296 lines
8.1 KiB
C
296 lines
8.1 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_SHORT 0x02
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#define FLAG_SIGN 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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Uint8 ptr;
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Uint16 dat[256];
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} Stack16;
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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;
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Stack16 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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Uint16 bytes2short(Uint8 a, Uint8 b) { return (a << 8) + b; }
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Uint8 rampeek8(Uint16 s) { return cpu.ram.dat[s] & 0xff; }
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Uint8 mempeek8(Uint16 s) { return cpu.rom.dat[s]; }
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Uint16 mempeek16(Uint16 s) { return (cpu.rom.dat[s] << 8) + (cpu.rom.dat[s+1] & 0xff); }
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void wspush8(Uint8 b) { cpu.wst.dat[cpu.wst.ptr++] = b; }
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void wspush16(Uint16 s) { wspush8(s >> 8); wspush8(s & 0xff); }
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Uint8 wspop8(void) { return cpu.wst.dat[--cpu.wst.ptr]; }
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Uint16 wspop16(void) { return wspop8() + (wspop8() << 8); }
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Uint8 wspeek8(Uint8 o) { return cpu.wst.dat[cpu.wst.ptr - o]; }
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Uint16 wspeek16(Uint8 o) { return bytes2short(cpu.wst.dat[cpu.wst.ptr - o], cpu.wst.dat[cpu.wst.ptr - o + 1]); }
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Uint16 rspop16(void) { return cpu.rst.dat[--cpu.rst.ptr]; }
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void rspush16(Uint16 a) { cpu.rst.dat[cpu.rst.ptr++] = a; }
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/* new flexy pop/push */
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void op_brk() { setflag(FLAG_HALT, 1); }
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void op_rts() { cpu.rom.ptr = rspop16(); }
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void op_lit() { cpu.literal += cpu.rom.dat[cpu.rom.ptr++]; }
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void op_drp() { wspop8(); }
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void op_dup() { wspush8(wspeek8(1)); }
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void op_swp() { Uint8 b = wspop8(), a = wspop8(); wspush8(b); wspush8(a); }
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void op_ovr() { Uint8 a = wspeek8(2); wspush8(a); }
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void op_rot() { Uint8 c = wspop8(),b = wspop8(),a = wspop8(); wspush8(b); wspush8(c); wspush8(a); }
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void op_jmu() { cpu.rom.ptr = wspop16(); }
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void op_jsu() { rspush16(cpu.rom.ptr); cpu.rom.ptr = wspop16(); }
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void op_jmc() { Uint8 a = wspop8(); if(a) op_jmu(); }
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void op_jsc() { Uint8 a = wspop8(); if(a) op_jsu(); }
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void op_equ() { Uint8 a = wspop8(), b = wspop8(); wspush8(a == b); }
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void op_neq() { Uint8 a = wspop8(), b = wspop8(); wspush8(a != b); }
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void op_gth() { Uint8 a = wspop8(), b = wspop8(); wspush8(a < b); }
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void op_lth() { Uint8 a = wspop8(), b = wspop8(); wspush8(a > b); }
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void op_and() { Uint8 a = wspop8(), b = wspop8(); wspush8(a & b); }
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void op_ora() { Uint8 a = wspop8(), b = wspop8(); wspush8(a | b); }
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void op_rol() { Uint8 a = wspop8(), b = wspop8(); wspush8(a << b); }
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void op_ror() { Uint8 a = wspop8(), b = wspop8(); wspush8(a >> b); }
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void op_add() { Uint8 a = wspop8(), b = wspop8(); wspush8(a + b); }
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void op_sub() { Uint8 a = wspop8(), b = wspop8(); wspush8(a - b); }
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void op_mul() { Uint8 a = wspop8(), b = wspop8(); wspush8(a * b); }
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void op_div() { Uint8 a = wspop8(), b = wspop8(); wspush8(a / b); }
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void op_ldr() { wspush8(cpu.ram.dat[wspop16()]); }
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void op_str() { cpu.ram.dat[wspop16()] = wspop8(); }
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void op_pek() { wspush8(cpu.rom.dat[wspop16()]); }
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void op_pok() { printf("TODO:\n");}
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void op_drp16() { wspop16(); }
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void op_dup16() { wspush16(wspeek16(2)); }
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void op_swp16() { Uint16 b = wspop16(), a = wspop16(); wspush16(b); wspush16(a); }
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void op_ovr16() { Uint16 a = wspeek16(4); wspush16(a); }
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void op_rot16() { Uint16 c = wspop16(), b = wspop16(), a = wspop16(); wspush16(b); wspush16(c); wspush16(a); }
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void op_equ16() { Uint16 a = wspop16(), b = wspop16(); wspush16(a == b); }
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void op_neq16() { Uint16 a = wspop16(), b = wspop16(); wspush16(a != b); }
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void op_gth16() { Uint16 a = wspop16(), b = wspop16(); wspush16(a < b); }
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void op_lth16() { Uint16 a = wspop16(), b = wspop16(); wspush16(a > b); }
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void op_and16() { Uint16 a = wspop16(), b = wspop16(); wspush16(a & b); }
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void op_ora16() { Uint16 a = wspop16(), b = wspop16(); wspush16(a | b); }
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void op_rol16() { Uint16 a = wspop16(), b = wspop16(); wspush16(a << b); }
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void op_ror16() { Uint16 a = wspop16(), b = wspop16(); wspush16(a >> b); }
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void op_add16() { Uint16 a = wspop16(), b = wspop16(); wspush16(a + b); }
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void op_sub16() { Uint16 a = wspop16(), b = wspop16(); wspush16(a - b); }
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void op_mul16() { Uint16 a = wspop16(), b = wspop16(); wspush16(a * b); }
