dolphin/Source/UnitTests/Common/BitFieldTest.cpp

// Copyright 2014 Dolphin Emulator Project
// Licensed under GPLv2
// Refer to the license.txt file included.

#include <gtest/gtest.h>

#include "Common/BitField.h"
#include "Common/CommonTypes.h"

union TestUnion
{
	u64 hex;

	BitField< 0,64,u64> full_u64;   // spans whole storage
	BitField< 0,64,s64> full_s64;   // spans whole storage

	BitField< 9, 3,u64> regular_field_unsigned;  // a plain bitfield
	BitField< 9, 3,u64> regular_field_unsigned2; // Just the very same bitfield again
	BitField< 9, 3,s64> regular_field_signed;    // Same bitfield, but different sign

	BitField<30, 4,s64> at_dword_boundary;  // goes over the boundary of two u32 values

	BitField<15, 1,s64> signed_1bit;  // allowed values: -1 and 0
};

// table of raw numbers to test with
static u64 table[] =
{
	0x0000000000000000ull, // all zero
	0xffffffffffffffffull, // all one
	0x7fffffffffffffffull, // all one apart from the sign bit
	0x8000000000000000ull, // all zero apart from the sign bit
	0x8000000000000048ull, // regular_field = 0b1001

	// "random" numbers
	0x0F7B8B1ABD9B8D3Full,
	0xA8B86F73FDAADD2Dull,
	0x1B17A557BFEB351Dull,
	0xE3354268B0C2395Bull,
};

// Verify that bitfields in a union have the same underlying data
TEST(BitField, Storage)
{
	TestUnion object;

	EXPECT_EQ((void*)&object.hex, (void*)&object.regular_field_unsigned);
	EXPECT_EQ(sizeof(TestUnion), sizeof(object.hex));
	EXPECT_EQ(sizeof(TestUnion), sizeof(object.full_u64));
	EXPECT_EQ(sizeof(TestUnion), sizeof(object.full_s64));
	EXPECT_EQ(sizeof(TestUnion), sizeof(object.regular_field_unsigned));
	EXPECT_EQ(sizeof(TestUnion), sizeof(object.regular_field_signed));
	EXPECT_EQ(sizeof(TestUnion), sizeof(object.at_dword_boundary));
	EXPECT_EQ(sizeof(TestUnion), sizeof(object.signed_1bit));

	// Now write some values to one field and check if this reflects properly
	// in the others.
	for (u64 val : table)
	{
		object.hex = val;
		EXPECT_EQ(object.hex, object.full_u64);
		EXPECT_EQ(object.regular_field_unsigned, object.regular_field_unsigned2);

		object.regular_field_unsigned = val & 0x3;
		EXPECT_EQ(object.hex, object.full_u64);
		EXPECT_EQ(object.regular_field_unsigned, object.regular_field_unsigned2);
	}
}

TEST(BitField, Read)
{
	TestUnion object;

	for (u64 val : table)
	{
		object.hex = val;

		// Make sure reading/casting does not behave completely idiotic
		EXPECT_EQ(object.full_u64, (u64)object.full_u64);
		EXPECT_EQ(object.full_s64, (s64)object.full_s64);
		EXPECT_EQ(object.regular_field_unsigned, (u64)object.regular_field_unsigned);
		EXPECT_EQ(object.regular_field_unsigned2, (u64)object.regular_field_unsigned2);
		EXPECT_EQ(object.regular_field_signed, (s64)object.regular_field_signed);
		EXPECT_EQ(object.at_dword_boundary, (s64)object.at_dword_boundary);
		EXPECT_EQ(object.signed_1bit, (s64)object.signed_1bit);

		// Now make sure the value is indeed correct
		EXPECT_EQ(val, object.full_u64);
		EXPECT_EQ(*(s64*)&val, object.full_s64);
		EXPECT_EQ((val >> 9) & 0x7, object.regular_field_unsigned);
		EXPECT_EQ((val >> 9) & 0x7, object.regular_field_unsigned2);
		EXPECT_EQ(((s64)(object.hex << 52)) >> 61, object.regular_field_signed);
		EXPECT_EQ(((s64)(object.hex << 30)) >> 60, object.at_dword_boundary);
		EXPECT_EQ(((object.hex >> 15) & 1) ? -1 : 0, object.signed_1bit);
	}
}

TEST(BitField, Assignment)
{
	TestUnion object;

	for (u64 val : table)
	{
		// Assignments with fixed values
		object.full_u64 = val;
		EXPECT_EQ(val, object.full_u64);

		object.full_s64 = (s64)val;
		EXPECT_EQ(val, object.full_u64);

		object.regular_field_unsigned = val;
		EXPECT_EQ(val & 0x7, object.regular_field_unsigned);

		object.at_dword_boundary = val;
		EXPECT_EQ(((s64)(val << 60)) >> 60, object.at_dword_boundary);

		object.signed_1bit = val;
		EXPECT_EQ((val & 1) ? -1 : 0, object.signed_1bit);

		object.regular_field_signed = val;
		EXPECT_EQ(((s64)(object.hex << 61)) >> 61, object.regular_field_signed);

		// Assignment from other BitField
		object.at_dword_boundary = object.regular_field_signed;
		EXPECT_EQ(object.regular_field_signed, object.at_dword_boundary);
	}
}

// Test class behavior on oddly aligned structures.
TEST(BitField, Alignment)
{
	#pragma pack(1)
	struct OddlyAlignedTestStruct
	{
		u8 padding;
		TestUnion obj;
	};
	#pragma pack()

	GC_ALIGNED16(OddlyAlignedTestStruct test_struct);
	TestUnion& object = test_struct.obj;
	static_assert(alignof(decltype(test_struct.obj.signed_1bit)) == 1,
		"Incorrect variable alignment");

	for (u64 val : table)
	{
		// Assignments with fixed values
		object.full_u64 = val;
		EXPECT_EQ(val, object.full_u64);

		object.full_s64 = (s64)val;
		EXPECT_EQ(val, object.full_u64);

		object.regular_field_unsigned = val;
		EXPECT_EQ(val & 0x7, object.regular_field_unsigned);

		object.at_dword_boundary = val;
		EXPECT_EQ(((s64)(val << 60)) >> 60, object.at_dword_boundary);

		object.signed_1bit = val;
		EXPECT_EQ((val & 1) ? -1 : 0, object.signed_1bit);

		object.regular_field_signed = val;
		EXPECT_EQ(((s64)(object.hex << 61)) >> 61, object.regular_field_signed);

		// Assignment from other BitField
		object.at_dword_boundary = object.regular_field_signed;
		EXPECT_EQ(object.regular_field_signed, object.at_dword_boundary);
	}
}