Aegisub/automation/include/unicode.lua

122 lines
3.1 KiB
Lua

--[[
Copyright (c) 2007, Niels Martin Hansen, Rodrigo Braz Monteiro
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 Aegisub Group 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.
]]
-- Unicode (UTF-8) support functions for Aegisub Automation 4 Lua
-- http://www.ietf.org/rfc/rfc2279.txt
module("unicode")
-- Return the number of bytes occupied by the character starting at the i'th byte in s
function charwidth(s, i)
local b = s:byte(i)
if b < 128 then
return 1
elseif b < 224 then
return 2
elseif b < 240 then
return 3
elseif b < 248 then
return 4
elseif b < 252 then
return 5
else
return 6
end
-- Actually there are more possibilities, but those aren't really legal
end
-- Returns an iterator function for iterating over the characters in s
function chars(s)
local curchar, i = 0, 1
local function itor()
if i > s:len() then
return nil
end
local width = charwidth(s, i)
local j = i
curchar = curchar + 1
i = i + width
return s:sub(j, i-1), curchar
end
return itor
end
-- Returns the number of characters in s
-- Runs in O(s:len()) time!
function len(s)
local n = 0
for c in chars(s) do
n = n + 1
end
return n
end
-- Get codepoint of first char in s
function codepoint(s)
-- Basic case, ASCII
local b = s:byte(1)
if s:byte(1) < 128 then
return s:byte(1)
end
-- Use a naive decoding algorithm, and assume input is valid
local res, w = 0
if b < 224 then
-- prefix byte is 110xxxxx
res = b - 192
w = 2
elseif b < 240 then
-- prefix byte is 11100000
res = b - 224
w = 3
elseif b < 248 then
-- prefix byte is 11110000
res = b - 240
w = 4
elseif b < 252 then
-- prefix byte is 11111000
res = b - 248
w = 5
else
-- prefix byte is 11111100
res = b - 252
w = 6
end
for i = 2, w do
res = res*64 + s:byte(i) - 128
end
return res
end