libringbuffer/shm.h

   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/usterr-signal-safe.h>
  14 #include "ust/core.h"
  15 #include "shm_types.h"
  16
  17 #define SHM_MAGIC       0x54335433
  18 #define SHM_MAJOR       0
  19 #define SHM_MINOR       1
  20
  21 /*
  22  * Pointer dereferencing. We don't trust the shm_ref, so we validate
  23  * both the index and offset with known boundaries.
  24  */
  25 static inline
  26 char *_shmp(struct shm_object_table *table, struct shm_ref *ref)
  27 {
  28         struct shm_object *obj;
  29         size_t index, offset;
  30
  31         index = (size_t) ref->index;
  32         if (unlikely(index >= table->allocated_len))
  33                 return NULL;
  34         obj = &table->objects[index];
  35         offset = (size_t) ref->offset;
  36         if (unlikely(offset >= obj->memory_map_size))
  37                 return NULL;
  38         return &obj->memory_map[offset];
  39 }
  40
  41 #define shmp(handle, ref)                                               \
  42         ({                                                              \
  43                 __typeof__((ref)._type) ____ptr_ret;                    \
  44                 ____ptr_ret = (__typeof__(____ptr_ret)) _shmp((handle)->table, &(ref)._ref);    \
  45                 ____ptr_ret;                                            \
  46         })
  47
  48 static inline
  49 void _set_shmp(struct shm_ref *ref, struct shm_ref src)
  50 {
  51         *ref = src;
  52 }
  53
  54 #define set_shmp(ref, src)      _set_shmp(&(ref)._ref, src)
  55
  56 struct shm_object_table *shm_object_table_create(size_t max_nb_obj);
  57 void shm_object_table_destroy(struct shm_object_table *table);
  58 struct shm_object *shm_object_table_append(struct shm_object_table *table,
  59                                            size_t memory_map_size);
  60
  61 /*
  62  * zalloc_shm - allocate memory within a shm object.
  63  *
  64  * Shared memory is already zeroed by shmget.
  65  * *NOT* multithread-safe (should be protected by mutex).
  66  * Returns a -1, -1 tuple on error.
  67  */
  68 struct shm_ref zalloc_shm(struct shm_object *obj, size_t len);
  69 void align_shm(struct shm_object *obj, size_t align);
  70
  71 #endif /* _LIBRINGBUFFER_SHM_H */