DataReader Class

從輸入資料流讀取資料。

語法


var dataReader = new Windows.Storage.Streams.DataReader();

屬性

[MarshalingBehavior(Agile)]
[Threading(Both)]
[Version(0x06020000)]

成員

DataReader類別 具有下列類型的成員:

建構函式

DataReader類別 具有這些建構函式。

建構函式描述
DataReader Creates and initializes a new instance of the data reader.

 

方法

The DataReader 類別 擁有這些方法。 使用 C#、Visual Basic 和 C++,它也會繼承方法自Object 類別.

方法描述
Close [C++, JavaScript]Closes the current stream and releases system resources.
DetachBuffer Detaches the buffer that is associated with the data reader.
DetachStream Detaches the stream that is associated with the data reader.
Dispose [C#, VB]Performs tasks associated with freeing, releasing, or resetting unmanaged resources.
FromBuffer Creates a new instance of the data reader with data from the specified buffer.
LoadAsync Loads data from the input stream.
ReadBoolean Reads a Boolean value from the input stream.
ReadBuffer Reads a buffer from the input stream.
ReadByte Reads a byte value from the input stream.
ReadBytes Reads an array of byte values from the input stream.
ReadDateTime Reads a date and time value from the input stream.
ReadDouble Reads a floating-point value from the input stream.
ReadGuid Reads a GUID value from the input stream.
ReadInt16 Reads a 16-bit integer value from the input stream.
ReadInt32 Reads a 32-bit integer value from the input stream.
ReadInt64 Reads a 64-bit integer value from the input stream.
ReadSingle Reads a floating-point value from the input stream.
ReadString Reads a string value from the input stream.
ReadTimeSpan Reads a time-interval value from the input stream.
ReadUInt16 Reads a 16-bit unsigned integer from the input stream.
ReadUInt32 Reads a 32-bit unsigned integer from the input stream.
ReadUInt64 Reads a 64-bit unsigned integer from the input stream.

 

屬性

DataReader類別 擁有這些屬性。

屬性存取類型描述

ByteOrder

讀取/寫入Gets or sets the byte order of the data in the input stream.

InputStreamOptions

讀取/寫入Gets or sets the read options for the input stream.

UnconsumedBufferLength

唯讀Gets the size of the buffer that has not been read.

UnicodeEncoding

讀取/寫入Gets or sets the Unicode character encoding for the input stream.

 

範例

下列範例示範如何讀取和寫入資料至記憶體中資料流。如需完整程式碼範例,請參閱讀取和寫入資料範例



(function () {
    "use strict";
    var page = WinJS.UI.Pages.define("/html/write-read-stream.html", {
        ready: function (element, options) {
            var sourceElement = document.getElementById("ElementsToSend");
            sourceElement.innerHTML = "Hello;World;1 2 3 4 5;Très bien!;Goodbye";
            var sendButton = document.getElementById("SendButton");
            sendButton.addEventListener("click", transferData);
        }
    });

function transferData() {
        var sourceElement = document.getElementById("ElementsToSend");
        var destinationElement = document.getElementById("scenario1Output");

        // First a DataWriter object is created, backed by an in-memory stream where 
        // the data will be stored.
        var writer = Windows.Storage.Streams.DataWriter(
            new Windows.Storage.Streams.InMemoryRandomAccessStream());
        writer.unicodeEncoding = Windows.Storage.Streams.UnicodeEncoding.utf8;
        writer.byteOrder = Windows.Storage.Streams.ByteOrder.littleEndian;

        // We separate the contents of the sourceElement div in multiple strings 
        // using ';' as the separator. Each string will be written separately.
        var elements = sourceElement.innerHTML.split(";");
        elements.forEach(function (element) {
            var codeUnits = writer.measureString(element);
            writer.writeInt32(codeUnits);
            writer.writeString(element);
        });

        var reader;
        var stream;

        // The call to store async sends the actual contents of the writer 
        // to the backing stream.
        writer.storeAsync().then(function () {
            // For the in-memory stream implementation we are using, the flushAsync call 
            // is superfluous, but other types of streams may require it.
            return writer.flushAsync();
        }).then(function () {
            // We detach the stream to prolong its useful lifetime. Were we to fail 
            // to detach the stream, the call to writer.close() would close the underlying 
            // stream, preventing its subsequent use by the DataReader below. Most clients 
            // of DataWriter will have no reason to use the underlying stream after 
            // writer.close() is called, and will therefore have no reason to call
            // writer.detachStream(). Note that once we detach the stream, we assume 
            // responsibility for closing the stream subsequently; after the stream 
            // has been detached, a call to writer.close() will have no effect on the stream.
            stream = writer.detachStream();
            // Make sure the stream is read from the beginning in the reader 
            // we are creating below.
            stream.seek(0);
            // Most DataWriter clients will not call writer.detachStream(), 
            // and furthermore will be working with a file-backed or network-backed stream, 
            // rather than an in-memory-stream. In such cases, it would be particularly 
            // important to call writer.close(). Doing so is always a best practice.
            writer.close();

            reader = new Windows.Storage.Streams.DataReader(stream);
            // The encoding and byte order need to match the settings of the writer 
            // we previously used.
            reader.unicodeEncoding = Windows.Storage.Streams.UnicodeEncoding.utf8;
            reader.byteOrder = Windows.Storage.Streams.ByteOrder.littleEndian;
            // Once we have written the contents successfully we load the stream, 
            // this is also an asynchronous operation
            return reader.loadAsync(stream.size);
        }).done(function () {
            var receivedStrings = "";
            // Keep reading until we consume the complete stream
            while (reader.unconsumedBufferLength > 0) {
                // Note that the call to readString requires a length of "code units" 
                // to read. This is the reason each string is preceeded by its length 
                // when "on the wire".
                var codeUnitsToRead = reader.readInt32();
                receivedStrings += reader.readString(codeUnitsToRead) + "<br/>";
            }
            // Calling reader.close() closes the underlying stream. It would be particularly important
            // to call reader.close() if the underlying stream were file-backed or 
            // network-backed. Note that this call to reader.close() satisfies 
            // our obligation to close the stream previously detached from DataReader.
            reader.close();
            destinationElement.innerHTML = receivedStrings;
        });
    };
})();


需求

支援的最小用戶端

Windows 8 [僅限 Windows 市集應用程式]

支援的最小伺服器

Windows Server 2012 [僅限 Windows 市集應用程式]

支援的最小電話

Windows Phone 8

命名空間

Windows.Storage.Streams
Windows::Storage::Streams [C++]

Metadata

Windows.winmd

請參閱

讀取和寫入資料範例
StreamSocket 範例
DataReaderLoadOperation
DataWriter

 

 

顯示:
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