（翻译）UTF-8 字符集基础（二）

UTF-8 C++ 程序编码示例：

 

下面是四个C++函数，他们分别实现2字节和4字节UNICODE和UTF-8之间的转换。

 

#define         MASKBITS                0x3F
#define         MASKBYTE                0x80
#define         MASK2BYTES              0xC0
#define         MASK3BYTES              0xE0
#define         MASK4BYTES              0xF0
#define         MASK5BYTES              0xF8
#define         MASK6BYTES              0xFC

typedef unsigned short   Unicode2Bytes;
typedef unsigned int     Unicode4Bytes;

void UTF8Encode2BytesUnicode(std::vector< Unicode2Bytes > input,
                             std::vector< byte >& output)
{
   for(int i=0; i < input.size(); i++)
   {
      // 0xxxxxxx
      if(input[i] < 0x80)
      {
         output.push_back((byte)input[i]);
      }
      // 110xxxxx 10xxxxxx
      else if(input[i] < 0x800)
      {
         output.push_back((byte)(MASK2BYTES | input[i] >> 6));
         output.push_back((byte)(MASKBYTE | input[i] & MASKBITS));
      }
      // 1110xxxx 10xxxxxx 10xxxxxx
      else if(input[i] < 0x10000)
      {
         output.push_back((byte)(MASK3BYTES | input[i] >> 12));
         output.push_back((byte)(MASKBYTE | input[i] >> 6 & MASKBITS));
         output.push_back((byte)(MASKBYTE | input[i] & MASKBITS));
      }
   }
}

 

void UTF8Decode2BytesUnicode(std::vector< byte > input,
                             std::vector< Unicode2Bytes >& output)
{
   for(int i=0; i < input.size();)
   {
      Unicode2Bytes ch;

      // 1110xxxx 10xxxxxx 10xxxxxx
      if((input[i] & MASK3BYTES) == MASK3BYTES)
      {
         ch = ((input[i] & 0x0F) << 12) | (
               (input[i+1] & MASKBITS) << 6)
              | (input[i+2] & MASKBITS);
         i += 3;
      }
      // 110xxxxx 10xxxxxx
      else if((input[i] & MASK2BYTES) == MASK2BYTES)
      {
         ch = ((input[i] & 0x1F) << 6) | (input[i+1] & MASKBITS);
         i += 2;
      }
      // 0xxxxxxx
      else if(input[i] < MASKBYTE)
      {
         ch = input[i];
         i += 1;
      }

      output.push_back(ch);
   }
}

 

void UTF8Encode4BytesUnicode(std::vector< Unicode4Bytes > input,
                             std::vector< byte >& output)
{
   for(int i=0; i < input.size(); i++)
   {
      // 0xxxxxxx
      if(input[i] < 0x80)
      {
         output.push_back((byte)input[i]);
      }
      // 110xxxxx 10xxxxxx
      else if(input[i] < 0x800)
      {
         output.push_back((byte)(MASK2BYTES | input[i] > 6));
         output.push_back((byte)(MASKBYTE | input[i] & MASKBITS));
      }
      // 1110xxxx 10xxxxxx 10xxxxxx
      else if(input[i] < 0x10000)
      {
         output.push_back((byte)(MASK3BYTES | input[i] >> 12));
         output.push_back((byte)(MASKBYTE | input[i] >> 6 & MASKBITS));
         output.push_back((byte)(MASKBYTE | input[i] & MASKBITS));
      }
      // 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
      else if(input[i] < 0x200000)
      {
         output.push_back((byte)(MASK4BYTES | input[i] >> 18));
         output.push_back((byte)(MASKBYTE | input[i] >> 12 & MASKBITS));
         output.push_back((byte)(MASKBYTE | input[i] >> 6 & MASKBITS));
         output.push_back((byte)(MASKBYTE | input[i] & MASKBITS));
      }
      // 111110xx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx
      else if(input[i] < 0x4000000)
      {
         output.push_back((byte)(MASK5BYTES | input[i] >> 24));
         output.push_back((byte)(MASKBYTE | input[i] >> 18 & MASKBITS));
         output.push_back((byte)(MASKBYTE | input[i] >> 12 & MASKBITS));
         output.push_back((byte)(MASKBYTE | input[i] >> 6 & MASKBITS));
         output.push_back((byte)(MASKBYTE | input[i] & MASKBITS));
      }
      // 1111110x 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx
      else if(input[i] < 0x8000000)
      {
         output.push_back((byte)(MASK6BYTES | input[i] >> 30));
         output.push_back((byte)(MASKBYTE | input[i] >> 18 & MASKBITS));
         output.push_back((byte)(MASKBYTE | input[i] >> 12 & MASKBITS));
         output.push_back((byte)(MASKBYTE | input[i] >> 6 & MASKBITS));
         output.push_back((byte)(MASKBYTE | input[i] & MASKBITS));
      }
   }
}

void UTF8Decode4BytesUnicode(std::vector< byte > input,
                             std::vector< Unicode4Bytes >& output)
{
   for(int i=0; i < input.size();)
   {
      Unicode4Bytes ch;

      // 1111110x 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx
      if((input[i] & MASK6BYTES) == MASK6BYTES)
      {
         ch = ((input[i] & 0x01) << 30) | ((input[i+1] & MASKBITS) << 24)
              | ((input[i+2] & MASKBITS) << 18) | ((input[i+3]
                        & MASKBITS) << 12)
              | ((input[i+4] & MASKBITS) << 6) | (input[i+5] & MASKBITS);
         i += 6;
      }
      // 111110xx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx
      else if((input[i] & MASK5BYTES) == MASK5BYTES)
      {
         ch = ((input[i] & 0x03) << 24) | ((input[i+1]
                & MASKBITS) << 18)
              | ((input[i+2] & MASKBITS) << 12) | ((input[i+3]
                  & MASKBITS) << 6)
              | (input[i+4] & MASKBITS);
         i += 5;
      }
      // 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
      else if((input[i] & MASK4BYTES) == MASK4BYTES)
      {
         ch = ((input[i] & 0x07) << 18) | ((input[i+1]
                & MASKBITS) << 12)
              | ((input[i+2] & MASKBITS) << 6) | (input[i+3] & MASKBITS);
         i += 4;
      }
      // 1110xxxx 10xxxxxx 10xxxxxx
      else if((input[i] & MASK3BYTES) == MASK3BYTES)
      {
         ch = ((input[i] & 0x0F) << 12) | ((input[i+1] & MASKBITS) << 6)
              | (input[i+2] & MASKBITS);
         i += 3;
      }
      // 110xxxxx 10xxxxxx
      else if((input[i] & MASK2BYTES) == MASK2BYTES)
      {
         ch = ((input[i] & 0x1F) << 6) | (input[i+1] & MASKBITS);
         i += 2;
      }
      // 0xxxxxxx
      else if(input[i] < MASKBYTE)
      {
         ch = input[i];
         i += 1;
      }
      output.push_back(ch);
   }
}

 

原文来自http://www.codeguru.com/Cpp/misc/misc/multi-lingualsupport/article.php/c10451/
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