DecoderReplacementFallback Kelas
Definisi
Penting
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Menyediakan mekanisme penanganan kegagalan, yang disebut fallback, untuk urutan byte input yang dikodekan yang tidak dapat dikonversi ke karakter output. Fallback memancarkan string pengganti yang ditentukan pengguna alih-alih urutan byte input yang didekode. Kelas ini tidak dapat diwariskan.
public ref class DecoderReplacementFallback sealed : System::Text::DecoderFallbackpublic sealed class DecoderReplacementFallback : System.Text.DecoderFallback[System.Serializable]
public sealed class DecoderReplacementFallback : System.Text.DecoderFallbacktype DecoderReplacementFallback = class
inherit DecoderFallback[<System.Serializable>]
type DecoderReplacementFallback = class
inherit DecoderFallbackPublic NotInheritable Class DecoderReplacementFallback
Inherits DecoderFallback- Warisan
- Atribut
Contoh
Contoh kode berikut menunjukkan DecoderReplacementFallback kelas .
// This example demonstrates the DecoderReplacementFallback class.
using System;
using System.Text;
class Sample
{
public static void Main()
{
// Create an encoding, which is equivalent to calling the
// ASCIIEncoding class constructor.
// The DecoderReplacementFallback parameter specifies that the
// string "(error)" is to replace characters that cannot be decoded.
// An encoder replacement fallback is also specified, but in this code
// example the encoding operation cannot fail.
Encoding ae = Encoding.GetEncoding(
"us-ascii",
new EncoderReplacementFallback("(unknown)"),
new DecoderReplacementFallback("(error)"));
string inputString = "XYZ";
string decodedString;
string twoNewLines = "\n\n";
byte[] encodedBytes = new byte[ae.GetByteCount(inputString)];
int numberOfEncodedBytes = 0;
// --------------------------------------------------------------------------
Console.Clear();
// Display the name of the encoding.
Console.WriteLine("The name of the encoding is \"{0}\".\n", ae.WebName);
// Display the input string in text.
Console.WriteLine("Input string ({0} characters): \"{1}\"",
inputString.Length, inputString);
// Display the input string in hexadecimal.
Console.Write("Input string in hexadecimal: ");
foreach (char c in inputString.ToCharArray())
{
Console.Write("0x{0:X2} ", (int)c);
}
Console.Write(twoNewLines);
// --------------------------------------------------------------------------
// Encode the input string.
Console.WriteLine("Encode the input string...");
numberOfEncodedBytes = ae.GetBytes(inputString, 0, inputString.Length,
encodedBytes, 0);
// Display the encoded bytes.
Console.WriteLine("Encoded bytes in hexadecimal ({0} bytes):\n",
numberOfEncodedBytes);
foreach (byte b in encodedBytes)
{
Console.Write("0x{0:X2} ", (int)b);
}
Console.Write(twoNewLines);
// --------------------------------------------------------------------------
// Replace the encoded byte sequences for the characters 'X' and 'Z' with the
// value 0xFF, which is outside the valid range of 0x00 to 0x7F for
// ASCIIEncoding. The resulting byte sequence is actually the beginning of
// this code example because it is the input to the decoder operation, and
// is equivalent to a corrupted or improperly encoded byte sequence.
encodedBytes[0] = 0xFF;
encodedBytes[2] = 0xFF;
Console.WriteLine("Display the corrupted byte sequence...");
Console.WriteLine("Encoded bytes in hexadecimal ({0} bytes):\n",
numberOfEncodedBytes);
foreach (byte b in encodedBytes)
{
Console.Write("0x{0:X2} ", (int)b);
}
Console.Write(twoNewLines);
// --------------------------------------------------------------------------
// Decode the encoded bytes.
Console.WriteLine("Compare the decoded bytes to the input string...");
decodedString = ae.GetString(encodedBytes);
// Display the input string and the decoded string for comparison.
Console.WriteLine("Input string: \"{0}\"", inputString);
Console.WriteLine("Decoded string:\"{0}\"", decodedString);
}
}
/*
This code example produces the following results:
The name of the encoding is "us-ascii".
Input string (3 characters): "XYZ"
Input string in hexadecimal: 0x58 0x59 0x5A
Encode the input string...
Encoded bytes in hexadecimal (3 bytes):
0x58 0x59 0x5A
Display the corrupted byte sequence...
Encoded bytes in hexadecimal (3 bytes):
0xFF 0x59 0xFF
Compare the decoded bytes to the input string...
Input string: "XYZ"
Decoded string:"(error)Y(error)"
*/
' This example demonstrates the DecoderReplacementFallback class.
Imports System.Text
Class Sample
Public Shared Sub Main()
' Create an encoding, which is equivalent to calling the
' ASCIIEncoding class constructor.
' The DecoderReplacementFallback parameter specifies that the
' string "(error)" is to replace characters that cannot be decoded.
' An encoder replacement fallback is also specified, but in this code
' example the encoding operation cannot fail.
Dim erf As New EncoderReplacementFallback("(unknown)")
Dim drf As New DecoderReplacementFallback("(error)")
Dim ae As Encoding = Encoding.GetEncoding("us-ascii", erf, drf)
Dim inputString As String = "XYZ"
Dim decodedString As String
Dim twoNewLines As String = vbCrLf & vbCrLf
Dim numberOfEncodedBytes As Integer = ae.GetByteCount(inputString)
' Counteract the compiler implicitly adding an extra element.
Dim encodedBytes(numberOfEncodedBytes - 1) As Byte
' --------------------------------------------------------------------------
Console.Clear()
' Display the name of the encoding.
