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/**
* Copyright (C) 2018-present MongoDB, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the Server Side Public License, version 1,
* as published by MongoDB, Inc.
*
* 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
* Server Side Public License for more details.
*
* You should have received a copy of the Server Side Public License
* along with this program. If not, see
* <http://www.mongodb.com/licensing/server-side-public-license>.
*
* 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 Server Side 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 <safeint.h>
#endif
namespace mongo {
/**
* Returns true if multiplying lhs by rhs would overflow. Otherwise, multiplies 64-bit signed
* or unsigned integers lhs by rhs and stores the result in *product.
*/
inline bool mongoSignedMultiplyOverflow64(int64_t lhs, int64_t rhs, int64_t* product);
inline bool mongoUnsignedMultiplyOverflow64(uint64_t lhs, uint64_t rhs, uint64_t* product);
/**
* Returns true if adding lhs and rhs would overflow. Otherwise, adds 64-bit signed or unsigned
* integers lhs and rhs and stores the result in *sum.
*/
inline bool mongoSignedAddOverflow64(int64_t lhs, int64_t rhs, int64_t* sum);
inline bool mongoUnsignedAddOverflow64(uint64_t lhs, uint64_t rhs, uint64_t* sum);
/**
* Returns true if subtracting rhs from lhs would overflow. Otherwise, subtracts 64-bit signed or
* unsigned integers rhs from lhs and stores the result in *difference.
*/
inline bool mongoSignedSubtractOverflow64(int64_t lhs, int64_t rhs, int64_t* difference);
inline bool mongoUnsignedSubtractOverflow64(uint64_t lhs, uint64_t rhs, uint64_t* difference);
#ifdef _MSC_VER
// The microsoft SafeInt functions return true on success, false on overflow. Unfortunately the
// MSVC2015 version contains a typo that prevents the signed variants from compiling in our
// environment.
// TODO The typo was fixed in MSVC2017 so we should try again after we upgrade our toolchain.
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 mongoUnsignedMultiplyOverflow64(uint64_t lhs, uint64_t rhs, uint64_t* product) {
return !msl::utilities::SafeMultiply(lhs, rhs, *product);
}
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 mongoUnsignedAddOverflow64(uint64_t lhs, uint64_t rhs, uint64_t* sum) {
return !msl::utilities::SafeAdd(lhs, rhs, *sum);
}
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;
}
inline bool mongoUnsignedSubtractOverflow64(uint64_t lhs, uint64_t rhs, uint64_t* difference) {
return !msl::utilities::SafeSubtract(lhs, rhs, *difference);
}
#else
// On GCC and CLANG we can use __builtin functions to perform these calculations. These return true
// on overflow and false on success.
inline bool mongoSignedMultiplyOverflow64(long lhs, long rhs, long* product) {
return __builtin_mul_overflow(lhs, rhs, product);
}
inline bool mongoSignedMultiplyOverflow64(long long lhs, long long rhs, long long* product) {
return __builtin_mul_overflow(lhs, rhs, product);
}
inline bool mongoUnsignedMultiplyOverflow64(unsigned long lhs,
unsigned long rhs,
unsigned long* product) {
return __builtin_mul_overflow(lhs, rhs, product);
}
inline bool mongoUnsignedMultiplyOverflow64(unsigned long long lhs,
unsigned long long rhs,
unsigned long long* product) {
return __builtin_mul_overflow(lhs, rhs, product);
}
inline bool mongoSignedAddOverflow64(long lhs, long rhs, long* sum) {
return __builtin_add_overflow(lhs, rhs, sum);
}
inline bool mongoSignedAddOverflow64(long long lhs, long long rhs, long long* sum) {
return __builtin_add_overflow(lhs, rhs, sum);
}
inline bool mongoUnsignedAddOverflow64(unsigned long lhs, unsigned long rhs, unsigned long* sum) {
return __builtin_add_overflow(lhs, rhs, sum);
}
inline bool mongoUnsignedAddOverflow64(unsigned long long lhs,
unsigned long long rhs,
unsigned long long* sum) {
return __builtin_add_overflow(lhs, rhs, sum);
}
inline bool mongoSignedSubtractOverflow64(long lhs, long rhs, long* difference) {
return __builtin_sub_overflow(lhs, rhs, difference);
}
inline bool mongoSignedSubtractOverflow64(long long lhs, long long rhs, long long* difference) {
return __builtin_sub_overflow(lhs, rhs, difference);
}
inline bool mongoUnsignedSubtractOverflow64(unsigned long lhs,
unsigned long rhs,
unsigned long* sum) {
return __builtin_sub_overflow(lhs, rhs, sum);
}
inline bool mongoUnsignedSubtractOverflow64(unsigned long long lhs,
unsigned long long rhs,
unsigned long long* sum) {
return __builtin_sub_overflow(lhs, rhs, sum);
}
#endif
} // namespace mongo
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