Quoted-Printable编码/解码c#类代码

在参照上篇文章《QuotedPrintable编码c#类代码》中给出的QuotedPrintable编码的c#类代码后，本篇将给出QuotedPrintable解码的C#类代码，该代码已经在VS.NET2003下编译并测试通过，现将编解码类和测试程序给出，仅供参考，不足处请读者指出。

QuotedPrintable编码/解码类：

using  System.Text;
using  System.IO;
using  System;
namespace  NoPaste
... {
    public class QuotedPrintable
    ...{
        /**//// <summary>
        /// QuotedPrintable解码函数
        /// </summary>
        /// <param name="input">需要解码的QuotedPrintable字符串</param>
        /// <returns>解码后的字符串</returns>
        public static string Decode(string input)
        ...{
            System.Text.Encoding encoding = System.Text.Encoding.GetEncoding("gb2312");

            StringBuilder result = new StringBuilder();
            StringReader sr = new StringReader(input);

            string line = sr.ReadLine();

            while( line!=null )
            ...{
                bool addCRLF = true;
                byte[] bytes = System.Text.Encoding.ASCII.GetBytes( line.ToCharArray() );

                for(int i=0;i<bytes.Length;i++)
                ...{
                    if( ( bytes[i]>=33 && bytes[i]<=60 ) || ( bytes[i]>=62 && bytes[i]<=126 ) || bytes[i]==9 || bytes[i]==32)
                    ...{
                        result.Append( Convert.ToChar( bytes[i] ) );
                        continue;
                    }
                    else if( bytes[i]==61 )
                    ...{
                        if( i==bytes.Length-1 )
                        ...{
                            //eg. = soft line break;
                            addCRLF = false;
                            break;
                        }
                        else if( bytes[i+1]==51 && bytes[i+2]==68 )
                        ...{
                            //eg. =3D
                            i++;i++;
                            result.Append( "=" );
                            continue;
                        }
                        else
                        ...{
                            //eg. =B7=D6
                            byte[] b = new byte[2];
                            b[0] = Convert.ToByte( Convert.ToChar(bytes[i+1]).ToString()+Convert.ToChar(bytes[i+2]).ToString(),16 );
                            i++;i++;i++;
                            b[1] = Convert.ToByte( Convert.ToChar(bytes[i+1]).ToString()+Convert.ToChar(bytes[i+2]).ToString(),16 );
                            i++;i++;

                            result.Append(encoding.GetString(b));
                            continue;
                        }

                    }
                }//end of for

                line = sr.ReadLine();
                if( line!=null && addCRLF )
                    result.Append(" ");    
            }//end of while
            return result.ToString();
        }

        public static string Encode(string input)
        ...{
            System.Text.Encoding encoding = System.Text.Encoding.GetEncoding("gb2312");
            const int MAXLINELENGTH = 76;
            int currentLineLength = 0;
            byte[] bytes = encoding.GetBytes(input.ToCharArray());
            StringBuilder result = new StringBuilder();

            for (int i = 0; i < bytes.Length; i++)
            ...{
                if (bytes[i] == 10 || bytes[i] == 13)
                ...{
                    if (bytes[i] == 13 && GetNextByte(i, bytes, 1) == 10)
                    ...{
                        CheckLineLength(MAXLINELENGTH, ref currentLineLength, 0, result);
                        result.Append(" ");
                        currentLineLength = 0;
                        i++;
                        continue;
                    }

                    if (bytes[i] == 10)
                    ...{
                        CheckLineLength(MAXLINELENGTH, ref currentLineLength, 0, result);
                        result.Append(" ");
                        currentLineLength = 0;
                    }

                    if (bytes[i] == 13)
                    ...{
                        CheckLineLength(MAXLINELENGTH, ref currentLineLength, 3, result);
                        result.Append("=" + ConvertToHex(bytes[i]));
                    }
                }
                else
                ...{
                    if ((bytes[i] >= 33 && bytes[i] <= 60) || (bytes[i] >= 62 && bytes[i] <= 126))
                    ...{
                        CheckLineLength(MAXLINELENGTH, ref currentLineLength, 1, result);
                        result.Append(System.Convert.ToChar(bytes[i]));
                    }
                    else
                    ...{
                        if (bytes[i] == 9 || bytes[i] == 32)
                        ...{
                            CheckLineLength(MAXLINELENGTH, ref currentLineLength, 0, result);
                            result.Append(System.Convert.ToChar(bytes[i]));
                            currentLineLength++;
                        }
                        else
                        ...{
                            CheckLineLength(MAXLINELENGTH, ref currentLineLength, 3, result);
                            result.Append("=" + ConvertToHex(bytes[i]));
                        }
                    }
                }
            }

            return result.ToString();
        }

        private static void CheckLineLength(int maxLineLength, ref int currentLineLength, int newStringLength, StringBuilder sb)
        ...{
            if (currentLineLength + 1 == maxLineLength || currentLineLength + newStringLength + 1 >= maxLineLength)
            ...{
                sb.Append("= ");
                currentLineLength = 0+newStringLength;
            }
            else
            ...{
                currentLineLength += newStringLength;
            }
        }

        private static int GetNextByte(int index, byte[] bytes, int shiftValue)
        ...{
            int newIndex = index + shiftValue;

            if (newIndex < 0 || newIndex > bytes.Length - 1 || bytes.Length == 0)
                return -1;
            else
                return bytes[newIndex];
        }

        private static string ConvertToHex(byte number)
        ...{
            string result = System.Convert.ToString(number, 16).ToUpper();
            return (result.Length == 2) ? result : "0" + result;
        }
    }
}

 

测试程序代码：

        [STAThread]
         static   void  Main( string [] args)
         ... {
            string init_str = "CSDN.NET - 中国最大的IT技术社区！";
            string encode_str = NoPaste.QuotedPrintable.Encode( init_str );
            string decode_str = NoPaste.QuotedPrintable.Decode( encode_str );

            Console.WriteLine(
                "需要进行QuotedPrintable编码的原始字符串： "+
                "    {0} "+
                "编码后得到的字符串： "+
                "    {1} "+
                "对编码后得到的字符串进行解码得到的字符串： "+
                "    {2} ",init_str,encode_str,decode_str);
            
        }

测试程序运行输出结果：