--- a/libtommath/bn_mp_fwrite.c	Wed Feb 28 22:11:39 2018 +0800
+++ b/libtommath/bn_mp_fwrite.c	Thu Oct 15 19:55:15 2020 +0800
@@ -1,54 +1,45 @@
-#include <tommath_private.h>
+#include "tommath_private.h"
 #ifdef BN_MP_FWRITE_C
-/* LibTomMath, multiple-precision integer library -- Tom St Denis
- *
- * LibTomMath is a library that provides multiple-precision
- * integer arithmetic as well as number theoretic functionality.
- *
- * The library was designed directly after the MPI library by
- * Michael Fromberger but has been written from scratch with
- * additional optimizations in place.
- *
- * The library is free for all purposes without any express
- * guarantee it works.
- *
- * Tom St Denis, [email protected], http://libtom.org
- */
+/* LibTomMath, multiple-precision integer library -- Tom St Denis */
+/* SPDX-License-Identifier: Unlicense */
 
-#ifndef LTM_NO_FILE
-int mp_fwrite(mp_int *a, int radix, FILE *stream)
+#ifndef MP_NO_FILE
+mp_err mp_fwrite(const mp_int *a, int radix, FILE *stream)
 {
    char *buf;
-   int err, len, x;
-   
-   if ((err = mp_radix_size(a, radix, &len)) != MP_OKAY) {
-      return err;
+   mp_err err;
+   int len;
+   size_t written;
+
+   /* TODO: this function is not in this PR */
+   if (MP_HAS(MP_RADIX_SIZE_OVERESTIMATE)) {
+      /* if ((err = mp_radix_size_overestimate(&t, base, &len)) != MP_OKAY)      goto LBL_ERR; */
+   } else {
+      if ((err = mp_radix_size(a, radix, &len)) != MP_OKAY) {
+         return err;
+      }
    }
 
-   buf = OPT_CAST(char) XMALLOC (len);
+   buf = (char *) MP_MALLOC((size_t)len);
    if (buf == NULL) {
       return MP_MEM;
    }
-   
-   if ((err = mp_toradix(a, buf, radix)) != MP_OKAY) {
-      XFREE (buf);
-      return err;
+
+   if ((err = mp_to_radix(a, buf, (size_t)len, &written, radix)) != MP_OKAY) {
+      goto LBL_ERR;
    }
-   
-   for (x = 0; x < len; x++) {
-       if (fputc(buf[x], stream) == EOF) {
-          XFREE (buf);
-          return MP_VAL;
-       }
+
+   if (fwrite(buf, written, 1uL, stream) != 1uL) {
+      err = MP_ERR;
+      goto LBL_ERR;
    }
-   
-   XFREE (buf);
-   return MP_OKAY;
+   err = MP_OKAY;
+
+
+LBL_ERR:
+   MP_FREE_BUFFER(buf, (size_t)len);
+   return err;
 }
 #endif
 
 #endif
-
-/* ref:         $Format:%D$ */
-/* git commit:  $Format:%H$ */
-/* commit time: $Format:%ai$ */