#ifndef OSMIUM_UTIL_MEMORY_MAPPING_HPP
#define OSMIUM_UTIL_MEMORY_MAPPING_HPP

/*

This file is part of Osmium (https://osmcode.org/libosmium).

Copyright 2013-2022 Jochen Topf <jochen@topf.org> and others (see README).

Boost Software License - Version 1.0 - August 17th, 2003

Permission is hereby granted, free of charge, to any person or organization
obtaining a copy of the software and accompanying documentation covered by
this license (the "Software") to use, reproduce, display, distribute,
execute, and transmit the Software, and to prepare derivative works of the
Software, and to permit third-parties to whom the Software is furnished to
do so, all subject to the following:

The copyright notices in the Software and this entire statement, including
the above license grant, this restriction and the following disclaimer,
must be included in all copies of the Software, in whole or in part, and
all derivative works of the Software, unless such copies or derivative
works are solely in the form of machine-executable object code generated by
a source language processor.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
DEALINGS IN THE SOFTWARE.

*/

#include <osmium/util/file.hpp>

#include <cassert>
#include <cerrno>
#include <cstddef>
#include <stdexcept>
#include <system_error>

#ifndef _WIN32
# include <sys/mman.h>
# include <sys/statvfs.h>
#else
# include <fcntl.h>
# include <io.h>
# include <windows.h>
# include <sys/types.h>
#endif

namespace osmium {

    inline namespace util {

        /**
         * Class for wrapping memory mapping system calls.
         *
         * Usage for anonymous mapping:
         * @code
         * MemoryMapping mapping{1024};          // create anonymous mapping with size
         * auto ptr = mapping.get_addr<char*>(); // get pointer to memory
         * mapping.unmap();                      // release mapping by calling unmap() (or at end of scope)
         * @endcode
         *
         * Or for file-backed mapping:
         * @code
         * int fd = ::open(...);
         * {
         *     MemoryMapping mapping{1024, MemoryMapping::mapping_mode::write_shared, fd, offset};
         *     // use mapping
         * }
         * ::close(fd);
         * @endcode
         *
         * If the file backing a file-backed mapping is not large enough, it
         * will be resized. This works, of course, only for writable files,
         * so for read-only files you have to make sure they are large enough
         * for any mapping you want.
         *
         * If you ask for a zero-sized mapping, a mapping of the systems page
         * size will be created instead. For file-backed mapping this will only
         * work if the file is writable.
         *
         * There are different implementations for Unix and Windows systems.
         * On Unix systems this wraps the mmap(), munmap(), and the mremap()
         * system calls. On Windows it wraps the CreateFileMapping(),
         * CloseHandle(), MapViewOfFile(), and UnmapViewOfFile() functions.
         *
         * On Windows the file will be set to binary mode before the memory
         * mapping.
         */
        class MemoryMapping {

        public:

            enum class mapping_mode {
                readonly      = 0,
                write_private = 1,
                write_shared  = 2
            };

        private:

            /// The size of the mapping
            std::size_t m_size;

            /// Offset into the file
            off_t m_offset;

            /// File handle we got the mapping from
            int m_fd;

            /// Mapping mode
            mapping_mode m_mapping_mode;

#ifdef _WIN32
            HANDLE m_handle;
#endif

            /// The address where the memory is mapped
            void* m_addr;

            bool is_valid() const noexcept;

            void make_invalid() noexcept;

#ifdef _WIN32
            using flag_type = DWORD;
#else
            using flag_type = int;
#endif

            flag_type get_protection() const noexcept;

            flag_type get_flags() const noexcept;

            static std::size_t check_size(std::size_t size) {
                if (size == 0) {
                    return osmium::get_pagesize();
                }
                return size;
            }

#ifdef _WIN32
            HANDLE get_handle() const noexcept;
            HANDLE create_file_mapping() const noexcept;
            void* map_view_of_file() const noexcept;
#endif

