自己实现虚拟机--推荐一个小而美简历项目（源码和实现讲解）

#include <stdio.h>#include <stdlib.h>#include <stdint.h>#include <string.h>#include <stdbool.h>
#include "vm_dbg.h"
#define NOPS (16)
#define OPC(i) ((i)>>12)#define DR(i) (((i)>>9)&0x7)#define SR1(i) (((i)>>6)&0x7)#define SR2(i) ((i)&0x7)#define FIMM(i) ((i>>5)&01)#define IMM(i) ((i)&0x1F)#define SEXTIMM(i) sext(IMM(i),5)#define FCND(i) (((i)>>9)&0x7)#define POFF(i) sext((i)&0x3F, 6)#define POFF9(i) sext((i)&0x1FF, 9)#define POFF11(i) sext((i)&0x7FF, 11)#define FL(i) (((i)>>11)&1)#define BR(i) (((i)>>6)&0x7)#define TRP(i) ((i)&0xFF)
bool running = true;
typedef void (*op_ex_f)(uint16_t i);typedef void (*trp_ex_f)();
enum { trp_offset = 0x20 };enum regist { R0 = 0, R1, R2, R3, R4, R5, R6, R7, RPC, RCND, RCNT };enum flags { FP = 1 << 0, FZ = 1 << 1, FN = 1 << 2 };
uint16_t mem[UINT16_MAX] = {0};uint16_t reg[RCNT] = {0};uint16_t PC_START = 0x3000;
static inline uint16_t mr(uint16_t address) { return mem[address];  }static inline void mw(uint16_t address, uint16_t val) { mem[address] = val; }static inline uint16_t sext(uint16_t n, int b) { return ((n>>(b-1))&1) ? (n|(0xFFFF << b)) : n; }static inline void uf(enum regist r) {    if (reg[r]==0) reg[RCND] = FZ;    else if (reg[r]>>15) reg[RCND] = FN;    else reg[RCND] = FP;}static inline void add(uint16_t i)  { reg[DR(i)] = reg[SR1(i)] + (FIMM(i) ? SEXTIMM(i) : reg[SR2(i)]); uf(DR(i)); }static inline void and(uint16_t i)  { reg[DR(i)] = reg[SR1(i)] & (FIMM(i) ? SEXTIMM(i) : reg[SR2(i)]); uf(DR(i)); }static inline void ldi(uint16_t i)  { reg[DR(i)] = mr(mr(reg[RPC]+POFF9(i))); uf(DR(i)); }static inline void not(uint16_t i)  { reg[DR(i)]=~reg[SR1(i)]; uf(DR(i)); }static inline void br(uint16_t i)   { if (reg[RCND] & FCND(i)) { reg[RPC] += POFF9(i); } }static inline void jsr(uint16_t i)  { reg[R7] = reg[RPC]; reg[RPC] = (FL(i)) ? reg[RPC] + POFF11(i) : reg[BR(i)]; }static inline void jmp(uint16_t i)  { reg[RPC] = reg[BR(i)]; }static inline void ld(uint16_t i)   { reg[DR(i)] = mr(reg[RPC] + POFF9(i)); uf(DR(i)); }static inline void ldr(uint16_t i)  { reg[DR(i)] = mr(reg[SR1(i)] + POFF(i)); uf(DR(i)); }static inline void lea(uint16_t i)  { reg[DR(i)] =reg[RPC] + POFF9(i); uf(DR(i)); }static inline void st(uint16_t i)   { mw(reg[RPC] + POFF9(i), reg[DR(i)]); }static inline void sti(uint16_t i)  { mw(mr(reg[RPC] + POFF9(i)), reg[DR(i)]); }static inline void str(uint16_t i)  { mw(reg[SR1(i)] + POFF(i), reg[DR(i)]); }static inline void rti(uint16_t i) {} // unusedstatic inline void res(uint16_t i) {} // unusedstatic inline void tgetc() { reg[R0] = getchar(); }static inline void tout() { fprintf(stdout, "%c", (char)reg[R0]); }static inline void tputs() {    uint16_t *p = mem + reg[R0];    while(*p) {        fprintf(stdout, "%c", (char)*p);        p++;    }}static inline void tin() { reg[R0] = getchar(); fprintf(stdout, "%c", reg[R0]); }static inline void tputsp() { /* Not Implemented */ }static inline void thalt() { running = false; } static inline void tinu16() { fscanf(stdin, "%hu", &reg[R0]); }static inline void toutu16() { fprintf(stdout, "%hu\n", reg[R0]); }trp_ex_f trp_ex[8] = { tgetc, tout, tputs, tin, tputsp, thalt, tinu16, toutu16 };static inline void trap(uint16_t i) { trp_ex[TRP(i)-trp_offset](); }op_ex_f op_ex[NOPS] = { /*0*/ br, add, ld, st, jsr, and, ldr, str, rti, not, ldi, sti, jmp, res, lea, trap };void start(uint16_t offset) {     reg[RPC] = PC_START + offset;    while(running) {        uint16_t i = mr(reg[RPC]++);        op_ex[OPC(i)](i);    }}void ld_img(char *fname, uint16_t offset) {    FILE *in = fopen(fname, "rb");    if (NULL==in) {        fprintf(stderr, "Cannot open file %s.\n", fname);        exit(1);        }    uint16_t *p = mem + PC_START + offset;    fread(p, sizeof(uint16_t), (UINT16_MAX-PC_START), in);    fclose(in);}int main(int argc, char **argv) {    ld_img(argv[1], 0x0);    fprintf(stdout, "Occupied memory after program load:\n");    fprintf_mem_nonzero(stdout, mem, UINT16_MAX);    start(0x0); // START PROGRAM    fprintf(stdout, "Occupied memory after program execution:\n");    fprintf_mem_nonzero(stdout, mem, UINT16_MAX);    fprintf(stdout, "Registers after program execution:\n");    fprintf_reg_all(stdout, reg, RCNT);    return 0;}