cpp fread

fread is a C++ function that is used to read data from a file. It is part of the C standard library and is declared in the <cstdio> header.

The fread function has the following syntax:

size_t fread(void ptr, size_t size, size_t count, FILE stream);

Here is an explanation of each parameter:

  1. ptr: It is a pointer to the data buffer where the read data will be stored.

  2. size: It specifies the size in bytes of each element to be read.

  3. count: It specifies the number of elements to be read.

  4. stream: It is a pointer to the FILE object that represents the file from which the data will be read.

The fread function reads count elements, each of size bytes, from the file pointed to by stream, and stores them in the buffer pointed to by ptr. It returns the total number of elements successfully read, which may be less than count if an error occurs or the end of the file is reached.

The fread function is commonly used to read binary data from a file. It is often used in conjunction with the fwrite function, which is used to write binary data to a file.

Here is an example usage of the fread function:

#include <cstdio>

int main() {
    FILE* file = fopen("data.bin", "rb");
    if (file != nullptr) {
        int data[10];
        size_t elements_read = fread(data, sizeof(int), 10, file);
        fclose(file);

        printf("Read %zu elements from the file.\n", elements_read);

        // Process the data...
    } else {
        printf("Failed to open the file.\n");
    }

    return 0;
}

In this example, the fopen function is used to open the file "data.bin" in binary mode for reading. If the file is successfully opened, an array data of type int is declared to store the read data. The fread function is then called to read 10 int values from the file into the data array. The number of elements successfully read is stored in the elements_read variable. Finally, the file is closed using the fclose function.

Note that error handling is important when using fread. It is necessary to check the return value of fread to ensure that the expected number of elements were read successfully. Additionally, it is important to handle any errors that may occur during file opening or reading.