// Copyright 2017 The Dawn Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#include "tests/DawnTest.h"

#include <array>
#include <cstring>

class BufferMappingTests : public DawnTest {
  protected:
    void MapAsyncAndWait(const wgpu::Buffer& buffer,
                         wgpu::MapMode mode,
                         size_t offset,
                         size_t size) {
        bool done = false;
        buffer.MapAsync(
            mode, offset, size,
            [](WGPUBufferMapAsyncStatus status, void* userdata) {
                ASSERT_EQ(WGPUBufferMapAsyncStatus_Success, status);
                *static_cast<bool*>(userdata) = true;
            },
            &done);

        while (!done) {
            WaitABit();
        }
    }

    wgpu::Buffer CreateMapReadBuffer(uint64_t size) {
        wgpu::BufferDescriptor descriptor;
        descriptor.size = size;
        descriptor.usage = wgpu::BufferUsage::MapRead | wgpu::BufferUsage::CopyDst;
        return device.CreateBuffer(&descriptor);
    }

    wgpu::Buffer CreateMapWriteBuffer(uint64_t size) {
        wgpu::BufferDescriptor descriptor;
        descriptor.size = size;
        descriptor.usage = wgpu::BufferUsage::MapWrite | wgpu::BufferUsage::CopySrc;
        return device.CreateBuffer(&descriptor);
    }
};

void CheckMapping(const void* actual, const void* expected, size_t size) {
    EXPECT_NE(actual, nullptr);
    if (actual != nullptr) {
        EXPECT_EQ(0, memcmp(actual, expected, size));
    }
}

// Test that the simplest map read works
TEST_P(BufferMappingTests, MapRead_Basic) {
    wgpu::Buffer buffer = CreateMapReadBuffer(4);

    uint32_t myData = 0x01020304;
    constexpr size_t kSize = sizeof(myData);
    queue.WriteBuffer(buffer, 0, &myData, kSize);

    MapAsyncAndWait(buffer, wgpu::MapMode::Read, 0, 4);
    CheckMapping(buffer.GetConstMappedRange(), &myData, kSize);
    CheckMapping(buffer.GetConstMappedRange(0, kSize), &myData, kSize);
    buffer.Unmap();
}

// Test map-reading a zero-sized buffer.
TEST_P(BufferMappingTests, MapRead_ZeroSized) {
    wgpu::Buffer buffer = CreateMapReadBuffer(0);

    MapAsyncAndWait(buffer, wgpu::MapMode::Read, 0, 0);
    ASSERT_NE(buffer.GetConstMappedRange(), nullptr);
    buffer.Unmap();
}

// Test map-reading with a non-zero offset
TEST_P(BufferMappingTests, MapRead_NonZeroOffset) {
    wgpu::Buffer buffer = CreateMapReadBuffer(12);

    uint32_t myData[3] = {0x01020304, 0x05060708, 0x090A0B0C};
    queue.WriteBuffer(buffer, 0, &myData, sizeof(myData));

    MapAsyncAndWait(buffer, wgpu::MapMode::Read, 8, 4);
    ASSERT_EQ(myData[2], *static_cast<const uint32_t*>(buffer.GetConstMappedRange(8)));
    buffer.Unmap();
}

// Map read and unmap twice. Test that both of these two iterations work.
TEST_P(BufferMappingTests, MapRead_Twice) {
    wgpu::Buffer buffer = CreateMapReadBuffer(4);

    uint32_t myData = 0x01020304;
    queue.WriteBuffer(buffer, 0, &myData, sizeof(myData));

    MapAsyncAndWait(buffer, wgpu::MapMode::Read, 0, 4);
    ASSERT_EQ(myData, *static_cast<const uint32_t*>(buffer.GetConstMappedRange()));
    buffer.Unmap();

    myData = 0x05060708;
    queue.WriteBuffer(buffer, 0, &myData, sizeof(myData));

    MapAsyncAndWait(buffer, wgpu::MapMode::Read, 0, 4);
    ASSERT_EQ(myData, *static_cast<const uint32_t*>(buffer.GetConstMappedRange()));
    buffer.Unmap();
}

