Starting Out with C++: Early Objects - EEMB DERSLER

Binary Files 865
If the data we are writing happens to be character data, there is no need to use the cast.
Here are some examples of writing character data.
char ch = 'X';
char charArray[5] = "Hello";
outFile.write(&ch, sizeof(ch));
outFile.write(charArray, sizeof(charArray));
There is a read member function in the istream and ifstream classes that can be used to
read binary data written by write. It takes as parameters the address of a buffer in which
the bytes read are to be stored, and the number of bytes to read:
read(addressOfBuffer, numberOfBytes)
The address of the buffer must be interpreted as a pointer to char using reinterpret_cast.
You can find out if the specified number of bytes was successfully read by calling the fail()
member function on the input stream.
Program 13-16 demonstrates the use of write and read. The program initializes an array
of integers and then stores the number of array entries in the array using the statements
int buffer[ ] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
int size = sizeof(buffer)/sizeof(buffer[0]);
Recall that the sizeof operator can be used on variables to determine the number of
bytes occupied by the variable. Here sizeof(buffer) returns the number of bytes allocated
to the array by the initialization statement, and sizeof(buffer[0]) returns the
number of bytes occupied by a single array entry. By dividing the former by the latter, we
obtain the number of array entries, which we then store in size.
Program 13-16 demonstrates the use of write and read.
Program 13-16
1 //This program uses the write and read functions.
2 #include
3 #include
4 using namespace std;
5
6 int main()
7 {
8 // File object used to access file.
9 fstream file("nums.dat", ios::out | ios::binary);
10 if (!file)
11 {
12 cout