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博客地址：http://blog.csdn.net/qq446569365
一个用于UTF8字符串操作的类，功能比较齐全，包括：string.utf8len UTF8字符串长度
string.utf8sub 对UTF8字符串进行切割
string.utf8upper 大写转换
string.utf8lower 小写转换
string.utf8reverse 字符串逆转
Github下载地址： https://github.com/ArcherPeng/utf8String4LUA
--===========================--
--===========================--
-- $Id: utf8.lua 147 2007-01-04 00:57:00Z pasta $
--
-- Provides UTF-8 aware string functions implemented in pure lua:
-- * string.utf8len(s)
-- * string.utf8sub(s, i, j)
-- * string.utf8reverse(s)
--
-- If utf8data.lua (containing the lower<->upper case mappings) is loaded, these
-- additional functions are available:
-- * string.utf8upper(s)
-- * string.utf8lower(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.
--]]
-- 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
local 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
-- returns the number of characters in a UTF-8 string
local function utf8len (s)
-- argument checking
if type(s) ~= "string" then
error("bad argument #1 to 'utf8len' (string expected, got ".. type(s).. ")")
end
local pos = 1
local bytes = s:len()
local len = 0
while pos <= bytes and len ~= chars do
local c = s:byte(pos)
len = len + 1
pos = pos + utf8charbytes(s, pos)
end
if chars ~= nil then
return pos - 1
end
return len
end
-- install in the string library
if not string.utf8len then
string.utf8len = utf8len
end
-- functions identically to string.sub except that i and j are UTF-8 characters
-- instead of bytes
local function utf8sub (s, i, j)
-- argument defaults
j = j or -1
-- argument checking
if type(s) ~= "string" then
error("bad argument #1 to 'utf8sub' (string expected, got ".. type(s).. ")")
end
if type(i) ~= "number" then
error("bad argument #2 to 'utf8sub' (number expected, got ".. type(i).. ")")
end
if type(j) ~= "number" then
error("bad argument #3 to 'utf8sub' (number expected, got ".. type(j).. ")")
end
local pos = 1
local bytes = s:len()
local len = 0
-- only set l if i or j is negative
local l = (i >= 0 and j >= 0) or s:utf8len()
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 s:sub(startByte, endByte)
end
-- install in the string library
if not string.utf8sub then
string.utf8sub = utf8sub
end
-- 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 function utf8upper (s)
return utf8replace(s, utf8_lc_uc)
end
-- install in the string library
if not string.utf8upper and utf8_lc_uc then
string.utf8upper = utf8upper
end
-- identical to string.lower except it knows about unicode simple case conversions
local function utf8lower (s)
return utf8replace(s, utf8_uc_lc)
end
-- install in the string library
if not string.utf8lower and utf8_uc_lc then
string.utf8lower = utf8lower
end
-- identical to string.reverse except that it supports UTF-8
local function utf8reverse (s)
-- argument checking
if type(s) ~= "string" then
error("bad argument #1 to 'utf8reverse' (string expected, got ".. type(s).. ")")
end
local bytes = s:len()
local pos = bytes
local charbytes
local newstr = ""
while pos > 0 do
c = s:byte(pos)
while c >= 128 and c <= 191 do
pos = pos - 1
c = s:byte(pos)
end
charbytes = utf8charbytes(s, pos)
newstr = newstr .. s:sub(pos, pos + charbytes - 1)
pos = pos - 1
end
return newstr
end
-- install in the string library
if not string.utf8reverse then
string.utf8reverse = utf8reverse
end