UTF32Encoding::GetCharCount Method (array<Byte>^, Int32, Int32)
Calculates the number of characters produced by decoding a sequence of bytes from the specified byte array.
Assembly: mscorlib (in mscorlib.dll)
public: virtual int GetCharCount( array<unsigned char>^ bytes, int index, int count ) override
Parameters
- bytes
-
Type:
array<System::Byte>^
The byte array containing the sequence of bytes to decode.
- index
-
Type:
System::Int32
The index of the first byte to decode.
- count
-
Type:
System::Int32
The number of bytes to decode.
Return Value
Type: System::Int32The number of characters produced by decoding the specified sequence of bytes.
| Exception | Condition |
|---|---|
| ArgumentNullException | bytes is null. |
| ArgumentOutOfRangeException | index or count is less than zero. -or- index and count do not denote a valid range in bytes. -or- The resulting number of bytes is greater than the maximum number that can be returned as an integer. |
| ArgumentException | Error detection is enabled, and bytes contains an invalid sequence of bytes. |
| DecoderFallbackException | A fallback occurred (see Character Encoding in the .NET Framework for complete explanation) -and- DecoderFallback is set to DecoderExceptionFallback. |
The GetCharCount method calculates the exact array size required by the GetChars method to store the resulting characters. To calculate the maximum array size, call the GetMaxCharCount method. The GetCharCount method generally allocates less memory, while the GetMaxCharCount method generally executes faster.
With error detection, an invalid sequence causes this method to throw a ArgumentException. Without error detection, invalid sequences are ignored, and no exception is thrown.
The following example encodes a string into an array of bytes, and then decodes the bytes into an array of characters.
using namespace System; using namespace System::Text; void PrintCountsAndChars( array<Byte>^bytes, Encoding^ enc ); int main() { // Create two instances of UTF32Encoding: one with little-endian byte order and one with big-endian byte order. UTF32Encoding^ u32LE = gcnew UTF32Encoding( false,true,true ); UTF32Encoding^ u32BE = gcnew UTF32Encoding( true,true,true ); // Create byte arrays from the same 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 = L"za\u0306\u01FD\u03B2\xD8FF\xDCFF"; // barrBE uses the big-endian byte order. array<Byte>^barrBE = gcnew array<Byte>(u32BE->GetByteCount( myStr )); u32BE->GetBytes( myStr, 0, myStr->Length, barrBE, 0 ); // barrLE uses the little-endian byte order. array<Byte>^barrLE = gcnew array<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 ); // Decode the byte arrays using an encoding with a different byte order. Console::Write( "BE array with LE encoding : " ); try { PrintCountsAndChars( barrBE, u32LE ); } catch ( System::ArgumentException^ e ) { Console::WriteLine( e->Message ); } Console::Write( "LE array with BE encoding : " ); try { PrintCountsAndChars( barrLE, u32BE ); } catch ( System::ArgumentException^ e ) { Console::WriteLine( e->Message ); } } void PrintCountsAndChars( array<Byte>^bytes, Encoding^ enc ) { // Display the name of the encoding used. Console::Write( "{0,-25} :", enc ); // 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. array<Char>^chars = gcnew array<Char>(iCC); enc->GetChars( bytes, 0, bytes->Length, 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 : 7 14 :za??�? LE array with LE encoding : System.Text.UTF32Encoding : 7 14 :za??�? BE array with LE encoding : System.Text.UTF32Encoding :Invalid byte was found at byte index 3. LE array with BE encoding : System.Text.UTF32Encoding :Invalid byte was found at byte index 3. */
Available since 10
.NET Framework
Available since 2.0