// Test map-reading a large buffer.
TEST_P(BufferMappingTests, MapRead_Large) {
    constexpr uint32_t kDataSize = 1000 * 1000;
    constexpr size_t kByteSize = kDataSize * sizeof(uint32_t);
    wgpu::Buffer buffer = CreateMapReadBuffer(kByteSize);

    std::vector<uint32_t> myData;
    for (uint32_t i = 0; i < kDataSize; ++i) {
        myData.push_back(i);
    }
    queue.WriteBuffer(buffer, 0, myData.data(), kByteSize);

    MapAsyncAndWait(buffer, wgpu::MapMode::Read, 0, kByteSize);
    EXPECT_EQ(nullptr, buffer.GetConstMappedRange(0, kByteSize + 4));
    EXPECT_EQ(0, memcmp(buffer.GetConstMappedRange(), myData.data(), kByteSize));
    EXPECT_EQ(0, memcmp(buffer.GetConstMappedRange(8), myData.data() + 2, kByteSize - 8));
    EXPECT_EQ(
        0, memcmp(buffer.GetConstMappedRange(8, kByteSize - 8), myData.data() + 2, kByteSize - 8));
    buffer.Unmap();

    MapAsyncAndWait(buffer, wgpu::MapMode::Read, 16, kByteSize - 16);
    // Size is too big.
    EXPECT_EQ(nullptr, buffer.GetConstMappedRange(16, kByteSize - 12));
    // Offset defaults to 0 which is less than 16
    EXPECT_EQ(nullptr, buffer.GetConstMappedRange());
    // Offset less than 8 is less than 16
    EXPECT_EQ(nullptr, buffer.GetConstMappedRange(8));

    // Test a couple values.
    EXPECT_EQ(0, memcmp(buffer.GetConstMappedRange(16), myData.data() + 4, kByteSize - 16));
    EXPECT_EQ(0, memcmp(buffer.GetConstMappedRange(24), myData.data() + 6, kByteSize - 24));

    buffer.Unmap();
}

// Test that GetConstMappedRange works inside map-read callback
TEST_P(BufferMappingTests, MapRead_InCallback) {
    constexpr size_t kBufferSize = 12;
    wgpu::Buffer buffer = CreateMapReadBuffer(kBufferSize);

    uint32_t myData[3] = {0x01020304, 0x05060708, 0x090A0B0C};
    static constexpr size_t kSize = sizeof(myData);
    queue.WriteBuffer(buffer, 0, &myData, kSize);

    struct UserData {
        bool done;
        wgpu::Buffer buffer;
        void* expected;
    };
    UserData user{false, buffer, &myData};

    buffer.MapAsync(
        wgpu::MapMode::Read, 0, kBufferSize,
        [](WGPUBufferMapAsyncStatus status, void* userdata) {
            UserData* user = static_cast<UserData*>(userdata);

            EXPECT_EQ(WGPUBufferMapAsyncStatus_Success, status);
            if (status == WGPUBufferMapAsyncStatus_Success) {
                CheckMapping(user->buffer.GetConstMappedRange(), user->expected, kSize);
                CheckMapping(user->buffer.GetConstMappedRange(0, kSize), user->expected, kSize);

                CheckMapping(user->buffer.GetConstMappedRange(8, 4),
                             static_cast<const uint32_t*>(user->expected) + 2, sizeof(uint32_t));

                user->buffer.Unmap();
            }
            user->done = true;
        },
        &user);

    while (!user.done) {
        WaitABit();
    }
}

// Test that the simplest map write works.
TEST_P(BufferMappingTests, MapWrite_Basic) {
    wgpu::Buffer buffer = CreateMapWriteBuffer(4);

    uint32_t myData = 2934875;
    MapAsyncAndWait(buffer, wgpu::MapMode::Write, 0, 4);
    ASSERT_NE(nullptr, buffer.GetMappedRange());
    ASSERT_NE(nullptr, buffer.GetConstMappedRange());
    memcpy(buffer.GetMappedRange(), &myData, sizeof(myData));
    buffer.Unmap();

    EXPECT_BUFFER_U32_EQ(myData, buffer, 0);
}

// Test that the simplest map write works with a range.
TEST_P(BufferMappingTests, MapWrite_BasicRange) {
    wgpu::Buffer buffer = CreateMapWriteBuffer(4);

    uint32_t myData = 2934875;
    MapAsyncAndWait(buffer, wgpu::MapMode::Write, 0, 4);
    ASSERT_NE(nullptr, buffer.GetMappedRange(0, 4));
    ASSERT_NE(nullptr, buffer.GetConstMappedRange(0, 4));
    memcpy(buffer.GetMappedRange(), &myData, sizeof(myData));
    buffer.Unmap();

