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Use std::is_signed and std::enable_if.

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This commit is contained in:
Kevin Backhouse 2022-10-27 11:09:25 +01:00 committed by Rosen Penev
parent 335e13251e
commit ddd7ccf722
2 changed files with 25 additions and 54 deletions
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45
src/safe_op.hpp
View File

@ -5,6 +5,7 @@
#include <limits>
#include <stdexcept>
#include <type_traits>
#ifdef _MSC_VER
#include <Intsafe.h>
@ -37,35 +38,6 @@ namespace Safe {
* is available.
*/
namespace Internal {
/*!
* @brief Helper struct to determine whether a type is signed or unsigned
*
* This struct is a backport of std::is_signed from C++11. It has a public
* enum with the property VALUE which is true when the type is signed or
* false if it is unsigned.
*/
template <typename T>
struct is_signed {
enum { VALUE = static_cast<T>(-1) < static_cast<T>(0) };
};
/*!
* @brief Helper struct for SFINAE, from C++11
* This struct has a public typedef called type typedef'd to T if B is
* true. Otherwise there is no typedef.
*/
template <bool B, class T = void>
struct enable_if {};
/*!
* @brief Specialization of enable_if for the case B == true
*/
template <class T>
struct enable_if<true, T> {
using type = T;
};
/*!
* @brief Check the addition of two numbers for overflows for signed
* integer types larger than int or with the same size as int.
@ -84,9 +56,8 @@ struct enable_if<true, T> {
* https://wiki.sei.cmu.edu/confluence/display/c/INT32-C.+Ensure+that+operations+on+signed+integers+do+not+result+in+overflow
*/
template <typename T>
typename enable_if<is_signed<T>::VALUE && sizeof(T) >= sizeof(int), bool>::type fallback_add_overflow(T summand_1,
T summand_2,
T& result) {
typename std::enable_if<std::is_signed<T>::value && sizeof(T) >= sizeof(int), bool>::type fallback_add_overflow(
T summand_1, T summand_2, T& result) {
if (((summand_2 >= 0) && (summand_1 > std::numeric_limits<T>::max() - summand_2)) ||
((summand_2 < 0) && (summand_1 < std::numeric_limits<T>::min() - summand_2))) {
return true;
@ -116,9 +87,8 @@ typename enable_if<is_signed<T>::VALUE && sizeof(T) >= sizeof(int), bool>::type
* https://wiki.sei.cmu.edu/confluence/display/c/INT02-C.+Understand+integer+conversion+rules
*/
template <typename T>
typename enable_if<is_signed<T>::VALUE && sizeof(T) < sizeof(int), bool>::type fallback_add_overflow(T summand_1,
T summand_2,
T& result) {
typename std::enable_if<std::is_signed<T>::value && sizeof(T) < sizeof(int), bool>::type fallback_add_overflow(
T summand_1, T summand_2, T& result) {
const int res = summand_1 + summand_2;
if ((res > std::numeric_limits<T>::max()) || (res < std::numeric_limits<T>::min())) {
return true;
@ -145,7 +115,8 @@ typename enable_if<is_signed<T>::VALUE && sizeof(T) < sizeof(int), bool>::type f
* https://wiki.sei.cmu.edu/confluence/display/c/INT30-C.+Ensure+that+unsigned+integer+operations+do+not+wrap
*/
template <typename T>
typename enable_if<!is_signed<T>::VALUE, bool>::type fallback_add_overflow(T summand_1, T summand_2, T& result) {
typename std::enable_if<!std::is_signed<T>::value, bool>::type fallback_add_overflow(T summand_1, T summand_2,
T& result) {
result = summand_1 + summand_2;
return result < summand_1;
}
@ -255,7 +226,7 @@ T add(T summand_1, T summand_2) {
* when `num == std::numeric_limits<T>::min()`.
*/
template <typename T>
typename Internal::enable_if<Internal::is_signed<T>::VALUE, T>::type abs(T num) throw() {
typename std::enable_if<std::is_signed<T>::value, T>::type abs(T num) throw() {
if (num == std::numeric_limits<T>::min()) {
return std::numeric_limits<T>::max();
}

34
unitTests/test_safe_op.cpp
View File

@ -26,42 +26,42 @@ struct AdditionTestValues;
* Overload for unsigned types.
*/
template <typename T>
struct AdditionTestValues<T, typename si::enable_if<!si::is_signed<T>::VALUE>::type> {
struct AdditionTestValues<T, typename std::enable_if<!std::is_signed<T>::VALUE>::type> {
static const size_t case_count = 5;
static const T summand[case_count];
static const bool overflow[case_count][case_count];
};
template <typename T>
const T AdditionTestValues<T, typename si::enable_if<!si::is_signed<T>::VALUE>::type>::summand[] = {
const T AdditionTestValues<T, typename std::enable_if<!std::is_signed<T>::VALUE>::type>::summand[] = {
0, 1, 2, static_cast<T>(std::numeric_limits<T>::max() - 1), std::numeric_limits<T>::max()};
template <typename T>
const bool
AdditionTestValues<T, typename si::enable_if<!si::is_signed<T>::VALUE>::type>::overflow[case_count][case_count] = {
// 0
{false, false, false, false, false},
// 1
{false, false, false, false, true},
// 2
{false, false, false, true, true},
// max - 1
{false, false, true, true, true},
// max
{false, true, true, true, true}};
const bool AdditionTestValues<
T, typename std::enable_if<!std::is_signed<T>::VALUE>::type>::overflow[case_count][case_count] = {
// 0
{false, false, false, false, false},
// 1
{false, false, false, false, true},
// 2
{false, false, false, true, true},
// max - 1
{false, false, true, true, true},
// max
{false, true, true, true, true}};
/*!
* Overload for signed integers
*/
template <typename T>
struct AdditionTestValues<T, typename si::enable_if<si::is_signed<T>::VALUE>::type> {
struct AdditionTestValues<T, typename std::enable_if<std::is_signed<T>::VALUE>::type> {
static const size_t case_count = 8;
static const T summand[case_count];
static const bool overflow[case_count][case_count];
};
template <typename T>
const T AdditionTestValues<T, typename si::enable_if<si::is_signed<T>::VALUE>::type>::summand[] = {
const T AdditionTestValues<T, typename std::enable_if<std::is_signed<T>::VALUE>::type>::summand[] = {
std::numeric_limits<T>::min(),
static_cast<T>(std::numeric_limits<T>::min() + 1),
-1,
@ -73,7 +73,7 @@ const T AdditionTestValues<T, typename si::enable_if<si::is_signed<T>::VALUE>::t
template <typename T>
const bool
AdditionTestValues<T, typename si::enable_if<si::is_signed<T>::VALUE>::type>::overflow[case_count][case_count] = {
AdditionTestValues<T, typename std::enable_if<std::is_signed<T>::VALUE>::type>::overflow[case_count][case_count] = {
// min
{true, true, true, false, false, false, false, false},
// min + 1