Re: Conversion from UTF32 to UTF8 for review

From:
"Leigh Johnston" <leigh@i42.co.uk>
Newsgroups:
comp.lang.c++,microsoft.public.vc.mfc
Date:
Mon, 31 May 2010 16:49:31 +0100
Message-ID:
<ndydnQRVj6kTR57RnZ2dnUVZ8qednZ2d@giganews.com>
"Peter Olcott" <NoSpam@OCR4Screen.com> wrote in message
news:t4SdneDjLJvMSJ7RnZ2dnUVZ_sudnZ2d@giganews.com...

I used the two tables from this link as the basis for my design:
http://en.wikipedia.org/wiki/UTF-8

I would like this reviewed for algorithm correctness:

void UnicodeEncodingConversion::
toUTF8(std::vector<uint32_t>& UTF32, std::vector<uint8_t>& UTF8) {
uint8_t Byte;
uint32_t CodePoint;
  UTF8.reserve(UTF32.size() * 4); // worst case
  for (uint32_t N = 0; N < UTF32.size(); N++) {
    CodePoint = UTF32[N];

    if (CodePoint <= 0x7F) {
      Byte = CodePoint;
    UTF8.push_back(Byte);
    }
    else if (CodePoint <= 0x7FF) {
      Byte = 0xC0 | (CodePoint >> 6);
      UTF8.push_back(Byte);
      Byte = 0x80 | (CodePoint & 0x3F);
      UTF8.push_back(Byte);
    }
    else if (CodePoint <= 0xFFFF) {
      Byte = 0xE0 | (CodePoint >> 12);
      UTF8.push_back(Byte);
      Byte = 0x80 | ((CodePoint >> 6) & 0x3F);
      UTF8.push_back(Byte);
      Byte = 0x80 | (CodePoint & 0x3F);
      UTF8.push_back(Byte);
    }
    else if (CodePoint <= 0x10FFFF) {
      Byte = 0xF0 | (CodePoint >> 18);
      UTF8.push_back(Byte);
      Byte = 0x80 | ((CodePoint >> 12) & 0x3F);
      UTF8.push_back(Byte);
      Byte = 0x80 | ((CodePoint >> 6) & 0x3F);
      UTF8.push_back(Byte);
      Byte = 0x80 | (CodePoint & 0x3F);
      UTF8.push_back(Byte);
    }
    else
      printf("%d is outside of the Unicode range!\n", CodePoint);
  }
}


Why on earth would you have such a function emit something to stdout?
Consider throwing an exception instead. Also printf sucks, this is a C++
newsgroup not a C newsgroup. I cannot be arsed reviewing the rest of your
algorithm as I generally don't do such things for free (for random people at
least). :)

/Leigh

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