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()

  alignas(16) 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);
  }
}