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 /*
  18  * Pointer dereferencing. We don't trust the shm_ref, so we validate
  19  * both the index and offset with known boundaries.
  20  */
  21 static inline
  22 char *_shmp_offset(struct shm_object_table *table, struct shm_ref *ref,
  23                    size_t idx, size_t elem_size)
  24 {
  25         struct shm_object *obj;
  26         size_t objindex, ref_offset;
  27
  28         objindex = (size_t) ref->index;
  29         if (unlikely(objindex >= table->allocated_len))
  30                 return NULL;
  31         obj = &table->objects[objindex];
  32         ref_offset = (size_t) ref->offset;
  33         ref_offset += idx * elem_size;
  34         /* Check if part of the element returned would exceed the limits. */
  35         if (unlikely(ref_offset + elem_size > obj->memory_map_size))
  36                 return NULL;
  37         return &obj->memory_map[ref_offset];
  38 }
  39
  40 #define shmp_index(handle, ref, index)                                  \
  41         ({                                                              \
  42                 __typeof__((ref)._type) ____ptr_ret;                    \
  43                 ____ptr_ret = (__typeof__(____ptr_ret)) _shmp_offset((handle)->table, &(ref)._ref, index, sizeof(*____ptr_ret));        \
  44                 ____ptr_ret;                                            \
  45         })
  46
  47 #define shmp(handle, ref)       shmp_index(handle, ref, 0)
  48
  49 static inline
  50 void _set_shmp(struct shm_ref *ref, struct shm_ref src)
  51 {
  52         *ref = src;
  53 }
  54
  55 #define set_shmp(ref, src)      _set_shmp(&(ref)._ref, src)
  56
  57 struct shm_object_table *shm_object_table_create(size_t max_nb_obj);
  58 void shm_object_table_destroy(struct shm_object_table *table);
  59 struct shm_object *shm_object_table_append(struct shm_object_table *table,
  60                                            size_t memory_map_size);
  61
  62 /*
  63  * zalloc_shm - allocate memory within a shm object.
  64  *
  65  * Shared memory is already zeroed by shmget.
  66  * *NOT* multithread-safe (should be protected by mutex).
  67  * Returns a -1, -1 tuple on error.
  68  */
  69 struct shm_ref zalloc_shm(struct shm_object *obj, size_t len);
  70 void align_shm(struct shm_object *obj, size_t align);
  71
  72 static inline
  73 int shm_get_wakeup_fd(struct shm_handle *handle, struct shm_ref *ref)
  74 {
  75         struct shm_object_table *table = handle->table;
  76         struct shm_object *obj;
  77         size_t index;
  78
  79         index = (size_t) ref->index;
  80         if (unlikely(index >= table->allocated_len))
  81                 return -EPERM;
  82         obj = &table->objects[index];
  83         return obj->wait_fd[1];
  84
  85 }
  86
  87 static inline
  88 int shm_get_wait_fd(struct shm_handle *handle, struct shm_ref *ref)
  89 {
  90         struct shm_object_table *table = handle->table;
  91         struct shm_object *obj;
  92         size_t index;
  93
  94         index = (size_t) ref->index;
  95         if (unlikely(index >= table->allocated_len))
  96                 return -EPERM;
  97         obj = &table->objects[index];
  98         return obj->wait_fd[0];
  99 }
 100
 101 #endif /* _LIBRINGBUFFER_SHM_H */