    EXPECT_BUFFER_U32_EQ(myData, buffer, 0);
}

// Test map-writing a zero-sized buffer.
TEST_P(BufferMappingTests, MapWrite_ZeroSized) {
    wgpu::Buffer buffer = CreateMapWriteBuffer(0);

    MapAsyncAndWait(buffer, wgpu::MapMode::Write, 0, 0);
    ASSERT_NE(buffer.GetConstMappedRange(), nullptr);
    ASSERT_NE(buffer.GetMappedRange(), nullptr);
    buffer.Unmap();
}

// Test map-writing with a non-zero offset.
TEST_P(BufferMappingTests, MapWrite_NonZeroOffset) {
    wgpu::Buffer buffer = CreateMapWriteBuffer(12);

    uint32_t myData = 2934875;
    MapAsyncAndWait(buffer, wgpu::MapMode::Write, 8, 4);
    memcpy(buffer.GetMappedRange(8), &myData, sizeof(myData));
    buffer.Unmap();

    EXPECT_BUFFER_U32_EQ(myData, buffer, 8);
}

// Map, write and unmap twice. Test that both of these two iterations work.
TEST_P(BufferMappingTests, MapWrite_Twice) {
    wgpu::Buffer buffer = CreateMapWriteBuffer(4);

    uint32_t myData = 2934875;
    MapAsyncAndWait(buffer, wgpu::MapMode::Write, 0, 4);
    memcpy(buffer.GetMappedRange(), &myData, sizeof(myData));
    buffer.Unmap();

    EXPECT_BUFFER_U32_EQ(myData, buffer, 0);

    myData = 9999999;
    MapAsyncAndWait(buffer, wgpu::MapMode::Write, 0, 4);
    memcpy(buffer.GetMappedRange(), &myData, sizeof(myData));
    buffer.Unmap();

    EXPECT_BUFFER_U32_EQ(myData, buffer, 0);
}

// Test mapping a large buffer.
TEST_P(BufferMappingTests, MapWrite_Large) {
    constexpr uint32_t kDataSize = 1000 * 1000;
    constexpr size_t kByteSize = kDataSize * sizeof(uint32_t);
    wgpu::Buffer buffer = CreateMapWriteBuffer(kDataSize * sizeof(uint32_t));

    std::vector<uint32_t> myData;
    for (uint32_t i = 0; i < kDataSize; ++i) {
        myData.push_back(i);
    }

    MapAsyncAndWait(buffer, wgpu::MapMode::Write, 16, kByteSize - 20);
    EXPECT_EQ(nullptr, buffer.GetMappedRange());
    EXPECT_EQ(nullptr, buffer.GetMappedRange(0));
    EXPECT_EQ(nullptr, buffer.GetMappedRange(8));
    EXPECT_EQ(nullptr, buffer.GetMappedRange(16, kByteSize - 8));
    memcpy(buffer.GetMappedRange(16), myData.data(), kByteSize - 20);
    buffer.Unmap();
    EXPECT_BUFFER_U32_RANGE_EQ(myData.data(), buffer, 16, kDataSize - 5);
}

// Stress test mapping many buffers.
TEST_P(BufferMappingTests, MapWrite_ManySimultaneous) {
    constexpr uint32_t kDataSize = 1000;
    std::vector<uint32_t> myData;
    for (uint32_t i = 0; i < kDataSize; ++i) {
        myData.push_back(i);
    }

    constexpr uint32_t kBuffers = 100;
    std::array<wgpu::Buffer, kBuffers> buffers;
    uint32_t mapCompletedCount = 0;