            // Get the available space on the file system where the file
            // behind fd is on. Return 0 if it can't be determined.
            static std::size_t available_space(int fd) {
#ifdef _WIN32
                return 0;
#else
                struct statvfs stat{};
                const int result = ::fstatvfs(fd, &stat);
                if (result != 0) {
                    return 0;
                }
                return stat.f_bsize * stat.f_bavail;
#endif
            }

            int resize_fd(int fd) const {
                // Anonymous mapping doesn't need resizing.
                if (fd == -1) {
                    return -1;
                }

                // Make sure the file backing this mapping is large enough.
                auto const current_file_size = osmium::file_size(fd);
                if (current_file_size < m_size + m_offset) {
                    const auto available = available_space(fd);
                    if (available > 0 && current_file_size + available <= m_size) {
                        throw std::system_error{ENOSPC, std::system_category(), "Could not resize file: Not enough space on filesystem"};
                    }

                    osmium::resize_file(fd, m_size + m_offset);
                }
                return fd;
            }

        public:

            /**
             * Create memory mapping of given size.
             *
             * If fd is not set (or fd == -1), an anonymous mapping will be
             * created, otherwise a mapping based on the file descriptor will
             * be created.
             *
             * @pre @code size > 0 @endcode or
             *      @code mode == write_shared || mode == write_private @endcode
             *
             * @param size Size of the mapping in bytes
             * @param mode Mapping mode: readonly, or writable (shared or private)
             * @param fd Open file descriptor of a file we want to map
             * @param offset Offset into the file where the mapping should start
             * @throws std::system_error if the mapping fails
             */
            MemoryMapping(std::size_t size, mapping_mode mode, int fd = -1, off_t offset = 0);

            /// You can not copy construct a MemoryMapping.
            MemoryMapping(const MemoryMapping&) = delete;

            /// You can not copy a MemoryMapping.
            MemoryMapping& operator=(const MemoryMapping&) = delete;

            /**
             * Move construct a mapping from another one. The other mapping
             * will be marked as invalid.
             */
            MemoryMapping(MemoryMapping&& other) noexcept;

            /**
             * Move a mapping. The other mapping will be marked as invalid.
             */
            MemoryMapping& operator=(MemoryMapping&& other) noexcept;

            /**
             * Releases the mapping by calling unmap(). Will never throw.
             * Call unmap() instead if you want to be notified of any error.
             */
            ~MemoryMapping() noexcept {
                try {
                    unmap();
                } catch (const std::system_error&) {
                    // Ignore any exceptions because destructor must not throw.
                }
            }

            /**
             * Unmap a mapping. If the mapping is not valid, it will do
             * nothing.
             *
             * @throws std::system_error if the unmapping fails
             */
            void unmap();

            /**
             * Resize a mapping to the given new size.
             *
             * On Linux systems this will use the mremap() function. On other
             * systems it will unmap and remap the memory. This can only be
             * done for file-based mappings, not anonymous mappings!
             *
             * @param new_size Number of bytes to resize to (must be > 0).
             *
             * @throws std::system_error if the remapping fails.
             */
            void resize(std::size_t new_size);

            /**
             * In a boolean context a MemoryMapping is true when it is a valid
             * existing mapping.
             */
            explicit operator bool() const noexcept {
                return is_valid();
            }

            /**
             * The number of bytes mapped. This is the same size you created
             * the mapping with. The actual mapping will probably be larger
             * because the system will round it to the page size.
             */
            std::size_t size() const noexcept {
                return m_size;
            }

            /**
             * The file descriptor this mapping was created from.
             *
             * @returns file descriptor, -1 for anonymous mappings
             */
            int fd() const noexcept {
                return m_fd;
            }

            /**
             * Was this mapping created as a writable mapping?
             */
            bool writable() const noexcept {
                return m_mapping_mode != mapping_mode::readonly;
            }

            /**
             * Get the address of the mapping as any pointer type you like.
             *
             * @pre is_valid()
             */
            template <typename T = void>
            T* get_addr() const noexcept {
                return reinterpret_cast<T*>(m_addr);
            }

