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);
}