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pokegb.cc w/o macros
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LICENSE
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
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pokegb.cc
/*
* Copyright (C) 2021 Ben Smith
*
* This software may be modified and distributed under the terms
* of the MIT license. See the LICENSE file for details.
*/
#include <SDL2/SDL.h>
#include <cstdint>
#include <fcntl.h>
#include <sys/mman.h>
#include <unistd.h>
#define OP4_NX8(_) case _: case _ + 8: case _ + 16: case _ + 24:
#define OP4_NX16_REL(_) \
case _: \
case _ + 16: \
case _ + 32: \
case _ + 48: \
opcode_rel = opcode - _;
#define OP5_FLAG(_, always) \
OP4_NX8(_) \
case always: \
carry = (opcode == always) || \
(F & F_mask[(opcode - _) / 8]) == F_equals[(opcode - _) / 8];
#define OP8_NX8_REL(_) OP4_NX8(_) OP4_NX8(_ + 32) opcode_rel = opcode - _;
#define OP7_PTR(_) \
case _: \
case _ + 1: \
case _ + 2: \
case _ + 3: \
case _ + 4: \
case _ + 5: \
case _ + 7: \
ptr8 = reg8_group[opcode & 7];
#define OP7_NX8(_) OP4_NX8(_) case _ + 32 : case _ + 40 : case _ + 56:
#define OP7_NX8_PTR(_) OP7_NX8(_) ptr8 = reg8_group[(opcode - _) / 8];
#define OP49_REL(_) \
OP7_NX8(_) \
OP7_NX8(_ + 1) \
OP7_NX8(_ + 2) \
OP7_NX8(_ + 3) \
OP7_NX8(_ + 4) \
OP7_NX8(_ + 5) \
OP7_NX8(_ + 7) \
opcode_rel = opcode - _;
#define OP56_PTR_REL(_) OP49_REL(_) OP7_PTR(_ + 48) opcode_rel = opcode - _;
#define OP9_IMM_PTR(_) \
case _ + 6: \
case _ + 70: \
OP7_PTR(_) \
operand = (opcode == _ + 6) ? read8() \
: (opcode == _ + 70) ? read8_pc() \
: *ptr8;
uint8_t opcode, opcode_rel, tmp8, operand, carry, neg, *rom0, *rom1, io[512], video_ram[8192],
work_ram[16384], *extram, *extrambank,
reg8[] = {19, 0, 216, 0, 77, 1, 176, 1, 254, 255}, &F = reg8[6],
&A = reg8[7], *reg8_group[] = {reg8 + 1, reg8, reg8 + 3, reg8 + 2,
reg8 + 5, reg8 + 4, &F, &A},
&IF = io[271], &LCDC = io[320], &LY = io[324], IME, halt, *ptr8;
uint8_t const *key_state;
uint16_t PC = 256, temp16, *reg16 = (uint16_t *)reg8, &HL = reg16[2],
&SP = reg16[4], &DIV = (uint16_t &)io[259], ppu_dot = 32, *ptr16,
*reg16_group1[] = {reg16, reg16 + 1, &HL, &SP},
*reg16_group2[] = {reg16, reg16 + 1, &HL, &HL}, prev_cycles, cycles;
int tmp, tmp2,
HL_add[] = {0, 0, 1, -1}, F_mask[] = {128, 128, 16, 16},
F_equals[] = {0, 128, 0, 16}, frame_buffer[23040],
palette[] = {-1, -23197, -65536, -16777216, -1, -8092417,
-12961132, -16777216, -1, -23197, -65536, -16777216};
void tick() { cycles += 4; }