        }; // class MemoryMapping

        /**
         * Anonymous memory mapping.
         *
         * Usage for anonymous mapping:
         * @code
         * AnonymousMemoryMapping mapping{1024}; // create anonymous mapping with size
         * auto ptr = mapping.get_addr<char*>(); // get pointer to memory
         * mapping.unmap();                      // release mapping by calling unmap() (or at end of scope)
         * @endcode
         */
        class AnonymousMemoryMapping : public MemoryMapping {

        public:

            explicit AnonymousMemoryMapping(std::size_t size) :
                MemoryMapping(size, mapping_mode::write_private) {
            }

#ifndef __linux__
            /**
             * On systems other than Linux anonymous mappings can not be
             * resized!
             */
            void resize(std::size_t) = delete;
#endif

        }; // class AnonymousMemoryMapping

        /**
         * A thin wrapper around the MemoryMapping class used when all the
         * data in the mapped memory is of the same type. Instead of thinking
         * about the number of bytes mapped, this counts sizes in the number
         * of objects of that type.
         *
         * Note that no effort is made to actually initialize the objects in
         * this memory. This has to be done by the caller!
         */
        template <typename T>
        class TypedMemoryMapping {

            MemoryMapping m_mapping;

        public:

            /**
             * Create anonymous typed memory mapping of given size.
             *
             * @param size Number of objects of type T to be mapped
             * @throws std::system_error if the mapping fails
             */
            explicit TypedMemoryMapping(std::size_t size) :
                m_mapping(sizeof(T) * size, MemoryMapping::mapping_mode::write_private) {
            }

            /**
             * Create file-backed memory mapping of given size. The file must
             * contain at least `sizeof(T) * size` bytes!
             *
             * @param size Number of objects of type T to be mapped
             * @param mode Mapping mode: readonly, or writable (shared or private)
             * @param fd Open file descriptor of a file we want to map
             * @param offset Offset into the file where the mapping should start
             * @throws std::system_error if the mapping fails
             */
            TypedMemoryMapping(std::size_t size, MemoryMapping::mapping_mode mode, int fd, off_t offset = 0) :
                m_mapping(sizeof(T) * size, mode, fd, sizeof(T) * offset) {
            }

            /// You can not copy construct a TypedMemoryMapping.
            TypedMemoryMapping(const TypedMemoryMapping&) = delete;

            /// You can not copy a TypedMemoryMapping.
            TypedMemoryMapping& operator=(const TypedMemoryMapping&) = delete;

            /**
             * Move construct a mapping from another one. The other mapping
             * will be marked as invalid.
             */
            TypedMemoryMapping(TypedMemoryMapping&& other) noexcept = default;

            /**
             * Move a mapping. The other mapping will be marked as invalid.
             */
            TypedMemoryMapping& operator=(TypedMemoryMapping&& other) noexcept = default;

            /**
             * Releases the mapping by calling unmap(). Will never throw.
             * Call unmap() instead if you want to be notified of any error.
             */
            ~TypedMemoryMapping() noexcept = default;

            /**
             * Unmap a mapping. If the mapping is not valid, it will do
             * nothing.
             *
             * @throws std::system_error if the unmapping fails
             */
            void unmap() {
                m_mapping.unmap();
            }

            /**
             * Resize a mapping to the given new size.
             *
             * On Linux systems this will use the mremap() function. On other
             * systems it will unmap and remap the memory. This can only be
             * done for file-based mappings, not anonymous mappings!
             *
             * @param new_size Number of objects of type T to resize to
             * @throws std::system_error if the remapping fails
             */
            void resize(std::size_t new_size) {
                m_mapping.resize(sizeof(T) * new_size);
            }

            /**
             * In a boolean context a TypedMemoryMapping is true when it is
             * a valid existing mapping.
             */
            explicit operator bool() const noexcept {
                return !!m_mapping;
            }

