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/* ----------------------------------------------------------
* 文件名称：Base64.cs
*
* 作者：秦建辉
*
* MSN：splashcn@msn.com
* QQ：36748897
*
* 博客：http://www.firstsolver.com/wordpress/
*
* 开发环境：
* Visual Studio V2010
* .NET Framework 4 Client Profile
*
* 版本历史：
* V1.1 2012年08月20日
* 改进解码算法，字符串中允许任意的空白字符、回车换行符、连字符
*
* V1.0 2012年05月30日
* Base64编解码
*
* 参考资料：
* http://www.openssl.org/
------------------------------------------------------------ */
using System;
using System.IO;
using System.Text;
namespace Splash.Util
{
/// <summary>
/// Base64 编解码
/// </summary>
public static class Base64
{
/// <summary>
/// Base64编码字符集
/// </summary>
private const String DATA_BIN2ASCII = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
/// <summary>
/// 将字节数组转换成 Base64 编码字符串
/// </summary>
/// <param name="inArray">要转换的字节数组</param>
/// <returns>转换后的 Base64 编码字符串</returns>
public static String EncodeBase64String(Byte[] inArray)
{
if (inArray == null) return null;
// 每3个字节转换成4个字符
Int32 Length = ((inArray.Length + 2) / 3) << 2;
StringBuilder sb = new StringBuilder(Length);
Int32 Index = 0;
for (Int32 i = inArray.Length; i > 0; i -= 3)
{
if (i >= 3)
{ // 将3字节数据转换成4个ASCII字符
Byte b0 = inArray[Index++];
Byte b1 = inArray[Index++];
Byte b2 = inArray[Index++];
sb.Append(DATA_BIN2ASCII[b0 >> 2]);
sb.Append(DATA_BIN2ASCII[((b0 << 4) | (b1 >> 4)) & 0x3F]);
sb.Append(DATA_BIN2ASCII[((b1 << 2) | (b2 >> 6)) & 0x3F]);
sb.Append(DATA_BIN2ASCII[b2 & 0x3F]);
}
else
{
Byte b0 = inArray[Index++];
Byte b1;
if (i == 2)
b1 = inArray[Index++];
else
b1 = 0;
sb.Append(DATA_BIN2ASCII[b0 >> 2]);
sb.Append(DATA_BIN2ASCII[((b0 << 4) | (b1 >> 4)) & 0x3F]);
if (i == 1)
sb.Append('=');
else
sb.Append(DATA_BIN2ASCII[(b1 << 2) & 0x3F]);
sb.Append('=');
}
}
return sb.ToString();
}
// private const Byte B64_ERROR = 0xFF; // 错误字符
// private const Byte B64_EOLN = 0xF0; // 换行\n
// private const Byte B64_CR = 0xF1; // 回车\r
// private const Byte B64_EOF = 0xF2; // 连字符-
// private const Byte B64_WS = 0xE0; // 跳格或者空格（\t、space）
private const Byte B64_NOT_BASE64 = 0xF3; // 空白字符、回车换行字符、连字符
/// <summary>
/// Base64 编码字符对应的序号列表
/// </summary>
private static readonly Byte[] DATA_ASCII2BIN = {
0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xE0,0xF0,0xFF,0xFF,0xF1,0xFF,0xFF,
0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
0xE0,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0x3E,0xFF,0xF2,0xFF,0x3F,
0x34,0x35,0x36,0x37,0x38,0x39,0x3A,0x3B,0x3C,0x3D,0xFF,0xFF,0xFF,0x00,0xFF,0xFF,
0xFF,0x00,0x01,0x02,0x03,0x04,0x05,0x06,0x07,0x08,0x09,0x0A,0x0B,0x0C,0x0D,0x0E,
0x0F,0x10,0x11,0x12,0x13,0x14,0x15,0x16,0x17,0x18,0x19,0xFF,0xFF,0xFF,0xFF,0xFF,
0xFF,0x1A,0x1B,0x1C,0x1D,0x1E,0x1F,0x20,0x21,0x22,0x23,0x24,0x25,0x26,0x27,0x28,
0x29,0x2A,0x2B,0x2C,0x2D,0x2E,0x2F,0x30,0x31,0x32,0x33,0xFF,0xFF,0xFF,0xFF,0xFF
};
/// <summary>
/// 将 Base64 编码字符串解码为字节数组
/// </summary>
/// <param name="base64String">用于解码的 Base64 编码字符串</param>
/// <returns>解码后的字节数组</returns>
/// <remarks>
/// 注意：
/// 1.字符串中允许任意的空白字符、回车换行符、连字符
/// 2.微软的Convert.FromBase64String不能处理连字符
/// </remarks>
public static Byte[] DecodeBase64(String base64String)
{
if (String.IsNullOrEmpty(base64String))
return null;
Int32 Length = base64String.Length;
using (MemoryStream memStream = new MemoryStream(((Length + 3) >> 2) * 3))
{
Int32 Index = 0;
Byte Previous = 0;
for (Int32 i = 0; i < Length; i++)
{
Int32 CharValue = base64String[i];
if (CharValue >= 0x80)
throw new ArgumentException(); // 错误字符
Byte OrderValue = DATA_ASCII2BIN[CharValue];
if (OrderValue == 0xFF)
throw new ArgumentException(); // 错误字符
// 跳过空白字符、回车换行字符、连字符
if ((OrderValue | 0x13) == B64_NOT_BASE64)
continue;
if (Index == 0)
{
if (CharValue == '=')
throw new ArgumentException();
Previous = OrderValue;
Index++;
}
else if (Index == 1)
{
if (CharValue == '=')
throw new ArgumentException();
memStream.WriteByte((Byte)((Previous << 2) | (OrderValue >> 4)));
Previous = OrderValue;
Index++;
}
else if (Index == 2)
{
if (CharValue == '=')
{ // 简化处理，不再判断第二个'='
Index = 0;
break;
}
memStream.WriteByte((Byte)((Previous << 4) | (OrderValue >> 2)));
Previous = OrderValue;
Index++;
}
else
{
Index = 0;
if (CharValue == '=') break;
memStream.WriteByte((Byte)((Previous << 6) | OrderValue));
}
} // End for
// 有效字符个数必须是4的倍数
if (Index == 0)
return memStream.ToArray();
else
throw new ArgumentException();
}
}
}
}