Module:Escape

Usage

This module is designed as an way to escape strings in a customized and efficient manner. It works by replacing characters that are preceded by your escape char (or phrase) There are two ways to call this module:

From another module:

local esc = require('Module:Escape')
esc:char(escape char (or sequence))
local to_escape = esc:text(string)
code that replaces or removes unescaped chars
local result = esc:undo(to_escape)

From a template:

{{invoke:Escape|main|mode=function|char=escape char (or sequence)|text}}

In a template, the most useful function is kill.

This module is primarily intended to be used by other modules. However all functions can be called in template space using |mode=the function you want to call followed by arguments.

All module functions (i.e. any func. other than main()) should be called using a colon (:), e.g. esc:char('%') or esc:kill{'{{example|\\}}}', '}'} == '{{example|}'

escape:text() escape:text()	This function takes only one argument: A string. All characters in this string which are preceded by the sequence set by escape:char() will be replaced with placeholders that can be converted back into that char by escape:undo()
escape:undo() escape:undo()	Takes two arguments: The string that may contain placeholders set by escape:text() Optional, a char to be placed in front of any characters that have been de-escaped. (i.e. if you need to re-escape those string with a different char)
escape:kill() escape:kill()	This is basically equivalent to calling string.gsub() on the string returned by escape:text() and feeding that result into escape:undo() in a single step. Takes three arguments: A string A sequence of characters to be removed from that string. (May use a string.gsub pattern) Optional, a char to be placed in front of any characters that have been de-escaped.
escape:char() escape:char()	This function's primary use is to initialize the patterns to scan a string for an escape/escaped sequence. It takes two arguments, the first being the escape character and the second being a table of arguments (optional). By default, this module will escape the \ char. To escape the { char instead, you can do require('Module:Escape'):char('{') (or esc:char('{') (presuming you stored the table returned by this module in the local variable esc). When called without the second argument, char() will return a table containing the functions. This allows, for example, escape:char('*'):kill('1*23', '%d') which would return '2' For the most part, there is very little reason to set |mode= in template space since the patterns it stores are not shared with other invokations of this module. Templates should instead use the |char= if a new escape sequence is desired. Shortcut If provided a second argument that is a table containing a {key = value} pair, such that the key is text, undo, or kill and the value is a table containing the arguments that would have been passed to those functions. For escape:undo(), will cause the escaescape:text() and escape:kill()

Caveats

• When using a multi-character escape sequence, this module only marks it using the byte value of the first character. Thus, escape:undo() will unescape, for example, all characters escaped with 'e' and 'esc' if both were used. In practice however this shouldn't be a problem as multiple escape sequences are pretty rare unless you're transitioning between multiple code languages. (Multiple multi-char escape sequences beginning with the same character are simply bad practice anyhow.)
• Since byte values are stored as numbers, it is not recommended for you to use a number as an escape sequence (though it may work just fine).
• Placeholder byte values separated with return ('\r') characters--chosen because they are seldom used at all, and virtually never used unpaired with '\n'; moreover, it is distinct from the markers generated by <nowiki>...</nowiki> or mw.text.nowiki() (which use the delete char). To set a different separator char, include the key-value pair {safeChr = alternate character} in the table that you pass to escape:char().

Speed

The following are benchmarks...

when executing the following module function:

 function p.test_kill500(frame)
  local esc = require('Module:Escape')
  for k = 1, 500 do
   local v = esc:kill(p.test_string2(), 'test')
  end
  return os.clock(esc)
 end

when repeating the following line 500 times in a template:

{{#invoke:Escape|main|mode=kill|{{#invoke:Escape/testcases|test_string2}}|test}}

0.767

All times in seconds. The module time x500 was calculated when you loaded this doc page (normally between 0.02 and 0.07). The template time x500 was recorded on Jan 15, 2015.

Examples

Template

Original:

Using internal method to remove {:

Using {{replace}} to remove {:

No removal of { between escape/unescape (escape char not restored):

Restore to original after escape

Remove the word test if not escaped and then place a different escape char in the place of the old escape char (for use by something else):

Note: The '%' char is a special in Lua, so use '%%' if that is the desired replacement. Otherwise, just a single char is fine (or a word).

Module

Here's some sample output from the debug consol below the module editor:

local escape = require('Module:Escape') test = '' test2 = escape:char('{'):text(test) =test2 test3 = escape:char('\\'):text(test2) =test3 test4 = escape:char('{', {undo = test3}) =test4 test4 = escape:char('\\', {undo = test3}) =test4 test5 = escape:char('{', {undo = test4}) =test5 == test false =escape:undo(test3)--doesn't work because char is still set to '{' in current session =escape:undo(test4) =escape:char('\\'):undo(test3) =escape:char('{', {undo = escape:char('\\'):undo(test3)}) =test == escape:char('{', {undo = escape:char('\\'):undo(test3)}) false =test == escape:char('{', {undo = escape:char('\\'):undo(test3, '\\')}) false local t = '' =t local e = require('Module:Escape') local t2 = escape:text(t) local t3 = string.gsub(t2, '{', ) local t4 = escape:undo(t3) =t4 test test { test, test, {,test \ local tk0 = escape:kill(t, '{') =tk0 == t4 true

---

local escape = {
	char = function(self, chr, args)
		args = args or {}
		local safe = args.safeChr or string.char(13)
		chr = tostring(chr or '\\')
		self[1] = ('%s0%%s%s'):format(
			('%x%s%s'):format(chr:byte(), safe, safe),
			('%s%x'):format(safe, chr:byte())
		)
		if not self[self[1]] then
			self[self[1]] = {
				char = chr,
				text = ('%s(.)'):format(chr),
				undo = self[1]:format'(%d+)'
			}
		end
		return args.text and self:text(args.text)
			or args.undo and self:undo(args.undo, chr)
			or args.kill and self:kill(args.kill)
			or self
	end,
	exec = function(self, text, mode, newEscape)
		local target = self[self[1] or self:char() and self[1]]
		for v in text:gfind(target[mode]) do
			text = text:gsub(
				mode == 'text' and
					('%s%s'):format(target.char, v:gsub('%W', '%%%1'))
					or self[1]:format(v),
				mode == 'text' and
					self[1]:format(v:byte())
					or (newEscape or '') .. v:char()
			)
		end
		return text
	end,
	text = function(self, text)
		return self:exec(type(text) == 'table' and text[1] or text, 'text')
	end,
	undo = function(self, text, newEscape)
		if type(text) == 'table' then
			text, newEscape = unpack(text)
		end
		return self:exec(text, 'undo', newEscape)
	end,
	kill = function(self, text, chars, newEscape)
		if type(text) == 'table' then
			text, chars, newEscape = unpack(text)
		end
		return self:undo(self:text(text):gsub(chars or '', ''), newEscape)
	end
}

function escape.main(frame)
	local args, family = {}, {frame:getParent(), frame}
	for f = 1, 2 do
		for k, v in pairs(family[f] and family[f].args or {}) do
			args[k] = args[k] or v:match('^%s*(.-)%s*$')
		end
	end
	if args.mode == 'char' then
		return escape:char(args.char or args[2], args)
	end
	return escape[args.mode](escape:char(args.char), args)
end

return escape