HexEncoding (C++)

Description

This example demonstrates the creation of a class named THexEncoding, derived from the TEncoding class. The methods you need to implement are GetByteCount, GetBytes, GetCharCount, GetChars, GetMaxByteCount, GetMaxCharCount, and GetPreamble.

Code

class THexEncoding:public TEncoding
{
protected:
        virtual int __fastcall GetByteCount(System::WideChar * Chars, int CharCount) = 0 /* overload */;
        virtual int __fastcall GetBytes(System::WideChar * Chars, int CharCount, System::PByte Bytes, int ByteCount) = 0 /* overload */;
        virtual int __fastcall GetCharCount(System::PByte Bytes, int ByteCount) = 0 /* overload */;
        virtual int __fastcall GetChars(System::PByte Bytes, int ByteCount, System::WideChar * Chars, int CharCount) = 0 /* overload */;
public:
        virtual int __fastcall GetMaxByteCount(int CharCount) = 0 ;
        virtual int __fastcall GetMaxCharCount(int ByteCount) = 0 ;
        virtual TBytes __fastcall GetPreamble(void) = 0 ;
};
 
int __fastcall THexEncoding::GetByteCount(System::WideChar * Chars, int CharCount)
{
        /* The result is the number of characters multiplied by 2 times the size of the wchar_t type. */
        return (CharCount * sizeof(wchar_t) * 2);
}
 
int __fastcall THexEncoding::GetBytes(System::WideChar * Chars, int CharCount, System::PByte Bytes, int ByteCount)
{
        /* The BinToHex method converts a binary value to its hexadecimal representation. */
        BinToHex(Chars, PAnsiChar(Bytes), CharCount * sizeof(wchar_t) * 2);
        /* This function returns nothing. */
}
 
int __fastcall THexEncoding::GetCharCount(System::PByte Bytes, int ByteCount)
{
        /* The result of this funcion is the number of bytes divided by 2. */
        return (ByteCount / 2);
}
 
int __fastcall THexEncoding::GetChars(System::PByte Bytes, int ByteCount, System::WideChar * Chars, int CharCount)
{
        /* The HexToBin method converts a hexadecimal value to its binary representation. */
        HexToBin(PAnsiChar(Bytes), Chars, ByteCount / sizeof(wchar_t));
        /* This function returns nothing. */
}
 
int __fastcall THexEncoding::GetMaxByteCount(int CharCount)
{
        /* The result of this function is the number of chars multiplied by 2. */
        return (CharCount * 2);
}
 
int __fastcall THexEncoding::GetMaxCharCount(int ByteCount)
{
        /* The result is the number of bytes divided by 2.  Add a 1 for safety reasons. */
        return ((ByteCount / 2) + 1);
}
 
TBytes __fastcall THexEncoding::GetPreamble(void)
{
        /* The result is nil because the use of a preamble is not supported. */
        return TBytes();
}

Uses

• System.SysUtils.TEncoding.GetByteCount ( fr | de | ja )
• System.SysUtils.TEncoding.GetBytes ( fr | de | ja )
• System.SysUtils.TEncoding.GetCharCount ( fr | de | ja )
• System.SysUtils.TEncoding.GetChars ( fr | de | ja )
• System.SysUtils.TEncoding.GetMaxByteCount ( fr | de | ja )
• System.SysUtils.TEncoding.GetMaxCharCount ( fr | de | ja )
• System.SysUtils.TEncoding.GetPreamble ( fr | de | ja )
• System.Classes.BinToHex ( fr | de | ja )
• System.Classes.HexToBin ( fr | de | ja )