UTF-8

From Second Life Wiki
Revision as of 03:12, 30 September 2014 by Pedro Oval (Talk | contribs)

Jump to: navigation, search

Second Life uses UTF-8 for storing and transmitting strings and with these functions you can work with Unicode characters. See: Unicode In 5 Minutes for a brief introduction to Unicode.


These functions are part of the Combined Library written by Strife Onizuka.

Limits under Mono

Unicode predominately contains simple characters. For the vast majority of the range of values, Unicode values are simply characters. However some Unicode values do not represent any character and are not valid, which under Mono results in one or more question marks ("?"). UnicodeIntegerToUTF8 and UTF8ToUnicodeInteger work perfectly for the simple characters; however not so well for the other values. More on these ranges can be found in the Unicode specification and Specials (Unicode block). While LSO doesn't care about these limitations, Mono does.

These integer ranges are ranges where UTF8ToUnicodeInteger() and UnicodeIntegerToUTF8() are NOT inverse functions of each other under Mono. Converting these integers to utf8 and back to integer may likely result in the integer 63 (the Unicode codepoint for "?"), no longer guaranteeing uniqueness:

  • [55296..57343] (2048 values). This corresponds to the surrogate area U+D800-U+DFFF, which is a reserved range because it's used by UTF-16 to represent the code points above U+FFFF.
  • [65534] U+FFFE is in fact THE intentionally "INVALID CHARACTER" UTF-8 code point. It is invalid by design.
  • [1114112 and above] can't be encoded because the Unicode range stops at U+10FFFF.

Standard

This version of UnicodeIntegerToUTF8 complies to the latest standard. LSO on the other hand complies to an earlier standard. The newer standard includes only a subset of the older standard. The extended range of the old standard went unused so this incompleteness is moot.

<lsl>string UnicodeIntegerToUTF8(integer input)//Mono Safe, LSLEditor Safe, LSO Incomplete {//LSO allows for the older UTF-8 range, this function only supports the new UTF-16 range.

   if(input > 0)
   {
       if(input <= 0x7FF)
       {//instead of a flat if else chain, this redistributes the fork load so that only the 4 byte characters result in 3 forks, all the other paths are 2 forks.
           if(input <= 0x7F){
               input = input << 24;
               jump quick_return;//saves us from the implicit double jump that using an else would cause.
           }
           input = 0xC0800000 | ((input << 18) & 0x1F000000) | ((input << 16) & 0x3F0000);
       }
       else if(input <= 0xFFFF)
           input = 0xE0808000 | ((input << 12) & 0x0F000000) | ((input << 10) & 0x3F0000) | ((input << 8) & 0x3F00);
       else if(input <= 0x10FFFF)
           input = 0xF0808080 | ((input << 06) & 0x07000000) | ((input << 04) & 0x3F0000) | ((input << 2) & 0x3F00) | (input & 0x3F);
       else
           jump error;//not in our range
       @quick_return;
       return llBase64ToString(llIntegerToBase64(input));
   }
   @error;
   return "";

}</lsl>

General Use

This version will work fine in LSO and Mono but not in LSLEditor.

<lsl>//===================================================// // Combined Library // // "Feb 4 2008", "08:35:00" // // Copyright (C) 2004-2008, Strife Onizuka (cc-by) // // http://creativecommons.org/licenses/by/3.0/ // //===================================================// //{

integer UTF8ToUnicodeInteger(string input)//LSLEditor Unsafe, LSO Safe {

   integer result = llBase64ToInteger(llStringToBase64(input = llGetSubString(input,0,0)));
   if(result & 0x80000000)//multibyte, continuing to use base64 is impractical because it requires smart shifting.
       return  (   (  0x0000003f &  result       ) |
                   (( 0x00003f00 &  result) >> 2 ) | 
                   (( 0x003f0000 &  result) >> 4 ) | 
                   (( 0x3f000000 & (result = (integer)("0x"+llGetSubString(input,-8,-1)))) >> 6 ) | 
                   (( 0x0000003f &  result) << 24) | 
                   (( 0x00000100 & (result = (integer)("0x"+llDeleteSubString(input = (string)llParseString2List(llEscapeURL(input),(list)"%",[]),-8,-1)))) << 22)
               ) & (  0x7FFFFFFF >> (5 * ((integer)(llLog(~result) / 0.69314718055994530941723212145818) - 25)));

