/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */

/* vim: set ts=8 sts=2 et sw=2 tw=80: */

/* This Source Code Form is subject to the terms of the Mozilla Public

 * License, v. 2.0. If a copy of the MPL was not distributed with this file,

 * You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "mozilla/Assertions.h"

#include "mozilla/WrappingOperations.h"

#include <stdint.h>

using mozilla::WrappingMultiply;

using mozilla::WrapToSigned;

// NOTE: In places below |-FOO_MAX - 1| is used instead of |-FOO_MIN| because

//       in C++ numeric literals are full expressions -- the |-| in a negative

//       number is technically separate.  So with most compilers that limit

//       |int| to the signed 32-bit range, something like |-2147483648| is

//       operator-() applied to an *unsigned* expression.  And MSVC, at least,

//       warns when you do that.  (The operation is well-defined, but it likely

//       doesn't do what was intended.)  So we do the usual workaround for this

//       (see your local copy of <stdint.h> for a likely demo of this), writing

//       it out by negating the max value and subtracting 1.

static_assert(WrapToSigned(uint8_t(17)) == 17,

              "no wraparound should work, 8-bit");

static_assert(WrapToSigned(uint8_t(128)) == -128,

              "works for 8-bit numbers, wraparound low end");

static_assert(WrapToSigned(uint8_t(128 + 7)) == -128 + 7,

              "works for 8-bit numbers, wraparound mid");

static_assert(WrapToSigned(uint8_t(128 + 127)) == -128 + 127,

              "works for 8-bit numbers, wraparound high end");

static_assert(WrapToSigned(uint16_t(12345)) == 12345,

              "no wraparound should work, 16-bit");

static_assert(WrapToSigned(uint16_t(32768)) == -32768,

              "works for 16-bit numbers, wraparound low end");

static_assert(WrapToSigned(uint16_t(32768 + 42)) == -32768 + 42,

              "works for 16-bit numbers, wraparound mid");

static_assert(WrapToSigned(uint16_t(32768 + 32767)) == -32768 + 32767,

              "works for 16-bit numbers, wraparound high end");

static_assert(WrapToSigned(uint32_t(8675309)) == 8675309,

              "no wraparound should work, 32-bit");

static_assert(WrapToSigned(uint32_t(2147483648)) == -2147483647 - 1,

              "works for 32-bit numbers, wraparound low end");

static_assert(WrapToSigned(uint32_t(2147483648 + 42)) == -2147483647 - 1 + 42,

              "works for 32-bit numbers, wraparound mid");

static_assert(WrapToSigned(uint32_t(2147483648 + 2147483647)) ==

                -2147483647 - 1 + 2147483647,

              "works for 32-bit numbers, wraparound high end");

static_assert(WrapToSigned(uint64_t(4152739164)) == 4152739164,

              "no wraparound should work, 64-bit");

static_assert(WrapToSigned(uint64_t(9223372036854775808ULL)) == -9223372036854775807LL - 1,

              "works for 64-bit numbers, wraparound low end");

static_assert(WrapToSigned(uint64_t(9223372036854775808ULL + 8005552368LL)) ==

                -9223372036854775807LL - 1 + 8005552368LL,

              "works for 64-bit numbers, wraparound mid");

static_assert(WrapToSigned(uint64_t(9223372036854775808ULL + 9223372036854775807ULL)) ==

                -9223372036854775807LL - 1 + 9223372036854775807LL,

              "works for 64-bit numbers, wraparound high end");

template<typename T>

inline constexpr bool

TestEqual(T aX, T aY)

{

  return aX == aY;

}

static void

TestWrappingMultiply8()

{

  MOZ_RELEASE_ASSERT(TestEqual(WrappingMultiply(uint8_t(0), uint8_t(128)),

                               uint8_t(0)),

                     "zero times anything is zero");

  MOZ_RELEASE_ASSERT(TestEqual(WrappingMultiply(uint8_t(128), uint8_t(1)),

                               uint8_t(128)),

                     "1 times anything is anything");

  MOZ_RELEASE_ASSERT(TestEqual(WrappingMultiply(uint8_t(2), uint8_t(128)),

                               uint8_t(0)),

                     "2 times high bit overflows, produces zero");

  MOZ_RELEASE_ASSERT(TestEqual(WrappingMultiply(uint8_t(8), uint8_t(16)),

                               uint8_t(128)),

                     "multiply that populates the high bit produces that value");

  MOZ_RELEASE_ASSERT(TestEqual(WrappingMultiply(uint8_t(127), uint8_t(127)),

                               uint8_t(1)),

                     "multiplying signed maxvals overflows all the way to 1");

