Encoding.GetCharCount Method

Definition

Namespace:

System.Text

Assemblies:

netstandard.dll, System.Runtime.dll

When overridden in a derived class, calculates the number of characters produced by decoding a sequence of bytes.

Overloads

GetCharCount(Byte[])	When overridden in a derived class, calculates the number of characters produced by decoding all the bytes in the specified byte array.
GetCharCount(ReadOnlySpan<Byte>)	When overridden in a derived class, calculates the number of characters produced by decoding the provided read-only byte span.
GetCharCount(Byte*, Int32)	When overridden in a derived class, calculates the number of characters produced by decoding a sequence of bytes starting at the specified byte pointer.
GetCharCount(Byte[], Int32, Int32)	When overridden in a derived class, calculates the number of characters produced by decoding a sequence of bytes from the specified byte array.

GetCharCount(Byte[])

Source:

Encoding.cs

When overridden in a derived class, calculates the number of characters produced by decoding all the bytes in the specified byte array.

C#

public virtual int GetCharCount(byte[] bytes);

Parameters

bytes

Byte[]

The byte array containing the sequence of bytes to decode.

Returns

Int32

The number of characters produced by decoding the specified sequence of bytes.

Exceptions

ArgumentNullException

bytes is null.

DecoderFallbackException

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

-and-

DecoderFallback is set to DecoderExceptionFallback.

Examples

The following example encodes a string into an array of bytes, and then decodes the bytes into an array of characters.

C#

using System;
using System.Text;

public class SamplesEncoding  {

   public static void Main()  {

      // Create two instances of UTF32Encoding: one with little-endian byte order and one with big-endian byte order.
      Encoding u32LE = Encoding.GetEncoding( "utf-32" );
      Encoding u32BE = Encoding.GetEncoding( "utf-32BE" );

      // Use a string containing the following characters:
      //    Latin Small Letter Z (U+007A)
      //    Latin Small Letter A (U+0061)
      //    Combining Breve (U+0306)
      //    Latin Small Letter AE With Acute (U+01FD)
      //    Greek Small Letter Beta (U+03B2)
      String myStr = "za\u0306\u01FD\u03B2";

      // Encode the string using the big-endian byte order.
      byte[] barrBE = new byte[u32BE.GetByteCount( myStr )];
      u32BE.GetBytes( myStr, 0, myStr.Length, barrBE, 0 );

      // Encode the string using the little-endian byte order.
      byte[] barrLE = new byte[u32LE.GetByteCount( myStr )];
      u32LE.GetBytes( myStr, 0, myStr.Length, barrLE, 0 );

      // Get the char counts, and decode the byte arrays.
      Console.Write( "BE array with BE encoding : " );
      PrintCountsAndChars( barrBE, u32BE );
      Console.Write( "LE array with LE encoding : " );
      PrintCountsAndChars( barrLE, u32LE );
   }

   public static void PrintCountsAndChars( byte[] bytes, Encoding enc )  {

      // Display the name of the encoding used.
      Console.Write( "{0,-25} :", enc.ToString() );

      // Display the exact character count.
      int iCC  = enc.GetCharCount( bytes );
      Console.Write( " {0,-3}", iCC );

      // Display the maximum character count.
      int iMCC = enc.GetMaxCharCount( bytes.Length );
      Console.Write( " {0,-3} :", iMCC );

      // Decode the bytes and display the characters.
      char[] chars = enc.GetChars( bytes );
      Console.WriteLine( chars );
   }
}


/* 
This code produces the following output.  The question marks take the place of characters that cannot be displayed at the console.

BE array with BE encoding : System.Text.UTF32Encoding : 5   12  :zăǽβ
LE array with LE encoding : System.Text.UTF32Encoding : 5   12  :zăǽβ

*/

Remarks

To calculate the exact array size required by GetChars(Byte[]) to store the resulting characters, you should use the GetCharCount(Byte[]) method. To calculate the maximum array size, you should use the GetMaxCharCount(Int32) method. The GetCharCount(Byte[]) method generally allows allocation of less memory, while the GetMaxCharCount method generally executes faster.