    // Create buffers and request mapping them.
    wgpu::BufferDescriptor descriptor;
    descriptor.size = static_cast<uint32_t>(kDataSize * sizeof(uint32_t));
    descriptor.usage = wgpu::BufferUsage::MapWrite | wgpu::BufferUsage::CopySrc;
    for (uint32_t i = 0; i < kBuffers; ++i) {
        buffers[i] = device.CreateBuffer(&descriptor);

        buffers[i].MapAsync(
            wgpu::MapMode::Write, 0, descriptor.size,
            [](WGPUBufferMapAsyncStatus status, void* userdata) {
                ASSERT_EQ(WGPUBufferMapAsyncStatus_Success, status);
                (*static_cast<uint32_t*>(userdata))++;
            },
            &mapCompletedCount);
    }

    // Wait for all mappings to complete
    while (mapCompletedCount != kBuffers) {
        WaitABit();
    }

    // All buffers are mapped, write into them and unmap them all.
    for (uint32_t i = 0; i < kBuffers; ++i) {
        memcpy(buffers[i].GetMappedRange(0, descriptor.size), myData.data(), descriptor.size);
        buffers[i].Unmap();
    }

    // Check the content of the buffers.
    for (uint32_t i = 0; i < kBuffers; ++i) {
        EXPECT_BUFFER_U32_RANGE_EQ(myData.data(), buffers[i], 0, kDataSize);
    }
}

// Test that the map offset isn't updated when the call is an error.
TEST_P(BufferMappingTests, OffsetNotUpdatedOnError) {
    uint32_t data[3] = {0xCA7, 0xB0A7, 0xBA7};
    wgpu::Buffer buffer = CreateMapReadBuffer(sizeof(data));
    queue.WriteBuffer(buffer, 0, data, sizeof(data));

    // Map the buffer but do not wait on the result yet.
    bool done = false;
    buffer.MapAsync(
        wgpu::MapMode::Read, 8, 4,
        [](WGPUBufferMapAsyncStatus status, void* userdata) {
            ASSERT_EQ(WGPUBufferMapAsyncStatus_Success, status);
            *static_cast<bool*>(userdata) = true;
        },
        &done);

    // Call MapAsync another time, it is an error because the buffer is already being mapped so
    // mMapOffset is not updated.
    ASSERT_DEVICE_ERROR(buffer.MapAsync(wgpu::MapMode::Read, 0, 4, nullptr, nullptr));

    while (!done) {
        WaitABit();
    }

    // mMapOffset has not been updated so it should still be 4, which is data[1]
    ASSERT_EQ(0, memcmp(buffer.GetConstMappedRange(8), &data[2], sizeof(uint32_t)));
}

// Test that Get(Const)MappedRange work inside map-write callback.
TEST_P(BufferMappingTests, MapWrite_InCallbackDefault) {
    wgpu::Buffer buffer = CreateMapWriteBuffer(4);

    static constexpr uint32_t myData = 2934875;
    static constexpr size_t kSize = sizeof(myData);

    struct UserData {
        bool done;
        wgpu::Buffer buffer;
    };
    UserData user{false, buffer};

    buffer.MapAsync(
        wgpu::MapMode::Write, 0, kSize,
        [](WGPUBufferMapAsyncStatus status, void* userdata) {
            UserData* user = static_cast<UserData*>(userdata);

            EXPECT_EQ(WGPUBufferMapAsyncStatus_Success, status);
            if (status == WGPUBufferMapAsyncStatus_Success) {
                EXPECT_NE(nullptr, user->buffer.GetConstMappedRange());
                void* ptr = user->buffer.GetMappedRange();
                EXPECT_NE(nullptr, ptr);
                if (ptr != nullptr) {
                    uint32_t data = myData;
                    memcpy(ptr, &data, kSize);
                }

                user->buffer.Unmap();
            }
            user->done = true;
        },
        &user);

    while (!user.done) {
        WaitABit();
    }

    EXPECT_BUFFER_U32_EQ(myData, buffer, 0);
}

// Test that Get(Const)MappedRange with range work inside map-write callback.
TEST_P(BufferMappingTests, MapWrite_InCallbackRange) {
    wgpu::Buffer buffer = CreateMapWriteBuffer(4);

    static constexpr uint32_t myData = 2934875;
    static constexpr size_t kSize = sizeof(myData);

    struct UserData {
        bool done;
        wgpu::Buffer buffer;
    };
    UserData user{false, buffer};

    buffer.MapAsync(
        wgpu::MapMode::Write, 0, kSize,
        [](WGPUBufferMapAsyncStatus status, void* userdata) {
            UserData* user = static_cast<UserData*>(userdata);

