common/bitfield: make it endianness-aware

This commit is contained in:
Weiyi Wang 2019-01-25 12:16:23 -05:00 committed by fearlessTobi
parent 71530781f3
commit 6b81ceb060
3 changed files with 100 additions and 3 deletions

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@ -34,6 +34,7 @@
#include <limits> #include <limits>
#include <type_traits> #include <type_traits>
#include "common/common_funcs.h" #include "common/common_funcs.h"
#include "common/swap.h"
/* /*
* Abstract bitfield class * Abstract bitfield class
@ -108,7 +109,7 @@
* symptoms. * symptoms.
*/ */
#pragma pack(1) #pragma pack(1)
template <std::size_t Position, std::size_t Bits, typename T> template <std::size_t Position, std::size_t Bits, typename T, typename EndianTag = LETag>
struct BitField { struct BitField {
private: private:
// We hide the copy assigment operator here, because the default copy // We hide the copy assigment operator here, because the default copy
@ -127,6 +128,8 @@ private:
// We store the value as the unsigned type to avoid undefined behaviour on value shifting // We store the value as the unsigned type to avoid undefined behaviour on value shifting
using StorageType = std::make_unsigned_t<UnderlyingType>; using StorageType = std::make_unsigned_t<UnderlyingType>;
using StorageTypeWithEndian = typename AddEndian<StorageType, EndianTag>::type;
public: public:
/// Constants to allow limited introspection of fields if needed /// Constants to allow limited introspection of fields if needed
static constexpr std::size_t position = Position; static constexpr std::size_t position = Position;
@ -172,7 +175,7 @@ public:
} }
constexpr FORCE_INLINE void Assign(const T& value) { constexpr FORCE_INLINE void Assign(const T& value) {
storage = (storage & ~mask) | FormatValue(value); storage = (static_cast<StorageType>(storage) & ~mask) | FormatValue(value);
} }
constexpr T Value() const { constexpr T Value() const {
@ -184,7 +187,7 @@ public:
} }
private: private:
StorageType storage; StorageTypeWithEndian storage;
static_assert(bits + position <= 8 * sizeof(T), "Bitfield out of range"); static_assert(bits + position <= 8 * sizeof(T), "Bitfield out of range");
@ -195,3 +198,6 @@ private:
static_assert(std::is_trivially_copyable_v<T>, "T must be trivially copyable in a BitField"); static_assert(std::is_trivially_copyable_v<T>, "T must be trivially copyable in a BitField");
}; };
#pragma pack() #pragma pack()
template <std::size_t Position, std::size_t Bits, typename T>
using BitFieldBE = BitField<Position, Bits, T, BETag>;

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@ -1,4 +1,5 @@
add_executable(tests add_executable(tests
common/bit_field.cpp
common/param_package.cpp common/param_package.cpp
common/ring_buffer.cpp common/ring_buffer.cpp
core/arm/arm_test_common.cpp core/arm/arm_test_common.cpp

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@ -0,0 +1,90 @@
// Copyright 2019 Citra Emulator Project
// Licensed under GPLv2 or any later version
// Refer to the license.txt file included.
#include <array>
#include <cstring>
#include <type_traits>
#include <catch2/catch.hpp>
#include "common/bit_field.h"
TEST_CASE("BitField", "[common]") {
enum class TestEnum : u32 {
A = 0b10111101,
B = 0b10101110,
C = 0b00001111,
};
union LEBitField {
u32_le raw;
BitField<0, 6, u32> a;
BitField<6, 4, s32> b;
BitField<10, 8, TestEnum> c;
BitField<18, 14, u32> d;
} le_bitfield;
union BEBitField {
u32_be raw;
BitFieldBE<0, 6, u32> a;
BitFieldBE<6, 4, s32> b;
BitFieldBE<10, 8, TestEnum> c;
BitFieldBE<18, 14, u32> d;
} be_bitfield;
static_assert(sizeof(LEBitField) == sizeof(u32));
static_assert(sizeof(BEBitField) == sizeof(u32));
static_assert(std::is_trivially_copyable_v<LEBitField>);
static_assert(std::is_trivially_copyable_v<BEBitField>);
std::array<u8, 4> raw{{
0b01101100,
0b11110110,
0b10111010,
0b11101100,
}};
std::memcpy(&le_bitfield, &raw, sizeof(raw));
std::memcpy(&be_bitfield, &raw, sizeof(raw));
// bit fields: 11101100101110'10111101'1001'101100
REQUIRE(le_bitfield.raw == 0b11101100'10111010'11110110'01101100);
REQUIRE(le_bitfield.a == 0b101100);
REQUIRE(le_bitfield.b == -7); // 1001 as two's complement
REQUIRE(le_bitfield.c == TestEnum::A);
REQUIRE(le_bitfield.d == 0b11101100101110);
le_bitfield.a.Assign(0b000111);
le_bitfield.b.Assign(-1);
le_bitfield.c.Assign(TestEnum::C);
le_bitfield.d.Assign(0b01010101010101);
std::memcpy(&raw, &le_bitfield, sizeof(raw));
// bit fields: 01010101010101'00001111'1111'000111
REQUIRE(le_bitfield.raw == 0b01010101'01010100'00111111'11000111);
REQUIRE(raw == std::array<u8, 4>{{
0b11000111,
0b00111111,
0b01010100,
0b01010101,
}});
// bit fields: 01101100111101'10101110'1011'101100
REQUIRE(be_bitfield.raw == 0b01101100'11110110'10111010'11101100);
REQUIRE(be_bitfield.a == 0b101100);
REQUIRE(be_bitfield.b == -5); // 1011 as two's complement
REQUIRE(be_bitfield.c == TestEnum::B);
REQUIRE(be_bitfield.d == 0b01101100111101);
be_bitfield.a.Assign(0b000111);
be_bitfield.b.Assign(-1);
be_bitfield.c.Assign(TestEnum::C);
be_bitfield.d.Assign(0b01010101010101);
std::memcpy(&raw, &be_bitfield, sizeof(raw));
// bit fields: 01010101010101'00001111'1111'000111
REQUIRE(be_bitfield.raw == 0b01010101'01010100'00111111'11000111);
REQUIRE(raw == std::array<u8, 4>{{
0b01010101,
0b01010100,
0b00111111,
0b11000111,
}});
}