diff options
author | Andy Schwerin <schwerin@mongodb.com> | 2016-05-06 15:59:01 -0400 |
---|---|---|
committer | Andy Schwerin <schwerin@mongodb.com> | 2016-05-09 13:19:13 -0400 |
commit | 97f24aa42d86dcadd789ba2c9e144709fa7a7aab (patch) | |
tree | 71adce4734327beefe3ac94b060902fed975552b /src/mongo/platform | |
parent | d1957fd1f86510c37a893ec3c51140cf004407d5 (diff) | |
download | mongo-97f24aa42d86dcadd789ba2c9e144709fa7a7aab.tar.gz |
SERVER-21404 Introduce some useful 64-bit arithmetic with overflow detection functions.
Diffstat (limited to 'src/mongo/platform')
-rw-r--r-- | src/mongo/platform/SConscript | 1 | ||||
-rw-r--r-- | src/mongo/platform/overflow_arithmetic.h | 126 | ||||
-rw-r--r-- | src/mongo/platform/overflow_arithmetic_test.cpp | 122 |
3 files changed, 249 insertions, 0 deletions
diff --git a/src/mongo/platform/SConscript b/src/mongo/platform/SConscript index 6f74069ce3d..518cc620f3f 100644 --- a/src/mongo/platform/SConscript +++ b/src/mongo/platform/SConscript @@ -28,3 +28,4 @@ env.CppUnitTest('process_id_test', 'process_id_test.cpp', LIBDEPS=['platform']) env.CppUnitTest('random_test', 'random_test.cpp', LIBDEPS=['$BUILD_DIR/mongo/base']) env.CppUnitTest('stack_locator_test', 'stack_locator_test.cpp', LIBDEPS=['platform']) env.CppUnitTest('decimal128_test', 'decimal128_test.cpp', LIBDEPS=['$BUILD_DIR/mongo/base']) +env.CppUnitTest('overflow_arithmetic_test', 'overflow_arithmetic_test.cpp') diff --git a/src/mongo/platform/overflow_arithmetic.h b/src/mongo/platform/overflow_arithmetic.h new file mode 100644 index 00000000000..8dc3940d0f4 --- /dev/null +++ b/src/mongo/platform/overflow_arithmetic.h @@ -0,0 +1,126 @@ +/* Copyright 2016 MongoDB, Inc. + * + * This program is free software: you can redistribute it and/or modify + * it under the terms of the GNU Affero General Public License, version 3, + * as published by the Free Software Foundation. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU Affero General Public License for more details. + * + * You should have received a copy of the GNU Affero General Public License + * along with this program. If not, see <http://www.gnu.org/licenses/>. + * + * As a special exception, the copyright holders give permission to link the + * code of portions of this program with the OpenSSL library under certain + * conditions as described in each individual source file and distribute + * linked combinations including the program with the OpenSSL library. You + * must comply with the GNU Affero General Public License in all respects + * for all of the code used other than as permitted herein. If you modify + * file(s) with this exception, you may extend this exception to your + * version of the file(s), but you are not obligated to do so. If you do not + * wish to do so, delete this exception statement from your version. If you + * delete this exception statement from all source files in the program, + * then also delete it in the license file. + */ + +#pragma once + +#include <cstdint> + +#ifdef _MSC_VER +#include <intrin.h> +#endif + +namespace mongo { + +/** + * Returns true if multiplying lhs by rhs would overflow. Otherwise, ultiplies 64-bit signed + * integers lhs by rhs and stores the result in *product. + */ +inline bool mongoSignedMultiplyOverflow64(int64_t lhs, int64_t rhs, int64_t* product); + +/** + * Returns true if adding lhs and rhs would overflow. Otherwise, adds 64-bit signed integers lhs and + * rhs and stores the result in *sum. + */ +inline bool mongoSignedAddOverflow64(int64_t lhs, int64_t rhs, int64_t* sum); + +/** + * Returns true if subtracting rhs from lhs would overflow. Otherwise, subtracts 64-bit signed + * integers rhs from lhs and stores the result in *difference. + */ +inline bool mongoSignedSubtractOverflow64(int64_t lhs, int64_t