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#ifndef SIGCHAIN_H
#define SIGCHAIN_H
/**
* Code often wants to set a signal handler to clean up temporary files or
* other work-in-progress when we die unexpectedly. For multiple pieces of
* code to do this without conflicting, each piece of code must remember
* the old value of the handler and restore it either when:
*
* 1. The work-in-progress is finished, and the handler is no longer
* necessary. The handler should revert to the original behavior
* (either another handler, SIG_DFL, or SIG_IGN).
*
* 2. The signal is received. We should then do our cleanup, then chain
* to the next handler (or die if it is SIG_DFL).
*
* Sigchain is a tiny library for keeping a stack of handlers. Your handler
* and installation code should look something like:
*
* ------------------------------------------
* void clean_foo_on_signal(int sig)
* {
* clean_foo();
* sigchain_pop(sig);
* raise(sig);
* }
*
* void other_func()
* {
* sigchain_push_common(clean_foo_on_signal);
* mess_up_foo();
* clean_foo();
* }
* ------------------------------------------
*
*/
/**
* Handlers are given the typedef of sigchain_fun. This is the same type
* that is given to signal() or sigaction(). It is perfectly reasonable to
* push SIG_DFL or SIG_IGN onto the stack.
*/
typedef void (*sigchain_fun)(int);
/* You can sigchain_push and sigchain_pop individual signals. */
int sigchain_push(int sig, sigchain_fun f);
int sigchain_pop(int sig);
/**
* push the handler onto the stack for the common signals:
* SIGINT, SIGHUP, SIGTERM, SIGQUIT and SIGPIPE.
*/
void sigchain_push_common(sigchain_fun f);
void sigchain_pop_common(void);
#endif /* SIGCHAIN_H */
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