在C中传递子字符串

Question

我昨晚花了很多时间调试这段代码.我有两个数据文本文件,都包含18000个字符.我想将这些18000分成两个子串,每个子串100个,这使得180次迭代.

棘手的是,在前180次迭代中,两个子串的大小都很好.在18次迭代之后,子串的大小为0.

两个文件都正确打开.我可以打印它们等等.我尝试以我能想到的所有可能方式分配子字符串,但到目前为止找不到解决方案.

int main(int argc, char const *argv[]) { 

    //Ive loaded two files into two strings buff1 and buff2 both size of 18000 chars
    //It works fine with small data example, I dunno why but eventually I have work with much more bigger data set
    //Id like to divide them into 100 char long pieces and do some stuff with that 

    char *substrA;      //substring for buff1
    char *substrB;      //substring for buff2

    substrA = malloc((wlen+1)*sizeof(char));        //word length wlen=100
    substrA = malloc((wlen+1)*sizeof(char));

    for (int i= 0; i <numOfSubProblems; ++i){   //numOfSubProblems = 18000/100

        strncpy(substrA, buff1+i*wlen, wlen);
        strncpy(substrB, buff2+i*wlen, wlen);
        substrA[wlen] = '\0';
        substrA[wlen] = '\0';

        int lenA = strlen(substrA);
        int lenB = strlen(substrB);
        printf("STRA a STR B: %d %d \n",lenA,lenB);

        DoSomething(substrA,substrB,i);  //some parser and other functionality
    }
    return 0;
}

Answer 1

strncpy不会终止目标字符串.所以你必须这样做

strncpy(subA, buff1+i*wlen, wlen);
subA[wlen] = '\0';
strncpy(subB, buff2+i*wlen, wlen);
subB[wlen] = '\0';

否则你不能使用strlen,并且在这样做的时候访问它们后面的缓冲区.