The method of C language functions having a variable size parameter

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Provided: ANSI C in order to improve portability, provides ease of use a set of macros vararg through the header file stdarg.h

We consider writing a copycat version of the printf (), named tiny_printf ()
The first parameter tiny_printf () to specify the type of follow-up of each parameter, the second parameter specifies the start value required output
tiny_printf ( "sdd", " result .. ", 3, 5) ;

#include <stdio.h>
#include <stdarg.h>
#include <assert.h>

void tiny_printf(char *format, ...)   //原型声明的参数中出现…， 对于这部分的参数是不会做类型检查的
{
    int i;
    va_list ap;    //typedef char *  va_list;

    va_start(ap, format);    //使指针 ap 指向参数 format 的下一个位置,得到了第一个参数
    for (i = 0; format[i] != '\0'; i++) {
        switch (format[i]) {
            case 's':
            printf("%s ", va_arg(ap, char*));   
            break;
            case 'd':
            printf("%d ", va_arg(ap, int));
            break;
            default:
            assert(0);
        }
    }
    va_end(ap);  //标准里指出了对于具有 va_start()的函数需要写 va_end()
    putchar('\n');
}

int main(void)
{
    tiny_printf("sdd", "result..", 3, 5);

    return 0;
}

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