Simulated int128 type.

src/int128_struct.h

@@ -0,0 +1,14 @@
+#ifndef SECP256K1_INT128_STRUCT_H
+#define SECP256K1_INT128_STRUCT_H
+
+#include <stdint.h>
+#include "util.h"
+
+typedef struct {
+  uint64_t lo;
+  uint64_t hi;
+} secp256k1_uint128;
+
+typedef secp256k1_uint128 secp256k1_int128;
+
+#endif