uint8_t mem_access(uint16_t addr, uint8_t val, int write) {
tick();
switch (addr >> 12) {
case 2: case 3:
// Change ROM bank
if (write)
rom1 = rom0 + ((val ? val & 63 : 1) << 14);
case 0: case 1:
return rom0[addr];
case 4: case 5:
// Change RAM bank
if (write && val <= 3)
extrambank = extram + (val << 13);
case 6: case 7:
return rom1[addr & 16383];
case 8: case 9:
addr &= 8191;
if (write)
video_ram[addr] = val;
return video_ram[addr];
case 10: case 11:
addr &= 8191;
if (write)
extrambank[addr] = val;
return extrambank[addr];
case 15:
if (addr >= 65024) {
if (write) {
// DMA transfer to OAM
if (addr == 65350)
for (int y = 160; --y >= 0;)
io[y] = mem_access(val * 256 + y, 0, 0);
io[addr & 511] = val;
}
// Read JOYP
if (addr == 65280) {
if (!(io[256] & 16))
return ~(16 + key_state[SDL_SCANCODE_DOWN] * 8 +
key_state[SDL_SCANCODE_UP] * 4 +
key_state[SDL_SCANCODE_LEFT] * 2 +
key_state[SDL_SCANCODE_RIGHT]);
if (!(io[256] & 32))
return ~(32 + key_state[SDL_SCANCODE_RETURN] * 8 +
key_state[SDL_SCANCODE_TAB] * 4 +
key_state[SDL_SCANCODE_Z] * 2 +
key_state[SDL_SCANCODE_X]);
return 255;
}
return io[addr & 511];
}
case 12 ... 14:
addr &= 16383;
if (write)
work_ram[addr] = val;
return work_ram[addr];
}
}
uint8_t read8(uint16_t addr = HL) { return mem_access(addr, 0, 0); }
void write8(uint8_t val, uint16_t addr = HL) { mem_access(addr, val, 1); }
void set_flags(uint8_t mask, int Z, int N, int H, int C) {
F = (F & mask) | (!Z * 128 + N * 64 + H * 32 + C * 16);
}
uint8_t read8_pc() { return read8(PC++); }
uint16_t read16(uint16_t &addr = PC) {
tmp8 = read8(addr++);
return read8(addr++) * 256 + tmp8;
}
void push(uint16_t val) {
write8(val >> 8, --SP);
write8(val, --SP);
tick();
}
int main() {
rom1 = (rom0 = (uint8_t *)mmap(0, 1048576, PROT_READ, MAP_SHARED,
open("rom.gb", O_RDONLY), 0)) +
32768;
tmp = open("rom.sav", O_CREAT|O_RDWR, 0666);
ftruncate(tmp, 32768);
extrambank = extram =
(uint8_t *)mmap(0, 32768, PROT_READ | PROT_WRITE, MAP_SHARED, tmp, 0);
LCDC = 145;
DIV = 44032;
SDL_Init(SDL_INIT_VIDEO);
SDL_Renderer *renderer = SDL_CreateRenderer(
SDL_CreateWindow("pokegb", 0, 0, 800, 720, SDL_WINDOW_SHOWN), -1,
SDL_RENDERER_PRESENTVSYNC);
SDL_Texture *texture = SDL_CreateTexture(
renderer, SDL_PIXELFORMAT_RGBA32, SDL_TEXTUREACCESS_STREAMING, 160, 144);
key_state = SDL_GetKeyboardState(0);
while (1) {
prev_cycles = cycles;
if (IME & IF & io[511]) {
// Handle interrupt (VBlank only)
IF = halt = IME = 0;
cycles += 8;
carry = 1;
temp16 = 64;
goto CALL;
} else if (halt)
tick();
else
switch (opcode = read8_pc()) {
case 0: // NOP