            EXPECT_EQ(WGPUBufferMapAsyncStatus_Success, status);
            if (status == WGPUBufferMapAsyncStatus_Success) {
                EXPECT_NE(nullptr, user->buffer.GetConstMappedRange(0, kSize));
                void* ptr = user->buffer.GetMappedRange(0, kSize);
                EXPECT_NE(nullptr, ptr);
                if (ptr != nullptr) {
                    uint32_t data = myData;
                    memcpy(ptr, &data, kSize);
                }

                user->buffer.Unmap();
            }
            user->done = true;
        },
        &user);

    while (!user.done) {
        WaitABit();
    }

    EXPECT_BUFFER_U32_EQ(myData, buffer, 0);
}

DAWN_INSTANTIATE_TEST(BufferMappingTests,
                      D3D12Backend(),
                      MetalBackend(),
                      OpenGLBackend(),
                      VulkanBackend());

class BufferMappedAtCreationTests : public DawnTest {
  protected:
    static void MapCallback(WGPUBufferMapAsyncStatus status, void* userdata) {
        EXPECT_EQ(WGPUBufferMapAsyncStatus_Success, status);
        *static_cast<bool*>(userdata) = true;
    }

    const void* MapAsyncAndWait(const wgpu::Buffer& buffer, wgpu::MapMode mode, size_t size) {
        bool done = false;
        buffer.MapAsync(mode, 0, size, MapCallback, &done);

        while (!done) {
            WaitABit();
        }

        return buffer.GetConstMappedRange(0, size);
    }

    void UnmapBuffer(const wgpu::Buffer& buffer) {
        buffer.Unmap();
    }

    wgpu::Buffer BufferMappedAtCreation(wgpu::BufferUsage usage, uint64_t size) {
        wgpu::BufferDescriptor descriptor;
        descriptor.size = size;
        descriptor.usage = usage;
        descriptor.mappedAtCreation = true;
        return device.CreateBuffer(&descriptor);
    }

    wgpu::Buffer BufferMappedAtCreationWithData(wgpu::BufferUsage usage,
                                                const std::vector<uint32_t>& data) {
        size_t byteLength = data.size() * sizeof(uint32_t);
        wgpu::Buffer buffer = BufferMappedAtCreation(usage, byteLength);
        memcpy(buffer.GetMappedRange(), data.data(), byteLength);
        return buffer;
    }
};

// Test that the simplest mappedAtCreation works for MapWrite buffers.
TEST_P(BufferMappedAtCreationTests, MapWriteUsageSmall) {
    uint32_t myData = 230502;
    wgpu::Buffer buffer = BufferMappedAtCreationWithData(
        wgpu::BufferUsage::MapWrite | wgpu::BufferUsage::CopySrc, {myData});
    UnmapBuffer(buffer);
    EXPECT_BUFFER_U32_EQ(myData, buffer, 0);
}

// Test that the simplest mappedAtCreation works for MapRead buffers.
TEST_P(BufferMappedAtCreationTests, MapReadUsageSmall) {
    uint32_t myData = 230502;
    wgpu::Buffer buffer = BufferMappedAtCreationWithData(wgpu::BufferUsage::MapRead, {myData});
    UnmapBuffer(buffer);

    const void* mappedData = MapAsyncAndWait(buffer, wgpu::MapMode::Read, 4);
    ASSERT_EQ(myData, *reinterpret_cast<const uint32_t*>(mappedData));
    UnmapBuffer(buffer);
}

// Test that the simplest mappedAtCreation works for non-mappable buffers.
TEST_P(BufferMappedAtCreationTests, NonMappableUsageSmall) {
    uint32_t myData = 4239;
    wgpu::Buffer buffer = BufferMappedAtCreationWithData(wgpu::BufferUsage::CopySrc, {myData});
    UnmapBuffer(buffer);

    EXPECT_BUFFER_U32_EQ(myData, buffer, 0);
}

// Test mappedAtCreation for a large MapWrite buffer
TEST_P(BufferMappedAtCreationTests, MapWriteUsageLarge) {
    constexpr uint64_t kDataSize = 1000 * 1000;
    std::vector<uint32_t> myData;
    for (uint32_t i = 0; i < kDataSize; ++i) {
        myData.push_back(i);
    }

    wgpu::Buffer buffer = BufferMappedAtCreationWithData(
        wgpu::BufferUsage::MapWrite | wgpu::BufferUsage::CopySrc, {myData});
    UnmapBuffer(buffer);

