lib/qobj.h

   1 /*
   2  * Copyright (c) 2015-16  David Lamparter, for NetDEF, Inc.
   3  *
   4  * Permission to use, copy, modify, and distribute this software for any
   5  * purpose with or without fee is hereby granted, provided that the above
   6  * copyright notice and this permission notice appear in all copies.
   7  *
   8  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
   9  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  10  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  11  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  12  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  13  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  14  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  15  */
  16
  17 #ifndef _QOBJ_H
  18 #define _QOBJ_H
  19
  20 #include <stdint.h>
  21 #include <stdlib.h>
  22 #include <stddef.h>
  23
  24 /* reserve a specific amount of bytes for a struct, which can grow up to
  25  * that size (or be dummy'd out if not needed)
  26  *
  27  * note the padding's array size will be an error if it gets negative or zero;
  28  * this is intentional to prevent the struct from growing beyond the allocated
  29  * space.
  30  */
  31 #define RESERVED_SPACE_STRUCT(name, fieldname, size)                           \
  32         struct {                                                               \
  33                 struct name fieldname;                                         \
  34                 char padding##fieldname[size - sizeof(struct name)];           \
  35         };
  36
  37 /* don't need struct definitions for these here.  code actually using
  38  * these needs to define the struct *before* including this header.
  39  * HAVE_QOBJ_xxx should be defined to +1 in that case, like this:
  40  *
  41  * #if defined(HAVE_QOBJ_NODETYPE_CLI) && HAVE_QOBJ_NODETYPE_CLI < 0
  42  * #error include files are in wrong order
  43  * #else
  44  * #define HAVE_QOBJ_NODETYPE_CLI 1
  45  * struct qobj_nodetype_cli { ... }
  46  * #endif
  47  */
  48 #ifndef HAVE_QOBJ_NODETYPE_CLI
  49 #define HAVE_QOBJ_NODETYPE_CLI -1
  50 struct qobj_nodetype_cli {
  51         int dummy;
  52 };
  53 #endif
  54
  55 #ifndef HAVE_QOBJ_NODETYPE_CAPNP
  56 #define HAVE_QOBJ_NODETYPE_CAPNP -1
  57 struct qobj_nodetype_capnp {
  58         int dummy;
  59 };
  60 #endif
  61
  62 /* each different kind of object will have a global variable of this type,
  63  * which can be used by various other pieces to store type-related bits.
  64  * type equality can be tested as pointer equality. (cf. QOBJ_GET_TYPESAFE)
  65  */
  66 struct qobj_nodetype {
  67         ptrdiff_t node_member_offset;
  68         RESERVED_SPACE_STRUCT(qobj_nodetype_cli, cli, 256)
  69         RESERVED_SPACE_STRUCT(qobj_nodetype_capnp, capnp, 256)
  70 };
  71
  72 /* anchor to be embedded somewhere in the object's struct */
  73 struct qobj_node {
  74         uint64_t nid;
  75         struct qobj_nodetype *type;
  76 };
  77
  78 #define QOBJ_FIELDS struct qobj_node qobj_node;
  79
  80 /* call these at the end of any _create function (QOBJ_REG)
  81  * and beginning of any _destroy function (QOBJ_UNREG) */
  82 #define QOBJ_REG(n, structname) qobj_reg(&n->qobj_node, &qobj_t_##structname)
  83 #define QOBJ_UNREG(n) qobj_unreg(&n->qobj_node)
  84
  85 /* internals - should not be directly used without a good reason
  86  *
  87  * note: qobj_get is essentially never safe to use in MT context because
  88  * the object could be deleted by another thread -- and worse, it could be
  89  * of the "wrong" type and deleted.
  90  *
  91  * with qobj_get_typed, the type check is done under lock, which means that
  92  * it can be used as long as another lock prevents the deletion of objects
  93  * of the expected type.
  94  *
  95  * in the long this may need another touch, e.g. built-in per-object locking.
  96  */
  97 void qobj_reg(struct qobj_node *node, struct qobj_nodetype *type);
  98 void qobj_unreg(struct qobj_node *node);
  99 struct qobj_node *qobj_get(uint64_t id);
 100 void *qobj_get_typed(uint64_t id, struct qobj_nodetype *type);
 101
 102 /* type declarations */
 103 #define DECLARE_QOBJ_TYPE(structname)                                          \
 104         extern struct qobj_nodetype qobj_t_##structname;
 105 #define DEFINE_QOBJ_TYPE(structname)                                           \
 106         struct qobj_nodetype qobj_t_##structname = {                           \
 107                 .node_member_offset =                                          \
 108                         (ptrdiff_t)offsetof(struct structname, qobj_node)};
 109 #define DEFINE_QOBJ_TYPE_INIT(structname, ...)                                 \
 110         struct qobj_nodetype qobj_t_##structname = {                           \
 111                 .node_member_offset =                                          \
 112                         (ptrdiff_t)offsetof(struct structname, qobj_node),     \
 113                 __VA_ARGS__};
 114
 115 /* ID dereference with typecheck.
 116  * will return NULL if id not found or wrong type. */
 117 #define QOBJ_GET_TYPESAFE(id, structname)                                      \
 118         ((struct structname *)qobj_get_typed((id), &qobj_t_##structname))
 119
 120 #define QOBJ_ID(ptr) ((ptr)->qobj_node.nid)
 121 #define QOBJ_ID_0SAFE(ptr)                                                     \
 122         ({                                                                     \
 123                 typeof(ptr) _ptr = (ptr);                                      \
 124                 _ptr ? _ptr->qobj_node.nid : 0ULL;                             \
 125         })
 126
 127 void qobj_init(void);
 128 void qobj_finish(void);
 129
 130 #endif /* _QOBJ_H */