Bewerken

Delen via

UTF7Encoding.GetMaxByteCount(Int32) Method

  • Reference

Definition

Namespace:
System.Text
Assemblies:
mscorlib.dll, System.Text.Encoding.Extensions.dll
Assembly:
System.Text.Encoding.Extensions.dll
Assembly:
mscorlib.dll
Assembly:
netstandard.dll
Source:
UTF7Encoding.cs
Source:
UTF7Encoding.cs
Source:
UTF7Encoding.cs

Calculates the maximum number of bytes produced by encoding the specified number of characters.

public:
 override int GetMaxByteCount(int charCount);
public override int GetMaxByteCount (int charCount);
override this.GetMaxByteCount : int -> int
Public Overrides Function GetMaxByteCount (charCount As Integer) As Integer

Parameters

charCount
Int32

The number of characters to encode.

Returns

Int32

The maximum number of bytes produced by encoding the specified number of characters.

Exceptions

ArgumentOutOfRangeException

charCount is less than zero.

-or-

The resulting number of bytes is greater than the maximum number that can be returned as an int.

EncoderFallbackException

A fallback occurred (for more information, see Character Encoding in .NET)

-and-

EncoderFallback is set to EncoderExceptionFallback.

Examples

The following code example demonstrates how to use the GetMaxByteCount method to return the maximum number of bytes required to encode a specified number of characters.

using namespace System;
using namespace System::Text;
int main()
{
   UTF7Encoding^ utf7 = gcnew UTF7Encoding;
   int charCount = 2;
   int maxByteCount = utf7->GetMaxByteCount( charCount );
   Console::WriteLine( "Maximum of {0} bytes needed to encode {1} characters.", maxByteCount, charCount );
}

using System;
using System.Text;

class UTF7EncodingExample {
    public static void Main() {
        UTF7Encoding utf7 = new UTF7Encoding();
        int charCount = 2;
        int maxByteCount = utf7.GetMaxByteCount(charCount);
        Console.WriteLine(
            "Maximum of {0} bytes needed to encode {1} characters.",
            maxByteCount,
            charCount
        );
    }
}

Imports System.Text

Class UTF7EncodingExample
    
    Public Shared Sub Main()
        Dim utf7 As New UTF7Encoding()
        Dim charCount As Integer = 2
        Dim maxByteCount As Integer = utf7.GetMaxByteCount(charCount)
        Console.WriteLine( _
            "Maximum of {0} bytes needed to encode {1} characters.", _
            maxByteCount, _
            charCount _
        )
    End Sub
End Class

Remarks

To calculate the exact array size required by GetBytes to store the resulting bytes, the application uses GetByteCount. To calculate the maximum array size, the application should use GetMaxByteCount. The GetByteCount method generally allows allocation of less memory, while the GetMaxByteCount method generally executes faster.

GetMaxByteCount is a worst-case number, including the worst case for the currently selected EncoderFallback. If a fallback is chosen with a potentially large string, GetMaxByteCount can return large values.

In most cases, this method returns reasonable numbers for small strings. For large strings, you might have to choose between using very large buffers and catching errors in the rare case that a more reasonable buffer is exceeded. You might also want to consider a different approach using GetByteCount or Encoder.Convert. While UTF-7 is very efficient at encoding ASCII data, one byte per character, it is extremely inefficient for other data. As remarked above, GetMaxByteCount deals with a worst case. If the data to be encoded is largely ASCII, and especially if the ASCII characters cluster together, UTF-7 is significantly more efficient than the number returned by this method suggests.

GetMaxByteCount has no relation to GetChars. If your application needs a similar function to use with GetChars, it should use GetMaxCharCount.

Note

GetMaxByteCount(N) is not necessarily the same value as N* GetMaxByteCount(1).

Applies to

See also