power_play/src/asset_cache/asset_cache.c

/* TODO: Remove this entire layer */

AC_SharedState AC_shared_state = ZI;

////////////////////////////////////////////////////////////
//~ Startup

void AC_Startup(void)
{
    __prof;
    AC_SharedState *g = &AC_shared_state;
    g->store_arena = AcquireArena(Gibi(64));
}

////////////////////////////////////////////////////////////
//~ Hash

u64 AC_HashFromKey(String key)
{
    /* TODO: Better hash */
    return HashFnv64(Fnv64Basis, key);
}

////////////////////////////////////////////////////////////
//~ Cache

void AC_RefreshDebugTable(void)
{
#if RtcIsEnabled
    AC_SharedState *g = &AC_shared_state;
    Lock lock = LockE(&g->dbg_table_mutex);
    ZeroArray(g->dbg_table);
    g->dbg_table_count = 0;
    for (u64 i = 0; i < countof(g->lookup); ++i)
    {
        AC_Asset *asset = &g->lookup[i];
        if (asset->hash != 0)
        {
            g->dbg_table[g->dbg_table_count++] = asset;
        }
    }
    Unlock(&lock);
#endif
}

/* Returns first matching slot or first empty slot if not found.
 * Check returned slot->hash != 0 for presence. */
AC_Asset *AC_GetAssetCacheSlotLocked(Lock *lock, String key, u64 hash)
{
    AC_SharedState *g = &AC_shared_state;
    AssertLockedES(lock, &g->lookup_mutex);
    LAX lock;

    u64 index = hash % countof(g->lookup);
    for (;;)
    {
        AC_Asset *slot = &g->lookup[index];
        if (slot->hash)
        {
            /* Occupied */
            if (hash == slot->hash && MatchString(key, slot->key))
            {
                /* Matched slot */
                return slot;
            }
            else
            {
                ++index;
                if (index >= countof(g->lookup))
                {
                    index = 0;
                }
            }
        }
        else
        {
            /* Empty slot */
            return slot;
        }
    }
}

/* `key` text is copied by this function
 *
 * Returns existing asset entry or inserts a new one.
 *
 * If is_first_touch (out parameter) is set to 1, then the caller has
 * inserted the asset into the cache.
 *
 * */
AC_Asset *AC_TouchCache(String key, u64 hash, b32 *is_first_touch)
{
    AC_Asset *asset = 0;
    AC_SharedState *g = &AC_shared_state;

    /* Lookup */
    {
        Lock lock = LockS(&g->lookup_mutex);
        asset = AC_GetAssetCacheSlotLocked(&lock, key, hash);
        Unlock(&lock);
    }

    /* Insert if not found */
    if (asset->hash)
    {
        if (is_first_touch)
        {
            *is_first_touch = 0;
        }
    }
    else
    {
        Lock lock = LockE(&g->lookup_mutex);

        /* Re-check asset presence in case it was inserted since lock */
        asset = AC_GetAssetCacheSlotLocked(&lock, key, hash);

        if (!asset->hash)
        {
            if (g->num_assets >= AC_MaxAssets)
            {
                Panic(Lit("Max assets reached"));
            }
            String key_stored = ZI;
            {
                /* Copy key to store */
                AC_Store store = AC_OpenStore();
                key_stored = PushString(store.arena, key);
                AC_CloseStore(&store);
            }
            /* Initialize asset data */
            LogInfoF("Inserting asset cache entry for \"%F\"", FmtString(key));
            *asset = (AC_Asset) {
                .status = ASSET_STATUS_UNINITIALIZED,
                .hash = hash,
                .key = key_stored
            };
            if (is_first_touch)
            {
                *is_first_touch = 1;
            }
            ++g->num_assets;

            AC_RefreshDebugTable();
        }

        Unlock(&lock);
    }

    return asset;
}

////////////////////////////////////////////////////////////
//~ Status

/* Call this once asset job has been created */
void AC_MarkLoading(AC_Asset *asset)
{
    asset->status = ASSET_STATUS_LOADING;
}

/* Call this once asset job has finished */
void AC_MarkReady(AC_Asset *asset, void *store_data)
{
    asset->store_data = store_data;
    asset->status = ASSET_STATUS_READY;
    SetFence(&asset->ready_fence, 1);
}

void AC_YieldOnAssetReady(AC_Asset *asset)
{
    YieldOnFence(&asset->ready_fence, 1);
}

////////////////////////////////////////////////////////////
//~ Store

void *AC_DataFromStore(AC_Asset *asset)
{
    if (asset->status == ASSET_STATUS_READY)
    {
        return asset->store_data;
    }
    else
    {
        return 0;
    }
}

/* Asset store should be opened to allocate memory to the store arena */
AC_Store AC_OpenStore(void)
{
    AC_SharedState *g = &AC_shared_state;
    Lock lock = LockE(&g->store_mutex);
    AC_Store store = {
        .lock = lock,
        .arena = g->store_arena
    };
    return store;
}

void AC_CloseStore(AC_Store *store)
{
    Unlock(&store->lock);
}