vg_async.h

   1 /* Copyright (C) 2021-2023 Harry Godden (hgn) - All Rights Reserved
   2  *
   3  * primateves that you use when you need to run something from another thread
   4  * back in the main loop of vg, at the start of each frame
   5  */
   6
   7 #ifndef VG_ASYNC_H
   8 #define VG_ASYNC_H
   9
  10 #define VG_GAME
  11 #include "vg/vg.h"
  12 static void vg_assert_thread( enum vg_thread_purpose required );
  13
  14 typedef struct vg_async_item vg_async_item;
  15
  16 struct vg_async_item{
  17    vg_async_item *next;
  18
  19    void *payload;
  20    u32 size;
  21
  22    void (*fn_runner)( void *payload, u32 size );
  23 };
  24
  25 struct vg_async{
  26    void *buffer;
  27
  28    vg_async_item *start, *end;
  29
  30    SDL_sem *sem_wait_for_flush;
  31    SDL_SpinLock sl_index;
  32 }
  33 static vg_async;
  34
  35 static enum vg_thread_purpose vg_thread_purpose(void);
  36 static enum engine_status _vg_engine_status(void);
  37
  38 /*
  39  * Allocate an asynchronous call with a bit of memory
  40  */
  41 static vg_async_item *vg_async_alloc( u32 size )
  42 {
  43    /* ditch out here if engine crashed. this serves as the 'quit checking' */
  44    if( _vg_engine_status() == k_engine_status_crashed ){
  45       assert( vg_thread_purpose() == k_thread_purpose_loader );
  46       longjmp( vg.env_loader_exit, 1 );
  47    }
  48
  49    SDL_AtomicLock( &vg_async.sl_index );
  50
  51    u32 total_allocation = vg_align8(size) + vg_align8(sizeof(vg_async_item)),
  52        remaining        = vg_linear_remaining( vg_async.buffer ),
  53        capacity         = vg_linear_get_capacity( vg_async.buffer );
  54
  55    if( total_allocation > capacity ){
  56       SDL_AtomicUnlock( &vg_async.sl_index );
  57       vg_error( "Requested: %umb. Buffer size: %umb\n",
  58                   (total_allocation/1024)/1024,
  59                   (capacity/1024)/1024 );
  60
  61       vg_fatal_error( "async alloc invalid size\n" );
  62    }
  63
  64    if( total_allocation > remaining ){
  65       SDL_AtomicUnlock( &vg_async.sl_index );
  66       SDL_SemWait( vg_async.sem_wait_for_flush );
  67       SDL_AtomicLock( &vg_async.sl_index );
  68
  69       remaining = vg_linear_remaining( vg_async.buffer );
  70       capacity = vg_linear_get_capacity( vg_async.buffer );
  71
  72       assert( remaining == capacity );
  73       assert( vg_async.start == NULL );
  74       assert( vg_async.end   == NULL );
  75    }
  76
  77    void *block = vg_linear_alloc( vg_async.buffer, total_allocation );
  78
  79    vg_async_item *entry = block;
  80    entry->next = NULL;
  81
  82    if( size ) entry->payload = ((u8*)block) + vg_align8(sizeof(vg_async_item));
  83    else entry->payload = NULL;
  84
  85    entry->size = size;
  86    entry->fn_runner = NULL;
  87
  88    if( vg_async.end ){
  89       vg_async.end->next = entry;
  90       vg_async.end = entry;
  91    }else{
  92       vg_async.start = entry;
  93       vg_async.end = entry;
  94    }
  95
  96    SDL_AtomicUnlock( &vg_async.sl_index );
  97
  98    return entry;
  99 }
 100
 101 /*
 102  * Wait until the current stack of async calls is completely flushed out
 103  */
 104 static void vg_async_stall(void)
 105 {
 106    vg_assert_thread(k_thread_purpose_loader);
 107    vg_info( "async_stall: %d\n", SDL_SemValue( vg_async.sem_wait_for_flush ) );
 108    SDL_SemWait( vg_async.sem_wait_for_flush );
 109 }
 110
 111 /*
 112  * Mark the call as being filled and ready to go
 113  */
 114 static void vg_async_dispatch( vg_async_item *item,
 115                                   void (*runner)( void *payload, u32 size ) )
 116 {
 117    vg_assert_thread(k_thread_purpose_loader);
 118    if( SDL_SemValue(vg_async.sem_wait_for_flush) )
 119       SDL_SemWait(vg_async.sem_wait_for_flush);
 120
 121    SDL_AtomicLock( &vg_async.sl_index );
 122    item->fn_runner = runner;
 123    SDL_AtomicUnlock( &vg_async.sl_index );
 124 }
 125
 126 /*
 127  * Make a simple async call without allocating extra.
 128  */
 129 static void vg_async_call( void (*runner)( void *payload, u32 size ),
 130                               void *payload, u32 size )
 131 {
 132    vg_assert_thread(k_thread_purpose_loader);
 133    vg_async_item *call = vg_async_alloc(0);
 134    call->payload = payload;
 135    call->size = size;
 136    vg_async_dispatch( call, runner );
 137 }
 138
 139 /*
 140  * Run as much of the async buffer as possible
 141  */
 142 static void vg_run_async_checked(void)
 143 {
 144    SDL_AtomicLock( &vg_async.sl_index );
 145
 146    while( vg_async.start ){
 147       vg_async_item *entry = vg_async.start;
 148
 149       if( entry->fn_runner ){
 150          entry->fn_runner( entry->payload, entry->size );
 151          vg_async.start = entry->next;
 152
 153          if( vg_async.start == NULL ){
 154             vg_async.end = NULL;
 155
 156             vg_linear_clear( vg_async.buffer );
 157
 158             if( !SDL_SemValue( vg_async.sem_wait_for_flush ) ){
 159                SDL_SemPost( vg_async.sem_wait_for_flush );
 160             }
 161          }
 162       }
 163       else{
 164          SDL_AtomicUnlock( &vg_async.sl_index );
 165          return;
 166       }
 167
 168       /* TODO: if exceed max frametime.... */
 169    }
 170
 171    if( !SDL_SemValue( vg_async.sem_wait_for_flush ) ){
 172       SDL_SemPost( vg_async.sem_wait_for_flush );
 173    }
 174
 175    SDL_AtomicUnlock( &vg_async.sl_index );
 176 }
 177
 178 static void vg_async_init(void)
 179 {
 180    vg_async.sem_wait_for_flush = SDL_CreateSemaphore(0);
 181    vg_async.buffer = vg_create_linear_allocator( NULL, 50*1024*1024,
 182                                                  VG_MEMORY_SYSTEM );
 183 }
 184
 185 #endif /* VG_ASYNC_H */