Luna/libs/libc/src/init.cpp

#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

static void terminate_libc()
{
    fclose(stdout);
    fclose(stderr);
    fclose(stdin);
}

static void initialize_random()
{
    unsigned int seed = 3735928559U;

    FILE* fp = fopen("/dev/random", "rw");
    if (!fp)
    {
        errno = 0;
        goto failed_to_read_dev_random;
    }

    fread(&seed, sizeof(seed), 1, fp);
    if (ferror(fp))
    {
        errno = 0;
        fclose(fp);
        goto failed_to_read_dev_random;
    }

    fclose(fp);

failed_to_read_dev_random:
    srand(seed); // If we failed, this will be seeded with a known value. Else, it will be seeded with a random value
                 // from the kernel.
    return;
}

static void check_for_file(int fd, FILE** target_stream, const char* path, const char* mode)
{
    if (lseek(fd, 0, SEEK_CUR) < 0)
    {
        if (errno == EBADF) *target_stream = fopen(path, mode);
        else
            exit(-127);
        if (!*target_stream) exit(-127);
        errno = 0;
    }
    else { *target_stream = fdopen(fd, mode); }
}

extern "C" void initialize_libc()
{
    check_for_file(STDIN_FILENO, &stdin, "/dev/kbd", "r");
    check_for_file(STDOUT_FILENO, &stdout, "/dev/console", "rw");
    check_for_file(STDERR_FILENO, &stderr, "/dev/console", "rw");

    initialize_random();
    atexit(terminate_libc);
}