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--- Extract delimited Lua sequences from strings.
-- Inspired by Damian Conway's Text::Balanced in Perl. <br/>
-- <ul>
-- <li>[1] <a href="http://lua-users.org/wiki/LuaBalanced">Lua Wiki Page</a></li>
-- <li>[2] http://search.cpan.org/dist/Text-Balanced/lib/Text/Balanced.pm</li>
-- </ul> <br/>
-- <pre class=example>
-- local lb = require "pl.luabalanced"
-- --Extract Lua expression starting at position 4.
-- print(lb.match_expression("if x^2 + x > 5 then print(x) end", 4))
-- --> x^2 + x > 5 16
-- --Extract Lua string starting at (default) position 1.
-- print(lb.match_string([["test\"123" .. "more"]]))
-- --> "test\"123" 12
-- </pre>
-- (c) 2008, David Manura, Licensed under the same terms as Lua (MIT license).
-- @class module
-- @name pl.luabalanced
local M = {}
local assert = assert
-- map opening brace <-> closing brace.
local ends = { ['('] = ')', ['{'] = '}', ['['] = ']' }
local begins = {}; for k,v in pairs(ends) do begins[v] = k end
-- Match Lua string in string <s> starting at position <pos>.
-- Returns <string>, <posnew>, where <string> is the matched
-- string (or nil on no match) and <posnew> is the character
-- following the match (or <pos> on no match).
-- Supports all Lua string syntax: "...", '...', [[...]], [=[...]=], etc.
local function match_string(s, pos)
pos = pos or 1
local posa = pos
local c = s:sub(pos,pos)
if c == '"' or c == "'" then
pos = pos + 1
while 1 do
pos = assert(s:find("[" .. c .. "\\]", pos), 'syntax error')
if s:sub(pos,pos) == c then
local part = s:sub(posa, pos)
return part, pos + 1
else
pos = pos + 2
end
end
else
local sc = s:match("^%[(=*)%[", pos)
if sc then
local _; _, pos = s:find("%]" .. sc .. "%]", pos)
assert(pos)
local part = s:sub(posa, pos)
return part, pos + 1
else
return nil, pos
end
end
end
M.match_string = match_string
-- Match bracketed Lua expression, e.g. "(...)", "{...}", "[...]", "[[...]]",
-- [=[...]=], etc.
-- Function interface is similar to match_string.
local function match_bracketed(s, pos)
pos = pos or 1
local posa = pos
local ca = s:sub(pos,pos)
if not ends[ca] then
return nil, pos
end
local stack = {}
while 1 do
pos = s:find('[%(%{%[%)%}%]\"\']', pos)
assert(pos, 'syntax error: unbalanced')
local c = s:sub(pos,pos)
if c == '"' or c == "'" then
local part; part, pos = match_string(s, pos)
assert(part)
elseif ends[c] then -- open
local mid, posb
if c == '[' then mid, posb = s:match('^%[(=*)%[()', pos) end
if mid then
pos = s:match('%]' .. mid .. '%]()', posb)
assert(pos, 'syntax error: long string not terminated')
if #stack == 0 then
local part = s:sub(posa, pos-1)
return part, pos
end
else
stack[#stack+1] = c
pos = pos + 1
end
else -- close
assert(stack[#stack] == assert(begins[c]), 'syntax error: unbalanced')
stack[#stack] = nil
if #stack == 0 then
local part = s:sub(posa, pos)
return part, pos+1
end
pos = pos + 1
end
end
end
M.match_bracketed = match_bracketed
-- Match Lua comment, e.g. "--...\n", "--[[...]]", "--[=[...]=]", etc.
-- Function interface is similar to match_string.
local function match_comment(s, pos)
pos = pos or 1
if s:sub(pos, pos+1) ~= '--' then
return nil, pos
end
pos = pos + 2
local partt, post = match_string(s, pos)
if partt then
return '--' .. partt, post
end
local part; part, pos = s:match('^([^\n]*\n?)()', pos)
return '--' .. part, pos
end
-- Match Lua expression, e.g. "a + b * c[e]".
