Code complet pour BasicReaderWriter

Code complet pour une classe et des méthodes de lecture et d’écriture de fichiers de données binaires en général. Utilisé par la classe BasicLoader.

Cette rubrique contient les sections suivantes :

• Technologies
• Exigences
• Afficher le code (C++)

Emplacement de téléchargement

Cet exemple n’est pas disponible pour le téléchargement.

Technologies

Langages de programmation - C++
Modèles de programmation - Windows Runtime

Spécifications

Client minimum pris en charge - Windows 10
Serveur minimum pris en charge - Windows Server 2016 Technical Preview

Afficher le code (C++)

BasicReaderWriter.h

//// THIS CODE AND INFORMATION IS PROVIDED "AS IS" WITHOUT WARRANTY OF
//// ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO
//// THE IMPLIED WARRANTIES OF MERCHANTABILITY AND/OR FITNESS FOR A
//// PARTICULAR PURPOSE.
////
//// Copyright (c) Microsoft Corporation. All rights reserved

#pragma once

#include <ppltasks.h>

// A simple reader/writer class that provides support for reading and writing
// files on disk. Provides synchronous and asynchronous methods.
ref class BasicReaderWriter
{
private:
    Windows::Storage::StorageFolder^ m_location;
    Platform::String^ m_locationPath;

internal:
    BasicReaderWriter();
    BasicReaderWriter(
        _In_ Windows::Storage::StorageFolder^ folder
        );

    Platform::Array<byte>^ ReadData(
        _In_ Platform::String^ filename
        );

    concurrency::task<Platform::Array<byte>^> ReadDataAsync(
        _In_ Platform::String^ filename
        );

    uint32 WriteData(
        _In_ Platform::String^ filename,
        _In_ const Platform::Array<byte>^ fileData
        );

    concurrency::task<void> WriteDataAsync(
        _In_ Platform::String^ filename,
        _In_ const Platform::Array<byte>^ fileData
        );
};

BasicReaderWriter.cpp

using namespace Microsoft::WRL;
using namespace Windows::Storage;
using namespace Windows::Storage::FileProperties;
using namespace Windows::Storage::Streams;
using namespace Windows::Foundation;
using namespace Windows::ApplicationModel;
using namespace concurrency;

BasicReaderWriter::BasicReaderWriter()
{
    m_location = Package::Current->InstalledLocation;
    m_locationPath = Platform::String::Concat(m_location->Path, "\\");
}

BasicReaderWriter::BasicReaderWriter(
    _In_ Windows::Storage::StorageFolder^ folder
    )
{
    m_location = folder;
    Platform::String^ path = m_location->Path;
    if (path->Length() == 0)
    {
        // Applications are not permitted to access certain
        // folders, such as the Documents folder, using this
        // code path.  In such cases, the Path property for
        // the folder will be an empty string.
        throw ref new Platform::FailureException();
    }
    m_locationPath = Platform::String::Concat(path, "\\");
}

Platform::Array<byte>^ BasicReaderWriter::ReadData(
    _In_ Platform::String^ filename
    )
{
    CREATEFILE2_EXTENDED_PARAMETERS extendedParams = {0};
    extendedParams.dwSize = sizeof(CREATEFILE2_EXTENDED_PARAMETERS);
    extendedParams.dwFileAttributes = FILE_ATTRIBUTE_NORMAL;
    extendedParams.dwFileFlags = FILE_FLAG_SEQUENTIAL_SCAN;
    extendedParams.dwSecurityQosFlags = SECURITY_ANONYMOUS;
    extendedParams.lpSecurityAttributes = nullptr;
    extendedParams.hTemplateFile = nullptr;

    Wrappers::FileHandle file(
        CreateFile2(
            Platform::String::Concat(m_locationPath, filename)->Data(),
            GENERIC_READ,
            FILE_SHARE_READ,
            OPEN_EXISTING,
            &extendedParams
            )
        );
    if (file.Get() == INVALID_HANDLE_VALUE)
    {
        throw ref new Platform::FailureException();
    }

    FILE_STANDARD_INFO fileInfo = {0};
    if (!GetFileInformationByHandleEx(
        file.Get(),
        FileStandardInfo,
        &fileInfo,
        sizeof(fileInfo)
        ))
    {
        throw ref new Platform::FailureException();
    }

    if (fileInfo.EndOfFile.HighPart != 0)
    {
        throw ref new Platform::OutOfMemoryException();
    }

    Platform::Array<byte>^ fileData = ref new Platform::Array<byte>(fileInfo.EndOfFile.LowPart);

    if (!ReadFile(
        file.Get(),
        fileData->Data,
        fileData->Length,
        nullptr,
        nullptr
        ))
    {
        throw ref new Platform::FailureException();
    }

    return fileData;
}

task<Platform::Array<byte>^> BasicReaderWriter::ReadDataAsync(
    _In_ Platform::String^ filename
    )
{
    return task<StorageFile^>(m_location->GetFileAsync(filename)).then([=](StorageFile^ file)
    {
        return FileIO::ReadBufferAsync(file);
    }).then([=](IBuffer^ buffer)
    {
        auto fileData = ref new Platform::Array<byte>(buffer->Length);
        DataReader::FromBuffer(buffer)->ReadBytes(fileData);
        return fileData;
    });
}

uint32 BasicReaderWriter::WriteData(
    _In_ Platform::String^ filename,
    _In_ const Platform::Array<byte>^ fileData
    )
{
    CREATEFILE2_EXTENDED_PARAMETERS extendedParams = {0};
    extendedParams.dwSize = sizeof(CREATEFILE2_EXTENDED_PARAMETERS);
    extendedParams.dwFileAttributes = FILE_ATTRIBUTE_NORMAL;
    extendedParams.dwFileFlags = FILE_FLAG_SEQUENTIAL_SCAN;
    extendedParams.dwSecurityQosFlags = SECURITY_ANONYMOUS;
    extendedParams.lpSecurityAttributes = nullptr;
    extendedParams.hTemplateFile = nullptr;

    Wrappers::FileHandle file(
        CreateFile2(
            Platform::String::Concat(m_locationPath, filename)->Data(),
            GENERIC_WRITE,
            0,
            CREATE_ALWAYS,
            &extendedParams
            )
        );
    if (file.Get() == INVALID_HANDLE_VALUE)
    {
        throw ref new Platform::FailureException();
    }

    DWORD numBytesWritten;
    if (
        !WriteFile(
            file.Get(),
            fileData->Data,
            fileData->Length,
            &numBytesWritten,
            nullptr
            ) ||
        numBytesWritten != fileData->Length
        )
    {
        throw ref new Platform::FailureException();
    }

    return numBytesWritten;
}

task<void> BasicReaderWriter::WriteDataAsync(
    _In_ Platform::String^ filename,
    _In_ const Platform::Array<byte>^ fileData
    )
{
    return task<StorageFile^>(m_location->CreateFileAsync(filename, CreationCollisionOption::ReplaceExisting)).then([=](StorageFile^ file)
    {
        FileIO::WriteBytesAsync(file, fileData);
    });
}