添加结构体以动态改变内存空间量

Question

该代码的数据结构必须是它的编写方式。我在打印和添加到内存位置时遇到问题。我认为我的添加功能可以正常工作，但我不确定。我认为我没有正确移动内存来打印和添加。

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

/********************************************
Creates more memory for size (strut * rec+1)
*********************************************/

employee *create(int record){
employee *new_employee = malloc(sizeof(employee) * (record+1));

return new_employee;    
 }

/********************************************
Copies the data from one structure to a new structure with 
size "structure" multipled by rec+1
 ***********************************************/
   employee *copy(employee *data, int record){
    employee *new_employee = create(record);

memcpy(new_employee, data, record * sizeof(employee));
/*  
int i;
    for(i = 0; i<record;i++){
        new_employee->first = data->first;
        new_employee->last = data->last;
        new_employee->start_date = data->start_date;
        new_employee->sal = data->sal;
        data++;
    }
*/  
    /********************
    Needs to free the old struct
    *********************/
    //deleteData(data, record);

return new_employee;
}
/********************************************
Function prints everything in the struct
*********************************************/
void printStruct(employee *data, int record){

employee *head = data;
employee *employeeDB = head;
int i;  
    for(i = 0; i<record; i++){
        printf("\nEntry: %d\n", i+1);           
        printf("The employee's name is %s %s\n", employeeDB->first, employeeDB->last);
        printf("The employee was hired on: %s\n", employeeDB->start_date);
        printf("The employee make $%f\n\n", employeeDB->sal);   
        employeeDB++;       
    }
}
/******************************************
Function frees the old data base
*******************************************/
void deleteData(employee *data, int record){
int i;
    for(i = 0; i<record; i++){
        free(data->first);
        free(data->last);
        free(data->start_date);
        data++;
    }
    free(data);
}
/******************************************
Adds an employee to the new structure
*******************************************/
employee *add(employee *data,char *fname, char *lname, char *date, float salary, int record){

fprintf(stderr, "\n\nEmployee data = %s for record # %d\n\n", data->first, record);
employee *head = create(record);
employee *employeeDB = head;
/*
employeeDB = copy(data, record);
fprintf(stderr, "Copied %d records\n", record);
*/

//
//      
//  
//  BUILD NEW EMPLOYEE
    employee * new_employee = malloc(sizeof(employee));
    new_employee->first = fname;
    new_employee->last = lname;
    new_employee->start_date = date;
    new_employee->sal = salary;

//  COPY EXISING DATA TO EMPLOYEEDB
    memmove(employeeDB,data,sizeof(employee));;

    fprintf(stderr, "Now the first record has first = %s\n", employeeDB->first);
    fprintf(stderr, "Now the first record(head) has first = %s\n", head->first);

    // MOVE HEAD
    employeeDB = employeeDB + record;

    memmove(employeeDB, new_employee, sizeof(employee));
    fprintf(stderr, "Now the first record has first = %s\n", employeeDB->first);
    fprintf(stderr, "Now the first record(head) has first = %s\n", head->first);

//
//
//
//
return head;
}




/**************************
Starts of the main function
***************************/

int main(void){
        //Keeps track of the number of records that are in the structure
int rec = 0;
        //Keeps the number of accesses to the structure. Even with the one entry the structure has not been accessed. 
int acc = 0;
        //Holds the input information for the menu
int input;
        //holds the information for inputing user first name
char fname[MAXSIZE];
        //holds the information for inputing user last name
char lname[MAXSIZE];
        //holds the information for for the startdate
char start[MAXSIZE];
        //holds the information for the salary;
float sal;


/*********************************
This next section adds an employee to the record
************************************/
//This creates the first entry to the dynamic structure.
employee *data_base = create(rec);
data_base->first = "FIRST";
data_base->last = "LAST";
data_base->start_date = "June-20th-2006";
data_base->sal = 55555.55;
//increase the number of records    
rec = rec+1;

/**********************************
/*
This starts the while loop that creates the menu for the user to choose from

**********************************/

while(1){
    printf("\nWELCOME TO myEMPLOYEE DATABASE\n");
    printf("\n------------------\n");
    printf("\nMENU");
    printf("\n1. Print All Records\n");
    printf("2. Print Number of Records\n");
    printf("3. Print Size of database\n");
    printf("4. Add an Employee\n");
    printf("5. Delete all Employee\n");
    printf("6. Print number of accesses to database\n");    
    printf("7. EXIT\n");
    printf("\nENTER SELECTION:  ");



    /* This scanf functions scans for the appropiate input, if the input is
     not one of the selection items the program exits*/

    scanf("%d", &input);

    switch (input) {
        case 1:         
            printStruct(data_base, rec);
            acc = acc + 1;
            break;
        case 2:
            printf("The number of records are %d\n", rec);
            acc = acc + 1;
            break;
        case 3:
            printf("The size of the data base is %d\n", sizeof(employee) * rec);
            acc = acc + 1;              
            break;
        case 4:

            printf("\nPlease enter the employee's first name:");
            scanf("%s", fname);
            printf("\nPlease enter the employee's last name:");
            scanf("%s", lname);
            printf("\nPlease enter the employee's start date (Month-Day-Year):");
            scanf("%s", start);
            printf("\nPlease enther the employee's salaray:");
            scanf("%f", &sal);
            acc = acc + 1;              

            break;
        case 5:

            break;
        case 6:
            printf("The number of accesses to the data is: %d", acc);
            break;
        case 7:
            printf("The program has exited");
            return 1;

        default:
            // If a wrong selection is entered it will display this message. 
            printf("Please enter a selection 1-7"); 

    }   
}

}


/*

Header file for pointer.c



*/
#include <string.h>
#define MAXSIZE 255;
typedef struct info {
char *first;
char *last;
char *start_date;
float sal;
}employee; 



 employee *create(int record);
 employee *copy(employee *data, int record);
 void printStruct(employee *data, int record);
 void deleteData(employee *data, int record);
 employee *add(employee *data,char *fname, char *lname, char *date, float salary, int record);

Answer 1

删除 #define MAXSIZE 255; 末尾的 ;。无论您在何处使用 MAXSIZE，它都会被 255; 替换，因此 char fname[255;]; 显然是无效的。

#define MAXSIZE 255