基本编程元素用到的技巧

最新推荐文章于 2025-12-22 11:29:49 发布

原创最新推荐文章于 2025-12-22 11:29:49 发布 · 424 阅读

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当你想了解一个函数（或方法）在做什么，你可以如下策略：

根据函数名猜测
阅读函数头的注释
分析函数是如何被使用
阅读函数体內的代码
查询外部程序文档
养成碰到库函数就阅读文档的习惯（传送门如何查看函数）

注释是重点啊啊啊！强行观看，下面上“热腾腾”开源代码

      <span style="font-size:18px;">  /*<span style="color: rgb(255, 0, 0);">返回值储存于整型变量中</span>*/
	while ((<span style="color: rgb(255, 0, 0);">c</span> = getopt (argc, argv, "t:")) != -1) {
		switch (c) {
		case 't':
			getstops(optarg);
			break;
                /*<span style="color: rgb(255, 0, 0);">二者共用一段代码</span>*/
		case '?':
		default:
			usage();
			/* NOTREACHED */
		}
	}
</span>

<span style="font-size:18px;">	        case 'a':
			fts_options |= FTS_SEEDOT;
			/* <span style="color:#ff0000;">FALLTHROUGH </span>
                        <span style="color:#ff0000;">没有break，return，continue时，用一条注释进行说明.接着判断'</span><span style="color: rgb(255, 0, 0); font-family: SimSun;">A'</span>
                        */
		case 'A':
			f_listdot = 1;
			break</span>

<span style="font-size:18px;">        case BATCH:
		writefile(time(NULL), 'b');
		break;
        /*<span style="color:#ff0000;">捕获产生意外值的程序错误提醒程序维护者</span>*/
	default:
		panic("Internal error");
		break;</span>

<span style="font-size:18px;">    while ((c = getchar()) != EOF) {
                        /*<span style="color:#ff0000;">switch语句用作程序字符处理循环的一部分</span>*/
			switch (c) {
			case '\t':
				if (nstops == 0) {
					do {
						putchar(' ');
						column++;
					} while (column & 07);
					continue;
				}
				if (nstops == 1) {
					do {
						putchar(' ');
						column++;
					} while (((column - 1) % tabstops[0]) != (tabstops[0] - 1));
					continue;
				}
				for (n = 0; n < nstops; n++)
					if (tabstops[n] > column)
						break;
				if (n == nstops) {
					putchar(' ');
					column++;
					continue;
				}
				while (column < tabstops[n]) {
					putchar(' ');
					column++;
				}
				continue;

			case '\b':
				if (column)
					column--;
				putchar('\b');
				continue;
                        /*<span style="color:#ff0000;">所有其他字符*</span>/
			default:
				putchar(c);
				column++;
				continue;

			case '\n':
				putchar(c);
				column = 0;
				continue;
			}
		}
	} while (argc > 0);
	exit(0);
}
</span>

<span style="font-size:18px;">if ((<span style="color:#ff0000;">dd = opendir(dir)) == NULL)</span>
		return (CC_ERROR);
	words = sl_init();
        /*<span style="color:#ff0000;">循环处理库函数返回的结果集</span>*/
	for (<span style="color:#ff0000;">dp = readdir(dd); dp != NULL; dp = readdir(dd)</span>)</span>

<span style="font-size:18px;"><span style="color:#ff0000;">for (cnt = 1, t = p; cnt <= cnt_orig; ++t, ++cnt)</span> {
		t->lno = lno;
		t->coff = 0;
		t->soff = cnt;
		SMAP_FLUSH(t);
		if (vs_line(sp, t, NULL, NULL))
			return (1);
	} </span>

<span style="font-size:18px;">void
transition(s)
	state_t s;
{
    /*<span style="color:#ff0000;">无限循环控制所有的unix进程
     在大多的情况下，无限循环用来表达循环开始或结束时退出条件无法确定的循环
     return，break，exit退出
</span>     */
     for (;;) {
		s = (state_t) (*s)();
#ifndef LETS_GET_SMALL
		quiet = 0;
#endif
	}
}
</span>