            /**
             * The number of objects of class T mapped. This is the same size
             * you created the mapping with. The actual mapping will probably
             * be larger because the system will round it to the page size.
             */
            std::size_t size() const noexcept {
                assert(m_mapping.size() % sizeof(T) == 0);
                return m_mapping.size() / sizeof(T);
            }

            /**
             * The file descriptor this mapping was created from.
             *
             * @returns file descriptor, -1 for anonymous mappings
             */
            int fd() const noexcept {
                return m_mapping.fd();
            }

            /**
             * Was this mapping created as a writable mapping?
             */
            bool writable() const noexcept {
                return m_mapping.writable();
            }

            /**
             * Get the address of the beginning of the mapping.
             *
             * @pre is_valid()
             */
            T* begin() noexcept {
                return m_mapping.get_addr<T>();
            }

            /**
             * Get the address one past the end of the mapping.
             *
             * @pre is_valid()
             */
            T* end() noexcept {
                return m_mapping.get_addr<T>() + size();
            }

            /**
             * Get the address of the beginning of the mapping.
             *
             * @pre is_valid()
             */
            const T* cbegin() const noexcept {
                return m_mapping.get_addr<T>();
            }

            /**
             * Get the address one past the end of the mapping.
             *
             * @pre is_valid()
             */
            const T* cend() const noexcept {
                return m_mapping.get_addr<T>() + size();
            }

            /**
             * Get the address of the beginning of the mapping.
             *
             * @pre is_valid()
             */
            const T* begin() const noexcept {
                return m_mapping.get_addr<T>();
            }

            /**
             * Get the address one past the end of the mapping.
             *
             * @pre is_valid()
             */
            const T* end() const noexcept {
                return m_mapping.get_addr<T>() + size();
            }

        }; // class TypedMemoryMapping

        template <typename T>
        class AnonymousTypedMemoryMapping : public TypedMemoryMapping<T> {

        public:

            explicit AnonymousTypedMemoryMapping(std::size_t size) :
                TypedMemoryMapping<T>(size) {
            }

#ifndef __linux__
            /**
             * On systems other than Linux anonymous mappings can not be
             * resized!
             */
            void resize(std::size_t) = delete;
#endif

        }; // class AnonymousTypedMemoryMapping

    } // namespace util

} // namespace osmium

#ifndef _WIN32

// =========== Unix implementation =============

// MAP_FAILED is often a macro containing an old style cast
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wold-style-cast"

inline bool osmium::util::MemoryMapping::is_valid() const noexcept {
    return m_addr != MAP_FAILED; // NOLINT(cppcoreguidelines-pro-type-cstyle-cast,performance-no-int-to-ptr)
}

inline void osmium::util::MemoryMapping::make_invalid() noexcept {
    m_addr = MAP_FAILED; // NOLINT(cppcoreguidelines-pro-type-cstyle-cast,performance-no-int-to-ptr)
}

#pragma GCC diagnostic pop

// for BSD systems
#ifndef MAP_ANONYMOUS
# define MAP_ANONYMOUS MAP_ANON
#endif

inline int osmium::util::MemoryMapping::get_protection() const noexcept {
    if (m_mapping_mode == mapping_mode::readonly) {
        return PROT_READ;
    }
    return PROT_READ | PROT_WRITE; // NOLINT(hicpp-signed-bitwise)
}

inline int osmium::util::MemoryMapping::get_flags() const noexcept {
    if (m_fd == -1) {
        return MAP_PRIVATE | MAP_ANONYMOUS; // NOLINT(hicpp-signed-bitwise)
    }
    if (m_mapping_mode == mapping_mode::write_shared) {
        return MAP_SHARED;
    }
    return MAP_PRIVATE;
}

inline osmium::util::MemoryMapping::MemoryMapping(std::size_t size, mapping_mode mode, int fd, off_t offset) :
    m_size(check_size(size)),
    m_offset(offset),
    m_fd(resize_fd(fd)),
    m_mapping_mode(mode),
    m_addr(::mmap(nullptr, m_size, get_protection(), get_flags(), m_fd, m_offset)) {
    assert(!(fd == -1 && mode == mapping_mode::readonly));
    if (!is_valid()) {
        throw std::system_error{errno, std::system_category(), "mmap failed"};
    }
}

