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add: [imp] dataof

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mutouyun 2023-05-27 15:53:52 +08:00
parent ce04c79112
commit 07c13f1b3a
2 changed files with 111 additions and 0 deletions
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92
include/libimp/dataof.h Normal file
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@ -0,0 +1,92 @@
/**
* \file libimp/dataof.h
* \author mutouyun (orz@orzz.org)
* \brief Returns the data pointer of the given range
* \date 2023-05-27
*/
#pragma once
#include <type_traits> // std::declval, std::true_type, std::false_type
#include <cstddef> // std::size_t
#include "libimp/def.h"
#include "libimp/generic.h"
LIBIMP_NAMESPACE_BEG_
/**
* \see https://en.cppreference.com/w/cpp/iterator/data
*/
namespace detail_dataof {
template <typename T>
struct trait_has_data {
private:
template <typename Type>
static std::true_type check(decltype(std::declval<Type>().data())*);
template <typename Type>
static std::false_type check(...);
public:
using type = decltype(check<T>(nullptr));
constexpr static auto value = type::value;
};
template <typename T>
struct trait_has_Data {
private:
template <typename Type>
static std::true_type check(decltype(std::declval<Type>().Data())*);
template <typename Type>
static std::false_type check(...);
public:
using type = decltype(check<T>(nullptr));
constexpr static auto value = type::value;
};
template <typename C, bool = trait_has_data<C>::value
, bool = trait_has_Data<C>::value>
struct trait;
template <typename T, std::size_t N>
struct trait<T[N], false, false> {
constexpr static T const *dataof(T const (&arr)[N]) noexcept {
return arr;
}
constexpr static T *dataof(T (&arr)[N]) noexcept {
return arr;
}
};
template <typename C, bool B>
struct trait<C, true, B> {
template <typename T>
constexpr static auto dataof(T &&c) noexcept(noexcept(c.data())) {
return std::forward<T>(c).data();
}
};
template <typename C>
struct trait<C, false, true> {
template <typename T>
constexpr static auto dataof(T &&c) noexcept(noexcept(c.Data())) {
return std::forward<T>(c).Data();
}
};
template <typename C>
struct trait<C, false, false> {
template <typename T>
constexpr static T const *dataof(std::initializer_list<T> il) noexcept {
return il.begin();
}
};
} // namespace detail_dataof
template <typename T, typename R = detail_dataof::trait<std::remove_cv_t<std::remove_reference_t<T>>>>
constexpr auto dataof(T &&c) noexcept(noexcept(R::dataof(std::forward<T>(c)))) {
return R::dataof(std::forward<T>(c));
}
LIBIMP_NAMESPACE_END_

19
test/imp/test_imp_utility.cpp
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@ -8,6 +8,7 @@
#include "libimp/construct.h"
#include "libimp/pimpl.h"
#include "libimp/countof.h"
#include "libimp/dataof.h"
#include "libimp/horrible_cast.h"
#include "libimp/detect_plat.h"
#include "libimp/generic.h"
@ -100,9 +101,27 @@ TEST(utility, countof) {
std::vector<int> vec {1, 2, 3, 4, 5};
int arr[] {7, 6, 5, 4, 3, 2, 1};
auto il = {9, 7, 6, 4, 3, 1, 5};
EXPECT_EQ(imp::countof(sv) , sv.Size());
EXPECT_EQ(imp::countof(vec), vec.size());
EXPECT_EQ(imp::countof(arr), sizeof(arr) / sizeof(arr[0]));
EXPECT_EQ(imp::countof(il) , il.size());
}
TEST(utility, dataof) {
struct {
constexpr int *Data() const noexcept { return (int *)this; }
} sv;
EXPECT_FALSE(imp::detail_dataof::trait_has_data<decltype(sv)>::value);
EXPECT_TRUE (imp::detail_dataof::trait_has_Data<decltype(sv)>::value);
std::vector<int> vec {1, 2, 3, 4, 5};
int arr[] {7, 6, 5, 4, 3, 2, 1};
auto il = {9, 7, 6, 4, 3, 1, 5};
EXPECT_EQ(imp::dataof(sv) , sv.Data());
EXPECT_EQ(imp::dataof(vec), vec.data());
EXPECT_EQ(imp::dataof(arr), arr);
EXPECT_EQ(imp::dataof(il) , il.begin());
}
TEST(utility, horrible_cast) {