<span style="font-size:18px;">static void
getstops(cp)
	char *cp;
{
	int i;

	nstops = 0;
	for (;;) {
		i = 0;
               /*将字符串转换为数字*/
		while (*cp >= '0' && *cp <= '9')
			i = i * 10 + *cp++ - '0';
		/*<span style="color:#ff0000;">德摩根法则解开复杂的逻辑表达式*</span>/
		if (i <= 0 || i > 256) {
                /*<span style="color:#ff0000;">抱怨不合理的说明</span>*/
bad:
			fprintf(stderr, "Bad tab stop spec\n");
			exit(1);
		}
		/*<span style="color:#ff0000;">短路求值*</span>/
		if (nstops > 0 && i <= tabstops[nstops-1])
			goto bad;
		tabstops[nstops++] = i;
		/*<span style="color:#ff0000;">跳出循环，局部重构*</span>/
        if (*cp == 0)
		break;
	else if (*cp != ',' && *cp != ' ')
		goto bad;
        else
		cp++;
	}
}
</span>

<span style="font-size:18px;">/*<span style="color:#ff0000;">短路求值，只有t ＝= NULL时，才计算t->type的值*</span>/
if (t != NULL && t->type != TEOF && interactive && really_exit)
</span>

<span style="font-size:18px;">/*<span style="color:#ff0000;">移位运算符计算</span>*/
    n = ((dp - cp) << 2) + 1; /* 4 times + NULL */
</span>

<span style="font-size:18px;">int
atmresolve(rt, m, dst, desten)

register struct rtentry *rt;
struct mbuf *m;
register struct sockaddr *dst;
/*<span style="color:#ff0000;">有时也用标有in或out的注释来标记引用参数*/</span>
register struct atm_pseudohdr *desten;	/<span style="color:#ff0000;">* OUT *</span>/

{</span>

</pre><pre name="code" class="cpp"><span style="font-size:18px;">
</span>

<span style="font-size:18px;">     /*<span style="color: rgb(255, 0, 0);">初始化栈</span>*/
	stackp = de_stack;

	while ((code = getcode(zs)) > -1) {

		if ((code == CLEAR) && block_compress) {
			for (code = 255; code >= 0; code--)
				tab_prefixof(code) = 0;
			clear_flg = 1;
			free_ent = FIRST - 1;
			if ((code = getcode(zs)) == -1)	/* O, untimely death! */
				break;
		}
		incode = code;

		/* Special case for KwKwK string. */
		if (code >= free_ent) {
                        /*<span style="color: rgb(255, 0, 0);">将finchar压栈*</span>/
			*stackp++ = finchar;
			code = oldcode;
		}

		/* Generate output characters in reverse order. */
		while (code >= 256) {
			*stackp++ = tab_suffixof(code);
			code = tab_prefixof(code);
		}
		*stackp++ = finchar = tab_suffixof(code);

		/* And put them out in forward order.  */
middle:		do {
			if (count-- == 0)
				return (num);
                        /*<span style="color: rgb(255, 0, 0);">将栈顶内容弹到*bp中</span>*/
			*bp++ = *--stackp;
          } /*<span style="color: rgb(255, 0, 0);">检查栈是否为空*</span>/
        while (stackp > de_stack);</span><pre name="code" class="cpp" style="font-size: 18px;">利用指针方式访问基于数组的栈

<span style="font-size:18px;">char *inet_ntoa(ad)
  struct in_addr ad;
{
  unsigned long int s_ad;
  int a, b, c, d;
  /*<span style="color:#ff0000;">防止返回的数组的内存空间被重写*</span>/
  static char addr[20];
  
  s_ad = ad.s_addr;
  d = s_ad % 256;
  s_ad /= 256;
  c = s_ad % 256;
  s_ad /= 256;
  b = s_ad % 256;
  a = s_ad / 256;
  sprintf(addr, "%d.%d.%d.%d", a, b, c, d);
  
  return addr;
}</span>