1#ifndef EXCEPT_H
2#define EXCEPT_H
3/*=========================================================================*\
4* Exception control
5* LuaSocket toolkit (but completely independent from other modules)
6*
7* This provides support for simple exceptions in Lua. During the
8* development of the HTTP/FTP/SMTP support, it became aparent that
9* error checking was taking a substantial amount of the coding. These
10* function greatly simplify the task of checking errors.
11*
12* The main idea is that functions should return nil as their first return
13* values when they find an error, and return an error message (or value)
14* following nil. In case of success, as long as the first value is not nil,
15* the other values don't matter.
16*
17* The idea is to nest function calls with the "try" function. This function
18* checks the first value, and, if it's falsy, wraps the second value in a
19* table with metatable and calls "error" on it. Otherwise, it returns all
20* values it received. Basically, it works like the Lua "assert" function,
21* but it creates errors targeted specifically at "protect".
22*
23* The "newtry" function is a factory for "try" functions that call a
24* finalizer in protected mode before calling "error".
25*
26* The "protect" function returns a new function that behaves exactly like
27* the function it receives, but the new function catches exceptions thrown
28* by "try" functions and returns nil followed by the error message instead.
29*
30* With these three functions, it's easy to write functions that throw
31* exceptions on error, but that don't interrupt the user script.
32\*=========================================================================*/
33
34#include "lua.h"
35
36int except_open(lua_State *L);
37
38#endif
39