What is the most efficient way to transfer a file with a size of 193,778,360 bytes into memory in C, in order to compare it with an array[][] through scanning the memory?

edit

One efficient way to transfer the file into memory in C is to use the mmap() function, which maps the file into memory and allows direct access to its contents without having to read it into a buffer.

Here is an example code snippet using mmap():

#include <sys/mman.h>
#include <fcntl.h>
#include <unistd.h>

...

int fd = open("file.txt", O_RDONLY);
if (fd == -1) {
    perror("open");
    return -1;
}

char* map = mmap(NULL, 193778360, PROT_READ, MAP_PRIVATE, fd, 0);
if (map == MAP_FAILED) {
    perror("mmap");
    return -1;
}

close(fd);

// Access the contents of the file through the mapped memory
for (int i = 0; i < n; i++) {
    for (int j = 0; j < m; j++) {
        char val = map[i*m+j];
        // Compare with array[i][j]
    }
}

// Unmap the memory when done
munmap(map, 193778360);

In this example, the mmap() function is called with the file descriptor, size of the file, and flags to indicate that the memory should be read-only and mapped into private memory. The returned pointer to the mapped memory can then be used to access the contents of the file directly.

Note that the size of the memory mapped can be larger than the file, so make sure to access only the correct bytes of the file to avoid accessing uninitialized memory. Also, remember to unmap the memory when no longer needed to avoid memory leaks.