如何根据从二进制文件读取的数据动态分配结构字段？

我有一个看起来像这样的结构：

typedef struct Student {    //dynamically allocated structure
    char *first_name;
    char *last_name;
    float grade;
}Student;

我想要做的是从二进制文件中读取数据并为first_name和last_name字段动态分配内存。从普通的.txt文件读取时，我成功完成了这项任务。这是代码：

void Read_From_File(const char *file_name, Student *p_destination, const int number_of_students)
{
    FILE *p_file = fopen(file_name, "r");
    if (!p_file)
    {
        perror("Error opening the file. \n");
        exit(EXIT_FAILURE);
    }
    int index = 0;
    while (index < number_of_students)
    {
        unsigned char buffer[256];
        fscanf (p_file, "%s", buffer);
        p_destination[index].last_name = (char*)malloc(strlen(buffer) + 1);
        strcpy(p_destination[index].last_name, buffer);

        fscanf(p_file, "%s", buffer);
        p_destination[index].first_name = (char*)malloc(strlen(buffer) + 1);
        strcpy(p_destination[index].first_name, buffer);

        fscanf(p_file, "%f", &p_destination[index].grade);
        index++;
    }
    fclose(p_file);
}

这很简单，因为fscanf可以单独读取数据并具有类型说明符，如下所示：%s 姓氏/ %s 名字/ %f 等级。我不知道如何使用fread读取单个数据，就像我使用fscanf 一样。这是我到目前为止尝试过的，但它不起作用：

int number_of_students = 0;
unsigned char buffer[256];
char file_name[10];
FILE *p_file = NULL;
Student *p_students = NULL;

printf("Enter file name. \n");
scanf("%s", file_name);

p_file = fopen(file_name, "rb");

fread(&number_of_students, sizeof(number_of_students), 1, p_file);
p_students = (Student *)malloc(number_of_students * sizeof(Student));
if (!p_students)
{
    perror("Could not allocate memory. \n");
    exit(EXIT_FAILURE);
}

for (int index = 0; index < number_of_students; ++index)
{
    fread(buffer, sizeof(char), 1, p_file);
    p_students[index].last_name = (char *)malloc(strlen(buffer) + 1);
    if (!p_students[index].last_name)
    {
        printf("Could not allocate memory. \n");
        exit(EXIT_FAILURE);
    }
    strcpy(p_students[index].last_name, buffer);

    fread(buffer, sizeof(char), 1, p_file);
    p_students[index].first_name = (char *)malloc(strlen(buffer) + 1);
    if (!p_students[index].first_name)
    {
        printf("Could not allocate memory. \n");
        exit(EXIT_FAILURE);
    }
    strcpy(p_students[index].first_name, buffer);

    fread(&p_students[index].grade, sizeof(float), 1, p_file);
}
Print_Students(p_students, number_of_students);

此外，Print_Students函数如下所示：

void Print_Students(Student *p_students, int number_of_students)
{
    printf("================================================================================================\n");
    for (unsigned int index = 0; index < number_of_students; ++index)
    {
        printf("\t\t===================== Student %d =====================\n\n", index);
        printf("Last name: %s\n", p_students[index].last_name);
        printf("First name: %s\n", p_students[index].first_name);
        printf("Grade: %.2f\n", p_students[index].grade);
    }
    printf("\n");
}

input.txt 文件如下所示：

19
Terresa Minaya 9.50
Otto Pleiman 7 
Illa Holzman 5.25
Alona Greeson 3.40
Natalya Vickrey 10
Catrina Cho 9.34
Loida Dinapoli 9.43
Neely Mcelligott 8.30
Salome Urban 8.75
Rosetta Dagenhart 9.10
Diane Cooksey 10
Novella Longmire 3
Gilberte Manganaro 4
Joye Humbert 5
Justa Larock 6
Delana Bufkin 7
Genaro Kenison 8.98
Refugio Arena 4.56
Iona Nida 7.65

我将这个文件中的数据加载到我的学生向量中，然后我根据我的向量中的数据编写了input.bin文件。我使用以下代码写入二进制文件：

void Write_To_Binary(const char *file_name, Student *p_source, const int number_of_students)
{   
    size_t successfully_written = 0;
    FILE *p_file = fopen(file_name, "wb");
    if (!p_file)
    {
        perror("Error opening the file. \n");
        exit(EXIT_FAILURE);
    }
    successfully_written = fwrite(&number_of_students, sizeof(number_of_students), 1, p_file);
    if (successfully_written != 1)
    {
        perror("Error writing to the file. \n");
        exit(EXIT_FAILURE);
    }
    successfully_written = fwrite(p_source, sizeof(Student), number_of_students, p_file);
    if (successfully_written != number_of_students)
    {
        perror("Error writing all the student data. \n");
        exit(EXIT_FAILURE);
    }
    fclose(p_file);
}