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void op_div16() { Uint16 a = wspop16(), b = wspop16(); wspush16(a / b); }
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void (*ops8[])() = {
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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_pek, op_pok, op_brk, op_brk, op_brk, op_brk
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};
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void (*ops16[])() = {
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op_brk, op_rts, op_lit, op_drp16, op_dup16, op_swp16, op_ovr16, op_rot16,
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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_and16, op_ora16, op_rol16, op_ror16, op_add16, op_sub16, op_mul16, op_div16,
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op_ldr, op_str, op_pek, op_pok, op_brk, op_brk, op_brk, op_brk
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};
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Uint8 opr[][2] = { /* todo: 16 bits mode */
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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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size_t i;
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char *cptr = (char *)&cpu;
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for(i = 0; i < sizeof cpu; i++)
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cptr[i] = 0;
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}
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int
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error(char *name, int id)
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{
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printf("Error: %s[%04x], at 0x%04x\n", name, id, cpu.counter);
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return 0;
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}
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int
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device1(Uint8 *read, Uint8 *write)
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{
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printf("%c", *write);
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*write = 0;
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(void)read;
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return 0;
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}
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void
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opc(Uint8 src, Uint8 *op)
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{
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*op = src;
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*op &= ~(1 << 5);
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*op &= ~(1 << 6);
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*op &= ~(1 << 7);
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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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Uint8 op;
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/* when literal */
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if(cpu.literal > 0) {
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wspush8(instr);
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cpu.literal--;
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return 1;
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}
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/* when opcode */
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opc(instr, &op);
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setflag(FLAG_SHORT, (instr >> 5) & 1);
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setflag(FLAG_SIGN, (instr >> 6) & 1);
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if((instr >> 7) & 1)
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printf("Unused flag: %02x\n", instr);
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/* TODO: setflag(FLAG_B, (instr >> 6) & 1); */
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/* TODO: setflag(FLAG_C, (instr >> 7) & 1); */
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if(cpu.wst.ptr < opr[op][0])
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return error("Stack underflow", op);
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if(getflag(FLAG_SHORT))
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(*ops16[op])();
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else
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(*ops8[op])();
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cpu.counter++;
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return 1;
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}
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int
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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 = mempeek16(0xfffa);
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cpu.vframe = mempeek16(0xfffc);
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cpu.verror = mempeek16(0xfffe);
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/* eval reset */
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printf("\nPhase: reset\n");
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cpu.rom.ptr = cpu.vreset;
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while(!(cpu.status & FLAG_HALT) && eval()) {
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/* experimental */
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if(cpu.ram.dat[0xfff1])
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device1(&cpu.ram.dat[0xfff0], &cpu.ram.dat[0xfff1]);
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if(cpu.counter > 256)
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return error("Reached bounds", cpu.counter);
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}
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/*eval frame */
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printf("\nPhase: frame\n");
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setflag(FLAG_HALT, 0);
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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_SHORT) != 0,
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getflag(FLAG_SIGN) != 0,
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getflag(FLAG_TRAPS) != 0);
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printf("\n");
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return 1;
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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.", 0);
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if(!(f = fopen(argv[1], "rb")))
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return error("Missing input.", 0);
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if(!start(f))
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return error("Program error", 0);
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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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