#define BEGIN do{
#define END }while(0)

#define X_C8_PRELUDE \
    chip8* c8 = usrdat; \
    assert(c8); \
\
    if(c8->pc >= sizeof(c8->mem)) \
    { \
        report(ERR, "CHIP-8: PC(%04X) Overflow!\n", c8->pc); \
        c8->running = false; \
    } \
\
    if(c8->pc & 0x0001) \
    { \
        report(ERR, "CHIP-8: PC(%04X) is not aligned!\n", c8->pc); \
        c8->running = false; \
    }

#define X_C8_EPILOGUE \
BEGIN \
    c8->cycles++; \
    if((c8->cycles % C8_CYCLES_PER_FRAME) == 0) \
    { \
        if(c8->dt) c8->dt--; \
        if(c8->st) c8->st--; \
    } \
    c8->pc += 2; \
END

#define X_C8_ILL \
BEGIN \
    c8->running = false; \
    report(ERR, "Illegal instruction (%04X) @ %04X\n", instr, offset);  \
END

#define X_C8_CLS \
BEGIN \
    int i, lines = lengthof(c8->DISPLAY); \
    for(i = 0; i < lines; i++) c8->DISPLAY[i] = 0; \
END

#define X_C8_RET \
BEGIN \
    c8->pc = c8->STACK[--c8->sp]; \
END

#define X_C8_SYS X_C8_ILL

#define X_C8_JP \
BEGIN \
    c8->pc = nnn - 2; \
END

#define X_C8_CALL \
BEGIN \
    c8->STACK[c8->sp++] = c8->pc; \
    c8->pc = nnn; \
END

#define X_C8_LDI \
BEGIN \
    c8->i = nnn; \
END

#define X_C8_JPV \
BEGIN \
    c8->pc = nnn + c8->V[0] - 2; \
END

#define X_C8_SEB \
BEGIN \
    if(c8->V[x] == kk) c8->pc += 2; \
END

#define X_C8_SNEB \
BEGIN \
    if(c8->V[x] != kk) c8->pc += 2; \
END

#define X_C8_LD \
BEGIN \
    c8->V[x] = kk; \
END

#define X_C8_ADDB \
BEGIN \
    int tmp = (int)c8->V[x] + (int)kk; \
    c8->V[x] = tmp & 0xFF; \
END

#define X_C8_RND \
BEGIN \
    c8->V[x] = (rand() % 255) & kk; \
END

#define X_C8_SKP \
BEGIN \
    if(c8->keys & c8->V[x]) c8->pc += 2; \
END

#define X_C8_SKNP \
BEGIN \
    if(!(c8->keys & c8->V[x])) c8->pc += 2; \
END

#define X_C8_MVDT \
BEGIN \
    c8->V[x] = c8->dt; \
END

/* TODO: implement */
#define X_C8_LDK \
BEGIN \
    if(!c8->keys) c8->pc -= 2; \
END

#define X_C8_LDDT \
BEGIN \
    c8->dt = c8->V[x]; \
END

#define X_C8_LDST \
BEGIN \
    c8->st = c8->V[x]; \
END

#define X_C8_ADDI \
BEGIN \
    c8->i += c8->V[x]; \
END

#define X_C8_HEX \
BEGIN \
    usize m = (usize)(c8->RAM); \
    usize f = (usize)(c8->FONT); \
    c8->i = (f - m) + c8->V[x] * 5; \
END

#define X_C8_BCD \
BEGIN \
    c8->RAM[c8->i] = c8->V[x] / 100; \
    c8->RAM[c8->i + 1] = c8->V[x] % 100 / 10; \
    c8->RAM[c8->i + 2] = c8->V[x] % 10; \
END

#define X_C8_SAVE \
BEGIN \
    u8 i; \
    for(i = 0; i < x; i++) c8->RAM[c8->i + i] = c8->V[i]; \
END

#define X_C8_RESTORE \
BEGIN \
    u8 i; \
    for(i = 0; i < x; i++) c8->V[i] = c8->RAM[c8->i + i]; \
END

#define X_C8_SE \
BEGIN \
    if(c8->V[x] == c8->V[y]) c8->pc += 2; \
END

#define X_C8_MOVE \
BEGIN \
    c8->V[x] = c8->V[y]; \
END

#define X_C8_OR \
BEGIN \
    c8->V[x] |= c8->V[y]; \
END

#define X_C8_AND \
BEGIN \
    c8->V[x] &= c8->V[y]; \
END

#define X_C8_XOR \
BEGIN \
    c8->V[x] ^= c8->V[y]; \
END

#define X_C8_ADD \
BEGIN \
    int tmp = (int)c8->V[x] + (int)c8->V[y]; \
    c8->V[0xf] = tmp > 255; \
    c8->V[x]   = tmp; \
END

#define X_C8_SUB \
BEGIN \
    int tmp = (int)c8->V[x] - (int)c8->V[y]; \
    c8->V[0xf] = tmp > 0; \
    c8->V[x]   = tmp; \
END

#define X_C8_SHR \
BEGIN \
    c8->V[0xf] = (c8->V[y] & 0x1) ? 1 : 0; \
    c8->V[x]   = c8->V[y] >> 1; \
END

#define X_C8_SUBN \
BEGIN \
    int tmp = (int)c8->V[y] - (int)c8->V[x]; \
    c8->V[0xf] = tmp > 0; \
    c8->V[x]   = tmp; \
END

#define X_C8_SHL \
BEGIN \
    c8->V[0xf] = (c8->V[y] & 0x80) ? 1 : 0; \
    c8->V[x]   = c8->V[y] << 1; \
END

#define X_C8_SNE \
BEGIN \
    if(c8->V[x] != c8->V[y]) c8->pc += 2; \
END


/* TODO: actually implement */
#define X_C8_DRW \
BEGIN \
    u8 l; \
    u8 cx = c8->V[x]; \
    u8 cy = c8->V[y]; \
    \
    for(l = 0; l < n; l++) \
        c8->DISPLAY[cy + l * cx] ^= c8->RAM[c8->i + l]; \
END

c8_decode_generate(exec)

#undef BEGIN
#undef END
#include "undef.c"