break;
OP4_NX16_REL(1) // LD r16, u16
*reg16_group1[opcode >> 4] = read16();
break;
OP4_NX16_REL(2) // LD (r16), A
write8(A, *reg16_group2[opcode >> 4]);
HL += HL_add[opcode_rel / 16];
break;
OP4_NX16_REL(3) // INC r16
(*reg16_group1[opcode >> 4])++;
tick();
break;
OP7_NX8_PTR(4) // INC r8
tmp8 = ++(*ptr8);
goto INC_FLAGS;
case 52: // INC (HL)
write8(tmp8 = read8() + 1);
INC_FLAGS:
set_flags(16, tmp8, 0, !(tmp8 & 15), 0);
break;
OP7_NX8_PTR(5) // DEC r8
tmp8 = --(*ptr8);
goto DEC_FLAGS;
case 53: // DEC (HL)
write8(tmp8 = read8() - 1);
DEC_FLAGS:
set_flags(16, tmp8, 1, tmp8 % 16 == 15, 0);
break;
OP7_NX8_PTR(6) // LD r8, u8
*ptr8 = read8_pc();
break;
case 7: // RLCA
A += A + (carry = A >> 7);
goto CARRY_FLAG;
OP4_NX16_REL(9) // ADD HL, r16
ptr16 = reg16_group1[opcode >> 4];
set_flags(128, 1, 0, HL % 4096 + *ptr16 % 4096 > 4095, HL + *ptr16 > 65535);
HL += *ptr16;
tick();
break;
OP4_NX16_REL(10) // LD A, (r16)
A = read8(*reg16_group2[opcode >> 4]);
HL += HL_add[opcode_rel / 16];
break;
OP4_NX16_REL(11) // DEC r16
(*reg16_group1[opcode >> 4])--;
tick();
break;
case 15: // RRCA
A = (carry = A & 1) * 128 + A / 2;
goto CARRY_FLAG;
case 23: // RLA
carry = A >> 7;
A += A + F / 16 % 2;
CARRY_FLAG:
set_flags(0, 1, 0, 0, carry);
break;
OP5_FLAG(32, 24) // JR i8 / JR <condition>, i8
tmp8 = read8_pc();
if (carry)
PC += (int8_t)tmp8, tick();
break;
case 39: // DAA
carry = tmp8 = 0;
if (F & 32 || (!(F & 64) && A % 15 > 9))
tmp8 = 6;
if (F & 16 || (!(F & 64) && A > 153))
tmp8 |= 96, carry = 1;
set_flags(65, A += (F & 64) ? -tmp8 : tmp8, 0, 0, carry);
break;
case 47: // CPL
A = ~A;
set_flags(129, 1, 1, 1, 0);
break;
case 54: // LD (HL), u8
write8(read8_pc());
break;
case 55: case 63: // SCF / CCF
set_flags(128, 1, 0, 0, opcode == 55 ? 1 : !(F & 16));
break;
OP7_NX8_PTR(70) // LD r8, (HL)
*ptr8 = read8();
break;
OP49_REL(64) // LD r8, r8
*reg8_group[opcode_rel / 8] = *reg8_group[opcode & 7];
break;
OP7_PTR(112) // LD (HL), r8
write8(*ptr8);
break;
case 118: // HALT
halt = 1;
break;
OP9_IMM_PTR(128) // ADD A, r8 / ADD A, (HL) / ADD A, u8
neg = carry = 0;
goto ALU;
OP9_IMM_PTR(136) // ADC A, r8 / ADC A, (HL) / ADC A, u8
neg = 0;
carry = F / 16 % 2;
goto ALU;
OP9_IMM_PTR(144) // SUB A, r8 / SUB A, (HL) / SUB A, u8
carry = 1;
goto SUBTRACT;
OP9_IMM_PTR(152) // SBC A, r8 / SBC A, (HL) / SBC A, u8
carry = !(F / 16 % 2);
SUBTRACT:
neg = 1;
operand = ~operand;
ALU:
set_flags(0, tmp8 = A + operand + carry, neg,
(A % 16 + operand % 16 + carry > 15) ^ neg,
(A + operand + carry > 255) ^ neg);
A = tmp8;
