-- Provides UTF-8 aware string functions implemented in pure lua: -- * string.utf8len(s) -- * string.utf8sub(s, i, j) -- -- All functions behave as their non UTF-8 aware counterparts with the exception -- that UTF-8 characters are used instead of bytes for all units. -- -- Note: all validations had been removed due to awesome usage specifics. --[[ Copyright (c) 2006-2007, Kyle Smith All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: * Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. * Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. * Neither the name of the author nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission. THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. --]] -- ABNF from RFC 3629 -- -- UTF8-octets = *( UTF8-char ) -- UTF8-char = UTF8-1 / UTF8-2 / UTF8-3 / UTF8-4 -- UTF8-1 = %x00-7F -- UTF8-2 = %xC2-DF UTF8-tail -- UTF8-3 = %xE0 %xA0-BF UTF8-tail / %xE1-EC 2( UTF8-tail ) / -- %xED %x80-9F UTF8-tail / %xEE-EF 2( UTF8-tail ) -- UTF8-4 = %xF0 %x90-BF 2( UTF8-tail ) / %xF1-F3 3( UTF8-tail ) / -- %xF4 %x80-8F 2( UTF8-tail ) -- UTF8-tail = %x80-BF -- -- returns the number of bytes used by the UTF-8 character at byte i in s -- also doubles as a UTF-8 character validator function utf8charbytes (s, i) -- argument defaults i = i or 1 local c = string.byte(s, i) -- determine bytes needed for character, based on RFC 3629 if c > 0 and c <= 127 then -- UTF8-1 return 1 elseif c >= 194 and c <= 223 then -- UTF8-2 local c2 = string.byte(s, i + 1) return 2 elseif c >= 224 and c <= 239 then -- UTF8-3 local c2 = s:byte(i + 1) local c3 = s:byte(i + 2) return 3 elseif c >= 240 and c <= 244 then -- UTF8-4 local c2 = s:byte(i + 1) local c3 = s:byte(i + 2) local c4 = s:byte(i + 3) return 4 end end -- returns the number of characters in a UTF-8 string function utf8len (s) local pos = 1 local bytes = string.len(s) local len = 0 while pos <= bytes and len ~= chars do local c = string.byte(s,pos) len = len + 1 pos = pos + utf8charbytes(s, pos) end if chars ~= nil then return pos - 1 end return len end -- functions identically to string.sub except that i and j are UTF-8 characters -- instead of bytes function utf8sub (s, i, j) j = j or -1 if i == nil then return "" end local pos = 1 local bytes = string.len(s) local len = 0 -- only set l if i or j is negative local l = (i >= 0 and j >= 0) or utf8len(s) local startChar = (i >= 0) and i or l + i + 1 local endChar = (j >= 0) and j or l + j + 1 -- can't have start before end! if startChar > endChar then return "" end -- byte offsets to pass to string.sub local startByte, endByte = 1, bytes while pos <= bytes do len = len + 1 if len == startChar then startByte = pos end pos = pos + utf8charbytes(s, pos) if len == endChar then endByte = pos - 1 break end end return string.sub(s, startByte, endByte) end -- replace UTF-8 characters based on a mapping table function utf8replace (s, mapping) local pos = 1 local bytes = string.len(s) local charbytes local newstr = "" while pos <= bytes do charbytes = utf8charbytes(s, pos) local c = string.sub(s, pos, pos + charbytes - 1) newstr = newstr .. (mapping[c] or c) pos = pos + charbytes end return newstr end