更新：我遵循了 iBug 的解决方案并且它有效。我更改了数据字段，如下所示： sizeof(last_name) last_name sizeof(first_name) first_name Grade。

我将在这里发布我用来写入 bin 文件并从中读取的函数。

这是函数Write_To_Binary

    void Write_To_Binary(const char *file_name, Student *p_source, const unsigned int number_of_students)
{
    FILE *p_file = fopen(file_name, "wb");
    if (!p_file)
    {
        perror("Error opening the file. \n");
        exit(EXIT_FAILURE);
    }

    size_t successfully_written = 0;
    successfully_written = fwrite(&number_of_students, sizeof(number_of_students), 1, p_file);
    if (successfully_written != 1)
    {
        printf("Error writing to the file. \n");
        exit(EXIT_FAILURE);
    }

    unsigned int width = 0, width1 = 0;
    for (unsigned int index = 0; index < number_of_students; ++index)
    {
        width = strlen(p_source[index].last_name) + 1;

        successfully_written = fwrite(&width, sizeof(width), 1, p_file);
        printf("Name: %s Width: %d \n", p_source[index].last_name, width);
        if (successfully_written != 1)
        {
            printf("Error writing to the file. \n");
            exit(EXIT_FAILURE);
        }

        successfully_written = fwrite(p_source[index].last_name, width, 1, p_file);
        if (successfully_written != 1)
        {
            printf("Error writing to the file. \n");
            exit(EXIT_FAILURE);
        }

        width = strlen(p_source[index].first_name) + 1;

        successfully_written = fwrite(&width, sizeof(width), 1, p_file);
        if (successfully_written != 1)
        {
            printf("Error writing to the file. \n");
            exit(EXIT_FAILURE);
        }

        successfully_written = fwrite(p_source[index].first_name, width, 1, p_file);
        if (successfully_written != 1)
        {
            printf("Error writing to the file. \n");
            exit(EXIT_FAILURE);
        }

        successfully_written = fwrite(&p_source[index].grade, sizeof(float), 1, p_file);
        if (successfully_written != 1)
        {
            printf("Error writing to the file. \n");
            exit(EXIT_FAILURE);
        }
    }

    fclose(p_file);
}

这是函数Read_From_Binary

void Read_From_Binary(const char *file_name, Student *p_destination)
{
    FILE *p_file = fopen(file_name, "rb");
    if (!p_file)
    {
        perror("Error opening file. \n");
        exit(EXIT_FAILURE);
    }

    unsigned int number_of_students = 0;
    size_t successfully_read;
    successfully_read = fread(&number_of_students, sizeof(number_of_students), 1, p_file);
    if (successfully_read != 1)
    {
        printf("Error reading the number of students. \n");
        exit(EXIT_FAILURE);
    }

    unsigned int width = 0;
    for (unsigned int index = 0; index < number_of_students; ++index)
    {
        successfully_read = fread(&width, sizeof(width), 1, p_file);
        if (successfully_read != 1)
        {
            printf("Error reading from the file. \n");
            exit(EXIT_FAILURE);
        }

        p_destination[index].last_name = (char*)malloc(width);
        if (!p_destination[index].last_name)
        {
            printf("Could not allocate memory. \n");
            exit(EXIT_FAILURE);
        }
        successfully_read = fread(p_destination[index].last_name, width, 1, p_file);
        if (successfully_read != 1)
        {
            printf("Error reading from the file. \n");
            exit(EXIT_FAILURE);
        }

        successfully_read = fread(&width, sizeof(width), 1, p_file);
        if (successfully_read != 1)
        {
            printf("Error reading from the file. \n");
            exit(EXIT_FAILURE);
        }

        p_destination[index].first_name = (char*)malloc(width);
        if (!p_destination[index].first_name)
        {
            printf("Could not allocate memory. \n");
            exit(EXIT_FAILURE);
        }
        successfully_read = fread(p_destination[index].first_name, width, 1, p_file);
        if (successfully_read != 1)
        {
            printf("Error reading from the file. \n");
            exit(EXIT_FAILURE);
        }

        successfully_read = fread(&p_destination[index].grade, sizeof(float), 1, p_file);
        if (successfully_read != 1)
        {
            printf("Error reading from the file. \n");
            exit(EXIT_FAILURE);
        }
    }

    fclose(p_file);
}