232 lines
5.2 KiB
C
232 lines
5.2 KiB
C
#include <stdio.h>
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/*
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Copyright (c) 2021 Devine Lu Linvega
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Permission to use, copy, modify, and distribute this software for any
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purpose with or without fee is hereby granted, provided that the above
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copyright notice and this permission notice appear in all copies.
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THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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WITH REGARD TO THIS SOFTWARE.
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*/
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#define FLAG_HALT 0x01
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#define FLAG_ZERO 0x02
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#define FLAG_CARRY 0x04
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#define FLAG_TRAPS 0x08
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typedef unsigned char Uint8;
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typedef unsigned short Uint16;
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typedef struct {
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Uint8 ptr;
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Uint8 dat[256];
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} Stack;
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typedef struct {
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Uint16 ptr;
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Uint8 dat[65536];
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} Memory;
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typedef struct {
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Uint8 literal, status;
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Uint16 counter, vreset, vframe, verror;
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Stack wst, rst;
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Memory rom, ram;
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} Computer;
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Computer cpu;
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#pragma mark - Helpers
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void
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setflag(char flag, int b)
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{
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if(b)
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cpu.status |= flag;
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else
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cpu.status &= (~flag);
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}
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int
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getflag(char flag)
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{
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return cpu.status & flag;
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}
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void
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echos(Stack *s, Uint8 len, char *name)
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{
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int i;
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printf("%s\n", name);
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for(i = 0; i < len; ++i) {
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if(i % 16 == 0)
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printf("\n");
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printf("%02x%c", s->dat[i], s->ptr == i ? '<' : ' ');
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}
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printf("\n\n");
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}
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void
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echom(Memory *m, Uint8 len, char *name)
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{
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int i;
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printf("%s\n", name);
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for(i = 0; i < len; ++i) {
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if(i % 16 == 0)
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printf("\n");
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printf("%02x ", m->dat[i]);
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}
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printf("\n\n");
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}
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#pragma mark - Operations
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/* clang-format off */
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Uint8 mempoke8(Uint16 p) { return cpu.rom.dat[p+1] & 0xff; }
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Uint16 mempoke16(Uint16 p) { return (cpu.rom.dat[p] << 8) + (cpu.rom.dat[p+1] & 0xff); }
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void wspush(Uint8 b) { cpu.wst.dat[cpu.wst.ptr++] = b; }
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Uint8 wspop(void) { return cpu.wst.dat[--cpu.wst.ptr]; }
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void wspush16(Uint16 s) {
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printf("0x%04x\n", s);
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}
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Uint16 wspop16(void) { return wspop() + (wspop() << 8); }
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Uint8 wspeek(void) { return cpu.wst.dat[cpu.wst.ptr - 1]; }
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void rspush(Uint8 b) { cpu.rst.dat[cpu.rst.ptr++] = b; }
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Uint8 rspop(void) { return cpu.rst.dat[--cpu.rst.ptr]; }
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void op_brk() { setflag(FLAG_HALT, 1); }
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void op_rts() { cpu.rom.ptr = rspop(); }
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void op_lit() { cpu.literal += cpu.rom.dat[cpu.rom.ptr++]; }
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void op_drp() { wspop(); }
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void op_dup() { wspush(wspeek()); }
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void op_swp() { Uint8 b = wspop(), a = wspop(); wspush(b); wspush(a); }
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void op_ovr() { wspush(cpu.wst.dat[cpu.wst.ptr - 2]); }
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void op_rot() { Uint8 c = wspop(),b = wspop(),a = wspop(); wspush(b); wspush(c); wspush(a); }
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void op_jmu() { cpu.rom.ptr = wspop(); }
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void op_jsu() { rspush(cpu.rom.ptr); cpu.rom.ptr = wspop(); }
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void op_jmc() { if(wspop()) op_jmu(); }
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void op_jsc() { if(wspop()) op_jsu(); }
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void op_equ() { wspush(wspop() == wspop()); }
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void op_neq() { wspush(wspop() != wspop()); }
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void op_gth() { wspush(wspop() < wspop()); }
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void op_lth() { wspush(wspop() > wspop()); }
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void op_and() { wspush(wspop() & wspop()); }
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void op_ora() { wspush(wspop() | wspop()); }