    EXPECT_BUFFER_U32_RANGE_EQ(myData.data(), buffer, 0, kDataSize);
}

// Test mappedAtCreation for a large MapRead buffer
TEST_P(BufferMappedAtCreationTests, MapReadUsageLarge) {
    constexpr uint64_t kDataSize = 1000 * 1000;
    std::vector<uint32_t> myData;
    for (uint32_t i = 0; i < kDataSize; ++i) {
        myData.push_back(i);
    }

    wgpu::Buffer buffer = BufferMappedAtCreationWithData(wgpu::BufferUsage::MapRead, myData);
    UnmapBuffer(buffer);

    const void* mappedData =
        MapAsyncAndWait(buffer, wgpu::MapMode::Read, kDataSize * sizeof(uint32_t));
    ASSERT_EQ(0, memcmp(mappedData, myData.data(), kDataSize * sizeof(uint32_t)));
    UnmapBuffer(buffer);
}

// Test mappedAtCreation for a large non-mappable buffer
TEST_P(BufferMappedAtCreationTests, NonMappableUsageLarge) {
    constexpr uint64_t kDataSize = 1000 * 1000;
    std::vector<uint32_t> myData;
    for (uint32_t i = 0; i < kDataSize; ++i) {
        myData.push_back(i);
    }

    wgpu::Buffer buffer = BufferMappedAtCreationWithData(wgpu::BufferUsage::CopySrc, {myData});
    UnmapBuffer(buffer);

    EXPECT_BUFFER_U32_RANGE_EQ(myData.data(), buffer, 0, kDataSize);
}

// Test destroying a non-mappable buffer mapped at creation.
// This is a regression test for an issue where the D3D12 backend thought the buffer was actually
// mapped and tried to unlock the heap residency (when actually the buffer was using a staging
// buffer)
TEST_P(BufferMappedAtCreationTests, DestroyNonMappableWhileMappedForCreation) {
    wgpu::Buffer buffer = BufferMappedAtCreation(wgpu::BufferUsage::CopySrc, 4);
    buffer.Destroy();
}

// Test destroying a mappable buffer mapped at creation.
TEST_P(BufferMappedAtCreationTests, DestroyMappableWhileMappedForCreation) {
    wgpu::Buffer buffer = BufferMappedAtCreation(wgpu::BufferUsage::MapRead, 4);
    buffer.Destroy();
}

// Test that mapping a buffer is valid after mappedAtCreation and Unmap
TEST_P(BufferMappedAtCreationTests, CreateThenMapSuccess) {
    static uint32_t myData = 230502;
    wgpu::Buffer buffer = BufferMappedAtCreationWithData(
        wgpu::BufferUsage::MapWrite | wgpu::BufferUsage::CopySrc, {myData});
    UnmapBuffer(buffer);

    EXPECT_BUFFER_U32_EQ(myData, buffer, 0);

    bool done = false;
    buffer.MapAsync(
        wgpu::MapMode::Write, 0, 4,
        [](WGPUBufferMapAsyncStatus status, void* userdata) {
            ASSERT_EQ(WGPUBufferMapAsyncStatus_Success, status);
            *static_cast<bool*>(userdata) = true;
        },
        &done);

    while (!done) {
        WaitABit();
    }

    UnmapBuffer(buffer);
}

// Test that is is invalid to map a buffer twice when using mappedAtCreation
TEST_P(BufferMappedAtCreationTests, CreateThenMapBeforeUnmapFailure) {
    uint32_t myData = 230502;
    wgpu::Buffer buffer = BufferMappedAtCreationWithData(
        wgpu::BufferUsage::MapWrite | wgpu::BufferUsage::CopySrc, {myData});

    ASSERT_DEVICE_ERROR([&]() {
        bool done = false;
        buffer.MapAsync(
            wgpu::MapMode::Write, 0, 4,
            [](WGPUBufferMapAsyncStatus status, void* userdata) {
                ASSERT_EQ(WGPUBufferMapAsyncStatus_Error, status);
                *static_cast<bool*>(userdata) = true;
            },
            &done);

        while (!done) {
            WaitABit();
        }
    }());

