Add tests for bigint.

Signed-off-by: Daira Hopwood <daira@jacaranda.org>

Makefile

@@ -68,7 +68,8 @@ ifeq ($(CURVE),BN128)
 	AR_LIBS += $(DEPINST)/lib/libzm.a
 endif
 
-EXECUTABLES = \
+# FIXME: most of these are broken due to removed code.
+DISABLED_EXECUTABLES = \
 	src/algebra/curves/tests/test_bilinearity \
 	src/algebra/curves/tests/test_groups \
 	src/algebra/fields/tests/test_fields \
@@ -107,6 +108,8 @@ EXECUTABLES = \
 	src/zk_proof_systems/zksnark/ram_zksnark/profiling/profile_ram_zksnark \
 	src/zk_proof_systems/zksnark/ram_zksnark/tests/test_ram_zksnark
 
+EXECUTABLES = \
+	src/algebra/fields/tests/test_bigint
 
 EXECUTABLES_WITH_GTEST = \
 	src/gadgetlib2/examples/tutorial \

src/algebra/fields/tests/test_bigint.cpp

@@ -0,0 +1,107 @@
+/**
+ *****************************************************************************
+ * @author     This file is part of libsnark, developed by SCIPR Lab
+ *             and contributors (see AUTHORS).
+ * @copyright  MIT license (see LICENSE file)
+ *****************************************************************************/
+
+#include "algebra/fields/bigint.hpp"
+
+using namespace libsnark;
+
+void test_bigint()
+{
+    static_assert(ULONG_MAX == 0xFFFFFFFFFFFFFFFFul, "unsigned long not 64-bit");
+    static_assert(GMP_NUMB_BITS == 64, "GMP limb not 64-bit");
+
+    const char *b1_decimal = "76749407";
+    const char *b2_decimal = "435020359732196472065729437602";
+    const char *b3_decimal = "33387554642372758038536799358397002014";
+    const char *b2_binary = "0000000000000000000000000000010101111101101000000110100001011010"
+                            "1101101010001001000001101000101000100110011001110001111110100010";
+
+    bigint<1> b0 = bigint<1>(0ul);
+    bigint<1> b1 = bigint<1>(b1_decimal);
+    bigint<2> b2 = bigint<2>(b2_decimal);
+
+    assert(b0.as_ulong() == 0ul);
+    assert(b0.is_zero());
+    assert(b1.as_ulong() == 76749407ul);
+    assert(!(b1.is_zero()));
+    assert(b2.as_ulong() == 15747124762497195938ul);
+    assert(!(b2.is_zero()));
+    assert(b0 != b1);
+    assert(!(b0 == b1));
+
+    assert(b2.max_bits() == 128);
+    assert(b2.num_bits() == 99);
+    for (size_t i = 0; i < 128; i++) {
+        assert(b2.test_bit(i) == (b2_binary[127-i] == '1'));
+    }
+
+    bigint<3> b3 = b2 * b1;
+
+    assert(b3 == bigint<3>(b3_decimal));
+    assert(!(b3.is_zero()));
+
+    bigint<3> b3a { b3 };
+    assert(b3a == bigint<3>(b3_decimal));
+    assert(b3a == b3);
+    assert(!(b3a.is_zero()));
+
+    mpz_t m3;
+    mpz_init(m3);
+    b3.to_mpz(m3);
+    bigint<3> b3b { m3 };
+    assert(b3b == b3);
+
+    bigint<2> quotient;
+    bigint<2> remainder;
+    bigint<3>::div_qr(quotient, remainder, b3, b2);
+    assert(quotient.num_bits() < GMP_NUMB_BITS);
+    assert(quotient.as_ulong() == b1.as_ulong());
+    bigint<1> b1inc = bigint<1>("76749408");
+    bigint<1> b1a = quotient.shorten(b1inc, "test");
+    assert(b1a == b1);
+    assert(remainder.is_zero());
+    remainder.limit(b2, "test");
+
+    try {
+        (void)(quotient.shorten(b1, "test"));
+        assert(false);
+    } catch (std::domain_error) {}
+    try {
+        remainder.limit(remainder, "test");
+        assert(false);
+    } catch (std::domain_error) {}
+
+    bigint<1> br = bigint<1>("42");
+    b3 += br;
+    assert(b3 != b3a);
+    assert(b3 > b3a);
+    assert(!(b3a > b3));
+
+    bigint<3>::div_qr(quotient, remainder, b3, b2);
+    assert(quotient.num_bits() < GMP_NUMB_BITS);
+    assert(quotient.as_ulong() == b1.as_ulong());
+    assert(remainder.num_bits() < GMP_NUMB_BITS);
+    assert(remainder.as_ulong() == 42);
+
+    b3a.clear();
+    assert(b3a.is_zero());
+    assert(b3a.num_bits() == 0);
+    assert(!(b3.is_zero()));
+
+    bigint<4> bx = bigint<4>().randomize();
+    bigint<4> by = bigint<4>().randomize();
+    assert(!(bx == by));
+
+    // TODO: test serialization
+}
+
+int main(void)
+{
+    test_bigint();
+    return 0;
+}
+