【本文连接】
http://www.cnblogs.com/hellogiser/p/strcpy_vs_memcpy.html
【分析】
strcpy和memcpy都是标准C库函数，它们有下面的特点。 strcpy提供了字符串的复制。即strcpy只用于字符串复制，并且它不仅复制字符串内容之外，还会复制字符串的结束符。
已知strcpy函数的原型是
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char *strcpy(char *dest, const char *src);
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memcpy提供了一般内存的复制。即memcpy对于需要复制的内容没有限制，因此用途更广。
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void *memcpy( void *dest, const void *src, size_t count );
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strcpy和memcpy主要有以下3方面的区别。
1、复制的内容不同。strcpy只能复制字符串，而memcpy可以复制任意内容，例如字符数组、整型、结构体、类等。
2、复制的方法不同。strcpy不需要指定长度，它遇到被复制字符的串结束符"\0"才结束，所以容易溢出。memcpy则是根据其第3个参数决定复制的长度。
3、用途不同。通常在复制字符串时用strcpy，而需要复制其他类型数据时则一般用memcpy
【代码】
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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <iostream>
using namespace std;
/*
* copy strings by \0
* (1) not check overlapping
* (2) dest mush have enough space to contain the same C string as src including the \0
* */
char *my_strcpy(char *dest, const char *src)
{
if(src == NULL || dest == NULL)
return NULL;
char *d = dest;
const char *s = src;
while((*d++ = *s++) != '\0') // notice here
;
return dest;
/* support chaining
* int len = strlen(my_strcpy(dest,src));
* */
}
/*
* not check overlapping
* optimization: copy by word(4 or 8 bytes) instead of by 1 byte
* */
void *my_memcpy(void *dest, const void *src, size_t count)
{
if(src == NULL || dest == NULL)
return NULL;
char *d = (char *)dest;
const char *s = (const char *)src;
while(count--)
{
*d ++ = *s ++;
}
return dest;
}
/*
* check overlapping
* optimization: copy by word(4 or 8 bytes) instead of by 1 byte
* */
/*
* d == s
* d <s, copying from the beginning
* d >s, copying from the end
* */
void *my_memmove(void *dest, const void *src, size_t count)
{
if(src == NULL || dest == NULL)
return NULL;
char *d = (char *)dest;
const char *s = (const char *)src;
if(d < s)
{
//copy from the beginning
while(count--)
{
*d++ = *s++;
}
}
else if(d > s)
{
//copy from the end
;
s = s + count - ;
while(count--)
{
*d-- = *s--;
}
}
else
{
// do nothing
}
return dest;
}
void test_case()
{
char str1[] = "sample string";
];
];
my_strcpy(str2, str1);
my_strcpy(str3, "copy successful");
printf("str1: %s\nstr2: %s\nstr3: %s\n", str1, str2, str3);
}
void test_case2()
{
];
const char *src = "hello";
my_memcpy(dest, src, strlen(src) + );
printf("%s\n", dest);
}
int main()
{
test_case();
test_case2();
;
}
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【参考】
http://www.cnblogs.com/stoneJin/archive/2011/09/16/2179248.html
http://www.cplusplus.com/reference/cstring/strcpy/
