c - 如何将信息从 txt 文件传输到结构的动态 vector

Question

我正在尝试将驱动程序的信息从 txt 文件传输到结构的动态 vector 。我有一个像这样的txt文件:

Paulo Andrade
2  23  12  1995  76  0.5  0 

Faisca
3   1   1  1980  50  9.5  1    

Diana Alves Pombo
4  1  10  1990  55  4.5  0 

Ana Luisa Freitas
7  12  7  1976  68  1.0  3

第一行是司机的名字，第二行是司机的身份证、出生日期、体重、经历和处罚。

我需要创建带有动态 vector 的结构来保存每个驱动程序的信息，但我的问题是动态 vector 。有人可以帮我吗？

Answer 1

它是动态分配的数组，使用malloc然后realloc来更改(增加)其大小

例如:

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

typedef struct Driver {
  char * name;
  int ID;
  int day;
  int month;
  int year;
  int weight;
  float experience;
  int punishment;
} Driver;

int main(int argc, char ** argv)
{
  if (argc != 2) {
    printf("Usage : %s <file>\n", *argv);
    return -1;
  }
  
  FILE * fp = fopen(argv[1], "r");
  
  if (fp == NULL) {
    fprintf(stderr, "cannot open '%s'\n", argv[1]);
    return -1;
  }
  
  char line[128];
  Driver * drivers = malloc(0); /* initial allocation, here empty */
  int n = 0;
  
  while (fgets(line, sizeof(line), fp) != NULL) {
    /* remove \n */
    char * p = strchr(line, '\n');
    
    if (p != NULL)
      *p = 0;
    
    drivers = realloc(drivers, (n + 1) * sizeof(Driver)); /* resize to add one element */
    
    Driver * d = &drivers[n++];
    
    d->name = strdup(line);
    if ((fgets(line, sizeof(line), fp) == NULL) ||
        (sscanf(line, "%d %d %d %d %d %f %d",
                &d->ID, &d->day, &d->month, &d->year,
                &d->weight, &d->experience, &d->punishment)
        != 7)) {
      fprintf(stderr, "invalid file driver #%d\n", n);
      fclose(fp);
      return -1;
    }
  }
  fclose(fp);
  
  /* check */
  Driver * sup = drivers + n;
  
  for (Driver * d = drivers; d != sup; ++d)
    printf("%s : ID=%d birthdate=%d/%d/%d weight=%d experience=%f punishment=%d\n",
           d->name, d->ID,
           d->day, d->month, d->year,
           d->weight, d->experience, d->punishment);

  return 0;
}

编译和执行:

pi@raspberrypi:/tmp $ gcc -g -pedantic -Wextra -Wall d.c
pi@raspberrypi:/tmp $ cat f
Paulo Andrade
2  23  12  1995  76  0.5  0 
Faisca
3   1   1  1980  50  9.5  1    
Diana Alves Pombo
4  1  10  1990  55  4.5  0 
Ana Luisa Freitas
7  12  7  1976  68  1.0  3
pi@raspberrypi:/tmp $ ./a.out f
Paulo Andrade : ID=2 birthdate=23/12/1995 weight=76 experience=0.500000 punishment=0
Faisca : ID=3 birthdate=1/1/1980 weight=50 experience=9.500000 punishment=1
Diana Alves Pombo : ID=4 birthdate=1/10/1990 weight=55 experience=4.500000 punishment=0
Ana Luisa Freitas : ID=7 birthdate=12/7/1976 weight=68 experience=1.000000 punishment=3
pi@raspberrypi:/tmp $ 

初始malloc(0)可能看起来很奇怪，但需要在使用realloc之后或者如果您愿意的话Driver * drivers = NULL; 。我每次只多分配一个条目，也可以一开始malloc超过0个元素，然后在需要时再realloc多一个元素，以获得更好的性能，以防有最终数组中有很多元素。

警告drivers = realloc(drivers, ...)可以或不移动分配的数组以便能够找到更多空间，但您总是需要假设它的地址发生变化，这就是为什么我在 drivers

中重新分配结果