  MOZ_RELEASE_ASSERT(TestEqual(WrappingMultiply(int8_t(0), int8_t(-128)),

                               int8_t(0)),

                     "zero times anything is zero");

  MOZ_RELEASE_ASSERT(TestEqual(WrappingMultiply(int8_t(-128), int8_t(1)),

                               int8_t(-128)),

                     "1 times anything is anything");

  MOZ_RELEASE_ASSERT(TestEqual(WrappingMultiply(int8_t(2), int8_t(-128)),

                               int8_t(0)),

                     "2 times min overflows, produces zero");

  MOZ_RELEASE_ASSERT(TestEqual(WrappingMultiply(int8_t(16), int8_t(24)),

                               int8_t(-128)),

                     "multiply that populates the sign bit produces minval");

  MOZ_RELEASE_ASSERT(TestEqual(WrappingMultiply(int8_t(8), int8_t(16)),

                               int8_t(-128)),

                     "multiply that populates the sign bit produces minval");

  MOZ_RELEASE_ASSERT(TestEqual(WrappingMultiply(int8_t(127), int8_t(127)),

                               int8_t(1)),

                     "multiplying maxvals overflows all the way to 1");

}

static void

TestWrappingMultiply16()

{

  MOZ_RELEASE_ASSERT(TestEqual(WrappingMultiply(uint16_t(0), uint16_t(32768)),

                               uint16_t(0)),

                     "zero times anything is zero");

  MOZ_RELEASE_ASSERT(TestEqual(WrappingMultiply(uint16_t(32768), uint16_t(1)),

                               uint16_t(32768)),

                     "1 times anything is anything");

  MOZ_RELEASE_ASSERT(TestEqual(WrappingMultiply(uint16_t(2), uint16_t(32768)),

                               uint16_t(0)),

                     "2 times high bit overflows, produces zero");

  MOZ_RELEASE_ASSERT(TestEqual(WrappingMultiply(uint16_t(3), uint16_t(32768)),

                               uint16_t(-32768)),

                     "3 * 32768 - 65536 is 32768");

  MOZ_RELEASE_ASSERT(TestEqual(WrappingMultiply(uint16_t(64), uint16_t(512)),

                               uint16_t(32768)),

                     "multiply that populates the high bit produces that value");

  MOZ_RELEASE_ASSERT(TestEqual(WrappingMultiply(uint16_t(32767), uint16_t(32767)),

                               uint16_t(1)),

                    "multiplying signed maxvals overflows all the way to 1");

  MOZ_RELEASE_ASSERT(TestEqual(WrappingMultiply(int16_t(0), int16_t(-32768)),

                               int16_t(0)),

                     "zero times anything is zero");

  MOZ_RELEASE_ASSERT(TestEqual(WrappingMultiply(int16_t(-32768), int16_t(1)),

                               int16_t(-32768)),

                     "1 times anything is anything");

  MOZ_RELEASE_ASSERT(TestEqual(WrappingMultiply(int16_t(-456), int16_t(123)),

                               int16_t(9448)),

                     "multiply opposite signs, then add 2**16 for the result");

  MOZ_RELEASE_ASSERT(TestEqual(WrappingMultiply(int16_t(2), int16_t(-32768)),

                               int16_t(0)),

                     "2 times min overflows, produces zero");

  MOZ_RELEASE_ASSERT(TestEqual(WrappingMultiply(int16_t(64), int16_t(512)),

                               int16_t(-32768)),

                     "multiply that populates the sign bit produces minval");

  MOZ_RELEASE_ASSERT(TestEqual(WrappingMultiply(int16_t(32767), int16_t(32767)),

                               int16_t(1)),

                     "multiplying maxvals overflows all the way to 1");

}

static void

TestWrappingMultiply32()

{

  MOZ_RELEASE_ASSERT(TestEqual(WrappingMultiply(uint32_t(0), uint32_t(2147483648)),

                               uint32_t(0)),

                    "zero times anything is zero");

  MOZ_RELEASE_ASSERT(TestEqual(WrappingMultiply(uint32_t(42), uint32_t(17)),

                               uint32_t(714)),

                     "42 * 17 is 714 without wraparound");

  MOZ_RELEASE_ASSERT(TestEqual(WrappingMultiply(uint32_t(2147483648), uint32_t(1)),

                               uint32_t(2147483648)),

                     "1 times anything is anything");

  MOZ_RELEASE_ASSERT(TestEqual(WrappingMultiply(uint32_t(2), uint32_t(2147483648)),

