BinaryReader.Read Method (Byte(), Int32, Int32)
Reads the specified number of bytes from the stream, starting from a specified point in the byte array.
Assembly: mscorlib (in mscorlib.dll)
Public Overridable Function Read ( buffer As Byte(), index As Integer, count As Integer ) As Integer
Parameters
- buffer
-
Type:
System.Byte()
The buffer to read data into.
- index
-
Type:
System.Int32
The starting point in the buffer at which to begin reading into the buffer.
- count
-
Type:
System.Int32
The number of bytes to read.
Return Value
Type: System.Int32The number of bytes read into buffer. This might be less than the number of bytes requested if that many bytes are not available, or it might be zero if the end of the stream is reached.
| Exception | Condition |
|---|---|
| ArgumentException | The buffer length minus index is less than count. -or- The number of decoded characters to read is greater than count. This can happen if a Unicode decoder returns fallback characters or a surrogate pair. |
| ArgumentNullException | buffer is null. |
| ArgumentOutOfRangeException | index or count is negative. |
| ObjectDisposedException | The stream is closed. |
| IOException | An I/O error occurs. |
BinaryReader does not restore the file position after an unsuccessful read operation.
For a list of common I/O tasks, see Common I-O Tasks.
The following example shows how to write binary data by using memory as a backing store. It displays a message to the console that indicates whether the data was written correctly.
Imports System.IO Module Module1 Sub Main() Const upperBound As Integer = 1000 Dim dataArray(upperBound) As Byte Dim verifyArray(upperBound) As Byte Dim randomGenerator As New Random randomGenerator.NextBytes(dataArray) Using binWriter As New BinaryWriter(New MemoryStream()) Console.WriteLine("Writing the data.") binWriter.Write(dataArray, 0, dataArray.Length) Using binReader As New BinaryReader(binWriter.BaseStream) binReader.BaseStream.Position = 0 If binReader.Read(verifyArray, 0, dataArray.Length) <> dataArray.Length Then Console.WriteLine("Error writing the data.") Return End If End Using End Using For i As Integer = 0 To upperBound If verifyArray(i) <> dataArray(i) Then Console.WriteLine("Error writing the data.") Return End If Next i Console.WriteLine("The data was written and verified.") End Sub End Module
This example reads the contents of a file and displays each byte's numeric value in 16-column format. The end of the file that is being read is detected when the Read method returns zero bytes.
Imports System Imports System.IO Imports System.Text Module Module1 Private ReadOnly CHUNK_SIZE As Integer = 1024 Public Sub Main(args() As String) If ((args.Length = 0) OrElse Not File.Exists(args(0))) Then Console.WriteLine("Please provide an existing file name.") Else Using fs As FileStream = New FileStream(args(0), FileMode.Open, FileAccess.Read) Using br As New BinaryReader(fs, New ASCIIEncoding()) Dim chunk(CHUNK_SIZE) As Byte chunk = br.ReadBytes(CHUNK_SIZE) While chunk.Length > 0 DumpBytes(chunk, chunk.Length) chunk = br.ReadBytes(CHUNK_SIZE) End While End Using End Using End If End Sub Public Sub DumpBytes(bdata() As Byte, len As Integer) Dim i As Integer Dim j As Integer = 0 Dim dchar As Char ' 3 * 16 chars for hex display, 16 chars for text and 8 chars ' for the 'gutter' int the middle. Dim dumptext As New StringBuilder(" ", 16 * 4 + 8) For i = 0 To len - 1 dumptext.Insert(j * 3, String.Format("{0:X2} ", CType(bdata(i), Integer))) dchar = Convert.ToChar(bdata(i)) ' replace 'non-printable' chars with a '.'. If Char.IsWhiteSpace(dchar) Or Char.IsControl(dchar) Then dchar = "." End If dumptext.Append(dchar) j += 1 If j = 16 Then Console.WriteLine(dumptext) dumptext.Length = 0 dumptext.Append(" ") j = 0 End If Next i ' display the remaining line If j > 0 Then ' add blank hex spots to align the 'gutter'. For i = j To 15 dumptext.Insert(j * 3, " ") Next i Console.WriteLine(dumptext) End If End Sub End Module
Available since 8
.NET Framework
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1