;;;; entropy-linux.scm
;;;; Kon Lovett, Oct '17

(module entropy-linux

(;export
  make-entropy-source-getrandom)

(import scheme)

(import chicken)

(use entropy-source entropy-procedure)

;;; Entropy from getentropy

#>
#if defined __GLIBC__ && defined __linux__

# define _GNU_SOURCE 1
# include <sys/types.h>
# include <unistd.h>

# if __GLIBC__ > 2 || __GLIBC_MINOR__ > 24
# include <sys/random.h>

static int
linux_getentropy( void *buf, size_t buflen )
{
  return getentropy( buf, buflen );
}

# else /* older glibc */
#   include <sys/syscall.h>
#   include <errno.h>

static int
linux_getentropy( void *buf, size_t buflen )
{
  if( buflen > 256 ) {
    errno = EIO;
    return -1;
  }
  return syscall(SYS_getrandom, buf, buflen, 0);
}

# endif

#endif
<#

(cond-expand
  (linux
    (define (make-entropy-source-getrandom)
      (make-entropy-source/procedure
        getrandom_u8proc
        getrandom_f64proc
        "getrandom"
        'getrandom
        "Entropy from getrandom") ) )
  (else
    (define (make-entropy-source-getrandom)
     (void) ) ) )

(register-entropy-source! 'getrandom make-entropy-source-getrandom)

) ;module entropy-linux