// (( 0x00000100 & (result = (integer)("0x"+llDeleteSubString(input,-8,-1)))) << 22) // ) & ( 0x7FFFFFFF >> (30 - (5 * (llStringLength(input = (string)llParseString2List(llEscapeURL(input),(list)"%",[])) >> 1))));

   return result >> 24;

}

string UnicodeIntegerToUTF8(integer input)//LSLEditor Unsafe, LSO Safe {

   integer bytes = llCeil((llLog(input) / 0.69314718055994530941723212145818));
   string result = "%" + byte2hex((input >> (6 * bytes)) | ((0x3F80 >> bytes) << !(bytes = ((input >= 0x80) * (bytes + ~(((1 << bytes) - input) > 0)) / 5))));
   while (bytes)
       result += "%" + byte2hex((((input >> (6 * (bytes = ~-bytes))) | 0x80) & 0xBF));
   return llUnescapeURL(result);

}

string byte2hex(integer x)//LSLEditor Safe, LSO Safe {//Helper function for use with unicode characters.

   integer y = (x >> 4) & 0xF;
   return llGetSubString(hexc, y, y) + llGetSubString(hexc, x & 0xF, x & 0xF);

}//This function would benefit greatly from the DUP opcode, it would remove 19 bytes.

string hexc="0123456789ABCDEF";

//} Combined Library</lsl>

LSLEditor Safe

This version will work in Mono, LSO & LSLEditor. There will be a slight performance hit in LSO as compared to the LSLEditor Unsafe version.

<lsl>//===================================================// // Combined Library // // "Feb 4 2008", "08:38:13" // // Copyright (C) 2004-2008, Strife Onizuka (cc-by) // // http://creativecommons.org/licenses/by/3.0/ // //===================================================// //{

integer UTF8ToUnicodeInteger(string input)//LSLEditor Safe, LSO Safe {

   integer result = llBase64ToInteger(llStringToBase64(input = llGetSubString(input,0,0)));
   if(result & 0x80000000){//multibyte, continuing to use base64 is impractical because it requires smart shifting.
       integer end = (integer)("0x"+llGetSubString(input = (string)llParseString2List(llEscapeURL(input),(list)"%",[]),-8,-1));
       integer begin = (integer)("0x"+llDeleteSubString(input,-8,-1));
       return  (   (  0x0000003f &  end       ) |
                   (( 0x00003f00 &  end) >> 2 ) | 
                   (( 0x003f0000 &  end) >> 4 ) | 
                   (( 0x3f000000 &  end) >> 6 ) |
                   (( 0x0000003f &  begin) << 24) |
                   (( 0x00000100 &  begin) << 22)
               ) & (0x7FFFFFFF >> (5 * ((integer)(llLog(~result) / 0.69314718055994530941723212145818) - 25)));
   }
   return result >> 24;

}

string UnicodeIntegerToUTF8(integer input)//LSLEditor Safe, LSO Safe {

   integer bytes = llCeil((llLog(input) / 0.69314718055994530941723212145818));
   bytes = (input >= 0x80) * (bytes + ~(((1 << bytes) - input) > 0)) / 5;//adjust
   string result = "%" + byte2hex((input >> (6 * bytes)) | ((0x3F80 >> bytes) << !bytes));
   while (bytes)
       result += "%" + byte2hex((((input >> (6 * (bytes = ~-bytes))) | 0x80) & 0xBF));
   return llUnescapeURL(result);

}

string byte2hex(integer x)//LSLEditor Safe, LSO Safe {//Helper function for use with unicode characters.

   integer y = (x >> 4) & 0xF;
   return llGetSubString(hexc, y, y) + llGetSubString(hexc, x & 0xF, x & 0xF);

}//This function would benefit greatly from the DUP opcode, it would remove 19 bytes.

string hexc="0123456789ABCDEF";

//} Combined Library</lsl>