DataReader Kelas

Definisi

Ruang nama:

Windows.Storage.Streams

Membaca data dari aliran input.

public ref class DataReader sealed : IClosable, IDataReader

/// [Windows.Foundation.Metadata.ContractVersion(Windows.Foundation.UniversalApiContract, 65536)]
/// [Windows.Foundation.Metadata.MarshalingBehavior(Windows.Foundation.Metadata.MarshalingType.Agile)]
/// [Windows.Foundation.Metadata.Threading(Windows.Foundation.Metadata.ThreadingModel.Both)]
/// [Windows.Foundation.Metadata.Activatable(Windows.Storage.Streams.IDataReaderFactory, 65536, "Windows.Foundation.UniversalApiContract")]
class DataReader final : IClosable, IDataReader

[Windows.Foundation.Metadata.ContractVersion(typeof(Windows.Foundation.UniversalApiContract), 65536)]
[Windows.Foundation.Metadata.MarshalingBehavior(Windows.Foundation.Metadata.MarshalingType.Agile)]
[Windows.Foundation.Metadata.Threading(Windows.Foundation.Metadata.ThreadingModel.Both)]
[Windows.Foundation.Metadata.Activatable(typeof(Windows.Storage.Streams.IDataReaderFactory), 65536, "Windows.Foundation.UniversalApiContract")]
public sealed class DataReader : System.IDisposable, IDataReader

function DataReader(inputStream)

Public NotInheritable Class DataReader
Implements IDataReader, IDisposable

Warisan

Object Platform::Object IInspectable DataReader

Atribut

ActivatableAttribute ContractVersionAttribute MarshalingBehaviorAttribute ThreadingAttribute

Penerapan

IClosable IDisposable IDataReader

Persyaratan Windows

Rangkaian perangkat	Windows 10 (diperkenalkan dalam 10.0.10240.0)
API contract	Windows.Foundation.UniversalApiContract (diperkenalkan dalam v1.0)

Contoh

Contoh kode berikut menunjukkan cara menulis dan membaca string ke aliran dalam memori. Untuk aplikasi sampel lengkap di C# dan di C++/CX, lihat Membuat serialisasi dan deserialisasi sampel data.

using System;
using System.Diagnostics;
using Windows.Foundation;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Navigation;

// This is the click handler for the 'Copy Strings' button.  Here we will parse the
// strings contained in the ElementsToWrite text block, write them to a stream using
// DataWriter, retrieve them using DataReader, and output the results in the
// ElementsRead text block.
private async void TransferData(object sender, RoutedEventArgs e)
{
    // Initialize the in-memory stream where data will be stored.
    using (var stream = new Windows.Storage.Streams.InMemoryRandomAccessStream())
    {
        // Create the data writer object backed by the in-memory stream.
        using (var dataWriter = new Windows.Storage.Streams.DataWriter(stream))
        {
            dataWriter.UnicodeEncoding = Windows.Storage.Streams.UnicodeEncoding.Utf8;
            dataWriter.ByteOrder = Windows.Storage.Streams.ByteOrder.LittleEndian;

            // Parse the input stream and write each element separately.
            string[] inputElements = ElementsToWrite.Text.Split(';');
            foreach (string inputElement in inputElements)
            {
                uint inputElementSize = dataWriter.MeasureString(inputElement);
                dataWriter.WriteUInt32(inputElementSize);
                dataWriter.WriteString(inputElement);
            }

            // Send the contents of the writer to the backing stream.
            await dataWriter.StoreAsync();

            // For the in-memory stream implementation we are using, the flushAsync call 
            // is superfluous,but other types of streams may require it.
            await dataWriter.FlushAsync();

            // In order to prolong the lifetime of the stream, detach it from the 
            // DataWriter so that it will not be closed when Dispose() is called on 
            // dataWriter. Were we to fail to detach the stream, the call to 
            // dataWriter.Dispose() would close the underlying stream, preventing 
            // its subsequent use by the DataReader below.
            dataWriter.DetachStream();
        }

