Import code from previous AssetBuilder version

thirdparty/libtommath/bn_mp_import.c

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+#include "tommath_private.h"
+#ifdef BN_MP_IMPORT_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
+ */
+
+/* based on gmp's mpz_import.
+ * see http://gmplib.org/manual/Integer-Import-and-Export.html
+ */
+int mp_import(mp_int *rop, size_t count, int order, size_t size,
+              int endian, size_t nails, const void *op)
+{
+   int result;
+   size_t odd_nails, nail_bytes, i, j;
+   unsigned char odd_nail_mask;
+
+   mp_zero(rop);
+
+   if (endian == 0) {
+      union {
+         unsigned int i;
+         char c[4];
+      } lint;
+      lint.i = 0x01020304;
+
+      endian = (lint.c[0] == '\x04') ? -1 : 1;
+   }
+
+   odd_nails = (nails % 8u);
+   odd_nail_mask = 0xff;
+   for (i = 0; i < odd_nails; ++i) {
+      odd_nail_mask ^= (unsigned char)(1u << (7u - i));
+   }
+   nail_bytes = nails / 8u;
+
+   for (i = 0; i < count; ++i) {
+      for (j = 0; j < (size - nail_bytes); ++j) {
+         unsigned char byte = *((unsigned char *)op +
+                                (((order == 1) ? i : ((count - 1u) - i)) * size) +
+                                ((endian == 1) ? (j + nail_bytes) : (((size - 1u) - j) - nail_bytes)));
+
+         if ((result = mp_mul_2d(rop, (j == 0u) ? (int)(8u - odd_nails) : 8, rop)) != MP_OKAY) {
+            return result;
+         }
+
+         rop->dp[0] |= (j == 0u) ? (mp_digit)(byte & odd_nail_mask) : (mp_digit)byte;
+         rop->used  += 1;
+      }
+   }
+
+   mp_clamp(rop);
+
+   return MP_OKAY;
+}
+
+#endif
+
+/* ref:         HEAD -> master, tag: v1.1.0 */
+/* git commit:  08549ad6bc8b0cede0b357a9c341c5c6473a9c55 */
+/* commit time: 2019-01-28 20:32:32 +0100 */