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1 files changed, 154 insertions, 0 deletions

diff --git a/utf8.lua b/utf8.lua
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+-- 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
+   
+   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