        // Create the input stream at position 0 so that the stream can be read 
        // from the beginning.
        using (var inputStream = stream.GetInputStreamAt(0))
        {
            using (var dataReader = new Windows.Storage.Streams.DataReader(inputStream))
            {
                // The encoding and byte order need to match the settings of the writer 
                // we previously used.
                dataReader.UnicodeEncoding = Windows.Storage.Streams.UnicodeEncoding.Utf8;
                dataReader.ByteOrder = Windows.Storage.Streams.ByteOrder.LittleEndian;

                // Once we have written the contents successfully we load the stream.
                await dataReader.LoadAsync((uint)stream.Size);

                var receivedStrings = "";

                // Keep reading until we consume the complete stream.
                while (dataReader.UnconsumedBufferLength > 0)
                {
                    // Note that the call to readString requires a length of "code units" 
                    // to read. This is the reason each string is preceded by its length 
                    // when "on the wire".
                    uint bytesToRead = dataReader.ReadUInt32();
                    receivedStrings += dataReader.ReadString(bytesToRead) + "\n";
                }

                // Populate the ElementsRead text block with the items we read 
                // from the stream.
                ElementsRead.Text = receivedStrings;
            }
        }
    }
}

#include "pch.h"
#include "WriteReadStream.h" // header file for WriteReadStream.xaml.
#include <sstream>

#include <winrt/Windows.Foundation.h>
#include <winrt/Windows.Storage.Streams.h>

using namespace winrt;

std::array<winrt::hstring, 5> m_inputElements{ L"Hello", L"World", L"1 2 3 4 5", L"Très bien!", L"Goodbye" };

WriteReadStream::WriteReadStream()
{
    InitializeComponent();

    // Populate the text block with the input elements.
    std::wstringstream stringstream;
    for (winrt::hstring const& element : m_inputElements)
    {
        stringstream << element.c_str() << L";";
    }
    ElementsToWrite().Text(stringstream.str().c_str());
}

// This is the click handler for the 'Copy Strings' button. Here we will parse the
// strings contained in the ElementsToWrite text block, write them to a stream using
// DataWriter, retrieve them using DataReader, and output the results in the
// ElementsRead text block.
winrt::Windows::Foundation::IAsyncAction WriteReadStream::TransferData(
    Windows::Foundation::IInspectable const& /* sender */,
    Windows::UI::Xaml::RoutedEventArgs const& /* args */)
{
    // Initialize the in-memory stream where data will be stored.
    Windows::Storage::Streams::InMemoryRandomAccessStream stream;

    // Create the DataWriter object backed by the in-memory stream. When
    // dataWriter goes out of scope, it closes the underlying stream.
    Windows::Storage::Streams::DataWriter dataWriter{ stream };
    dataWriter.UnicodeEncoding(Windows::Storage::Streams::UnicodeEncoding::Utf16LE);
    dataWriter.ByteOrder(Windows::Storage::Streams::ByteOrder::LittleEndian);

    // Create the data reader by using the input stream set at position 0 so that 
    // the stream will be read from the beginning regardless of the position that
    // the original stream ends up in after the store.
    Windows::Storage::Streams::IInputStream inputStream{ stream.GetInputStreamAt(0) };
    Windows::Storage::Streams::DataReader dataReader{ inputStream };
    // The encoding and byte order need to match the settings of the writer that
    // we previously used.
    dataReader.UnicodeEncoding(Windows::Storage::Streams::UnicodeEncoding::Utf16LE);
    dataReader.ByteOrder(Windows::Storage::Streams::ByteOrder::LittleEndian);

    // Write the input data to the output stream. Serialize the elements by writing
    // each string separately, preceded by its length in bytes.
    for (winrt::hstring const& element : m_inputElements)
    {
        dataWriter.WriteUInt32(element.size());
        dataWriter.WriteString(element);
    }

    // Send the contents of the writer to the backing stream.
    unsigned int bytesStored{ co_await dataWriter.StoreAsync() };

    // For the in-memory stream implementation we are using, the FlushAsync() call 
    // is superfluous, but other types of streams may require it.
    if (co_await dataWriter.FlushAsync())
    {
        try
        {
            // Once we've written the contents successfully, we load the stream.
            unsigned int bytesLoaded{ co_await dataReader.LoadAsync((unsigned int)stream.Size()) };

            std::wstringstream readFromStream;