    // mappedAtCreation is unaffected by the MapWrite error.
    UnmapBuffer(buffer);
}

// Test that creating a zero-sized buffer mapped is allowed.
TEST_P(BufferMappedAtCreationTests, ZeroSized) {
    wgpu::BufferDescriptor descriptor;
    descriptor.size = 0;
    descriptor.usage = wgpu::BufferUsage::Vertex;
    descriptor.mappedAtCreation = true;
    wgpu::Buffer buffer = device.CreateBuffer(&descriptor);

    ASSERT_NE(nullptr, buffer.GetMappedRange());

    // Check that unmapping the buffer works too.
    UnmapBuffer(buffer);
}

// Test that creating a zero-sized mapppable buffer mapped. (it is a different code path)
TEST_P(BufferMappedAtCreationTests, ZeroSizedMappableBuffer) {
    wgpu::BufferDescriptor descriptor;
    descriptor.size = 0;
    descriptor.usage = wgpu::BufferUsage::MapWrite;
    descriptor.mappedAtCreation = true;
    wgpu::Buffer buffer = device.CreateBuffer(&descriptor);

    ASSERT_NE(nullptr, buffer.GetMappedRange());

    // Check that unmapping the buffer works too.
    UnmapBuffer(buffer);
}

// Test that creating a zero-sized error buffer mapped. (it is a different code path)
TEST_P(BufferMappedAtCreationTests, ZeroSizedErrorBuffer) {
    DAWN_SKIP_TEST_IF(HasToggleEnabled("skip_validation"));

    wgpu::BufferDescriptor descriptor;
    descriptor.size = 0;
    descriptor.usage = wgpu::BufferUsage::MapWrite | wgpu::BufferUsage::Storage;
    descriptor.mappedAtCreation = true;
    wgpu::Buffer buffer;
    ASSERT_DEVICE_ERROR(buffer = device.CreateBuffer(&descriptor));

    ASSERT_NE(nullptr, buffer.GetMappedRange());
}

// Test the result of GetMappedRange when mapped at creation.
TEST_P(BufferMappedAtCreationTests, GetMappedRange) {
    wgpu::BufferDescriptor descriptor;
    descriptor.size = 4;
    descriptor.usage = wgpu::BufferUsage::CopyDst;
    descriptor.mappedAtCreation = true;
    wgpu::Buffer buffer = device.CreateBuffer(&descriptor);

    ASSERT_EQ(buffer.GetMappedRange(), buffer.GetConstMappedRange());
    ASSERT_NE(buffer.GetMappedRange(), nullptr);
    buffer.Unmap();
}

// Test the result of GetMappedRange when mapped at creation for a zero-sized buffer.
TEST_P(BufferMappedAtCreationTests, GetMappedRangeZeroSized) {
    wgpu::BufferDescriptor descriptor;
    descriptor.size = 0;
    descriptor.usage = wgpu::BufferUsage::CopyDst;
    descriptor.mappedAtCreation = true;
    wgpu::Buffer buffer = device.CreateBuffer(&descriptor);

    ASSERT_EQ(buffer.GetMappedRange(), buffer.GetConstMappedRange());
    ASSERT_NE(buffer.GetMappedRange(), nullptr);
    buffer.Unmap();
}

DAWN_INSTANTIATE_TEST(BufferMappedAtCreationTests,
                      D3D12Backend(),
                      D3D12Backend({}, {"use_d3d12_resource_heap_tier2"}),
                      MetalBackend(),
                      OpenGLBackend(),
                      VulkanBackend());

class BufferTests : public DawnTest {};

// Test that creating a zero-buffer is allowed.
TEST_P(BufferTests, ZeroSizedBuffer) {
    wgpu::BufferDescriptor desc;
    desc.size = 0;
    desc.usage = wgpu::BufferUsage::CopyDst;
    device.CreateBuffer(&desc);
}