                               uint32_t(0)),

                     "2 times high bit overflows, produces zero");

  MOZ_RELEASE_ASSERT(TestEqual(WrappingMultiply(uint32_t(8192), uint32_t(262144)),

                               uint32_t(2147483648)),

                     "multiply that populates the high bit produces that value");

  MOZ_RELEASE_ASSERT(TestEqual(WrappingMultiply(uint32_t(2147483647),

                                                uint32_t(2147483647)),

                               uint32_t(1)),

                     "multiplying signed maxvals overflows all the way to 1");

  MOZ_RELEASE_ASSERT(TestEqual(WrappingMultiply(int32_t(0), int32_t(-2147483647 - 1)),

                               int32_t(0)),

                     "zero times anything is zero");

  MOZ_RELEASE_ASSERT(TestEqual(WrappingMultiply(int32_t(-2147483647 - 1), int32_t(1)),

                               int32_t(-2147483647 - 1)),

                     "1 times anything is anything");

  MOZ_RELEASE_ASSERT(TestEqual(WrappingMultiply(int32_t(2), int32_t(-2147483647 - 1)),

                               int32_t(0)),

                     "2 times min overflows, produces zero");

  MOZ_RELEASE_ASSERT(TestEqual(WrappingMultiply(int32_t(-7), int32_t(-9)),

                               int32_t(63)),

                     "-7 * -9 is 63, no wraparound needed");

  MOZ_RELEASE_ASSERT(TestEqual(WrappingMultiply(int32_t(8192), int32_t(262144)),

                               int32_t(-2147483647 - 1)),

                     "multiply that populates the sign bit produces minval");

  MOZ_RELEASE_ASSERT(TestEqual(WrappingMultiply(int32_t(2147483647), int32_t(2147483647)),

                               int32_t(1)),

                     "multiplying maxvals overflows all the way to 1");

}

static void

TestWrappingMultiply64()

{

  MOZ_RELEASE_ASSERT(TestEqual(WrappingMultiply(uint64_t(0),

                                                uint64_t(9223372036854775808ULL)),

                               uint64_t(0)),

                     "zero times anything is zero");

  MOZ_RELEASE_ASSERT(TestEqual(WrappingMultiply(uint64_t(9223372036854775808ULL),

                                                uint64_t(1)),

                               uint64_t(9223372036854775808ULL)),

                     "1 times anything is anything");

  MOZ_RELEASE_ASSERT(TestEqual(WrappingMultiply(uint64_t(2),

                                                uint64_t(9223372036854775808ULL)),

                               uint64_t(0)),

                     "2 times high bit overflows, produces zero");

  MOZ_RELEASE_ASSERT(TestEqual(WrappingMultiply(uint64_t(131072),

                                                uint64_t(70368744177664)),

                               uint64_t(9223372036854775808ULL)),

                     "multiply that populates the high bit produces that value");

  MOZ_RELEASE_ASSERT(TestEqual(WrappingMultiply(uint64_t(9223372036854775807),

                                                uint64_t(9223372036854775807)),

                               uint64_t(1)),

                     "multiplying signed maxvals overflows all the way to 1");

  MOZ_RELEASE_ASSERT(TestEqual(WrappingMultiply(int64_t(0), int64_t(-9223372036854775807 - 1)),

                               int64_t(0)),

                     "zero times anything is zero");

  MOZ_RELEASE_ASSERT(TestEqual(WrappingMultiply(int64_t(-9223372036854775807 - 1),

                                                int64_t(1)),

                               int64_t(-9223372036854775807 - 1)),

                     "1 times anything is anything");

  MOZ_RELEASE_ASSERT(TestEqual(WrappingMultiply(int64_t(2),

                                                int64_t(-9223372036854775807 - 1)),

                               int64_t(0)),

                     "2 times min overflows, produces zero");

  MOZ_RELEASE_ASSERT(TestEqual(WrappingMultiply(int64_t(131072),

                                                int64_t(70368744177664)),

                               int64_t(-9223372036854775807 - 1)),

                     "multiply that populates the sign bit produces minval");

  MOZ_RELEASE_ASSERT(TestEqual(WrappingMultiply(int64_t(9223372036854775807),

                                                int64_t(9223372036854775807)),

                               int64_t(1)),

                     "multiplying maxvals overflows all the way to 1");

}

int

main()

{

  TestWrappingMultiply8();

  TestWrappingMultiply16();

  TestWrappingMultiply32();

  TestWrappingMultiply64();

  return 0;

}