Bigfoot/Bigfoot/Libs/System/File/MemoryMappedFile.cpp

/*********************************************************************
 * \file   MemoryMappedFile.cpp
 *
 * \author Romain BOULLARD
 * \date   August 2026
 *********************************************************************/
#include <System/File/MemoryMappedFile.hpp>

#include <System/SystemAssertHandler.hpp>

#include <string>

#ifdef BIGFOOT_WINDOWS
#include <Windows.h>
#elif defined BIGFOOT_LINUX
#include <fcntl.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <unistd.h>
#endif

namespace Bigfoot
{
MemoryMappedFile::MemoryMappedFile(const File& p_file)
{
    const File absoluteFile = p_file.ToAbsolute();
    const eastl::string_view path = absoluteFile.GetPath();

#ifdef BIGFOOT_WINDOWS
    m_fileHandle = CreateFileA(path.data(),
                               GENERIC_READ,
                               FILE_SHARE_READ,
                               nullptr,
                               OPEN_EXISTING,
                               FILE_ATTRIBUTE_NORMAL | FILE_FLAG_RANDOM_ACCESS,
                               nullptr);
    CRITICAL_ASSERT(SystemAssertHandler, m_fileHandle != INVALID_HANDLE_VALUE, "Failed to open file {}", path);

    LARGE_INTEGER fileSize {};
    [[maybe_unused]]
    const BOOL gotFileSize = GetFileSizeEx(m_fileHandle, &fileSize);
    CRITICAL_ASSERT(SystemAssertHandler, gotFileSize, "Failed to get the size of file {}", path);
    m_size = static_cast<std::size_t>(fileSize.QuadPart);

    if (m_size != 0)
    {
        m_mappingHandle = CreateFileMappingA(m_fileHandle, nullptr, PAGE_READONLY, 0, 0, nullptr);
        CRITICAL_ASSERT(SystemAssertHandler, m_mappingHandle != nullptr, "Failed create the file mapping {}", path);

        m_data = static_cast<std::byte*>(MapViewOfFile(m_mappingHandle, FILE_MAP_READ, 0, 0, 0));
        CRITICAL_ASSERT(SystemAssertHandler, m_data != nullptr, "Failed to map the file {}", path);
    }
#elif defined BIGFOOT_LINUX
    m_fileDescriptor = open(path.data(), O_RDONLY);
    CRITICAL_ASSERT(SystemAssertHandler, m_fileDescriptor != -1, "Failed to open file {}", path);

    struct stat fileStat {};
    [[maybe_unused]]
    const int statResult = fstat(m_fileDescriptor, &fileStat);
    CRITICAL_ASSERT(SystemAssertHandler, statResult == 0, "Failed to get the size of file {}", path);
    m_size = static_cast<std::size_t>(fileStat.st_size);

    if (m_size != 0)
    {
        void* const mapped = mmap(nullptr, m_size, PROT_READ, MAP_PRIVATE, m_fileDescriptor, 0);
        CRITICAL_ASSERT(SystemAssertHandler, mapped != MAP_FAILED, "Failed to map file {}", path);
        m_data = static_cast<std::byte*>(mapped);

        [[maybe_unused]]
        const int adviseResult = madvise(mapped, m_size, MADV_RANDOM);
    }
#else
    CRITICAL_ASSERT(SystemAssertHandler, false, "MemoryMappedFileBase is not implemented on this platform");
#endif
}

/****************************************************************************************/

MemoryMappedFile::~MemoryMappedFile()
{
#ifdef BIGFOOT_WINDOWS
    if (m_data != nullptr)
    {
        [[maybe_unused]]
        const BOOL unmapped = UnmapViewOfFile(m_data);
        CRITICAL_ASSERT(SystemAssertHandler, unmapped, "Failed to unmap the file");
    }

    if (m_mappingHandle != nullptr)
    {
        [[maybe_unused]]
        const BOOL closedMapping = CloseHandle(m_mappingHandle);
        CRITICAL_ASSERT(SystemAssertHandler, closedMapping, "Failed to close the file mapping");
    }

    if (m_fileHandle != INVALID_HANDLE_VALUE)
    {
        [[maybe_unused]]
        const BOOL closedFile = CloseHandle(m_fileHandle);
        CRITICAL_ASSERT(SystemAssertHandler, closedFile, "Failed to close the file");
    }
#elif defined BIGFOOT_LINUX
    if (m_data != nullptr)
    {
        [[maybe_unused]]
        const int unmapped = munmap(m_data, m_size);
        CRITICAL_ASSERT(SystemAssertHandler, unmapped == 0, "Failed to unmap the file");
    }

    if (m_fileDescriptor != -1)
    {
        [[maybe_unused]]
        const int closedFile = close(m_fileDescriptor);
        CRITICAL_ASSERT(SystemAssertHandler, closedFile == 0, "Failed to close the file");
    }
#else
    CRITICAL_ASSERT(SystemAssertHandler, false, "MemoryMappedFileBase is not implemented on this platform");
#endif
}

/****************************************************************************************/

eastl::span<const std::byte> MemoryMappedFile::GetData() const
{
    return eastl::span<const std::byte> {m_data, m_size};
}

