用C语言写一个串的堆分配存储结构

下面是一个用C语言实现的串的堆分配存储结构的示例代码：

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

typedef struct HString {
    char *ch; //指向字符串所在空间首地址
    int length; //记录字符串长度
} HString;

//初始化一个空串
void InitString(HString *s) {
    s->ch = (char *)malloc(sizeof(char));
    s->length = 0;
}

//销毁串
void DestroyString(HString *s) {
    free(s->ch);
    s->ch = NULL;
    s->length = 0;
}

//清空串
void ClearString(HString *s) {
    s->ch[0] = '\0';
    s->length = 0;
}

//判断串是否为空
int StringEmpty(HString *s) {
    return s->length == 0;
}

//获取串的长度
int StringLength(HString *s) {
    return s->length;
}

//复制串
void StringCopy(HString *s, HString *t) {
    if (s->ch) {
        free(s->ch);
        s->ch = NULL;
    }
    s->ch = (char *)malloc(sizeof(char) * (t->length + 1));
    strcpy(s->ch, t->ch);
    s->length = t->length;
}

//比较串
int StringCompare(HString *s, HString *t) {
    int i = 0;
    while (i < s->length && i < t->length) {
        if (s->ch[i] != t->ch[i]) {
            return s->ch[i] - t->ch[i];
        }
        i++;
    }
    return s->length - t->length;
}

//连接串
void StringConcat(HString *s, HString *t) {
    int len = s->length + t->length;
    char *new_ch = (char *)malloc(sizeof(char) * (len + 1));
    strcpy(new_ch, s->ch);
    strcat(new_ch, t->ch);
    free(s->ch);
    s->ch = new_ch;
    s->length = len;
}

//获取子串
void SubString(HString *sub, HString *s, int pos, int len) {
    if (pos < 1 || pos > s->length || len < 0 || pos + len - 1 > s->length) {
        printf("Error: invalid position or length.\n");
        return;
    }
    if (sub->ch) {
        free(sub->ch);
        sub->ch = NULL;
    }
    sub->ch = (char *)malloc(sizeof(char) * (len + 1));
    strncpy(sub->ch, s->ch + pos - 1, len);
    sub->ch[len] = '\0';
    sub->length = len;
}

//在串中查找子串
int Index(HString *s, HString *t, int pos) {
    int i = pos;
    int j = 1;
    while (i <= s->length && j <= t->length) {
        if (s->ch[i - 1] == t->ch[j - 1]) {
            i++;
            j++;
        } else {
            i = i - j + 2;
            j = 1;
        }
    }
    if (j > t->length) {
        return i - t->length;
    } else {
        return 0;
    }
}

//输出串
void PrintString(HString *s) {
    printf("%s\n", s->ch);
}

int main() {
    HString s, t, sub;
    InitString(&s);
    InitString(&t);
    InitString(&sub);

    //初始化串
    s.ch = "hello";
    s.length = strlen(s.ch);
    t.ch = "world";
    t.length = strlen(t.ch);

    //测试各个操作
    StringCopy(&sub, &s);
    StringConcat(&sub, &t);
    PrintString(&sub);
    SubString(&sub, &s, 2, 3);
    PrintString(&sub);
    printf("%d\n", Index(&s, &t, 1));

    //销毁串
    DestroyString(&s);
    DestroyString(&t);
    DestroyString(&sub);

    return 0;
}