字符串操作

#include <iostream>//内存拷贝 size 字节void* _memcpy(void* to, void* from, size_t size){    if (to == nullptr || from == nullptr || size <= 0){        return nullptr;    }    else    {        unsigned char* c_to = (unsigned char*)to;        unsigned char* c_from = (unsigned char*)from;        while (size-- > 0){            *c_to++ = *c_from++;        }        return to;    }}//字符串拷贝包括'\0'char* _strcpy(char* strDes, char const* strSrc){    if (strDes == nullptr || strSrc == nullptr){        return nullptr;    }    else{        char* str = strDes;        while ((*str++ = *strSrc++) != '\0');        return strDes;    }}//字符串的长度int strlength(const char* str){    if(str == nullptr)    {        return -1;    }    int max_int = ~(1 << (sizeof(int)*8 - 1));    const char* p = str;//暂存    while (*str != '\0'){        if (str - p + 1 > max_int){            return -1;        }        ++str;    }    return int(str - p);}//内存拷贝、安全的void* _memmove(void* to, void* from, size_t size){    if (to == nullptr || from == nullptr || size <= 0){        return nullptr;    }    else{        unsigned char* c_to = (unsigned char*)to;        unsigned char* c_from = (unsigned char*)from;        if (c_to < c_from)//目的地地址 < 源地地址 从头拷贝        {            while ((*c_to++ = *c_from++) != '\0');                  }        else{            while (size > 0){                *(c_to + size - 1) = *(c_from + size - 1);//从尾拷贝                --size;            }        }        return to;    }}//字符串翻转char* stringReserve(char* str){    if (str == nullptr){        return nullptr;    }    int strLen = strlen(str);    char* last = str + strLen - 1;    char* first = str;    while (first < last){        *first ^= *last;        *last ^= *first;        *first ^= *last;        ++first;        --last;    }    return str;}//字符串翻转递归算法char* stringReverse2(char* str, int len){    if (str == nullptr || len <= 1){        return str;    }    else{        *str ^= *(str + len - 1);        *(str + len - 1) ^= *str;        *str ^= *(str + len - 1);        return stringReverse2(str + 1, len - 2) - 1;    }}//字符串翻转但每个单词不翻转void stringTurn(char* str){    if (str == nullptr){        return;    }    char* pLen = str;    while (*pLen++ != '\0');    pLen -= 2;    char* fir = str;    while (fir < pLen){        *fir ^= *pLen;        *pLen ^= *fir;        *fir ^= *pLen;        ++fir;        --pLen;    }    while (*str != '\0' && *str == ' ')++str;    if (*str == '\0'){        return;    }    char* start = str;    while (*str++ != '\0'){        if (*str == ' ' || *str == '\0'){            char* end = str - 1;            while (start < end){                *start ^= *end;                *end ^= *start;                *start ^= *end;                ++start;                --end;            }            start = str + 1;        }    }}//翻转单词char* turnword(char* str){    if (str == nullptr){ return str; }    char* res = str;    while (*str != '\0' && *str == ' ')++str;//排除空格    if (*str == '\0')return str;    char* start = str;//单词的开始    while (*str++ != '\0'){        if (*str == '\0' || *str == ' '){//单词结束            char* end = str - 1;            while (start < end){//翻转单词                *start ^= *end;                *end ^= *start;                *start ^= *end;                --end;                ++start;            }            start = str + 1;        }    }    return res;}int main(){    char c_from[] = "ye chao";      char c_to[20];    _memcpy(c_to, c_from, sizeof(c_from) + 1);    std::cout << c_to << std::endl;    c_to[5] = '\0';    std::cout << c_to << std::endl;    std::cout << strlength("\0") << std::ends << strlength(c_from) << std::endl;    int memoryMove[10] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 0 };    _memmove(memoryMove+2, memoryMove , sizeof(int) * 4);    for (int i = 0; i < 10; i++)    {        std::cout << memoryMove[i] << " ";    }    char p[] = "12345";    std::cout << stringReserve(p) << std::endl;    char pp[] = "1234567890";    std::cout << stringReverse2(pp, strlen(pp)) <<std::endl;    char erre[] = "     123 45 abc      lixi  i";    std::cout << erre << std::endl;    stringTurn(erre);    std::cout << erre;    return 0;}