Applying quantifier to a sentence in Lua pattern

Question

So I am trying to parse out #define statements out of a C file using Lua patterns, but there is the case on multiline defines, where you might escape the newline character with a backslash.

In order for me to know where the define ends, I need to be able to define backslash + linebreak as if it were a single character so I can get the complement of that and then use the * quantifier on it and then count until the first non-escaped linebreak.

How do I do that?

Answer 1

You cannot simply replace all occurrences of "\\\n" with some temporary symbol, because a problem will arise with the line "c\\\\\n" in the following example.
Instead, you should implement mini-scanner for C source files:

local str = [[
#define x y
#define a b\
c\\
d();
#define z
]]

-- Print all #defines found in the text
local line = ""
for char in str:gmatch"\\?." do
   if char == "\n" then
      if line:sub(1, #"#define") == "#define" then
         print(line)
      end
      line = ""
   else
      line = line..char
   end
end

Output:

#define x y
#define a b\
c\\
#define z