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/*
* libstdgb - library of useful Game Boy operations
* Copyright (C) 2016-2017 Delwink, LLC
*
* Redistributions, modified or unmodified, in whole or in part, must retain
* applicable notices of copyright or other legal privilege, these conditions,
* and the following license terms and disclaimer. Subject to these
* conditions, each holder of copyright or other legal privileges, author or
* assembler, and contributor of this work, henceforth "licensor", hereby
* grants to any person who obtains a copy of this work in any form:
*
* 1. Permission to reproduce, modify, distribute, publish, sell, sublicense,
* use, and/or otherwise deal in the licensed material without restriction.
*
* 2. A perpetual, worldwide, non-exclusive, royalty-free, gratis, irrevocable
* patent license to make, have made, provide, transfer, import, use, and/or
* otherwise deal in the licensed material without restriction, for any and
* all patents held by such licensor and necessarily infringed by the form of
* the work upon distribution of that licensor's contribution to the work
* under the terms of this license.
*
* NO WARRANTY OF ANY KIND IS IMPLIED BY, OR SHOULD BE INFERRED FROM, THIS
* LICENSE OR THE ACT OF DISTRIBUTION UNDER THE TERMS OF THIS LICENSE,
* INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR
* A PARTICULAR PURPOSE, AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS,
* ASSEMBLERS, OR HOLDERS OF COPYRIGHT OR OTHER LEGAL PRIVILEGE BE LIABLE FOR
* ANY CLAIM, DAMAGES, OR OTHER LIABILITY, WHETHER IN ACTION OF CONTRACT,
* TORT, OR OTHERWISE ARISING FROM, OUT OF, OR IN CONNECTION WITH THE WORK OR
* THE USE OF OR OTHER DEALINGS IN THE WORK.
*/
#include "stdgb.h"
uint8_t (* const GB_OBJECTS)[GB_BYTES_PER_OBJ] = (void *) 0xDF00;
static uint8_t * const DPAD_STATE = (void *) 0xDFA0;
static uint8_t * const BTN_STATE = (void *) 0xDFA1;
void
gb_mbc5_select_rombank(uint16_t bank)
{
uint8_t upper = (bank & 0xFF00) >> 8;
uint8_t lower = bank & 0x00FF;
*((uint8_t *) 0x3000) = upper;
*((uint8_t *) 0x2000) = lower;
}
static void
invert_state(uint8_t *state)
{
*state = (~(*state)) & 0x0F;
}
void
gb_update_input_state()
{
// this routine is copied from the official Nintendo programming manual
__asm__("ld a, #0x20\n\t" // load flag to read d-pad input
"ld (#0xFF00), a\n\t" // make input request
"ld a, (#0xFF00)\n\t" // read input ports
"ld a, (#0xFF00)\n\t" // do this twice for necessary delay
"ld (#0xDFA0), a\n\t" // save it in *DPAD_STATE
"ld a, #0x10\n\t" // load flag to read button input
"ld (#0xFF00), a\n\t" // make input request
"ld a, (#0xFF00)\n\t" // read input ports
"ld a, (#0xFF00)\n\t" // do this six times for necessary delay
"ld a, (#0xFF00)\n\t"
"ld a, (#0xFF00)\n\t"
"ld a, (#0xFF00)\n\t"
"ld a, (#0xFF00)\n\t"
"ld (#0xDFA1), a\n\t" // save it in *BTN_STATE
"ld a, #0x30\n\t" // load flag to read nothing
"ld (#0xFF00), a"); // disable input reads
invert_state(DPAD_STATE);
invert_state(BTN_STATE);
}
uint8_t
gb_dpad_down(uint8_t direction)
{
return *DPAD_STATE & direction;
}
uint8_t
gb_button_down(uint8_t button)
{
return *BTN_STATE & button;
}
void
gb_enable_vblank()
{
*GB_INT_ENABLE |= GB_INT_VBLANK;
gb_enable_interrupts();
}
void
gb_wait_vblank()
{
do
{
gb_halt();
} while (!gb_have_vblank());
}
void
gb_define_tile(uint8_t start, const uint8_t *data)
{
uint8_t *tiles = GB_TILE_DATA;
gb_memcpy(&tiles[start * GB_BYTES_PER_TILE], data, GB_BYTES_PER_TILE);
}
void
gb_set_view(uint8_t x, uint8_t y)
{
*GB_SCROLL_X = x;
*GB_SCROLL_Y = y;
}
void
gb_shift_view(int8_t x, int8_t y)
{
*GB_SCROLL_X += x;
*GB_SCROLL_Y += y;
}
static void
copy_objects()
{
__asm__("ld a,#0xDF\n\t" // specify that objects are at 0xDF00
"ld (0xFF46),a\n\t" // start DMA copy
"ld a,#0x28\n" // set wait counter to 40
"obj_copy_wait:\n\t"
"dec a\n\t" // decrement counter
"jr nz,obj_copy_wait"); // wait until counter is zero
}
void
gb_init_objects()
{
gb_memcpy(GB_HRAM, (uint8_t *) copy_objects, 12);
memset(GB_OBJECTS, 0, GB_NUM_OBJECTS * GB_BYTES_PER_OBJ);
gb_update_objects();
}
void
gb_update_objects()
{
__asm__("jp 0xFF80"); // real function is at HRAM
}
void
gb_memcpy(uint8_t *dest, const uint8_t *src, uint8_t n)
{
while (n--)
*(dest++) = *(src++);
}
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