break;
OP9_IMM_PTR(160) // AND A, r8 / AND A, (HL) / AND A, u8
set_flags(0, A &= operand, 0, 1, 0);
break;
OP9_IMM_PTR(168) // XOR A, r8 / XOR A, (HL) / XOR A, u8
set_flags(0, A ^= operand, 0, 0, 0);
break;
OP9_IMM_PTR(176) // OR A, r8 / OR A, (HL) / OR A, u8
set_flags(0, A |= operand, 0, 0, 0);
break;
OP9_IMM_PTR(184) // CP A, r8 / CP A, (HL) / CP A, u8
set_flags(0, A != operand, 1, A % 16 < operand % 16, A < operand);
break;
case 217: // RETI
carry = IME = 1;
goto RET;
OP5_FLAG(192, 201) // RET / RET <condition>
RET:
tick();
if (carry)
PC = read16(SP);
break;
OP4_NX16_REL(193) // POP r16
reg16[opcode_rel >> 4] = read16(SP);
break;
OP5_FLAG(194, 195) // JP u16 / JP <condition>, u16
temp16 = read16();
if (carry)
PC = temp16, tick();
break;
OP5_FLAG(196, 205) // CALL u16 / CALL <condition>, u16
temp16 = read16();
CALL:
if (carry)
push(PC), PC = temp16;
break;
OP4_NX16_REL(197) // PUSH r16
push(reg16[opcode_rel >> 4]);
break;
case 203:
switch (opcode = read8_pc()) {
OP7_PTR(0) // RLC r8
*ptr8 += *ptr8 + (carry = *ptr8 / 128 % 2);
goto CARRY_ZERO_FLAGS_PTR;
OP7_PTR(8) // RRC r8
*ptr8 = (carry = *ptr8 & 1) * 128 + *ptr8 / 2;
goto CARRY_ZERO_FLAGS_PTR;
case 14: // RRC (HL)
tmp8 = read8();
carry = tmp8 & 1;
write8(tmp8 = carry * 128 + tmp8 / 2);
goto CARRY_ZERO_FLAGS_U;
OP7_PTR(16) // RL r8
carry = *ptr8 >> 7;
*ptr8 = *ptr8 * 2 + F / 16 % 2;
goto CARRY_ZERO_FLAGS_PTR;
OP7_PTR(24) // RR r8
carry = *ptr8 & 1;
*ptr8 = *ptr8 / 2 + ((F * 8) & 128);
goto CARRY_ZERO_FLAGS_PTR;
OP7_PTR(32) // SLA r8
carry = *ptr8 / 128 % 2;
*ptr8 *= 2;
goto CARRY_ZERO_FLAGS_PTR;
OP7_PTR(40) // SRA r8
carry = *ptr8 & 1;
*ptr8 = (int8_t)*ptr8 >> 1;
goto CARRY_ZERO_FLAGS_PTR;
OP7_PTR(48) // SWAP r8
set_flags(0, *ptr8 = *ptr8 * 16 + *ptr8 / 16, 0, 0, 0);
break;
case 54: // SWAP (HL)
tmp8 = read8();
carry = 0;
write8(tmp8 = tmp8 * 16 + tmp8 / 16);
CARRY_ZERO_FLAGS_U:
set_flags(0, tmp8, 0, 0, carry);
break;
OP7_PTR(56) // SRL r8
carry = *ptr8 & 1;
*ptr8 /= 2;
CARRY_ZERO_FLAGS_PTR:
set_flags(0, *ptr8, 0, 0, carry);
break;
OP8_NX8_REL(70) // BIT bit, r8
tmp8 = read8();
goto BIT_FLAGS;
OP56_PTR_REL(64) // BIT bit, (HL)
tmp8 = *ptr8;
BIT_FLAGS:
set_flags(16, tmp8 & (1 << opcode_rel / 8), 0, 1, 0);
break;
OP8_NX8_REL(134) // RES bit, (HL)
write8(read8() & ~(1 << opcode_rel / 8));
break;
OP56_PTR_REL(128) // RES bit, r8
*ptr8 &= ~(1 << opcode_rel / 8);
break;
OP8_NX8_REL(198) // SET bit, (HL)
write8(read8() | (1 << opcode_rel / 8));
break;
OP56_PTR_REL(192) // SET bit, r8
*ptr8 |= 1 << opcode_rel / 8;
break;
}
