/*
 * unistd.c — thin wrappers around raw syscalls.
 *
 * Each function here is a one-liner on purpose: the kernel is the API
 * (project guideline #6), and a wrapper that does more than translate
 * arguments is a wrapper that can lie. Error translation (kernel -errno
 * -> errno) happens inside syscall() itself.
 */

#include <errno.h>
#include <sys/syscall.h>
#include <unistd.h>

ssize_t read(int fd, void *buf, size_t count)
{
    return (ssize_t)syscall(SYS_read, fd, buf, count);
}

ssize_t write(int fd, const void *buf, size_t count)
{
    return (ssize_t)syscall(SYS_write, fd, buf, count);
}

int close(int fd)
{
    return (int)syscall(SYS_close, fd);
}

pid_t getpid(void)
{
    return (pid_t)syscall(SYS_getpid);
}

void _exit(int status)
{
    syscall(SYS_exit, status);
    for (;;)
        ; /* unreachable */
}

/* Stub: trivially a one-liner once wanted (SYS_unlink = 87 on x86_64). */
int unlink(const char *path)
{
    (void)path;
    errno = ENOSYS;
    return -1;
}