在go中使用lua示例, 基于gopher-lua!
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local pattern = '[%z\1-\127\194-\244][\128-\191]*'
-- helper function
local posrelat =
function (pos, len)
if pos < 0 then
pos = len + pos + 1
end
return pos
end
utf8 = {}
-- maps f over s's utf8 characters f can accept args: (visual_index, utf8_character, byte_index)
utf8.map =
function (s, f, no_subs)
local i = 0
if no_subs then
for b, e in s:gmatch('()' .. pattern .. '()') do
i = i + 1
local c = e - b
f(i, c, b)
end
else
for b, c in s:gmatch('()(' .. pattern .. ')') do
i = i + 1
f(i, c, b)
end
end
end
-- generator for the above -- to iterate over all utf8 chars
utf8.chars =
function (s, no_subs)
return coroutine.wrap(function () return utf8.map(s, coroutine.yield, no_subs) end)
end
-- returns the number of characters in a UTF-8 string
utf8.len =
function (s)
-- count the number of non-continuing bytes
return select(2, s:gsub('[^\128-\193]', ''))
end
utf8.GetMaxLenString =
function (s, maxlen, symbol)
-- s:待裁剪字符串,maxlen:最大长度,symbol:裁剪后补全符号
symbol = symbol or ""
local len = utf8.len(s)
local dstString = s
-- 超长,裁剪,加symbol
if len > maxlen then
dstString = utf8.sub(s, 1, maxlen)
dstString = dstString..symbol
end
return dstString
end
-- replace all utf8 chars with mapping
utf8.replace =
function (s, map)
return s:gsub(pattern, map)
end
-- reverse a utf8 string
utf8.reverse =
function (s)
-- reverse the individual greater-than-single-byte characters
s = s:gsub(pattern, function (c) return #c > 1 and c:reverse() end)
return s:reverse()
end
-- strip non-ascii characters from a utf8 string
utf8.strip =
function (s)
return s:gsub(pattern, function (c) return #c > 1 and '' end)
end
-- like string.sub() but i, j are utf8 strings
-- a utf8-safe string.sub()
utf8.sub =
function (s, i, j)
local l = utf8.len(s)
i = posrelat(i, l)
j = j and posrelat(j, l) or l
if i < 1 then i = 1 end
if j > l then j = l end
if i > j then return '' end
local diff = j - i
local iter = utf8.chars(s, true)
-- advance up to i
for _ = 1, i - 1 do iter() end
local c, b = select(2, iter())
-- i and j are the same, single-charaacter sub
if diff == 0 then
return string.sub(s, b, b + c - 1)
end
i = b
-- advance up to j
for _ = 1, diff - 1 do iter() end
c, b = select(2, iter())
return string.sub(s, i, b + c - 1)
end