024*1024, 
+                                                 VG_MEMORY_REALTIME );
+}
+
+#endif /* VG_ASYNC_H */