add fbase.h.

src/fbase.h

@@ -0,0 +1,33 @@
+#pragma once
+
+#include <gmp.h>
+#include <stdint.h>
+
+#include "group.h"
+
+#define FB_FRAMES 8
+typedef mpz_t fbase_unit[256];
+typedef fbase_unit   fbase_t[FB_FRAMES];
+typedef fbase_unit  *fbase_ptr;
+
+static inline void __attribute__((optimize("unroll-loops")))
+fb_powmp_ui(mpz_t rop, fbase_t pb, const uint64_t exp)
+{
+  const uint8_t *e = (uint8_t *) &exp;
+
+  mpz_mul_modp(rop, pb[0][e[0]], pb[1][e[1]]);
+  for (size_t j = 2; j < FB_FRAMES; j++) {
+    const size_t exp = e[j];
+    if (exp != 0) {
+      mpz_mul_modp(rop, rop,  pb[j][exp]);
+    }
+  }
+}
+
+fbase_ptr fb_init();
+void fb_set(fbase_t pb, const mpz_t n);
+void fb_set_small(fbase_t pb, const mpz_t n);
+void fb_clear(fbase_t pb);
+void fb_copy(fbase_t source, fbase_t dst);
+
+#define fb_init_set(pb, base) fb_init(pb); fb_set(pb, base)