Import code from previous AssetBuilder version

thirdparty/libtommath/bn_mp_read_signed_bin.c

@@ -0,0 +1,38 @@
+#include "tommath_private.h"
+#ifdef BN_MP_READ_SIGNED_BIN_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.
+ *
+ * SPDX-License-Identifier: Unlicense
+ */
+
+/* read signed bin, big endian, first byte is 0==positive or 1==negative */
+int mp_read_signed_bin(mp_int *a, const unsigned char *b, int c)
+{
+   int     res;
+
+   /* read magnitude */
+   if ((res = mp_read_unsigned_bin(a, b + 1, c - 1)) != MP_OKAY) {
+      return res;
+   }
+
+   /* first byte is 0 for positive, non-zero for negative */
+   if (b[0] == (unsigned char)0) {
+      a->sign = MP_ZPOS;
+   } else {
+      a->sign = MP_NEG;
+   }
+
+   return MP_OKAY;
+}
+#endif
+
+/* ref:         HEAD -> master, tag: v1.1.0 */
+/* git commit:  08549ad6bc8b0cede0b357a9c341c5c6473a9c55 */
+/* commit time: 2019-01-28 20:32:32 +0100 */