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void op_rol() { wspush(wspop() << 1); }
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void op_ror() { wspush(wspop() >> 1); }
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void op_add() { wspush(wspop() + wspop()); }
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void op_sub() { wspush(wspop() - wspop()); }
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void op_mul() { wspush(wspop() * wspop()); }
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void op_div() { wspush(wspop() / wspop()); }
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void op_ldr() { wspush(cpu.ram.dat[wspop16()]); }
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void op_str() { cpu.ram.dat[wspop16()] = wspop(); }
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void (*ops[])(void) = {
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op_brk, op_rts, op_lit, op_drp, op_dup, op_swp, op_ovr, op_rot,
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op_jmu, op_jsu, op_jmc, op_jsc, op_equ, op_neq, op_gth, op_lth,
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op_and, op_ora, op_rol, op_ror, op_add, op_sub, op_mul, op_div,
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op_ldr, op_str, op_brk, op_brk, op_brk, op_brk, op_brk, op_brk
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};
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Uint8 opr[][2] = {
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{0,0}, {0,0}, {0,0}, {1,0}, {0,1}, {1,1}, {0,1}, {3,3},
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{2,0}, {2,0}, {2,0}, {2,0}, {2,1}, {2,1}, {2,1}, {2,1},
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{1,0}, {1,0}, {1,0}, {1,0}, {2,1}, {0,0}, {0,0}, {0,0},
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{2,1}, {3,0}, {0,0}, {0,0}, {0,0}, {0,0}, {0,0}, {0,0}
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};
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/* clang-format on */
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void
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reset(void)
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{
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int i;
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cpu.status = 0x00;
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cpu.counter = 0x00;
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cpu.literal = 0x00;
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cpu.rom.ptr = 0x00;
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cpu.wst.ptr = 0x00;
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cpu.rst.ptr = 0x00;
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for(i = 0; i < 256; i++) {
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cpu.wst.dat[i] = 0x00;
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cpu.rst.dat[i] = 0x00;
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}
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}
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int
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error(char *name)
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{
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printf("Error: %s\n", name);
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return 0;
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}
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int
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eval(void)
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{
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Uint8 instr = cpu.rom.dat[cpu.rom.ptr++];
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if(cpu.literal > 0) {
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wspush(instr);
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cpu.literal--;
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return 1;
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}
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if(instr < 32) {
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if(cpu.wst.ptr < opr[instr][0])
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return error("Stack underflow");
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/* TODO stack overflow */
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(*ops[instr])();
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}
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if(instr > 0x10)
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setflag(FLAG_ZERO, 0);
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if(cpu.counter == 128) {
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printf("REACHED COUNTER\n");
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return 0;
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}
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cpu.counter++;
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return 1;
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}
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void
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start(FILE *f)
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{
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reset();
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fread(cpu.rom.dat, sizeof(cpu.rom.dat), 1, f);
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cpu.vreset = mempoke16(0xfffa);
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cpu.vframe = mempoke16(0xfffc);
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cpu.verror = mempoke16(0xfffe);
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/* eval reset */
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cpu.rom.ptr = cpu.vreset;
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while(!(cpu.status & FLAG_HALT) && eval())
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;
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/*eval frame */
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cpu.rom.ptr = cpu.vframe;
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while(!(cpu.status & FLAG_HALT) && eval())
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;
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/* debug */
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printf("ended @ %d steps | ", cpu.counter);
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printf("hf: %x zf: %x cf: %x tf: %x\n",
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getflag(FLAG_HALT) != 0,
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getflag(FLAG_ZERO) != 0,
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getflag(FLAG_CARRY) != 0,
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getflag(FLAG_TRAPS) != 0);
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printf("\n");
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}
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int
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main(int argc, char *argv[])
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{
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FILE *f;
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if(argc < 2)
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return error("No input.");
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if(!(f = fopen(argv[1], "rb")))
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return error("Missing input.");
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start(f);
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/* print result */
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echos(&cpu.wst, 0x40, "stack");
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echom(&cpu.ram, 0x40, "ram");
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return 0;
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}
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