pvbemu/core/bus.c

/* This file is included into vb.c and cannot be compiled on its own. */
#ifdef VBAPI



/***************************** Utility Functions *****************************/

/* Read a data unit from a memory buffer */
static int32_t busReadBuffer(uint8_t *mem, int type) {

    /* Little-endian implementation */
    #ifdef VB_LITTLEENDIAN
        switch (type) {
            case VB_S8 : return *(int8_t   *)mem;
            case VB_U8 : return *            mem;
            case VB_S16: return *(int16_t  *)mem;
            case VB_U16: return *(uint16_t *)mem;
        }
        return *(int32_t *)mem;

    /* Generic implementation */
    #else
        switch (type) {
            case VB_S8 : return (int8_t) *mem;
            case VB_U8 : return          *mem;
            case VB_S16: return (int16_t ) (int8_t) mem[1] <<  8 | mem[0];
            case VB_U16: return (uint16_t)          mem[1] <<  8 | mem[0];
        }
        return (int32_t ) mem[3] << 24 | (uint32_t) mem[2] << 16 |
               (uint32_t) mem[1] <<  8 |            mem[0];
    #endif

}

/* Write a data unit to a memory buffer */
static void busWriteBuffer(uint8_t *mem, int type, int32_t value) {

    /* Little-endian implementation */
    #ifdef VB_LITTLEENDIAN
        switch (type) {
            case VB_S16: case VB_U16: *(uint16_t *)mem = value; return;
            case VB_S8 : case VB_U8 : *            mem = value; return;
        }
        *(int32_t *)mem = value;

    /* Generic implementation */
    #else
        switch (type) {
            case VB_S32:
                mem[3] = value >> 24;
                mem[2] = value >> 16;
                /* Fallthrough */
            case VB_S16:
            case VB_U16:
                mem[1] = value >>  8;
        }
        mem[0] = value;
    #endif

}



/***************************** Module Functions ******************************/

/* Read a data unit from the bus */
static int32_t busRead(VB *sim, uint32_t address, int type, int debug) {

    /* Force address alignment */
    address &= ~((uint32_t) TYPE_SIZES[type] - 1);

    /* Process by address range */
    switch (address >> 24 & 7) {
        case 0 : return 0; /* VIP */
        case 1 : return 0 * debug; /* VSU */
        case 2 : return 0; /* Miscellaneous hardware */
        case 3 : return 0; /* Unmapped */
        case 4 : return 0; /* Game pak expansion */
        case 5 : return /* WRAM */
            busReadBuffer(&sim->wram[address & 0xFFFF], type);
        case 6 : return sim->cart.sram == NULL ? 0 : /* Game pak RAM */
            busReadBuffer(&sim->cart.sram
                [address & (sim->cart.sramSize - 1)], type);
        default: return sim->cart.rom  == NULL ? 0 : /* Game pak ROM */
            busReadBuffer(&sim->cart.rom
                [address & (sim->cart.romSize  - 1)], type);
    }

}

/* Write a data unit to the bus */
static void busWrite(
    VB *sim, uint32_t address, int type, uint32_t value, int debug) {

    /* Force address alignment */
    address &= ~((uint32_t) TYPE_SIZES[type] - 1);

    /* Process by address range */
    switch (address >> 24 & 7) {
        case 0 : return; /* VIP */
        case 1 : return; /* VSU */
        case 2 : return; /* Miscellaneous hardware */
        case 3 : return; /* Unmapped */
        case 4 : return; /* Game pak expansion */
        case 5 : /* WRAM */
            busWriteBuffer(&sim->wram[address & 0xFFFF], type, value);
            return;
        case 6 : /* Cartridge RAM */
            if (sim->cart.sram != NULL)
                busWriteBuffer(&sim->cart.sram
                    [address & (sim->cart.sramSize - 1)], type, value);
            return;
        default: /* Cartridge ROM */
            if (debug && sim->cart.rom != NULL)
                busWriteBuffer(&sim->cart.rom
                    [address & (sim->cart.romSize - 1)], type, value);
    }

}



#endif /* VBAPI */
dBuffer(vb->cart.rom, vb->cart.romSize, address, type);
    }

    /* Unreachable */
    return 0;
}

/* Write a typed value to the simulation bus */
static void busWrite(VB *vb,uint32_t address,int type,int32_t value,int debug){

    /* Processing by address region */
    switch (address >> 24 & 7) {
        case 0: break; /* VIP */
        case 1: break; /* VSU */
        case 2: break; /* Misc. hardware */
        case 3: break; /* Unmapped */
        case 4: break; /* Game pak expansion */
        case 5:        /* WRAM */
            busWriteBuffer(vb->wram    ,0x10000         ,address,type,value);
            break;
        case 6:        /* Game pak RAM */
            busWriteBuffer(vb->cart.ram,vb->cart.ramSize,address,type,value);
            break;
        case 7:        /* Game pak ROM */
            busWriteBuffer(vb->cart.rom,vb->cart.romSize,address,type,value);
            break;
    }

    return;
    debug = debug ? debug : 0;
}



#endif /* VBAPI */