BufferedStream.Read 方法

定义

命名空间:

System.IO

程序集:

System.Runtime.dll

重载

Read(Span<Byte>)	将当前缓冲流中的字节复制到字节跨度，并按读取的字节数向前移动缓冲流中的位置。
Read(Byte[], Int32, Int32)	将字节从当前缓冲流复制到数组。

Read(Span<Byte>)

Source:

BufferedStream.cs

将当前缓冲流中的字节复制到字节跨度，并按读取的字节数向前移动缓冲流中的位置。

public:
 override int Read(Span<System::Byte> destination);

public override int Read (Span<byte> destination);

override this.Read : Span<byte> -> int

Public Overrides Function Read (destination As Span(Of Byte)) As Integer

参数

destination

Span<Byte>

内存的区域。 当此方法返回时，此区域的内容将替换为从当前源读取的字节。

返回

Int32

读入缓冲区中的总字节数。 如果很多字节当前不可用，则这可小于在缓冲区中分配的字节数；如果已到达流结尾，则为零 (0)。

注解

CanRead使用 属性确定当前实例是否支持读取。 ReadAsync使用 方法从当前流异步读取。

此方法的实现从当前流中读取最大字节数 buffer.Length ，并将其存储在 中 buffer。 流中的当前位置按读取的字节数提前;但是，如果发生异常，流中的当前位置保持不变。 实现返回读取的字节数。 实现将阻止，直到至少一个字节的数据可以读取，如果没有任何数据可用。 Read 仅当流中没有更多数据且预期不会再 (（例如关闭的套接字或文件) 末尾）时才返回 0。 实现可以自由地返回比请求的字节少，即使尚未到达流的末尾。

用于 BinaryReader 读取基元数据类型。

Read(Byte[], Int32, Int32)

Source:

BufferedStream.cs

将字节从当前缓冲流复制到数组。

public:
 override int Read(cli::array <System::Byte> ^ buffer, int offset, int count);

public override int Read (byte[] buffer, int offset, int count);

override this.Read : byte[] * int * int -> int

Public Overrides Function Read (buffer As Byte(), offset As Integer, count As Integer) As Integer

参数

buffer

Byte[]

将字节复制到的缓冲区。

offset

Int32

缓冲区中的字节偏移量，从此处开始读取字节。

count

Int32

要读取的字节数。

返回

Int32

读入 array 中的总字节数。 如果可用的字节没有所请求的那么多，总字节数可能小于请求的字节数；或者如果在可读取任何数据前就已到达流的末尾，则为零。

例外

ArgumentException

array 的长度减去 offset 小于 count。

ArgumentNullException

array 为 null。

ArgumentOutOfRangeException

offset 或 count 为负数。

IOException

流未打开或为 null。

NotSupportedException

流不支持读取。

ObjectDisposedException

在流关闭后调用方法。

示例

此代码示例是为 BufferedStream 类提供的一个更大示例的一部分。

// Receive data using the BufferedStream.
Console::WriteLine(  "Receiving data using BufferedStream." );
bytesReceived = 0;
startTime = DateTime::Now;
while ( bytesReceived < numberOfLoops * receivedData->Length )
{
   bytesReceived += bufStream->Read( receivedData, 0, receivedData->Length );
}

bufferedTime = (DateTime::Now - startTime).TotalSeconds;
Console::WriteLine( "{0} bytes received in {1} seconds.\n", bytesReceived.ToString(), bufferedTime.ToString(  "F1" ) );

// Receive data using the BufferedStream.
Console.WriteLine("Receiving data using BufferedStream.");
bytesReceived = 0;
startTime = DateTime.Now;

int numBytesToRead = receivedData.Length;

while (numBytesToRead > 0)
{
    // Read may return anything from 0 to numBytesToRead.
    int n = bufStream.Read(receivedData,0, receivedData.Length);
    // The end of the file is reached.
    if (n == 0)
        break;
    bytesReceived += n;
    numBytesToRead -= n;
}

bufferedTime = (DateTime.Now - startTime).TotalSeconds;
Console.WriteLine("{0} bytes received in {1} seconds.\n",
    bytesReceived.ToString(),
    bufferedTime.ToString("F1"));

// Receive data using the BufferedStream.
printfn "Receiving data using BufferedStream."
bytesReceived <- 0
let startTime = DateTime.Now

let mutable numBytesToRead = receivedData.Length

let mutable broken = false
while not broken && numBytesToRead > 0 do
    // Read may return anything from 0 to numBytesToRead.
    let n = bufStream.Read(receivedData,0, receivedData.Length)
    // The end of the file is reached.
    if n = 0 then
        broken <- true
    else
        bytesReceived <- bytesReceived + n
        numBytesToRead <- numBytesToRead - n

let bufferedTime = (DateTime.Now - startTime).TotalSeconds
printfn $"{bytesReceived} bytes received in {bufferedTime:F1} seconds.\n"

' Receive data using the BufferedStream.
Console.WriteLine("Receiving data using BufferedStream.")
bytesReceived = 0
startTime = DateTime.Now

Dim numBytesToRead As Integer = receivedData.Length
Dim n As Integer
Do While numBytesToRead > 0

    'Read my return anything from 0 to numBytesToRead
    n = bufStream.Read(receivedData, 0, receivedData.Length)
    'The end of the file is reached.
    If n = 0 Then
        Exit Do
    End If

    bytesReceived += n
    numBytesToRead -= n
Loop

bufferedTime = DateTime.Now.Subtract(startTime).TotalSeconds
Console.WriteLine("{0} bytes received in {1} " & _
    "seconds." & vbCrLf, _
    bytesReceived.ToString(), _
    bufferedTime.ToString("F1"))

注解

Read仅当到达流的末尾时，方法才会返回 0。 在所有其他情况下， Read 始终在返回之前从流中至少读取一个字节。 根据定义，如果在调用 Read时流中没有数据可用，则 Read 方法返回 0， () 自动到达流的末尾。 实现可以自由地返回比请求的字节少，即使尚未到达流的末尾。

用于 BinaryReader 读取基元数据类型。

另请参阅

• BlockCopy(Array, Int32, Array, Int32, Int32)
• CanRead
• Write(Byte[], Int32, Int32)
• 文件和流 I/O
• 如何：从文件中读取文本
• 如何：将文本写入文件