inline osmium::util::MemoryMapping::MemoryMapping(MemoryMapping&& other) noexcept :
    m_size(other.m_size),
    m_offset(other.m_offset),
    m_fd(other.m_fd),
    m_mapping_mode(other.m_mapping_mode),
    m_addr(other.m_addr) {
    other.make_invalid();
}

inline osmium::util::MemoryMapping& osmium::util::MemoryMapping::operator=(osmium::util::MemoryMapping&& other) noexcept {
    try {
        unmap();
    } catch (const std::system_error&) {
        // Ignore unmap error. It should never happen anyway and we can't do
        // anything about it here.
    }
    m_size         = other.m_size;
    m_offset       = other.m_offset;
    m_fd           = other.m_fd;
    m_mapping_mode = other.m_mapping_mode;
    m_addr         = other.m_addr;
    other.make_invalid();
    return *this;
}

inline void osmium::util::MemoryMapping::unmap() {
    if (is_valid()) {
        if (::munmap(m_addr, m_size) != 0) {
            throw std::system_error{errno, std::system_category(), "munmap failed"};
        }
        make_invalid();
    }
}

inline void osmium::util::MemoryMapping::resize(std::size_t new_size) {
    assert(new_size > 0 && "can not resize to zero size");
    if (m_fd == -1) { // anonymous mapping
#ifdef __linux__
        m_addr = ::mremap(m_addr, m_size, new_size, MREMAP_MAYMOVE);
        if (!is_valid()) {
            throw std::system_error{errno, std::system_category(), "mremap failed"};
        }
        m_size = new_size;
#else
        assert(false && "can't resize anonymous mappings on non-linux systems");
#endif
    } else { // file-based mapping
        unmap();
        m_size = new_size;
        resize_fd(m_fd);
        m_addr = ::mmap(nullptr, new_size, get_protection(), get_flags(), m_fd, m_offset);
        if (!is_valid()) {
            throw std::system_error{errno, std::system_category(), "mmap (remap) failed"};
        }
    }
}

#else

// =========== Windows implementation =============

/* References:
 * CreateFileMapping: https://msdn.microsoft.com/en-us/library/aa366537(VS.85).aspx
 * CloseHandle:       https://msdn.microsoft.com/en-us/library/ms724211(VS.85).aspx
 * MapViewOfFile:     https://msdn.microsoft.com/en-us/library/aa366761(VS.85).aspx
 * UnmapViewOfFile:   https://msdn.microsoft.com/en-us/library/aa366882(VS.85).aspx
 */

namespace osmium {

    inline namespace util {

        inline DWORD dword_hi(uint64_t x) {
            return static_cast<DWORD>(x >> 32);
        }

        inline DWORD dword_lo(uint64_t x) {
            return static_cast<DWORD>(x & 0xffffffff);
        }

    } // namespace util

} // namespace osmium

inline DWORD osmium::util::MemoryMapping::get_protection() const noexcept {
    switch (m_mapping_mode) {
        case mapping_mode::readonly:
            return PAGE_READONLY;
        case mapping_mode::write_private:
            return PAGE_WRITECOPY;
        default: // mapping_mode::write_shared
            break;
    }
    return PAGE_READWRITE;
}

inline DWORD osmium::util::MemoryMapping::get_flags() const noexcept {
    switch (m_mapping_mode) {
        case mapping_mode::readonly:
            return FILE_MAP_READ;
        case mapping_mode::write_private:
            return FILE_MAP_COPY;
        default: // mapping_mode::write_shared
            break;
    }
    return FILE_MAP_WRITE;
}

inline HANDLE osmium::util::MemoryMapping::get_handle() const noexcept {
    if (m_fd == -1) {
        return INVALID_HANDLE_VALUE;
    }
    return reinterpret_cast<HANDLE>(_get_osfhandle(m_fd));
}

