漫话Redis源码之一百一十五

涛歌依旧

于 2022-04-24 22:38:09 发布

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分类专栏： S1: C/C++ s2: 实用代码文章标签： c++

本文链接：https://blog.youkuaiyun.com/stpeace/article/details/124087397

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S1: C/C++ 同时被 2 个专栏收录

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本文介绍了如何使用C语言定义宏和函数，处理命令行参数，包括解析选项如版本显示、文件操作等。重点在于doargs函数的实现，展示了如何根据选项执行不同的操作。

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这里的功能比较直观，有点C基础的都能懂：

#define	IS(s)	(strcmp(argv[i],s)==0)

static int doargs(int argc, char* argv[])
{
 int i;
 int version=0;
 if (argv[0]!=NULL && *argv[0]!=0) progname=argv[0];
 for (i=1; i<argc; i++)
 {
  if (*argv[i]!='-')			/* end of options; keep it */
   break;
  else if (IS("--"))			/* end of options; skip it */
  {
   ++i;
   if (version) ++version;
   break;
  }
  else if (IS("-"))			/* end of options; use stdin */
   break;
  else if (IS("-l"))			/* list */
   ++listing;
  else if (IS("-o"))			/* output file */
  {
   output=argv[++i];
   if (output==NULL || *output==0) usage(LUA_QL("-o") " needs argument");
   if (IS("-")) output=NULL;
  }
  else if (IS("-p"))			/* parse only */
   dumping=0;
  else if (IS("-s"))			/* strip debug information */
   stripping=1;
  else if (IS("-v"))			/* show version */
   ++version;
  else					/* unknown option */
   usage(argv[i]);
 }
 if (i==argc && (listing || !dumping))
 {
  dumping=0;
  argv[--i]=Output;
 }
 if (version)
 {
  printf("%s  %s\n",LUA_RELEASE,LUA_COPYRIGHT);
  if (version==argc-1) exit(EXIT_SUCCESS);
 }
 return i;
}

#define toproto(L,i) (clvalue(L->top+(i))->l.p)

static const Proto* combine(lua_State* L, int n)
{
 if (n==1)
  return toproto(L,-1);
 else
 {
  int i,pc;
  Proto* f=luaF_newproto(L);
  setptvalue2s(L,L->top,f); incr_top(L);
  f->source=luaS_newliteral(L,"=(" PROGNAME ")");
  f->maxstacksize=1;
  pc=2*n+1;
  f->code=luaM_newvector(L,pc,Instruction);
  f->sizecode=pc;
  f->p=luaM_newvector(L,n,Proto*);
  f->sizep=n;
  pc=0;
  for (i=0; i<n; i++)
  {
   f->p[i]=toproto(L,i-n-1);
   f->code[pc++]=CREATE_ABx(OP_CLOSURE,0,i);
   f->code[pc++]=CREATE_ABC(OP_CALL,0,1,1);
  }
  f->code[pc++]=CREATE_ABC(OP_RETURN,0,1,0);
  return f;
 }
}

static int writer(lua_State* L, const void* p, size_t size, void* u)
{
 UNUSED(L);
 return (fwrite(p,size,1,(FILE*)u)!=1) && (size!=0);
}

struct Smain {
 int argc;
 char** argv;
};

static int pmain(lua_State* L)
{
 struct Smain* s = (struct Smain*)lua_touserdata(L, 1);
 int argc=s->argc;
 char** argv=s->argv;
 const Proto* f;
 int i;
 if (!lua_checkstack(L,argc)) fatal("too many input files");
 for (i=0; i<argc; i++)
 {
  const char* filename=IS("-") ? NULL : argv[i];
  if (luaL_loadfile(L,filename)!=0) fatal(lua_tostring(L,-1));
 }
 f=combine(L,argc);
 if (listing) luaU_print(f,listing>1);
 if (dumping)
 {
  FILE* D= (output==NULL) ? stdout : fopen(output,"wb");
  if (D==NULL) cannot("open");
  lua_lock(L);
  luaU_dump(L,f,writer,D,stripping);
  lua_unlock(L);
  if (ferror(D)) cannot("write");
  if (fclose(D)) cannot("close");
 }
 return 0;
}

int main(int argc, char* argv[])
{
 lua_State* L;
 struct Smain s;
 int i=doargs(argc,argv);
 argc-=i; argv+=i;
 if (argc<=0) usage("no input files given");
 L=lua_open();
 if (L==NULL) fatal("not enough memory for state");
 s.argc=argc;
 s.argv=argv;
 if (lua_cpcall(L,pmain,&s)!=0) fatal(lua_tostring(L,-1));
 lua_close(L);
 return EXIT_SUCCESS;
}