Miscellaneous utilities

Utility functions that did not fit into other modules. More...

Data Structures
struct	ratelimit_state_t
	Control structure used for rate limiting. More...

Macros
#define	containerof(ptr, type, member)   ((type *) (((char *) ptr) - offsetof(type, member)))
#define	lengthof(x)   ((sizeof(x) / sizeof(*(x))))
#define	verify(x)   assert(x)
#define	RATELIMIT_TO(n, window, fn)
	Ratelimit a single expression. More...
#define	RATELIMIT(fn)   RATELIMIT_TO(3, 10, fn)
	Ratelimit a single expression using default ratelimiter values. More...

Functions
int32_t	cyclecmp32 (uint32_t a, uint32_t b)
	Compares values that may be subject to overflow. More...
bool	ratelimit_check (ratelimit_state_t *rs, uint32_t n, uint32_t window)
	Check that the rate limiter has not triggered. More...
void	rf_internal_out_of_memory (void)
void *	xmalloc (size_t sz)

Detailed Description

Utility functions that did not fit into other modules.

Macro Definition Documentation

#define containerof	(		ptr,
			type,
			member
	)		((type *) (((char *) ptr) - offsetof(type, member)))

This macro is similar to the Linux kernel's container_of() macro but doesn't use the GNU extension needed to assure type safety.

Definition at line 35 of file util.h.

#define lengthof

(

x

)

((sizeof(x) / sizeof(*(x))))

Determine the number of elements in a statically allocated array.

There's no compile-time checks to this macro. Abuse it and you'll just get the wrong result!

Definition at line 44 of file util.h.

#define RATELIMIT

(

fn

)

RATELIMIT_TO(3, 10, fn)

Ratelimit a single expression using default ratelimiter values.

Definition at line 106 of file util.h.

#define RATELIMIT_TO	(		n,
			window,
			fn
	)

Value:

{                                                                      \
                static ratelimit_state_t rs_;                                  \
                if (ratelimit_check(&rs_, n, window))                          \
                        (fn);                                                  \
        }

Ratelimit a single expression.

The expression will automatically be provides a private ratelimit_state_t;

Definition at line 96 of file util.h.

#define verify

(

x

)

assert(x)

Definition at line 55 of file util.h.

Function Documentation

int32_t cyclecmp32	(	uint32_t	a,
		uint32_t	b
	)

Compares values that may be subject to overflow.

This comparision assumes that 0 > 0xffffffff because, in 32-bit unsigned maths, 0 == 0xffffffff + 1. This is particular useful for working with 32-bit representations of time.

Returns

>0 if a > b

0 if a == b

<0 if a < b

Definition at line 19 of file util.c.

bool ratelimit_check	(	ratelimit_state_t *	rs,
		uint32_t	n,
		uint32_t	window
	)

Check that the rate limiter has not triggered.

The rate limiter will trigger if there are more than n events each window.

Returns

true, if the ratelimited activity should be performed; false otherwise.

Definition at line 24 of file util.c.

void rf_internal_out_of_memory

(

void

)

Out of memory hook.

Todo:

Currently out_of_memory cannot actually be hooked

Definition at line 40 of file util.c.

void* xmalloc

(

size_t

sz

)

Definition at line 45 of file util.c.