The GetCharCount(Byte[]) method determines how many characters result in decoding a sequence of bytes, and the GetChars(Byte[]) method performs the actual decoding. The Encoding.GetChars method expects discrete conversions, in contrast to the Decoder.GetChars method, which handles multiple passes on a single input stream.

Several versions of GetCharCount and GetChars are supported. The following are some programming considerations for use of these methods:

• Your app might need to decode multiple input bytes from a code page and process the bytes using multiple calls. In this case, you probably need to maintain state between calls.

• If your app handles string outputs, you should use the GetString method. Since this method must check string length and allocate a buffer, it is slightly slower, but the resulting String type is to be preferred.

• The byte version of GetChars(Byte*, Int32, Char*, Int32) allows some fast techniques, particularly with multiple calls to large buffers. Bear in mind, however, that this method version is sometimes unsafe, since pointers are required.

• If your app must convert a large amount of data, it should reuse the output buffer. In this case, the GetChars(Byte[], Int32, Int32, Char[], Int32) version that supports output character buffers is the best choice.

• Consider using the Decoder.Convert method instead of GetCharCount. The conversion method converts as much data as possible and throws an exception if the output buffer is too small. For continuous decoding of a stream, this method is often the best choice.

See also

• GetChars
• GetMaxCharCount(Int32)
• GetDecoder()

GetCharCount(ReadOnlySpan<Byte>)

Source:

Encoding.cs

When overridden in a derived class, calculates the number of characters produced by decoding the provided read-only byte span.

C#

public virtual int GetCharCount(ReadOnlySpan<byte> bytes);

Parameters

bytes

ReadOnlySpan<Byte>

A read-only byte span to decode.

Returns

Int32

The number of characters produced by decoding the byte span.

Remarks

To calculate the exact array size that GetChars requires to store the resulting characters, you should use the GetCharCount method. To calculate the maximum array size, use the GetMaxCharCount method. The GetCharCount method generally allows allocation of less memory, while the GetMaxCharCount method generally executes faster.

The GetCharCount method determines how many characters result in decoding a sequence of bytes, and the GetChars method performs the actual decoding. The GetChars method expects discrete conversions, in contrast to the Decoder.GetChars method, which handles multiple passes on a single input stream.

Several versions of GetCharCount and GetChars are supported. The following are some programming considerations for use of these methods:

• Your app might need to decode multiple input bytes from a code page and process the bytes using multiple calls. In this case, you probably need to maintain state between calls.

• If your app handles string outputs, it is recommended to use the GetString method. Since this method must check string length and allocate a buffer, it is slightly slower, but the resulting String type is to be preferred.

• If your app must convert a large amount of data, it should reuse the output buffer. In this case, the GetChars(Byte[], Int32, Int32, Char[], Int32) version that supports output character buffers is the best choice.

• Consider using the Decoder.Convert method instead of GetCharCount. The conversion method converts as much data as possible and throws an exception if the output buffer is too small. For continuous decoding of a stream, this method is often the best choice.

GetCharCount(Byte*, Int32)

Source:

Encoding.cs

Important

This API is not CLS-compliant.

When overridden in a derived class, calculates the number of characters produced by decoding a sequence of bytes starting at the specified byte pointer.

C#

[System.CLSCompliant(false)]
public virtual int GetCharCount(byte* bytes, int count);

Parameters

bytes

Byte*

A pointer to the first byte to decode.

count

Int32

The number of bytes to decode.

Returns

Int32

The number of characters produced by decoding the specified sequence of bytes.

Attributes

CLSCompliantAttribute

Exceptions

ArgumentNullException

bytes is null.

ArgumentOutOfRangeException

count is less than zero.