/****************************************************************************************/

WritableMemoryMappedFile::WritableMemoryMappedFile(const File& p_file, const std::size_t p_size):
    m_size(p_size)
{
    const File absoluteFile = p_file.ToAbsolute();
    const eastl::string_view path = absoluteFile.GetPath();

#ifdef BIGFOOT_WINDOWS
    m_fileHandle =
        CreateFileA(path.data(), GENERIC_READ | GENERIC_WRITE, 0, nullptr, OPEN_ALWAYS, FILE_ATTRIBUTE_NORMAL, nullptr);
    CRITICAL_ASSERT(SystemAssertHandler, m_fileHandle != INVALID_HANDLE_VALUE, "Failed to create file {}", path);

    const LARGE_INTEGER size {.QuadPart = static_cast<LONGLONG>(p_size)};
    m_mappingHandle = CreateFileMappingA(m_fileHandle, nullptr, PAGE_READWRITE, size.HighPart, size.LowPart, nullptr);
    CRITICAL_ASSERT(SystemAssertHandler, m_mappingHandle != nullptr, "Failed create the file mapping {}", path);

    m_data = static_cast<std::byte*>(MapViewOfFile(m_mappingHandle, FILE_MAP_WRITE, 0, 0, 0));
    CRITICAL_ASSERT(SystemAssertHandler, m_data != nullptr, "Failed to map the file {}", path);
#elif defined BIGFOOT_LINUX
    m_fileDescriptor = open(path.data(), O_RDWR | O_CREAT, S_IRUSR | S_IWUSR);
    CRITICAL_ASSERT(SystemAssertHandler, m_fileDescriptor != -1, "Failed to create file {}", path);

    struct stat fileStat {};
    fstat(m_fileDescriptor, &fileStat);
    if (static_cast<std::size_t>(fileStat.st_size) < p_size)
    {
        [[maybe_unused]]
        const int truncateResult = ftruncate(m_fileDescriptor, static_cast<off_t>(p_size));
        CRITICAL_ASSERT(SystemAssertHandler, truncateResult == 0, "Failed to size file {}", path);
    }

    void* const mapped = mmap(nullptr, m_size, PROT_READ | PROT_WRITE, MAP_SHARED, m_fileDescriptor, 0);
    CRITICAL_ASSERT(SystemAssertHandler, mapped != MAP_FAILED, "Failed to map file {}", path);
    m_data = static_cast<std::byte*>(mapped);
#else
    CRITICAL_ASSERT(SystemAssertHandler, false, "MemoryMappedFileBase is not implemented on this platform");
#endif
}

/****************************************************************************************/

WritableMemoryMappedFile::~WritableMemoryMappedFile()
{
#ifdef BIGFOOT_WINDOWS
    if (m_data != nullptr)
    {
        [[maybe_unused]]
        const BOOL unmapped = UnmapViewOfFile(m_data);
        CRITICAL_ASSERT(SystemAssertHandler, unmapped, "Failed to unmap the file");
    }

    if (m_mappingHandle != nullptr)
    {
        [[maybe_unused]]
        const BOOL closedMapping = CloseHandle(m_mappingHandle);
        CRITICAL_ASSERT(SystemAssertHandler, closedMapping, "Failed to close the file mapping");
    }

    if (m_fileHandle != INVALID_HANDLE_VALUE)
    {
        [[maybe_unused]]
        const BOOL closedFile = CloseHandle(m_fileHandle);
        CRITICAL_ASSERT(SystemAssertHandler, closedFile, "Failed to close the file");
    }
#elif defined BIGFOOT_LINUX
    if (m_data != nullptr)
    {
        [[maybe_unused]]
        const int unmapped = munmap(m_data, m_size);
        CRITICAL_ASSERT(SystemAssertHandler, unmapped == 0, "Failed to unmap the file");
    }

    if (m_fileDescriptor != -1)
    {
        [[maybe_unused]]
        const int closedFile = close(m_fileDescriptor);
        CRITICAL_ASSERT(SystemAssertHandler, closedFile == 0, "Failed to close the file");
    }
#else
    CRITICAL_ASSERT(SystemAssertHandler, false, "MemoryMappedFileBase is not implemented on this platform");
#endif
}

/****************************************************************************************/

eastl::span<std::byte> WritableMemoryMappedFile::GetData() const
{
    return eastl::span<std::byte> {m_data, m_size};
}

/****************************************************************************************/

void WritableMemoryMappedFile::Prefetch(const std::size_t p_offset, const std::size_t p_size) const
{
#ifdef BIGFOOT_WINDOWS
    WIN32_MEMORY_RANGE_ENTRY range {.VirtualAddress = m_data + p_offset, .NumberOfBytes = p_size};
    [[maybe_unused]]
    const BOOL prefetched = PrefetchVirtualMemory(GetCurrentProcess(), 1, &range, 0);
#elif defined BIGFOOT_LINUX
    [[maybe_unused]]
    const int adviseResult = madvise(m_data + p_offset, p_size, MADV_WILLNEED);
#else
    CRITICAL_ASSERT(SystemAssertHandler, false, "MemoryMappedFileBase is not implemented on this platform");
#endif
}
}   // namespace Bigfoot