标准仿C语言 memset、memcpy、memmove函数(含C#版)

标准仿C语言  memset、memcpy、memmove函数

      前段时间，移植了C的网络加解密算法到C#，其中遇到很多问题，核心问题大多都是字节拷贝问题，今天有时间整理了一下相关的API，废话不多说直接贴源码:(值得注意的是memmove函数，支持数据重叠，详情参照http://blog.csdn.net/yujun_wu/article/details/4999565)

一> C++版

/* * @brief: 将dst中当前位置后面的 count 个字节用 val 替换并返回 dst * @param s- 数据内存的起始地址* @param c- 替换后的值* @param n- 要替换的长度* @return 返回原数据首地址*/void* memset(void* s, int c, size_t n){assert(s);unsigned char* p = (unsigned char*)s;while (n > 0){*p++ = (unsigned char)c;--n;}return s;}/** @brief: 用于从src拷贝count个字节到dest，如果目标区域和源区域有重叠的话，memmove能够保证源串在被覆盖之前将重叠区域的字节拷贝到目标区域中。但复制后src内容会被更改。但是当目标区域与源区域没有重叠则和memcpy函数功能相同* @param dst- 目标内存地址* @param src- 原内存地址* @param count- 要拷贝的长度* @return 返回dst地址*/void* memmove(void* dst, const void* src, size_t count){assert(dst);assert(src);void * ret = dst;if (dst <= src || (char *)dst >= ((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(ret);}/** @brief: 用于从src拷贝count个字节到dest(不能包含重叠)* @param dst- 目标内存地址* @param src- 原内存地址* @param count- 要拷贝的长度* @return 返回dst地址*/void* memcpy(void* dst, const void* src, size_t count){assert(dst);assert(src);void* ret = dst;/** copy from lower addresses to higher addresses*/while (count--){*(char *)dst = *(char *)src;dst = (char *)dst + 1;src = (char *)src + 1;}return(ret);}

二> C#版

// 标准仿C memcpy函数unsafe public void* memcpy(void* dst, void* src, uint count){System.Diagnostics.Debug.Assert(dst != null);System.Diagnostics.Debug.Assert(src != null);void* ret = dst;/** copy from lower addresses to higher addresses*/while (count-- > 0){*(char*)dst = *(char*)src;dst = (char*)dst + 1;src = (char*)src + 1;}return (ret);}// 标准仿C memmove函数unsafe public void* memmove(void* dst, void* src, uint count){System.Diagnostics.Debug.Assert(dst != null);System.Diagnostics.Debug.Assert(src != null);void* ret = dst;if (dst <= src || (char *)dst >= ((char *)src + count)){while (count-- > 0){*(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-- > 0){*(char*)dst = *(char*)src;dst = (char*)dst - 1;src = (char*)src - 1;}}return(ret);}// 标准仿C memset函数unsafe public void* memset(void* s, int c, uint n){byte* p = (byte*)s;while (n > 0){*p++ = (byte)c;--n;}return s;}