无符号整数转换为字符串及其SSE优化

extern const char digit1[101] =
"00000000001111111111222222222233333333334444444444"
"55555555556666666666777777777788888888889999999999";
extern const char digit2[101] =
"01234567890123456789012345678901234567890123456789"
"01234567890123456789012345678901234567890123456789";

// 把无符号整数转换为字符串，返回字符串范围是[buffer + begin, buffer + bufLen]
size_t uintToBuffer(char* const buffer, size_t bufLen, uint64_t v)
{
         extern const char digit1[101], digit2[101];
         for (;;)
         {
                   if (v < 100)
                   {
                            if (v < 10)
                            {
                                     buffer[--bufLen] = static_cast<char>(v + '0');
                            }
                            else
                            {
                                     size_t r = static_cast<size_t>(v);
                                     bufLen -= 2;
                                     buffer[bufLen] = digit1[r];
                                     buffer[bufLen + 1] = digit2[r];
                            }
                            break;
                   }
                   uint64_t t = v;
                   v /= 100;
                   size_t r = static_cast<size_t>(t - v * 100);
                   bufLen -= 2;
                   buffer[bufLen] = digit1[r];
                   buffer[bufLen + 1] = digit2[r];
         }
         return bufLen;
}

 

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