C language: Use the realloc function to expand the memory size dynamically allocated by malloc or calloc.

C language: Use the realloc function to expand the memory size dynamically allocated by malloc or calloc.

# Include <stdio. h>

# Include <stdlib. h>

# Include <time. h>

Typedef struct

{

Char name [32];

Int age;

Char gender;

Float score [3];

} Student;

Typedef struct

{

Student * pData; // Student Information

Int size; // capacity

Int count; // number of current records

} Database;

// Initialize the database

Int initDatabase (Database * db );

// Destroy the database

Void destoryDatabase (Database * db );

// Insert a data entry

Int insertData (Database * db, Student stu );

// Print the database content

Void printDatabase (Database * db );

// Randomly generate data

Int myrandom (int range)

{

// Generate a random number in the range

Return rand () % range;

}

Int main ()

{

// Initialize Random Seed

Srand (unsigned) time (NULL ));

 

Database db;

// Initialize the database

If (initDatabase (& db )! = 0)

{

Printf ("database initialization failed! \ N ");

Return-1;

}

// Insert data in batches

For (int I = 0; I <20; I ++)

{

Student stu;

Sprintf (stu. name, "name % d", I );

Stu. age = myrandom (30 );

Stu. gender = myrandom (2 )? 'M': 'F ';

Stu. score [0] = myrandom (0, 100 );

Stu. score [1] = myrandom (100 );

Stu. score [2] = myrandom (100 );

If (insertData (& db, stu )! = 0)

{

Printf ("insertion failed! ");

Break;

}

}

// Print the database

PrintDatabase (& db );

// Destroy the database

DestoryDatabase (& db );

Return 0;

}

// Initialize the database

Int initDatabase (Database * db)

{

Db-> size = 10;

Db-> count = 0;

Db-> pData = (Student *) calloc (db-> size, sizeof (Student ));

Printf ("% p \ n", db-> pData );

If (db-> pData! = NULL)

{

Return 0;

}

Return-1;

}

// Destroy the database

Void destoryDatabase (Database * db)

{

Free (db-> pData );

Db-> pData = NULL;

}

// Insert a data entry

Int insertData (Database * db, Student stu)

{

// Determine whether the space is full before insertion

If (db-> count = db-> size) // if it is full, expand the space first.

{

Db-> size * = 22; // the new size is twice the original size.

// Use realloc to expand space

Db-> pData = (Student *) realloc (db-> pData, db-> size * sizeof (Student ));

Printf ("% p \ n", db-> pData );

If (db-> pData = NULL)

{

Return-1;

}

}

// Insert a new record

Db-> pData [db-> count] = stu;

Db-> count ++;

Return 0;

}

// Print the database content

Void printDatabase (Database * db)

{

Printf ("database size: % d, number of existing records: % d \ n", db-> size, db-> count );

Printf ("name, age, gender, mathematics, Chinese, English \ n ");

For (int I = 0; I <db-> count; I ++)

{

Printf ("% 8s \ t % 2d \ t % c \ t %. 2f \ t %. 2f \ t %. 2f \ t \ n ",

Db-> pData [I]. name,

Db-> pData [I]. age,

Db-> pData [I]. gender,

Db-> pData [I]. score [0],

Db-> pData [I]. score [1],

Db-> pData [I]. score [2]);

}

}