MultiCraft/builtin/utf8lib/init.lua

--[[
$Id: utf8.lua 179 2009-04-03 18:10:03Z pasta $

Provides UTF-8 aware string functions implemented in pure lua:
*	string.upper(s)
*	string.lower(s)

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.

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.

Based on:	https://github.com/Planimeter/grid-sdk/blob/master/public/utf8.lua
Changed by:	MultiCraft Development Team (2019)
Note:		Now used very minimal version, with the support of only lower and upper.
			Only latin and russian letters are supported.
			Support for additional characters will be added as the game localizes.
]]

-- 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

	-- argument checking
	if type(s) ~= "string" then
		error("bad argument #1 to 'utf8charbytes' (string expected, got ".. type(s).. ")")
	end
	if type(i) ~= "number" then
		error("bad argument #2 to 'utf8charbytes' (number expected, got ".. type(i).. ")")
	end

	local c = s:byte(i)

	-- determine bytes needed for character, based on RFC 3629
	-- validate byte 1
	if c > 0 and c <= 127 then
		-- UTF8-1
		return 1
	elseif c >= 194 and c <= 223 then
		-- UTF8-2
		local c2 = s:byte(i + 1)

		if not c2 then
			error("UTF-8 string terminated early")
		end

		-- validate byte 2
		if c2 < 128 or c2 > 191 then
			error("Invalid UTF-8 character")
		end

		return 2
	elseif c >= 224 and c <= 239 then
		-- UTF8-3
		local c2 = s:byte(i + 1)
		local c3 = s:byte(i + 2)

		if not c2 or not c3 then
			error("UTF-8 string terminated early")
		end

		-- validate byte 2
		if c == 224 and (c2 < 160 or c2 > 191) then
			error("Invalid UTF-8 character")
		elseif c == 237 and (c2 < 128 or c2 > 159) then
			error("Invalid UTF-8 character")
		elseif c2 < 128 or c2 > 191 then
			error("Invalid UTF-8 character")
		end

		-- validate byte 3
		if c3 < 128 or c3 > 191 then
			error("Invalid UTF-8 character")
		end

		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)

		if not c2 or not c3 or not c4 then
			error("UTF-8 string terminated early")
		end

		-- validate byte 2
		if c == 240 and (c2 < 144 or c2 > 191) then
			error("Invalid UTF-8 character")
		elseif c == 244 and (c2 < 128 or c2 > 143) then
			error("Invalid UTF-8 character")
		elseif c2 < 128 or c2 > 191 then
			error("Invalid UTF-8 character")
		end

		-- validate byte 3
		if c3 < 128 or c3 > 191 then
			error("Invalid UTF-8 character")
		end

		-- validate byte 4
		if c4 < 128 or c4 > 191 then
			error("Invalid UTF-8 character")
		end

		return 4
	else
		error("Invalid UTF-8 character")
	end
end

dofile(core.get_builtin_path() .. "utf8lib" .. DIR_DELIM .. "utf8data.lua")

-- replace UTF-8 characters based on a mapping table
local function utf8replace(s, mapping)
	-- argument checking
	if type(s) ~= "string" then
		error("bad argument #1 to 'utf8replace' (string expected, got ".. type(s).. ")")
	end
	if type(mapping) ~= "table" then
		error("bad argument #2 to 'utf8replace' (table expected, got ".. type(mapping).. ")")
	end

	local pos = 1
	local bytes = s:len()
	local charbytes
	local newstr = ""

	while pos <= bytes do
		charbytes = utf8charbytes(s, pos)
		local c = s:sub(pos, pos + charbytes - 1)
		newstr = newstr .. (mapping[c] or c)
		pos = pos + charbytes
	end

	return newstr
end

-- identical to string.upper except it knows about unicode simple case conversions
local origupper = string.upper
function string.upper(s)
	return origupper(utf8replace(s, utf8_lc_uc))
end

-- identical to string.lower except it knows about unicode simple case conversions
local origlower = string.lower
function string.lower(s)
	return origlower(utf8replace(s, utf8_uc_lc))
end