// Test that creating a very large buffers fails gracefully.
TEST_P(BufferTests, CreateBufferOOM) {
    // TODO(http://crbug.com/dawn/27): Missing support.
    DAWN_SKIP_TEST_IF(IsOpenGL());
    DAWN_SKIP_TEST_IF(IsOpenGLES());
    DAWN_SKIP_TEST_IF(IsAsan());

    wgpu::BufferDescriptor descriptor;
    descriptor.usage = wgpu::BufferUsage::CopyDst;

    descriptor.size = std::numeric_limits<uint64_t>::max();
    ASSERT_DEVICE_ERROR(device.CreateBuffer(&descriptor));

    // UINT64_MAX may be special cased. Test a smaller, but really large buffer also fails
    descriptor.size = 1ull << 50;
    ASSERT_DEVICE_ERROR(device.CreateBuffer(&descriptor));
}

// Test that a very large buffer mappedAtCreation fails gracefully.
TEST_P(BufferTests, BufferMappedAtCreationOOM) {
    // TODO(http://crbug.com/dawn/27): Missing support.
    DAWN_SKIP_TEST_IF(IsOpenGL());
    DAWN_SKIP_TEST_IF(IsOpenGLES());
    DAWN_SKIP_TEST_IF(IsAsan());

    // Test non-mappable buffer
    {
        wgpu::BufferDescriptor descriptor;
        descriptor.size = 4;
        descriptor.usage = wgpu::BufferUsage::CopyDst;
        descriptor.mappedAtCreation = true;

        // Control: test a small buffer works.
        device.CreateBuffer(&descriptor);

        // Test an enormous buffer fails
        descriptor.size = std::numeric_limits<uint64_t>::max();
        ASSERT_DEVICE_ERROR(device.CreateBuffer(&descriptor));

        // UINT64_MAX may be special cased. Test a smaller, but really large buffer also fails
        descriptor.size = 1ull << 50;
        ASSERT_DEVICE_ERROR(device.CreateBuffer(&descriptor));
    }

    // Test mappable buffer
    {
        wgpu::BufferDescriptor descriptor;
        descriptor.size = 4;
        descriptor.usage = wgpu::BufferUsage::CopySrc | wgpu::BufferUsage::MapWrite;
        descriptor.mappedAtCreation = true;

        // Control: test a small buffer works.
        device.CreateBuffer(&descriptor);

        // Test an enormous buffer fails
        descriptor.size = std::numeric_limits<uint64_t>::max();
        ASSERT_DEVICE_ERROR(device.CreateBuffer(&descriptor));

        // UINT64_MAX may be special cased. Test a smaller, but really large buffer also fails
        descriptor.size = 1ull << 50;
        ASSERT_DEVICE_ERROR(device.CreateBuffer(&descriptor));
    }
}

// Test that mapping an OOM buffer fails gracefully
TEST_P(BufferTests, CreateBufferOOMMapAsync) {
    // TODO(http://crbug.com/dawn/27): Missing support.
    DAWN_SKIP_TEST_IF(IsOpenGL());
    DAWN_SKIP_TEST_IF(IsOpenGLES());
    DAWN_SKIP_TEST_IF(IsAsan());

    auto RunTest = [this](const wgpu::BufferDescriptor& descriptor) {
        wgpu::Buffer buffer;
        ASSERT_DEVICE_ERROR(buffer = device.CreateBuffer(&descriptor));

        bool done = false;
        ASSERT_DEVICE_ERROR(buffer.MapAsync(
            wgpu::MapMode::Write, 0, 4,
            [](WGPUBufferMapAsyncStatus status, void* userdata) {
                EXPECT_EQ(status, WGPUBufferMapAsyncStatus_Error);
                *static_cast<bool*>(userdata) = true;
            },
            &done));

        while (!done) {
            WaitABit();
        }
    };

    wgpu::BufferDescriptor descriptor;
    descriptor.usage = wgpu::BufferUsage::CopySrc | wgpu::BufferUsage::MapWrite;

    // Test an enormous buffer
    descriptor.size = std::numeric_limits<uint64_t>::max();
    RunTest(descriptor);

    // UINT64_MAX may be special cased. Test a smaller, but really large buffer also fails
    descriptor.size = 1ull << 50;
    RunTest(descriptor);
}

DAWN_INSTANTIATE_TEST(BufferTests,
                      D3D12Backend(),
                      MetalBackend(),
                      OpenGLBackend(),
                      OpenGLESBackend(),
                      VulkanBackend());