inline HANDLE osmium::util::MemoryMapping::create_file_mapping() const noexcept {
    if (m_fd != -1) {
        _setmode(m_fd, _O_BINARY);
    }
    return CreateFileMapping(get_handle(),
                             nullptr,
                             get_protection(),
                             osmium::dword_hi(static_cast<uint64_t>(m_size) + m_offset),
                             osmium::dword_lo(static_cast<uint64_t>(m_size) + m_offset),
                             nullptr);
}

inline void* osmium::util::MemoryMapping::map_view_of_file() const noexcept {
    return MapViewOfFile(m_handle,
                         get_flags(),
                         osmium::dword_hi(m_offset),
                         osmium::dword_lo(m_offset),
                         m_size);
}

inline bool osmium::util::MemoryMapping::is_valid() const noexcept {
    return m_addr != nullptr;
}

inline void osmium::util::MemoryMapping::make_invalid() noexcept {
    m_addr = nullptr;
}

// GetLastError() returns a DWORD (A 32-bit unsigned integer), but the error
// code for std::system_error is an int. So we convert this here and hope
// it all works.
inline int last_error() noexcept {
    return static_cast<int>(GetLastError());
}

inline osmium::util::MemoryMapping::MemoryMapping(std::size_t size, MemoryMapping::mapping_mode mode, int fd, off_t offset) :
    m_size(check_size(size)),
    m_offset(offset),
    m_fd(resize_fd(fd)),
    m_mapping_mode(mode),
    m_handle(create_file_mapping()),
    m_addr(nullptr) {

    if (!m_handle) {
        throw std::system_error{last_error(), std::system_category(), "CreateFileMapping failed"};
    }

    m_addr = map_view_of_file();
    if (!is_valid()) {
        throw std::system_error{last_error(), std::system_category(), "MapViewOfFile failed"};
    }
}

inline osmium::util::MemoryMapping::MemoryMapping(MemoryMapping&& other) noexcept :
    m_size(other.m_size),
    m_offset(other.m_offset),
    m_fd(other.m_fd),
    m_mapping_mode(other.m_mapping_mode),
    m_handle(std::move(other.m_handle)),
    m_addr(other.m_addr) {
    other.make_invalid();
    other.m_handle = nullptr;
}

inline osmium::util::MemoryMapping& osmium::util::MemoryMapping::operator=(osmium::util::MemoryMapping&& other) noexcept {
    try {
        unmap();
    } catch (const std::system_error&) {
        // Ignore unmap error. It should never happen anyway and we can't do
        // anything about it here.
    }
    m_size         = other.m_size;
    m_offset       = other.m_offset;
    m_fd           = other.m_fd;
    m_mapping_mode = other.m_mapping_mode;
    m_handle       = std::move(other.m_handle);
    m_addr         = other.m_addr;
    other.make_invalid();
    other.m_handle = nullptr;
    return *this;
}

inline void osmium::util::MemoryMapping::unmap() {
    if (is_valid()) {
        if (!UnmapViewOfFile(m_addr)) {
            throw std::system_error{last_error(), std::system_category(), "UnmapViewOfFile failed"};
        }
        make_invalid();
    }

    if (m_handle) {
        if (!CloseHandle(m_handle)) {
            throw std::system_error{last_error(), std::system_category(), "CloseHandle failed"};
        }
        m_handle = nullptr;
    }
}

inline void osmium::util::MemoryMapping::resize(std::size_t new_size) {
    unmap();

    m_size = new_size;
    resize_fd(m_fd);

    m_handle = create_file_mapping();
    if (!m_handle) {
        throw std::system_error{last_error(), std::system_category(), "CreateFileMapping failed"};
    }

    m_addr = map_view_of_file();
    if (!is_valid()) {
        throw std::system_error{last_error(), std::system_category(), "MapViewOfFile failed"};
    }
}

#endif

#endif // OSMIUM_UTIL_MEMORY_MAPPING_HPP