Fan.Sys.InStream.readUtfString C# (CSharp) Method

        private string readUtfString()
        {
            // read two-byte Length
              int len1 = r();
              int len2 = r();
              if ((len1 | len2) < 0) throw IOErr.make("Unexpected end of stream").val;
              int utflen = len1 << 8 | len2;

              char[] buf = new char[utflen]; // char buffer we read into
              int bnum = 0, cnum = 0;        // byte count, char count

              // read the chars
              int c, c2, c3;
              while (bnum < utflen)
              {
            c = r(); bnum++;
            if (c < 0) throw IOErr.make("Unexpected end of stream").val;
            switch (c >> 4) {
              case 0: case 1: case 2: case 3: case 4: case 5: case 6: case 7:
            /* 0xxxxxxx*/
            buf[cnum++]=(char)c;
            break;
              case 12: case 13:
            /* 110x xxxx   10xx xxxx*/
            if (bnum >= utflen) throw IOErr.make("UTF encoding error").val;
            c2 = r(); bnum++;
            if (c2 < 0) throw IOErr.make("Unexpected end of stream").val;
            if ((c2 & 0xC0) != 0x80) throw IOErr.make("UTF encoding error").val;
            buf[cnum++]=(char)(((c & 0x1F) << 6) | (c2 & 0x3F));
            break;
              case 14:
            /* 1110 xxxx  10xx xxxx  10xx xxxx */
            if (bnum+1 >= utflen) throw IOErr.make("UTF encoding error").val;
            c2 = r(); bnum++;
            c3 = r(); bnum++;
            if ((c2|c3) < 0) throw IOErr.make("Unexpected end of stream").val;
            if (((c2 & 0xC0) != 0x80) || ((c3 & 0xC0) != 0x80))  throw IOErr.make("UTF encoding error").val;
            buf[cnum++]=(char)(((c & 0x0F) << 12) | ((c2 & 0x3F) << 6) | ((c3 & 0x3F) << 0));
            break;
              default:
            /* 10xx xxxx,  1111 xxxx */
            throw IOErr.make("UTF encoding error").val;
            }
              }

              // allocate as string
              return new string(buf, 0, cnum);
        }