如何创建结构体数组 [英] how to create array of struct

问题描述

我想实现一个搜索表， 这是数据:

I want to implement a searching table and here's the data:

20130610    Diamond CoinMate    11.7246 15.7762 2897
20130412    Diamond Bithumb     0.209   0.2293  6128
20130610    OKCash  Bithumb     0.183   0.2345  2096
20130412    Ethereum    Chbtc   331.7282    401.486 136786
20170610    OKCash  Tidex       0.0459  0.0519  66
...

和我的代码

typedef struct data{
    int *date;
    string currency[100];
    string exchange[100];
    double *low;
    double *high;
    int *daily_cap;
} Data;

int main()
{
    FILE *fp = fopen("test_data.txt", "r");
    Data tmp[50];
    int i = 0;
    while (!feof(fp)){
        fscanf(fp, "%d%s%s%f%f%7d", &tmp[i].date, tmp[i].currency, tmp[i].exchange, &tmp[i].low, &tmp[i].high, &tmp[i].daily_cap);
        i++;
    }
    fclose(fp);
}

但是第一个问题是我无法创建一个大型数组来存储我的结构体

but the first problem is that I can't create a large array to store my struct like

Data tmp[1000000]

甚至我只尝试50个元素，完成main()时程序都会崩溃. 谁能告诉我如何解决它或给我一个更好的方法，谢谢.

and even I try just 50 elements , the program break down when finish main(). can anyone tell how to fix it or give me a better method, thanks.

推荐答案

您不能将值扫描到未分配的空间，换句话说，您需要为struct中的所有那些指针留出空间，切换到

You can not scan a value to an unallocated space, in other words, you need room for all those pointers in the struct, switch to

typedef struct data{
    int date;
    string currency[100];
    string exchange[100];
    double low;
    double high;
    int daily_cap;
} Data;

或在使用它们之前使用malloc为这些指针分配空间.

Or use malloc to assign space to those pointers before using them.

while (!feof(fp)){
   tmp[i].date = malloc(sizeof(int));
   ...

但是在这种情况下，您无需将此类成员的地址传递给fscanf，因为它们已经是指针:

But in this case, you don't need to pass the address of such members to fscanf since they are already pointers:

fscanf(fp, "%d%s%s%f%f%7d", &tmp[i].date, ..

应该是

fscanf(fp, "%d%s%s%lf%lf%7d", tmp[i].date, ...

请注意，double希望使用%lf而不是%f

Notice that double wants %lf instead of %f

这也很令人困惑:

typedef struct data{
    int *date;
    string currency[100];
    ...

string是char的typedef吗?我认为您的意思是string currency;，因为string通常是char *的别名，在这种情况下，您也需要为该成员提供空间:currency = malloc(100);

Is string a typedef of char? I think you mean string currency; since string is usually an alias of char *, in this case you need room for this member too: currency = malloc(100);

最后，看看为什么是"while(！feof(file ))"总是错吗?

简短的摘要中有太多错误，建议您阅读一本不错的C书.

There are too many errors in a short snippet, I suggest you to read a good C book.

使用动态内存更正了您的代码，该代码使您可以为大量数据保留空间(请参阅@LuisColorado的其他答案)，并使用fgets和sscanf而不是fscanf:

Your code corrected using dynamic memory that allows you to reserve space for a big amount of data (see the other answer of @LuisColorado) and using fgets and sscanf instead of fscanf:

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

typedef struct data{
    int date;
    char currency[100];
    char exchange[100];
    double low;
    double high;
    int daily_cap;
} Data;

int main(void)
{
    FILE *fp = fopen("test_data.txt", "r");
    /* Always check the result of fopen */
    if (fp == NULL) {
        perror("fopen");
        exit(EXIT_FAILURE);
    }

    Data *tmp;
    tmp = malloc(sizeof(*tmp) * 50);
    if (tmp == NULL) {
        perror("malloc");
        exit(EXIT_FAILURE);
    }

    char buf[512];
    int i = 0;
    /* Check that you don't read more than 50 lines */
    while ((i < 50) && (fgets(buf, sizeof buf, fp))) {
        sscanf(buf, "%d%99s%99s%lf%lf%7d", &tmp[i].date, tmp[i].currency, tmp[i].exchange, &tmp[i].low, &tmp[i].high, &tmp[i].daily_cap);
        i++;
    }
    fclose(fp);
    /* Always clean what you use */
    free(tmp);
    return 0;
}

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