-- Function interface is similar to match_string.
local wordop = {['and']=true, ['or']=true, ['not']=true}
local is_compare = {['>']=true, ['<']=true, ['~']=true}
local function match_expression(s, pos)
pos = pos or 1
local _
local posa = pos
local lastident
local poscs, posce
while pos do
local c = s:sub(pos,pos)
if c == '"' or c == "'" or c == '[' and s:find('^[=%[]', pos+1) then
local part; part, pos = match_string(s, pos)
assert(part, 'syntax error')
elseif c == '-' and s:sub(pos+1,pos+1) == '-' then
-- note: handle adjacent comments in loop to properly support
-- backtracing (poscs/posce).
poscs = pos
while s:sub(pos,pos+1) == '--' do
local part; part, pos = match_comment(s, pos)
assert(part)
pos = s:match('^%s*()', pos)
posce = pos
end
elseif c == '(' or c == '{' or c == '[' then
_, pos = match_bracketed(s, pos)
elseif c == '=' and s:sub(pos+1,pos+1) == '=' then
pos = pos + 2 -- skip over two-char op containing '='
elseif c == '=' and is_compare[s:sub(pos-1,pos-1)] then
pos = pos + 1 -- skip over two-char op containing '='
elseif c:match'^[%)%}%];,=]' then
local part = s:sub(posa, pos-1)
return part, pos
elseif c:match'^[%w_]' then
local newident,newpos = s:match('^([%w_]+)()', pos)
if pos ~= posa and not wordop[newident] then -- non-first ident
local pose = ((posce == pos) and poscs or pos) - 1
while s:match('^%s', pose) do pose = pose - 1 end
local ce = s:sub(pose,pose)
if ce:match'[%)%}\'\"%]]' or
ce:match'[%w_]' and not wordop[lastident]
then
local part = s:sub(posa, pos-1)
return part, pos
end
end
lastident, pos = newident, newpos
else
pos = pos + 1
end
pos = s:find('[%(%{%[%)%}%]\"\';,=%w_%-]', pos)
end
local part = s:sub(posa, #s)
return part, #s+1
end
M.match_expression = match_expression
-- Match name list (zero or more names). E.g. "a,b,c"
-- Function interface is similar to match_string,
-- but returns array as match.
local function match_namelist(s, pos)
pos = pos or 1
local list = {}
while 1 do
local c = #list == 0 and '^' or '^%s*,%s*'
local item, post = s:match(c .. '([%a_][%w_]*)%s*()', pos)
if item then pos = post else break end
list[#list+1] = item
end
return list, pos
end
M.match_namelist = match_namelist
-- Match expression list (zero or more expressions). E.g. "a+b,b*c".
-- Function interface is similar to match_string,
-- but returns array as match.
local function match_explist(s, pos)
pos = pos or 1
local list = {}
while 1 do
if #list ~= 0 then
local post = s:match('^%s*,%s*()', pos)
if post then pos = post else break end
end
local item; item, pos = match_expression(s, pos)
assert(item, 'syntax error')
list[#list+1] = item
end
return list, pos
end
M.match_explist = match_explist
-- Replace snippets of code in Lua code string <s>
-- using replacement function f(u,sin) --> sout.
-- <u> is the type of snippet ('c' = comment, 's' = string,
-- 'e' = any other code).
-- Snippet is replaced with <sout> (unless <sout> is nil or false, in
-- which case the original snippet is kept)
-- This is somewhat analogous to string.gsub .
local function gsub(s, f)
local pos = 1
local posa = 1
local sret = ''
while 1 do
pos = s:find('[%-\'\"%[]', pos)
if not pos then break end
if s:match('^%-%-', pos) then
local exp = s:sub(posa, pos-1)
if #exp > 0 then sret = sret .. (f('e', exp) or exp) end
local comment; comment, pos = match_comment(s, pos)
sret = sret .. (f('c', assert(comment)) or comment)
posa = pos
else
local posb = s:find('^[\'\"%[]', pos)
local str
if posb then str, pos = match_string(s, posb) end
if str then
local exp = s:sub(posa, posb-1)
if #exp > 0 then sret = sret .. (f('e', exp) or exp) end
sret = sret .. (f('s', str) or str)
posa = pos
else
pos = pos + 1
end
end
end
local exp = s:sub(posa)
if #exp > 0 then sret = sret .. (f('e', exp) or exp) end
return sret
end
M.gsub = gsub
return M
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