shmem.cpp

// Copyright (c) 2020 Egor Tensin <Egor.Tensin@gmail.com>
// This file is part of the "winapi-common" project.
// For details, see https://github.com/egor-tensin/winapi-common.
// Distributed under the MIT License.
 
#include <winapi/error.hpp>
#include <winapi/handle.hpp>
#include <winapi/shmem.hpp>
#include <winapi/utf8.hpp>
#include <winapi/utils.hpp>
 
#include <windows.h>
 
#include <cstddef>
#include <cstdint>
#include <string>
#include <utility>
 
namespace winapi {
namespace {
 
void* do_map(const Handle& mapping, std::size_t nb = 0) {
    const auto addr = ::MapViewOfFile(static_cast<HANDLE>(mapping), FILE_MAP_ALL_ACCESS, 0, 0, nb);
 
    if (addr == NULL) {
        throw error::windows(GetLastError(), "MapViewOfFile");
    }
 
    return addr;
}
 
} // namespace
 
void SharedMemory::Unmap::operator()(void* ptr) const {
    const auto ret = ::UnmapViewOfFile(ptr);
    assert(ret);
    WINAPI_UNUSED_PARAMETER(ret);
};
 
SharedMemory SharedMemory::create(const std::string& name, std::size_t nb) {
    const auto nb64 = static_cast<std::uint64_t>(nb);
    static_assert(sizeof(nb64) == 2 * sizeof(DWORD), "sizeof(DWORD) != 32");
 
    const auto nb_low = static_cast<DWORD>(nb64);
    const auto nb_high = static_cast<DWORD>(nb64 >> 32);
 
    const auto mapping_impl = ::CreateFileMappingW(
        INVALID_HANDLE_VALUE, NULL, PAGE_READWRITE, nb_high, nb_low, widen(name).c_str());
 
    if (mapping_impl == NULL) {
        throw error::windows(GetLastError(), "CreateFileMappingW");
    }
 
    Handle mapping{mapping_impl};
    const auto addr = do_map(mapping);
    return {std::move(mapping), addr};
}
 
SharedMemory SharedMemory::open(const std::string& name) {
    const auto mapping_impl = ::OpenFileMappingW(FILE_MAP_ALL_ACCESS, FALSE, widen(name).c_str());
 
    if (mapping_impl == NULL) {
        throw error::windows(GetLastError(), "OpenFileMappingW");
    }
 
    Handle mapping{mapping_impl};
    const auto addr = do_map(mapping);
    return {std::move(mapping), addr};
}
 
} // namespace winapi