New escaping system

luametalatex-pdf-escape.lua

@@ -0,0 +1,77 @@
+local mode = 6
+-- Control how much escaping is done... the mode is a bitset:
+-- Bit 0: Disable auto-detection of pre-escaped input
+-- Bit 1: Convert UTF-8 input to UTF-16
+-- Bit 2: Actually escape unescaped input instead of assuming that it is safe
+--
+-- This currently results in 8 modes. Mode 7 is recommended if you can control
+-- all new code, otherwise Mode 6 might be required. Code 0 is (mostly) compatible
+-- with other engines.
+--
+-- Also we have three distinct functions which relate to different uses.
+-- escape_text is for text strings and fully respects the mode.
+-- escape_bytes is for non-text byte strings and always acts as if Bit 1 is unset
+--    (after all, UTF-16 doesn't make sense for non-text strings)
+-- escape_raw always acts like mode 5 without the parens: Just escape, without any
+-- other auto-detection or conversion. (This is used for actual content text)
+local function setmode(new)
+  mode = new
+end
+local function is_escaped(s)
+  if mode & 1 == 1 then return false end
+  return (mode & 1 == 1) and (s:match("^%(.*%)$") or s:match("^<.*>$")) and true or false
+end
+local function to_utf16(s)
+  local i = 3
+  local bytes = {0xFE, 0xFF}
+  for _, c in utf8.codes(s) do
+    if c < 0x10000 then
+      -- assert(c < 0xD800 or c >= 0xE000)
+      bytes[i] = c >> 8
+      bytes[i+1] = c & 0xFF
+      i = i+2
+    else
+      c = c-0x10000
+      bytes[i] = 0xD8 | ((c>>18) & 3)
+      bytes[i+1] = (c>>10) & 0xFF
+      bytes[i+2] = 0xDC | ((c>>8) & 3)
+      bytes[i+3] = c & 0xFF
+      i = i+4
+    end
+  end
+  return string.char(table.unpack(bytes))
+end
+-- This is pretty much the minimal escaping possible: Only escape bytes which are 
+local l = lpeg
+local simple_char = 1-l.S'()\\'
+local semi_simple_char = simple_char + l.P'\\'/'\\\\'
+local nested = l.P{'(' * (semi_simple_char + l.V(1))^0 * ')'}
+local inner = (semi_simple_char + nested + (l.Cc'\\' * l.S'()'))^0 * -1
+local raw = l.Cs(inner)
+local patt = l.Cs(l.Cc'(' * inner * l.Cc')')
+local function escape_bytes(s)
+  if is_escaped(s) then return s end
+  if mode & 4 == 0 then
+    return '(' .. s .. ')'
+  end
+  return patt:match(s)
+end
+local function escape_text(s)
+  if is_escaped(s) then return s end
+  if mode & 2 == 2 then
+    s = to_utf16(s)
+  elseif mode & 4 == 0 then
+    return '(' .. s .. ')'
+  end
+  return patt:match(s)
+end
+local function escape_raw(s)
+  return raw:match(s)
+end
+
+return {
+  escape_raw = escape_raw,
+  escape_bytes = escape_bytes,
+  escape_text = escape_text,
+  setmode = setmode,
+}