DecoderFallbackException

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

-and-

DecoderFallback is set to DecoderExceptionFallback.

Remarks

To calculate the exact array size that GetChars requires to store the resulting characters, you should use the GetCharCount method. To calculate the maximum array size, use the GetMaxCharCount method. The GetCharCount method generally allows allocation of less memory, while the GetMaxCharCount method generally executes faster.

The GetCharCount method determines how many characters result in decoding a sequence of bytes, and the GetChars method performs the actual decoding. The GetChars method expects discrete conversions, in contrast to the Decoder.GetChars method, which handles multiple passes on a single input stream.

Several versions of GetCharCount and GetChars are supported. The following are some programming considerations for use of these methods:

• Your app might need to decode multiple input bytes from a code page and process the bytes using multiple calls. In this case, you probably need to maintain state between calls.

• If your app handles string outputs, it is recommended to use the GetString method. Since this method must check string length and allocate a buffer, it is slightly slower, but the resulting String type is to be preferred.

• The byte version of GetChars(Byte*, Int32, Char*, Int32) allows some fast techniques, particularly with multiple calls to large buffers. Bear in mind, however, that this method version is sometimes unsafe, since pointers are required.

• If your app must convert a large amount of data, it should reuse the output buffer. In this case, the GetChars(Byte[], Int32, Int32, Char[], Int32) version that supports output character buffers is the best choice.

• Consider using the Decoder.Convert method instead of GetCharCount. The conversion method converts as much data as possible and throws an exception if the output buffer is too small. For continuous decoding of a stream, this method is often the best choice.

See also

• GetChars
• GetMaxCharCount(Int32)
• GetDecoder()

GetCharCount(Byte[], Int32, Int32)

Source:

Encoding.cs

When overridden in a derived class, calculates the number of characters produced by decoding a sequence of bytes from the specified byte array.

C#

public abstract int GetCharCount(byte[] bytes, int index, int count);

Parameters

bytes

Byte[]

The byte array containing the sequence of bytes to decode.

index

Int32

The index of the first byte to decode.

count

Int32

The number of bytes to decode.

Returns

Int32

The number of characters produced by decoding the specified sequence of bytes.

Exceptions

ArgumentNullException

bytes is null.

ArgumentOutOfRangeException

index or count is less than zero.

-or-

index and count do not denote a valid range in bytes.

DecoderFallbackException

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

-and-

DecoderFallback is set to DecoderExceptionFallback.

Examples

The following example converts a string from one encoding to another.

C#

using System;
using System.Text;

class Example
{
   static void Main()
   {
      string unicodeString = "This string contains the unicode character Pi (\u03a0)";

      // Create two different encodings.
      Encoding ascii = Encoding.ASCII;
      Encoding unicode = Encoding.Unicode;

      // Convert the string into a byte array.
      byte[] unicodeBytes = unicode.GetBytes(unicodeString);

      // Perform the conversion from one encoding to the other.
      byte[] asciiBytes = Encoding.Convert(unicode, ascii, unicodeBytes);
         
      // Convert the new byte[] into a char[] and then into a string.
      char[] asciiChars = new char[ascii.GetCharCount(asciiBytes, 0, asciiBytes.Length)];
      ascii.GetChars(asciiBytes, 0, asciiBytes.Length, asciiChars, 0);
      string asciiString = new string(asciiChars);

      // Display the strings created before and after the conversion.
      Console.WriteLine("Original string: {0}", unicodeString);
      Console.WriteLine("Ascii converted string: {0}", asciiString);
   }
}
// The example displays the following output:
//    Original string: This string contains the unicode character Pi (Π)
//    Ascii converted string: This string contains the unicode character Pi (?)

The following example encodes a string into an array of bytes, and then decodes a range of the bytes into an array of characters.