            // Keep reading until we consume the complete stream.
            while (dataReader.UnconsumedBufferLength() > 0)
            {
                // Note that the call to ReadString requires a length of 
                // "code units" to read. This is the reason each string is 
                // preceded by its length when "on the wire".
                unsigned int bytesToRead{ dataReader.ReadUInt32() };
                readFromStream << dataReader.ReadString(bytesToRead).c_str() << std::endl;
            }

            // Populate the ElementsRead text block with the items we read from the stream
            ElementsRead().Text(readFromStream.str().c_str());
        }
        catch (winrt::hresult_error const& ex)
        {
            ElementsRead().Text(L"Error: " + ex.message());
        }
    }
}

#include "pch.h"
#include "WriteReadStream.xaml.h"

using namespace Concurrency;
using namespace DataReaderWriter;
using namespace Platform;
using namespace Windows::Storage::Streams;
using namespace Windows::UI::Xaml;
using namespace Windows::UI::Xaml::Controls;
using namespace Windows::UI::Xaml::Navigation;

Array<String^>^ _inputElements = ref new Array<String^>
{
    "Hello", "World", "1 2 3 4 5", "Très bien!", "Goodbye"
};

WriteReadStream::WriteReadStream()
{
    InitializeComponent();

    // Populate the text block with the input elements.
    ElementsToWrite->Text = "";
    for (unsigned int i = 0; i < _inputElements->Length; i++)
    {
        ElementsToWrite->Text += _inputElements[i] + ";";
    }
}

// Invoked when this page is about to be displayed in a Frame.
void WriteReadStream::OnNavigatedTo(NavigationEventArgs^ e)
{
    // Get a pointer to our main page.
    rootPage = MainPage::Current;
}

// This is the click handler for the 'Copy Strings' button.  Here we will parse the
// strings contained in the ElementsToWrite text block, write them to a stream using
// DataWriter, retrieve them using DataReader, and output the results in the
// ElementsRead text block.
void DataReaderWriter::WriteReadStream::TransferData(
Platform::Object^ sender, Windows::UI::Xaml::RoutedEventArgs^ e)
{
    // Initialize the in-memory stream where data will be stored.
    InMemoryRandomAccessStream^ stream = ref new InMemoryRandomAccessStream();

    // Create the DataWriter object backed by the in-memory stream.  When
    // dataWriter is deleted, it will also close the underlying stream.
    DataWriter^ dataWriter = ref new DataWriter(stream);
    dataWriter->UnicodeEncoding = UnicodeEncoding::Utf8;
    dataWriter->ByteOrder = ByteOrder::LittleEndian;

    // Create the data reader by using the input stream set at position 0 so that 
    // the stream will be read from the beginning regardless of where the position
    // the original stream ends up in after the store.
    IInputStream^ inputStream = stream->GetInputStreamAt(0);
    DataReader^ dataReader = ref new DataReader(inputStream);
    // The encoding and byte order need to match the settings of the writer 
    // we previously used.
    dataReader->UnicodeEncoding = UnicodeEncoding::Utf8;
    dataReader->ByteOrder = ByteOrder::LittleEndian;

    // Write the input data to the output stream.  Serialize the elements by writing
    // each string separately, preceded by its length.
    for (unsigned int i = 0; i < _inputElements->Length; i++) 
    {
        unsigned int inputElementSize = dataWriter->MeasureString(_inputElements[i]);
        dataWriter->WriteUInt32(inputElementSize);
        dataWriter->WriteString(_inputElements[i]);
    }

    // Send the contents of the writer to the backing stream.
    create_task(dataWriter->StoreAsync()).then([this, dataWriter] (unsigned int bytesStored)
    {
        // For the in-memory stream implementation we are using, the FlushAsync() call 
        // is superfluous, but other types of streams may require it.
        return dataWriter->FlushAsync();
    }).then([this, dataReader, stream] (bool flushOp)
    {
        // Once we have written the contents successfully we load the stream.
        return dataReader->LoadAsync((unsigned int) stream->Size);
    }).then([this, dataReader] (task<unsigned int> bytesLoaded)
    {
        try
        {
            // Check for possible exceptions that could have been thrown 
            // in the async call chain.
            bytesLoaded.get();

