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|
-- lib/lace/lex.lua
--
-- Lua Access Control Engine -- Ruleset lexer
--
-- Copyright 2012 Daniel Silverstone <dsilvers@digital-scurf.org>
--
-- For Licence terms, see COPYING
--
--- Lace Internals - Ruleset lexer.
--
-- The lexer for Lace is only used internally and is generally not accessed
-- from outside of Lace. It is exposed only for testing and validation
-- purposes.
local M = {}
local lexer_line_cache = {}
local lex_one_line
local function _lex_one_line(line, terminator)
local r = {}
local acc = ""
local c
local escaping = false
local quoting = false
local force_empty = false
local spos, cpos = 1, 0
while #line > 0 do
c, line = line:match("^(.)(.*)$")
cpos = cpos + 1
if escaping then
if quoting then
if c == "n" then
acc = acc .. "\n"
elseif c == "t" then
acc = acc .. "\t"
else
acc = acc .. c
end
else
acc = acc .. c
end
escaping = false
else
if c == terminator and quoting == false then
-- Reached the terminator, break out
break
elseif c == "'" and quoting == false then
-- Start single quotes
quoting = c
force_empty = true
elseif c == '"' and quoting == false then
-- Start double quotes
quoting = c
force_empty = true
elseif c == '[' and quoting == false then
if acc == "" then
-- Something worth lexing
local ltab, rest, warns = lex_one_line(line, "]")
-- For now, assume the accumulator is good enough
cpos = cpos + #line - #rest
r[#r+1] = { spos = spos, epos = cpos, sub = ltab }
spos = cpos + 1
line = rest
acc = ""
end
elseif c == "'" and quoting == c then
-- End single quotes
quoting = false
elseif c == '"' and quoting == c then
-- End double quotes
quoting = false
elseif c == "\\" then
-- A backslash, entering escaping mode
escaping = true
elseif quoting then
-- Within quotes, so accumulate
acc = acc .. c
elseif c == " " or c == "\t" then
-- A space (or tab) and not quoting, so clear the accumulator
if acc ~= "" or force_empty then
r[#r+1] = { spos = spos, epos = cpos - 1, str = acc }
spos = cpos + 1
force_empty = false
elseif cpos == spos then
-- Increment the start position since we've not found a word yet
spos = spos + 1
end
acc = ""
else
acc = acc .. c
end
end
end
if acc ~= "" or force_empty then
r[#r+1] = { spos = spos, epos = cpos, str = acc }
end
local warnings = {}
if quoting then
warnings[#warnings+1] = "Un-terminated quoted string"
end
if escaping then
warnings[#warnings+1] = "Un-used escape at end"
end
return r, line, warnings
end
function lex_one_line(line, terminator)
local tag = line .. "\n" .. tostring(terminator)
if not lexer_line_cache[tag] then
lexer_line_cache[tag] = { _lex_one_line(line, terminator) }
end
return lexer_line_cache[tag][1], lexer_line_cache[tag][2], lexer_line_cache[tag][3]
end
local cached_full_lexes = {}
--- Lexically analyse a ruleset.
-- @tparam string ruleset The ruleset to lex.
-- @tparam string sourcename The name of the source to go into debug info.
-- @treturn table A list of lexed lines, each line being a table of tokens
-- with their associated debug information.
function M.string(ruleset, sourcename)
if cached_full_lexes[sourcename] and
cached_full_lexes[sourcename][ruleset] then
return cached_full_lexes[sourcename][ruleset]
end
local lines = {}
local ret = { source = sourcename, lines = lines }
local n = 1
local warn
if ruleset:match("[^\n]$") then
ruleset = ruleset .. "\n"
end
for oneline in ruleset:gmatch("([^\n]*)\n") do
local linetab = { original = oneline }
if oneline:match("^[ \t]*#") or
oneline:match("^[ \t]*//") or
oneline:match("^[ \t]*%-%-") then
linetab.type = "comment"
elseif oneline:match("^[ \t]*$") then
linetab.type = "whitespace"
else
linetab.type = "rule"
linetab.content, rest_of_line, warn = lex_one_line(oneline)
assert(rest_of_line == "", "Content left after line lexing")
if #warn > 0 then
linetab.warnings = warn
end
end
lines[n] = linetab
n = n + 1
end
cached_full_lexes[sourcename] = cached_full_lexes[sourcename] or {}
cached_full_lexes[sourcename][ruleset] = ret
return ret
end
return M
|