Console.WriteLine("The name of the encoding is ""{0}""." & vbCrLf, ae.WebName)
' Display the input string in text.
Console.WriteLine("Input string ({0} characters): ""{1}""", _
inputString.Length, inputString)
' Display the input string in hexadecimal.
' Each element is converted to an integer with Convert.ToInt32.
Console.Write("Input string in hexadecimal: ")
Dim c As Char
For Each c In inputString.ToCharArray()
Console.Write("0x{0:X2} ", Convert.ToInt32(c))
Next c
Console.Write(twoNewLines)
' --------------------------------------------------------------------------
' Encode the input string.
Console.WriteLine("Encode the input string...")
numberOfEncodedBytes = ae.GetBytes(inputString, 0, inputString.Length, _
encodedBytes, 0)
' Display the encoded bytes.
' Each element is converted to an integer with Convert.ToInt32.
Console.WriteLine("Encoded bytes in hexadecimal ({0} bytes):" & vbCrLf, _
numberOfEncodedBytes)
Dim b As Byte
For Each b In encodedBytes
Console.Write("0x{0:X2} ", Convert.ToInt32(b))
Next b
Console.Write(twoNewLines)
' --------------------------------------------------------------------------
' Replace the encoded byte sequences for the characters 'X' and 'Z' with the
' value 0xFF, which is outside the valid range of 0x00 to 0x7F for
' ASCIIEncoding. The resulting byte sequence is actually the beginning of
' this code example because it is the input to the decoder operation, and
' is equivalent to a corrupted or improperly encoded byte sequence.
encodedBytes(0) = &HFF
encodedBytes(2) = &HFF
Console.WriteLine("Display the corrupted byte sequence...")
Console.WriteLine("Encoded bytes in hexadecimal ({0} bytes):" & vbCrLf, _
numberOfEncodedBytes)
For Each b In encodedBytes
Console.Write("0x{0:X2} ", Convert.ToInt32(b))
Next b
Console.Write(twoNewLines)
' --------------------------------------------------------------------------
' Decode the encoded bytes.
Console.WriteLine("Compare the decoded bytes to the input string...")
decodedString = ae.GetString(encodedBytes)
' Display the input string and the decoded string for comparison.
Console.WriteLine("Input string: ""{0}""", inputString)
Console.WriteLine("Decoded string:""{0}""", decodedString)
End Sub
End Class
'
'This code example produces the following results:
'
'The name of the encoding is "us-ascii".
'
'Input string (3 characters): "XYZ"
'Input string in hexadecimal: 0x58 0x59 0x5A
'
'Encode the input string...
'Encoded bytes in hexadecimal (3 bytes):
'
'0x58 0x59 0x5A
'
'Display the corrupted byte sequence...
'Encoded bytes in hexadecimal (3 bytes):
'
'0xFF 0x59 0xFF
'
'Compare the decoded bytes to the input string...
'Input string: "XYZ"
'Decoded string:"(error)Y(error)"
'
Keterangan
Alasan umum untuk operasi pengodean atau dekode gagal adalah jika kelas pengodean yang mendasar tidak memberikan pemetaan antara karakter dan urutan byte yang setara. Misalnya, ASCIIEncoding objek tidak dapat mendekode nilai byte yang lebih besar dari 0x7F. Jika urutan byte input tidak dapat dikonversi ke karakter output, objek DecoderReplacementFallback memancarkan string pengganti ke dalam output untuk mewakili urutan byte input asli. Proses konversi kemudian terus mendekode sisa input asli.
String pengganti yang DecoderReplacementFallback digunakan oleh objek ditentukan oleh panggilan ke konstruktor kelasnya. Dua opsi yang tersedia:
Penggantian dengan karakter default. Jika Anda memanggil DecoderReplacementFallback() konstruktor, karakter penggantinya adalah "?" (U+003F).
Penggantian dengan string pilihan Anda. Jika Anda memanggil DecoderReplacementFallback(String) konstruktor, Anda menyediakan string pengganti.
Kelas ini adalah salah satu dari dua kelas .NET Framework yang menerapkan strategi fallback yang berbeda untuk menangani kegagalan konversi decoding. Kelas lainnya adalah DecoderExceptionFallback kelas , yang melempar DecoderFallbackException ketika urutan byte yang tidak valid ditemui.
Konstruktor
| Nama | Deskripsi |
|---|---|
| DecoderReplacementFallback() |
Menginisialisasi instans baru dari kelas DecoderReplacementFallback. |
| DecoderReplacementFallback(String) |
Menginisialisasi instans DecoderReplacementFallback baru kelas menggunakan string pengganti yang ditentukan. |
Properti
| Nama | Deskripsi |
|---|---|
| DefaultString |
Mendapatkan string pengganti yang merupakan nilai DecoderReplacementFallback objek. |
| MaxCharCount |
Mendapatkan jumlah karakter dalam string pengganti untuk DecoderReplacementFallback objek. |
Metode
| Nama | Deskripsi |
|---|---|
| CreateFallbackBuffer() |
DecoderFallbackBuffer Membuat objek yang diinisialisasi dengan string pengganti objek iniDecoderReplacementFallback. |
| Equals(Object) |
Menunjukkan apakah nilai objek yang ditentukan sama dengan DecoderReplacementFallback objek. |
| GetHashCode() |
Mengambil kode hash untuk nilai DecoderReplacementFallback objek. |
| GetType() |
Mendapatkan Type instans saat ini. (Diperoleh dari Object) |
| MemberwiseClone() |
Membuat salinan dangkal dari Objectsaat ini. (Diperoleh dari Object) |
| ToString() |
Mengembalikan string yang mewakili objek saat ini. (Diperoleh dari Object) |
