ragb/io/ppu.c

#include <stdio.h>
#include <string.h>
#include <r_io.h>
#include <r_util.h>
#include <gb.h>
#include <ragb_sdl.h>

RIOPlugin r_io_plugin_gb_ppu;

static ut64 __lseek(RIO* io, RIODesc *desc, ut64 offset, int whence) {
	GBPPU *ppu = desc->data;
	ut64 seek = ppu->seek & 0xffff;
	switch (whence) {
	case R_IO_SEEK_SET:
		seek = R_MIN (GB_PPU_N_REGS, offset);
		break;
	case R_IO_SEEK_CUR:
		seek = R_MIN (GB_PPU_N_REGS, seek + offset);
		break;
	case R_IO_SEEK_END:
		seek = GB_PPU_N_REGS;
		break;
	}
	ppu->seek = (ppu->seek & (~0xffff)) | seek;
	return seek;
}

static bool __check(RIO *io, const char *pathname, bool many) {
	return r_str_startswith (pathname, "gb_ppu://");
}

static int __read(RIO *io, RIODesc *desc, ut8 *buf, int len) {
	GBPPU *ppu = desc->data;
	ut64 seek = ppu->seek & 0xffff;
	if (ppu->seek >= GB_PPU_N_REGS || len < 1) {
		return 0;
	}
	len = R_MIN (len, GB_PPU_N_REGS - seek);
	memcpy (buf, &ppu->buf[ppu->seek], len);
	seek += len;
	ppu->seek = (ppu->seek & (~0xffff)) | seek;
	return len;
}

static int __write(RIO *io, RIODesc *desc, const ut8 *buf, int len) {
	GBPPU *ppu = desc->data;
	ut64 seek = ppu->seek & 0xffff;
	if (ppu->seek >= GB_PPU_N_REGS || len < 1) {
		return 0;
	}
	len = R_MIN (len, GB_PPU_N_REGS - seek);
	ut32 i;
	for (i = 0; i < len; i++) {
		switch (seek) {
		case GB_PPU_STAT:
			ppu->buf[GB_PPU_STAT] = (buf[i] & 0xf8) | (ppu->buf[GB_PPU_STAT] & 0x7);
		case GB_PPU_LY:
			break;
		default:
			ppu->buf[seek] = buf[i];
			break;
		}
		seek++;
	}
	return len;
}

static bool __close(RIODesc *desc) {
	return true;
}

static RIODesc *__open(RIO *io, const char *pathname, int rw, int mode) {
	if (!r_str_startswith (pathname, "gb_ppu://")) {
		return NULL;
	}
	GBPPU *ppu = NULL;
	sscanf (pathname, "gb_ppu://%p", &ppu);
	RIODesc *desc = r_io_desc_new (io, &r_io_plugin_gb_ppu, pathname,
		R_PERM_RWX, mode, ppu);
	return desc;
}

RIOPlugin r_io_plugin_gb_ppu = {
	.meta = {
		.name = "gb_ppu",
		.desc = "gb_ppu",
		.license = "LGPL",
	},
	.uris = "gb_ppu://",
	.open = __open,
	.close = __close,
	.read = __read,
	.check = __check,
	.seek = __lseek,
	.write = __write,
};

GBPPU *gb_ppu_open (RIO *io, SDL_Renderer *renderer) {
	GBPPU *ppu = R_NEW0 (GBPPU);
	if (!ppu) {
		return NULL;
	}
	ppu->vram_fd = r_io_fd_open (io, "malloc//:0x2000", R_PERM_RWX, 0);
	if (ppu->vram_fd < 0) {
		free (ppu);
		return NULL;
	}
	char uri[64];
	sprintf (uri, "gb_ppu://%p", ppu);
	RIODesc *desc = r_io_desc_open_plugin (io, &r_io_plugin_gb_ppu, uri, R_PERM_RWX, 0);
	if (!desc) {
		r_io_fd_close (io, ppu->vram_fd);
		free (ppu);
		return NULL;
	}
	ppu->reg_fd = desc->fd;
	ppu->pixbuf = gb_pix_buf_new (renderer, 160, 144);
	if (!ppu->pixbuf) {
		r_io_desc_close (desc);
		r_io_fd_close (io, ppu->vram_fd);
		free (ppu);
		return NULL;
	}
	return ppu;
}

static ut32 gb_ppu_oam_scan_update (GB *gb, ut32 cycles) {
	if (gb->ppu->ost.addr >= 0xa0) {
		gb->ppu->ost.addr = 0;
		gb->ppu->ost.n_entries = 0;
	}
	if (cycles & 0x1) {
		R_LOG_WARN ("Odd amount of cycles");
	}
	if (gb->dma->seek & GB_DMA_ACTIVE) {
		const ut8 running_cycles = R_MIN (cycles, (0xa0 - gb->ppu->ost.addr) >> 1);
		//every oam entry costs 2 cycles
		gb->ppu->ost.addr += running_cycles << 1;
		cycles -= running_cycles;
		goto beach;
	}
	const ut8 height = gb->ppu->buf[GB_PPU_LCDC] & 0x3? 16: 8;
	const ut8 ly = gb->ppu->buf[GB_PPU_LY] + 16; 
	while (cycles && gb->ppu->ost.addr <= 0xa0) {
		if (gb->ppu->ost.n_entries < 10) {
			ut8 yx[2];
			r_io_fd_read_at (gb->io, gb->dma->oam_fd, (ut64)gb->ppu->ost.addr, yx, 2);
			if ((yx[0] <= ly) && (ly < (yx[0] + height))) {
				gb->ppu->ost.data[gb->ppu->ost.n_entries] =
					(gb->ppu->ost.addr << 8) | yx[1];
				gb->ppu->ost.n_entries++;
			}
		}
		gb->ppu->ost.addr += 4;
		cycles -= 2;
	}
beach:
	if (gb->ppu->ost.addr == 0xa0) {
		//indicate next mode
		gb->ppu->buf[GB_PPU_STAT] |= GB_PPU_STAT_MODE_RENDER;
	}
	return cycles;
}

void gb_ppu_update (GB *gb, ut32 cycles) {
	while (cycles) {
		switch (gb->ppu->buf[GB_PPU_STAT] & GB_PPU_STAT_MODE_MASK) {
		case GB_PPU_STAT_MODE_OAM_SCAN:
			cycles = gb_ppu_oam_scan_update (gb, cycles);
			break;
		case GB_PPU_STAT_MODE_RENDER:
			break;
		case GB_PPU_STAT_MODE_HBLANK:
			break;
		case GB_PPU_STAT_MODE_VBLANK:
			break;
		}
	}
	//TODO
}

void gb_ppu_close (GBPPU *ppu, RIO *io) {
	r_io_fd_close (io, ppu->vram_fd);
	r_io_fd_close (io, ppu->reg_fd);
	gb_pix_buf_free (ppu->pixbuf);
	free (ppu);
}