rhs, int64_t* difference); + + +#ifdef _MSC_VER + +// In MSVC, we use an MSVC intrinsic for the multiplication form of this calculation, and unsigned +// arithmetic and careful casting for addition and subtraction. + +inline bool mongoSignedMultiplyOverflow64(int64_t lhs, int64_t rhs, int64_t* product) { + int64_t hi; + *product = _mul128(lhs, rhs, &hi); + if (hi == 0) { + return *product < 0; + } + if (hi == -1) { + return *product >= 0; + } + return true; +} + +inline bool mongoSignedAddOverflow64(int64_t lhs, int64_t rhs, int64_t* sum) { + *sum = static_cast<int64_t>(static_cast<uint64_t>(lhs) + static_cast<uint64_t>(rhs)); + if (lhs >= 0 && rhs >= 0) { + return (*sum) < 0; + } + if (lhs < 0 && rhs < 0) { + return (*sum) >= 0; + } + return false; +} + +inline bool mongoSignedSubtractOverflow64(int64_t lhs, int64_t rhs, int64_t* difference) { + *difference = static_cast<int64_t>(static_cast<uint64_t>(lhs) - static_cast<uint64_t>(rhs)); + if (lhs >= 0 && rhs < 0) { + return (*difference) < 0; + } + if (lhs < 0 && rhs >= 0) { + return (*difference >= 0); + } + return false; +} + +#else + +// On GCC and CLANG we can use __builtin functions to perform these calculations. + +inline bool mongoSignedMultiplyOverflow64(long lhs, long rhs, long* product) { + return __builtin_smull_overflow(lhs, rhs, product); +} + +inline bool mongoSignedAddOverflow64(long lhs, long rhs, long* sum) { + return __builtin_saddl_overflow(lhs, rhs, sum); +} + +inline bool mongoSignedSubtractOverflow64(long lhs, long rhs, long* difference) { + return __builtin_ssubl_overflow(lhs, rhs, difference); +} + +inline bool mongoSignedMultiplyOverflow64(long long lhs, long long rhs, long long* product) { + return __builtin_smulll_overflow(lhs, rhs, product); +} + +inline bool mongoSignedAddOverflow64(long long lhs, long long rhs, long long* sum) { + return __builtin_saddll_overflow(lhs, rhs, sum); +} + +inline bool mongoSignedSubtractOverflow64(long long lhs, long long rhs, long long* difference) { + return __builtin_ssubll_overflow(lhs, rhs, difference); +} + +#endif + +} // namespace mongo diff --git a/src/mongo/platform/overflow_arithmetic_test.cpp b/src/mongo/platform/overflow_arithmetic_test.cpp new file mode 100644 index 00000000000..5a1851fbf81 --- /dev/null +++ b/src/mongo/platform/overflow_arithmetic_test.cpp @@ -0,0 +1,122 @@ +/* Copyright 2016 MongoDB, Inc. + * + * This program is free software: you can redistribute it and/or modify + * it under the terms of the GNU Affero General Public License, version 3, + * as published by the Free Software Foundation. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU Affero General Public License for more details. + * + * You should have received a copy of the GNU Affero General Public License + * along with this program. If not, see <http://www.gnu.org/licenses/>. + * + * As a special exception, the copyright holders give permission to link the + * code of portions of this program with the OpenSSL library under certain + * conditions as described in each individual source file and distribute + * linked combinations including the program with the OpenSSL library. You + * must comply with the GNU Affero General Public License in all respects + * for all of the code used other than as permitted herein. If you modify + * file(s) with this exception, you may extend this exception to your + * version of the file(s), but you are not obligated to do so. If you do not + * wish to do so, delete this exception statement from your version. If you + * delete this exception statement from all source files in the program, + * then also delete it in the license file. + */ + +#include "mongo/platform/basic.h" + +#include <limits> + +#include "mongo/platform/overflow_arithmetic.h" +#include "mongo/unittest/unittest.h" + +namespace