[lttng-ust.git] / libringbuffer / shm.h

#ifndef _LIBRINGBUFFER_SHM_H
#define _LIBRINGBUFFER_SHM_H

/*
 * libringbuffer/shm.h
 *
 * Copyright 2011 (c) - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
 *
 * Dual LGPL v2.1/GPL v2 license.
 */

#include <stdint.h>
#include "ust/core.h"

#define SHM_MAGIC	0x54335433
#define SHM_MAJOR	0
#define SHM_MINOR	1

/*
 * Defining a max shm offset, for debugging purposes.
 */
#if (CAA_BITS_PER_LONG == 32)
/* Define the maximum shared memory size to 128MB on 32-bit machines */
#define MAX_SHM_SIZE	134217728
#else
/* Define the maximum shared memory size to 8GB on 64-bit machines */
#define MAX_SHM_SIZE	8589934592
#endif

#define DECLARE_SHMP(type, name)	type *****name

struct shm_header {
	uint32_t magic;
	uint8_t major;
	uint8_t minor;
	uint8_t bits_per_long;
	size_t shm_size, shm_allocated;

	DECLARE_SHMP(struct channel, chan);
};

#define shmp(shm_offset)		\
	((__typeof__(****(shm_offset))) (((char *) &(shm_offset)) + (ptrdiff_t) (shm_offset)))

#define _shmp_abs(a)	((a < 0) ? -(a) : (a))

static inline
void _set_shmp(ptrdiff_t *shm_offset, void *ptr)
{
	*shm_offset = (((char *) ptr) - ((char *) shm_offset));
	assert(_shmp_abs(*shm_offset) < MAX_SHM_SIZE);
}

#define set_shmp(shm_offset, ptr)	\
	_set_shmp((ptrdiff_t *) ****(shm_offset), ptr)

/* Shared memory is already zeroed by shmget */
/* *NOT* multithread-safe (should be protected by mutex) */
static inline
void *zalloc_shm(struct shm_header *shm_header, size_t len)
{
	void *ret;

	if (shm_header->shm_size - shm_header->shm_allocated < len)
		return NULL;
	ret = (char *) shm_header + shm_header->shm_allocated;
	shm_header->shm_allocated += len;
	return ret;
}

#endif /* _LIBRINGBUFFER_SHM_H */
Commit	Line	Data
a6352fd4 MD	1	#ifndef _LIBRINGBUFFER_SHM_H
	2	#define _LIBRINGBUFFER_SHM_H
	3
	4	/*
	5	* libringbuffer/shm.h
	6	*
	7	* Copyright 2011 (c) - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
	8	*
	9	* Dual LGPL v2.1/GPL v2 license.
	10	*/
	11
	12	#include <stdint.h>
	13	#include "ust/core.h"
	14
	15	#define SHM_MAGIC 0x54335433
	16	#define SHM_MAJOR 0
	17	#define SHM_MINOR 1
	18
	19	/*
	20	* Defining a max shm offset, for debugging purposes.
	21	*/
	22	#if (CAA_BITS_PER_LONG == 32)
	23	/* Define the maximum shared memory size to 128MB on 32-bit machines */
	24	#define MAX_SHM_SIZE 134217728
	25	#else
	26	/* Define the maximum shared memory size to 8GB on 64-bit machines */
	27	#define MAX_SHM_SIZE 8589934592
	28	#endif
	29
	30	#define DECLARE_SHMP(type, name) type *****name
	31
	32	struct shm_header {
	33	uint32_t magic;
	34	uint8_t major;
	35	uint8_t minor;
	36	uint8_t bits_per_long;
	37	size_t shm_size, shm_allocated;
	38
	39	DECLARE_SHMP(struct channel, chan);
	40	};
	41
	42	#define shmp(shm_offset) \
	43	((__typeof__(***(shm_offset))) (((char ) &(shm_offset)) + (ptrdiff_t) (shm_offset)))
	44
	45	#define _shmp_abs(a) ((a < 0) ? -(a) : (a))
	46
	47	static inline
	48	void _set_shmp(ptrdiff_t shm_offset, void ptr)
	49	{
	50	shm_offset = (((char ) ptr) - ((char *) shm_offset));
	51	assert(_shmp_abs(*shm_offset) < MAX_SHM_SIZE);
	52	}
	53
	54	#define set_shmp(shm_offset, ptr) \
	55	_set_shmp((ptrdiff_t ) ***(shm_offset), ptr)
	56
	57	/* Shared memory is already zeroed by shmget */
	58	/* NOT multithread-safe (should be protected by mutex) */
	59	static inline
	60	void zalloc_shm(struct shm_header shm_header, size_t len)
	61	{
	62	void *ret;
	63
	64	if (shm_header->shm_size - shm_header->shm_allocated < len)
65	return NULL;
66	ret = (char *) shm_header + shm_header->shm_allocated;
67	shm_header->shm_allocated += len;
68	return ret;
69	}
70
71	#endif /* _LIBRINGBUFFER_SHM_H */