自己实现的字符串基本操作

 

#include "stdafx.h"



#include <stdio.h>

#include <stdlib.h>

#include <string.h>



#define TRUE   1

#define FALSE  0



#define BIG    1

#define EQUAL  0

#define SMALL -1



unsigned int strlenth(char *s)  /* 获取字符串长度 */

{

    unsigned int lenth = 0;



    if (!s)

        return 0;



    while ('\0' != s[lenth])

    {

        lenth++;

    }



    return lenth;

}



void strcopy(char **target, char *source)  /* 字符串拷贝 */

{

    unsigned int i = 0;

    unsigned int length = 0;

    char *pTmp = *target; 



    length = strlenth(source);

    while('\0' != source[i])

    {

        pTmp[i] = source[i];

        i++;

    }

    pTmp[i] = '\0';

}



int strcompare(char *s, char *t)  /* 字符串比较，s>t，则返回1；s=t，则返回0；s<t，则返回-1 */

{

    unsigned int uiIndex = 0;

    unsigned int uiLenOfS = strlenth(s);

    unsigned int uiLenOfT = strlenth(t);



    if (0 != uiLenOfS && 0 == uiLenOfT)        //如果s字符数不为0，而t字符数为0，则返回1

    {

        return BIG;

    }

    else if (0 == uiLenOfS && 0 != uiLenOfT)//如果s字符数为0，而t字符数不为0，则返回-1

    {

        return SMALL;

    }

    else if (0 == uiLenOfS && 0 == uiLenOfT)//如果s和t字符数都为0，则返回0。字符数为0的情况有空串或字符串指针为空

    {

        return EQUAL;

    }

    else                                    //s和t的字符数都不为0

    {

        /* 同时遍历两个字符串，只要有一个扫描完，就退出 */

        while ('\0' != s[uiIndex] && '\0' != t[uiIndex])

        {

            if (s[uiIndex] > t[uiIndex])

            {

                return BIG;

            }

            else if (s[uiIndex] < t[uiIndex])

            {

                return SMALL;

            }

            else 

            {

                ;

            }

            uiIndex++;

        }



        /* 扫描结束后，哪个字符串没扫描完，则说明这个字符串大；如果都扫描完了，说明相等 */

        if ('\0' != s[uiIndex] && '\0' == t[uiIndex] )

        {

            return BIG;

        }

        else if ('\0' == s[uiIndex] && '\0' != t[uiIndex] )

        {



            return SMALL;

        }

        else

        {

            return EQUAL;

        }

    }

}



void strcombine(char **s, char *t)  /* 字符串连接，将字符串t接到s后面，x为连接后的新串 */

{

    unsigned int uiLen = 0;

    char *pTmp = *s;

    if (NULL == s || NULL == t)

    {

        return;

    }



    uiLen = strlenth(pTmp) + strlenth(t);



    memcpy(pTmp + strlenth(pTmp), t, strlenth(t));

}



void strcatch(char *s, unsigned int index, unsigned int lenth, char **t)  /* 字符串截取，从第index个字符开始，截取lenth长度的字符串，并输出到字符串t */

{

    char *pTmp = *t;

    char *pSrc = s;



    if (NULL == s)

    {

        return;

    }

    if (index < 0 || lenth <= 0 || index + lenth >= strlenth(s))

    {

        return;

    }



    while (index--)

    {

        pSrc++;

    }

    memcpy(pTmp, pSrc, lenth);

}





bool strsubstr(char *s, char *sub)  /* 字符串子串查找，如果子串sub在s中存在，则返回1，否则返回0 */

{

    unsigned int uiIndexOfS = 0;

    unsigned int uiIndexOfSub = 0;

    unsigned int uiLenOfS = strlenth(s);

    unsigned int uiLenOfSub = strlenth(sub);





    if (NULL == s || NULL == sub)

    {

        return FALSE;

    }

    if (uiLenOfS < uiLenOfSub)        //如果子串长度大于原串，则返回0

    {

        return FALSE;

    }



    while ('\0' != s[uiIndexOfS])

    {

        if (s[uiIndexOfS] == sub[0])

        {

            while ('\0' != sub[uiIndexOfSub])

            {

                if (s[uiIndexOfS] != sub[uiIndexOfSub])

                {

                    return FALSE;

                }

                uiIndexOfS++;

                uiIndexOfSub++;

            }

            if ('\0' == sub[uiIndexOfSub])

            {

                return TRUE;

            }

        }

        uiIndexOfS++;

    }



    if ('\0' != sub[uiIndexOfSub])

    {

        return FALSE;

    }

    else 

    {

        return TRUE;

    }

}



int main()

{

    char str1[] = "Hello";

    char str2[] = " World";

    char str3[] = "Hello";

    char *str4 = (char*)malloc(100);

    if (!str4)

        return 0;

    memset(str4, 0, 100);

    

    char *str5 = (char*)malloc(100);

    if (!str5)

        return 0;

    memset(str5, 0, 100);



    strcopy(&str5, str1);

    strcombine(&str5, str2);

    strcatch(str5, 0, 5, &str4);

    printf("str5 = %s\n", str5);

    printf("The length of str1 is %u\n", strlenth(str1));

    printf("strcompare(str1, str2) = %d\n", strcompare(str1, str2));

    printf("strcompare(str1, str3) = %d\n", strcompare(str1, str3));

    printf("strsubstr(str5, str1) = %d\n", strsubstr(str5, str1));

    printf("Call strcatch(str5, 0, 5, &str4), str4 = %s\n", str4);

}