break;
case 224: case 226: // LD (FF00 + u8), A / LD (FF00 + C), A
write8(A, 65280 + (opcode == 224 ? read8_pc() : *reg8));
break;
case 233: // JP HL
PC = HL;
break;
case 234: // LD (u16), A
write8(A, read16());
break;
case 240: case 250: // LD A, (FF00 + u8) / LD A, (u16)
A = read8(opcode == 240 ? 65280 | read8_pc() : read16());
break;
case 243: case 251: // DI / EI
IME = opcode != 243;
break;
case 248: // LD HL, SP + i8
tmp8 = read8_pc();
set_flags(0, 1, 0, (uint8_t)SP + tmp8 > 255, SP % 16 + tmp8 % 16 > 15);
HL = SP + (int8_t)tmp8;
tick();
break;
case 249: // LD SP, HL
SP = HL;
tick();
break;
}
for (DIV += cycles - prev_cycles; prev_cycles++ != cycles;)
if (LCDC & 128) {
// Trigger VBlank interrupt
if (++ppu_dot == 1 && LY == 144)
IF |= 1;
if (ppu_dot == 456) {
if (LY < 144)
for (tmp = 160; --tmp >= 0;) {
// Draw background or window
uint8_t is_window =
LCDC & 32 && LY >= io[330] && tmp >= io[331] - 7,
x_offset = is_window ? tmp - io[331] + 7 : tmp + io[323],
y_offset = is_window ? LY - io[330] : LY + io[322];
uint16_t tile = video_ram[((LCDC & (is_window ? 64 : 8) ? 7 : 6)
<< 10) +
y_offset / 8 * 32 + x_offset / 8],
palette_index = 0;
x_offset = (x_offset ^ 7) & 7;
uint8_t
*tile_data =
&video_ram[(LCDC & 16 ? tile : 256 + (int8_t)tile) * 16 +
y_offset % 8 * 2],
color = (tile_data[1] >> x_offset) % 2 * 2 +
(*tile_data >> x_offset) % 2;
// Draw sprites
if (LCDC & 2)
for (uint8_t *sprite = io; sprite < io + 160; sprite += 4) {
uint8_t sprite_x = tmp - sprite[1] + 8,
sprite_y = LY - *sprite + 16;
if (sprite_x < 8 && sprite_y < 8) {
sprite_x ^= sprite[3] & 32 ? 0 : 7;
tile_data =
&video_ram[sprite[2] * 16 +
(sprite_y ^ (sprite[3] & 64 ? 7 : 0)) * 2];
uint8_t sprite_color = (tile_data[1] >> sprite_x) % 2 * 2 +
(*tile_data >> sprite_x) % 2;
if (!((sprite[3] & 128) && color) && sprite_color) {
color = sprite_color;
palette_index += 1 + !!(sprite[3] & 8);
break;
}
}
}
// Draw pixel
frame_buffer[LY * 160 + tmp] =
palette[(io[327 + palette_index] >> (2 * color)) % 4 +
palette_index * 4];
}
if (LY == 144) {
// Render frame buffer
void *pixels;
SDL_LockTexture(texture, 0, &pixels, &tmp);
for (tmp2 = 144; --tmp2 >= 0;)
memcpy((uint8_t *)pixels + tmp2 * tmp, frame_buffer + tmp2 * 160,
640);
SDL_UnlockTexture(texture);
SDL_RenderCopy(renderer, texture, 0, 0);
SDL_RenderPresent(renderer);
SDL_Event event;
while (SDL_PollEvent(&event))
if (event.type == SDL_QUIT)
return 0;
}
LY = (LY + 1) % 154;
ppu_dot = 0;
}
} else
LY = ppu_dot = 0;
}
}
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