mongo { +namespace { + +using limits = std::numeric_limits<int64_t>; + +#define assertArithOverflow(FN, LHS, RHS, EXPECT_OVERFLOW, EXPECTED_RESULT) \ + do { \ + const bool expectOverflow = EXPECT_OVERFLOW; \ + int64_t result; \ + ASSERT_EQ(expectOverflow, FN(LHS, RHS, &result)) << #FN "(" #LHS ", " #RHS; \ + if (!expectOverflow) { \ + ASSERT_EQ(EXPECTED_RESULT, result) << #FN "(" #LHS ", " #RHS " - >"; \ + } \ + } while (false) + +#define assertMultiplyNoOverflow(LHS, RHS, EXPECTED) \ + assertArithOverflow(mongoSignedMultiplyOverflow64, LHS, RHS, false, EXPECTED) +#define assertMultiplyWithOverflow(LHS, RHS) \ + assertArithOverflow(mongoSignedMultiplyOverflow64, LHS, RHS, true, 0) + +#define assertAddNoOverflow(LHS, RHS, EXPECTED) \ + assertArithOverflow(mongoSignedAddOverflow64, LHS, RHS, false, EXPECTED) +#define assertAddWithOverflow(LHS, RHS) \ + assertArithOverflow(mongoSignedAddOverflow64, LHS, RHS, true, 0) + +#define assertSubtractNoOverflow(LHS, RHS, EXPECTED) \ + assertArithOverflow(mongoSignedSubtractOverflow64, LHS, RHS, false, EXPECTED) +#define assertSubtractWithOverflow(LHS, RHS) \ + assertArithOverflow(mongoSignedSubtractOverflow64, LHS, RHS, true, 0) + +TEST(OverflowArithmetic, MultiplicationTests) { + assertMultiplyNoOverflow(0, limits::max(), 0); + assertMultiplyNoOverflow(0, limits::min(), 0); + assertMultiplyNoOverflow(1, limits::max(), limits::max()); + assertMultiplyNoOverflow(1, limits::min(), limits::min()); + assertMultiplyNoOverflow(-1, limits::max(), limits::min() + 1); + assertMultiplyNoOverflow(1000, 57, 57000); + assertMultiplyNoOverflow(1000, -57, -57000); + assertMultiplyNoOverflow(-1000, -57, 57000); + assertMultiplyNoOverflow(0x3fffffffffffffff, 2, 0x7ffffffffffffffe); + assertMultiplyNoOverflow(0x3fffffffffffffff, -2, -0x7ffffffffffffffe); + assertMultiplyNoOverflow(-0x3fffffffffffffff, -2, 0x7ffffffffffffffe); + + assertMultiplyWithOverflow(-1, limits::min()); + assertMultiplyWithOverflow(2, limits::max()); + assertMultiplyWithOverflow(-2, limits::max()); + assertMultiplyWithOverflow(2, limits::min()); + assertMultiplyWithOverflow(-2, limits::min()); + assertMultiplyWithOverflow(limits::min(), limits::max()); + assertMultiplyWithOverflow(limits::max(), limits::max()); + assertMultiplyWithOverflow(limits::min(), limits::min()); + assertMultiplyWithOverflow(1LL << 62, 8); + assertMultiplyWithOverflow(-(1LL << 62), 8); + assertMultiplyWithOverflow(-(1LL << 62), -8); +} + +TEST(OverflowArithmetic, AdditionTests) { + assertAddNoOverflow(0, limits::max(), limits::max()); + assertAddNoOverflow(-1, limits::max(), limits::max() - 1); + assertAddNoOverflow(0, limits::min(), limits::min()); + assertAddNoOverflow(1, limits::min(), limits::min() + 1); + assertAddNoOverflow(limits::max(), limits::min(), -1); + assertAddNoOverflow(1, 1, 2); + assertAddNoOverflow(-1, -1, -2); + + assertAddWithOverflow(limits::max(), 1); + assertAddWithOverflow(limits::max(), limits::max()); + assertAddWithOverflow(limits::min(), -1); + assertAddWithOverflow(limits::min(), limits::min()); +} + +TEST(OverflowArithmetic, SubtractionTests) { + assertSubtractNoOverflow(limits::max(), 0, limits::max()); + assertSubtractNoOverflow(limits::max(), 1, limits::max() - 1); + assertSubtractNoOverflow(limits::min(), 0, limits::min()); + assertSubtractNoOverflow(limits::min(), -1, limits::min() + 1); + assertSubtractNoOverflow(limits::max(), limits::max(), 0); + assertSubtractNoOverflow(limits::min(), limits::min(), 0); + + assertSubtractWithOverflow(0, limits::min()); + assertSubtractWithOverflow(limits::max(), -1); + assertSubtractWithOverflow(limits::max(), limits::min()); + assertSubtractWithOverflow(limits::min(), 1); + assertSubtractWithOverflow(limits::min(), limits::max()); +} + +} // namespace +} // namespace mongo |