strcpy()、memcpy()、memmove()、memset()的实现

strcpy(), 字符串拷贝. char *strcpy(char *strDest, const char *strSrc) { assert((strDest!=NULL) && (strSrc !=NULL)); char *address = strDest; while( (*strDest++ = * strSrc++) != '/0') NULL ; return address ; } memcpy, 拷贝不重叠的内存块 void *memcpy(void* pvTo, void* pvFrom, size_t size) //byte是java里的变量类型 { assert(pvTo != NULL && pvFrom != NULL); void* pbTo = (byte*)pvTo; void* pbFrom = (byte*)pvFrom; /* 内存块重叠吗？如果重叠，就使用memmove */ assert(pbTo>=pbFrom+size || pbFrom>=pbTo+size); while(size-->0) *pbTo++ == *pbFrom++; return pvTo; } void *MemCopy(void *dest,const void *src,size_t count) { char *pDest=static_cast(dest); const char *pSrc=static_cast(src); if( pDest>pSrc && pDest (char*)Src + count) { while(count--) { *(char*)Dst = *(char*)Src; Dst = (char*)Dst + 1; Src = (char*)Src + 1; } } else { Dst = (char*)Dst + count - 1; Src = (char*)Src + count - 1; while(count--) { *(char*)Dst = *(char*)Src; Dst = (char*)Dst -1 ; Src = (char*)Src -1 ; } } return pDst; } void* memmove(void *dest, const void *src,size_t n) { if (n == 0) return 0; if (dest == NULL) return 0; if (src == NULL) return 0; char *psrc = (char*)src; char *pdest = (char*)dest; if((dest <= psrc) || (pdest >= psrc + n)) /*检查是否有重叠问题 */ { for(int i=0; i < n; i++) /*正向拷贝*/ { *pdest = *psrc; psrc++; pdest++; } } else /*反向拷贝*/ { psrc += n; pdest += n; for(int i=0;i0) *pvTo++=(char)c; return buffer; }