03.编程实现strcpy

 03. 编程实现strcpy

    我们知道strcpy是字符串复制函数。

    定义于：

string.h

声明：

char *strcpy(char *dest, const char *src)

原型：

#ifdef _NC_RESTRICT
char *strcpy(char *restrict dest, const char *restrict src)
#else
char *strcpy(char *dest, const char* src)
#endif
{
    char *ret = dest;
    while (*dest++ = *src++)
        ;
    return ret;
}

1. 使用strlen实现

/*
 * exercise01.c
 *
 * Created on: 2012-11-5
 * Author: xiaobin
 *
 * Huawei face questions
 */

#include <stdio.h>
#include <string.h>

char *strcpy1(char *dest, const char *src)
{

    char *ret = dest;
    int len = strlen(src);

    int i = 0;
    while (len-- != 0) {
     ret[i] = src[i];
        i++;
    }

    return ret;
}


int main(int argc, char* argv[])
{
    char *s = "hello,world";
    char *d;
    strcpy1(d, s);
    printf("%s\n", d);
    return 0;
}

 计算源串的长度，然后循环赋值。

2. 无strlen实现

/*
 * exercise01.c
 *
 * Created on: 2012-11-5
 * Author: xiaobin
 *
 * Huawei face questions
 */

#include <stdio.h>
#include <string.h>

char *strcpy1(char *dest, const char *src)
{

    char *ret = dest;

    int i = 0;
    while (*src != 0) {
     ret[i] = *src;
        i++;
     *src++;
    }

    return ret;
}


int main(int argc, char* argv[])
{
    char *s = "hello,world";
    char *d;
    strcpy1(d, s);
    printf("%s\n", d);
    return 0;
}

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