            String^ readFromStream = "";

            // Keep reading until we consume the complete stream.
            while (dataReader->UnconsumedBufferLength > 0)
            {
                // Note that the call to ReadString requires a length of 
                // "code units" to read. This is the reason each string is 
                // preceded by its length when "on the wire".
                unsigned int bytesToRead = dataReader->ReadUInt32();
                readFromStream += dataReader->ReadString(bytesToRead) + "\n";
            }

            // Populate the ElementsRead text block with the items we read from the stream
            ElementsRead->Text = readFromStream;
        }
        catch (Exception^ e)
        {
            ElementsRead->Text = "Error: " + e->Message;
        }
    });
}

Keterangan

Instans objek DataReader tidak mendukung operasi baca bersamaan. Jika aplikasi secara bersamaan membaca atau mencopot aliran dari instans DataReader yang sedang dibaca, panggilan ke objek akan gagal dengan kesalahan HRESULT_FROM_WIN32(ERROR_INVALID_OPERATION).

Konstruktor

DataReader(IInputStream)

Membuat dan menginisialisasi instans baru pembaca data.

Properti

ByteOrder	Mendapatkan atau mengatur urutan byte data di aliran input.
InputStreamOptions	Mendapatkan atau mengatur opsi baca untuk aliran input.
UnconsumedBufferLength	Mendapatkan ukuran buffer yang belum dibaca.
UnicodeEncoding	Mendapatkan atau mengatur pengodean karakter Unicode untuk aliran input.

Metode

Close()	Menutup aliran saat ini dan merilis sumber daya sistem.
DetachBuffer()	Mencopot buffer yang terkait dengan pembaca data. Ini berguna jika Anda ingin mempertahankan buffer setelah Anda membuang pembaca data.
DetachStream()	Mencopot aliran yang terkait dengan pembaca data.
Dispose()	Melakukan tugas yang ditentukan aplikasi yang terkait dengan membebaskan, melepaskan, atau mereset sumber daya yang tidak terkelola.
FromBuffer(IBuffer)	Membuat instans baru pembaca data dengan data dari buffer yang ditentukan.
LoadAsync(UInt32)	Memuat data dari aliran input.
ReadBoolean()	Membaca nilai Boolean dari aliran input.
ReadBuffer(UInt32)	Membaca buffer dari aliran input.
ReadByte()	Membaca nilai byte dari aliran input.
ReadBytes(Byte[])	Membaca array nilai byte dari aliran input.
ReadDateTime()	Membaca nilai tanggal dan waktu dari aliran input.
ReadDouble()	Membaca nilai floating-point dari aliran input.
ReadGuid()	Membaca nilai GUID dari aliran input.
ReadInt16()	Membaca nilai bilangan bulat 16-bit dari aliran input.
ReadInt32()	Membaca nilai bilangan bulat 32-bit dari aliran input.
ReadInt64()	Membaca nilai bilangan bulat 64-bit dari aliran input.
ReadSingle()	Membaca nilai floating-point dari aliran input.
ReadString(UInt32)	Membaca nilai string dari aliran input.
ReadTimeSpan()	Membaca nilai interval waktu dari aliran input.
ReadUInt16()	Membaca bilangan bulat 16-bit yang tidak ditandatangani dari aliran input.
ReadUInt32()	Membaca bilangan bulat 32-bit yang tidak ditandatangani dari aliran input.
ReadUInt64()	Membaca bilangan bulat 64-bit yang tidak ditandatangani dari aliran input.

Lihat juga

• DataReaderLoadOperation
• DataWriter
• Membuat serialisasi dan deserialisasi sampel data (Windows 10)
• Sampel akses file (Windows 10)
• Sampel StreamSocket (Windows 10)
• Sampel perangkat USB kustom (Windows 10)
• Sampel DatagramSocket (Windows 10)