D语言转C语言：字符串替换函数的实现和性能对比

#include <stdio.h> #include <string.h> #include <stdlib.h> #include <ctype.h> #include <time.h>

// 判断两个字符是否相等，根据 isCaseSensitive 参数决定是否区分大小写 int charEqual(char a, char b, int isCaseSensitive) { if (isCaseSensitive) { return a == b; } else { return tolower(a) == tolower(b); } }

// 在字符串 haystack 中查找第一次出现 needle 的位置，返回指向该位置的指针，如果找不到则返回 null char* strstrCase(char* haystack, const char* needle, int isCaseSensitive) { if (!haystack || !needle || !*needle) { return haystack; }

size_t haystackLen = strlen(haystack);
size_t needleLen = strlen(needle);

if (needleLen > haystackLen)
{
    return NULL;
}

if (isCaseSensitive)
{
    return strstr(haystack, needle);
}

for (size_t i = 0; i <= haystackLen - needleLen; i++)
{
    int found = 1;
    for (size_t j = 0; j < needleLen; j++)
    {
        if (!charEqual(haystack[i + j], needle[j], isCaseSensitive))
        {
            found = 0;
            break;
        }
    }
    if (found)
    {
        return haystack + i;
    }
}

return NULL;

}

char* replaceCstr(const char* allStr, const char* searchStr, const char* replaceStr, int isCaseSensitive) { if (!allStr || !searchStr || !replaceStr || !searchStr) { return (char)allStr; }

char* result = NULL;

size_t searchStrLength = strlen(searchStr);
size_t replaceStrLength = strlen(replaceStr);
size_t count = 0;
char* p = (char*)allStr;

while ((p = strstrCase(p, searchStr, isCaseSensitive)) != NULL)
{
    count++;
    p += searchStrLength;
}

if (count == 0)
{
    return (char*)allStr;
}

size_t newStrLength = strlen(allStr) + count * (replaceStrLength - searchStrLength);
result = (char*) malloc(newStrLength + 1);

char* q = result;
p = (char*)allStr;

while (count-- > 0)
{
    char* r = strstrCase(p, searchStr, isCaseSensitive);
    long length = r - p;

    memmove(q, p, length);
    q += length;

    memcpy(q, replaceStr, replaceStrLength);
    q += replaceStrLength;

    p = r + searchStrLength;
}

strcpy(q, p);

return result;

}

int main() { clock_t start = clock();

char str[] = "hello, world!";
const char* oldptr = str;
char* now = NULL;
for (int ii = 0; ii < 10000000; ii++)
{
    now = replaceCstr(oldptr,"o","O",1);
    free(now);
    now = replaceCstr(oldptr,"l","1",1);
    free(now);
    now = replaceCstr(oldptr,",","",1);
    free(now);
    now = replaceCstr(oldptr,"!","",1);
    free(now);
    //str = str.replaceString("o", "0").replaceString("l", "1").replaceString(",", "").replaceString("!", "");
}

clock_t end = clock();
double time_spent = (double)(end - start) / CLOCKS_PER_SEC;
printf("C语言程序运行时间  ：%f\n", time_spent);

return 0;

}