C#

using System;
using System.Text;

public class SamplesEncoding  {

   public static void Main()  {

      // Create two instances of UTF32Encoding: one with little-endian byte order and one with big-endian byte order.
      Encoding u32LE = Encoding.GetEncoding( "utf-32" );
      Encoding u32BE = Encoding.GetEncoding( "utf-32BE" );

      // Use a string containing the following characters:
      //    Latin Small Letter Z (U+007A)
      //    Latin Small Letter A (U+0061)
      //    Combining Breve (U+0306)
      //    Latin Small Letter AE With Acute (U+01FD)
      //    Greek Small Letter Beta (U+03B2)
      String myStr = "za\u0306\u01FD\u03B2";

      // Encode the string using the big-endian byte order.
      byte[] barrBE = new byte[u32BE.GetByteCount( myStr )];
      u32BE.GetBytes( myStr, 0, myStr.Length, barrBE, 0 );

      // Encode the string using the little-endian byte order.
      byte[] barrLE = new byte[u32LE.GetByteCount( myStr )];
      u32LE.GetBytes( myStr, 0, myStr.Length, barrLE, 0 );

      // Get the char counts, decode eight bytes starting at index 0,
      // and print out the counts and the resulting bytes.
      Console.Write( "BE array with BE encoding : " );
      PrintCountsAndChars( barrBE, 0, 8, u32BE );
      Console.Write( "LE array with LE encoding : " );
      PrintCountsAndChars( barrLE, 0, 8, u32LE );
   }

   public static void PrintCountsAndChars( byte[] bytes, int index, int count, Encoding enc )  {

      // Display the name of the encoding used.
      Console.Write( "{0,-25} :", enc.ToString() );

      // Display the exact character count.
      int iCC  = enc.GetCharCount( bytes, index, count );
      Console.Write( " {0,-3}", iCC );

      // Display the maximum character count.
      int iMCC = enc.GetMaxCharCount( count );
      Console.Write( " {0,-3} :", iMCC );

      // Decode the bytes and display the characters.
      char[] chars = enc.GetChars( bytes, index, count );

      // The following is an alternative way to decode the bytes:
      // char[] chars = new char[iCC];
      // enc.GetChars( bytes, index, count, chars, 0 );

      Console.WriteLine( chars );
   }
}


/* 
This code produces the following output.  The question marks take the place of characters that cannot be displayed at the console.

BE array with BE encoding : System.Text.UTF32Encoding : 2   6   :za
LE array with LE encoding : System.Text.UTF32Encoding : 2   6   :za

*/

Remarks

To calculate the exact array size required by GetChars to store the resulting characters, you should use the GetCharCount method. To calculate the maximum array size, use the GetMaxCharCount method. The GetCharCount method generally allows allocation of less memory, while the GetMaxCharCount method generally executes faster.

The GetCharCount method determines how many characters result in decoding a sequence of bytes, and the GetChars method performs the actual decoding. The GetChars method expects discrete conversions, in contrast to the Decoder.GetChars method, which handles multiple passes on a single input stream.

Several versions of GetCharCount and GetChars are supported. The following are some programming considerations for use of these methods:

• Your app might need to decode multiple input bytes from a code page and process the bytes using multiple calls. In this case, you probably need to maintain state between calls.

• If your app handles string outputs, it is recommended to use the GetString method. Since this method must check string length and allocate a buffer, it is slightly slower, but the resulting String type is to be preferred.

• The byte version of GetChars(Byte*, Int32, Char*, Int32) allows some fast techniques, particularly with multiple calls to large buffers. Bear in mind, however, that this method version is sometimes unsafe, since pointers are required.

• If your app must convert a large amount of data, it should reuse the output buffer. In this case, the GetChars(Byte[], Int32, Int32, Char[], Int32) version that supports output character buffers is the best choice.

• Consider using the Decoder.Convert method instead of GetCharCount. The conversion method converts as much data as possible and throws an exception if the output buffer is too small. For continuous decoding of a stream, this method is often the best choice.

See also

• GetChars
• GetMaxCharCount(Int32)
• GetDecoder()