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 #include "typesafe.h"
  25
  26 #ifdef __cplusplus
  27 extern "C" {
  28 #endif
  29
  30 /* reserve a specific amount of bytes for a struct, which can grow up to
  31  * that size (or be dummy'd out if not needed)
  32  *
  33  * note the padding's array size will be an error if it gets negative or zero;
  34  * this is intentional to prevent the struct from growing beyond the allocated
  35  * space.
  36  */
  37 #ifndef __cplusplus
  38 #define RESERVED_SPACE_STRUCT(name, fieldname, size)                           \
  39         struct {                                                               \
  40                 struct name fieldname;                                         \
  41                 char padding##fieldname[size - sizeof(struct name)];           \
  42         };
  43 #else
  44 #define RESERVED_SPACE_STRUCT(name, fieldname, size)                           \
  45         struct name fieldname;                                                 \
  46         char padding##fieldname[size - sizeof(struct name)];
  47 #endif
  48
  49 /* don't need struct definitions for these here.  code actually using
  50  * these needs to define the struct *before* including this header.
  51  * HAVE_QOBJ_xxx should be defined to +1 in that case, like this:
  52  *
  53  * #if defined(HAVE_QOBJ_NODETYPE_CLI) && HAVE_QOBJ_NODETYPE_CLI < 0
  54  * #error include files are in wrong order
  55  * #else
  56  * #define HAVE_QOBJ_NODETYPE_CLI 1
  57  * struct qobj_nodetype_cli { ... }
  58  * #endif
  59  */
  60 #ifndef HAVE_QOBJ_NODETYPE_CLI
  61 #define HAVE_QOBJ_NODETYPE_CLI -1
  62 struct qobj_nodetype_cli {
  63         int dummy;
  64 };
  65 #endif
  66
  67 #ifndef HAVE_QOBJ_NODETYPE_CAPNP
  68 #define HAVE_QOBJ_NODETYPE_CAPNP -1
  69 struct qobj_nodetype_capnp {
  70         int dummy;
  71 };
  72 #endif
  73
  74 #include "typesafe.h"
  75
  76 /* each different kind of object will have a global variable of this type,
  77  * which can be used by various other pieces to store type-related bits.
  78  * type equality can be tested as pointer equality. (cf. QOBJ_GET_TYPESAFE)
  79  */
  80 struct qobj_nodetype {
  81         ptrdiff_t node_member_offset;
  82         RESERVED_SPACE_STRUCT(qobj_nodetype_cli, cli, 256)
  83         RESERVED_SPACE_STRUCT(qobj_nodetype_capnp, capnp, 256)
  84 };
  85
  86 PREDECL_HASH(qobj_nodes);
  87
  88 /* anchor to be embedded somewhere in the object's struct */
  89 struct qobj_node {
  90         uint64_t nid;
  91         struct qobj_nodes_item nodehash;
  92         const struct qobj_nodetype *type;
  93 };
  94
  95 #define QOBJ_FIELDS struct qobj_node qobj_node
  96
  97 /* call these at the end of any _create function (QOBJ_REG)
  98  * and beginning of any _destroy function (QOBJ_UNREG) */
  99 #define QOBJ_REG(n, structname) qobj_reg(&n->qobj_node, &qobj_t_##structname)
 100 #define QOBJ_UNREG(n) qobj_unreg(&n->qobj_node)
 101
 102 /* internals - should not be directly used without a good reason
 103  *
 104  * note: qobj_get is essentially never safe to use in MT context because
 105  * the object could be deleted by another thread -- and worse, it could be
 106  * of the "wrong" type and deleted.
 107  *
 108  * with qobj_get_typed, the type check is done under lock, which means that
 109  * it can be used as long as another lock prevents the deletion of objects
 110  * of the expected type.
 111  *
 112  * in the long this may need another touch, e.g. built-in per-object locking.
 113  */
 114 void qobj_reg(struct qobj_node *node, const struct qobj_nodetype *type);
 115 void qobj_unreg(struct qobj_node *node);
 116 struct qobj_node *qobj_get(uint64_t id);
 117 void *qobj_get_typed(uint64_t id, const struct qobj_nodetype *type);
 118
 119 /* type declarations */
 120 #define DECLARE_QOBJ_TYPE(structname)                                          \
 121         extern const struct qobj_nodetype qobj_t_##structname                  \
 122         /* end */
 123 #define DEFINE_QOBJ_TYPE(structname)                                           \
 124         const struct qobj_nodetype qobj_t_##structname = {                     \
 125                 .node_member_offset =                                          \
 126                         (ptrdiff_t)offsetof(struct structname, qobj_node)}     \
 127         /* end */
 128 #define DEFINE_QOBJ_TYPE_INIT(structname, ...)                                 \
 129         const struct qobj_nodetype qobj_t_##structname = {                     \
 130                 .node_member_offset =                                          \
 131                         (ptrdiff_t)offsetof(struct structname, qobj_node),     \
 132                 __VA_ARGS__}                                                   \
 133         /* end */
 134
 135 /* ID dereference with typecheck.
 136  * will return NULL if id not found or wrong type. */
 137 #define QOBJ_GET_TYPESAFE(id, structname)                                      \
 138         ((struct structname *)qobj_get_typed((id), &qobj_t_##structname))
 139
 140 #define QOBJ_ID(ptr) ((ptr)->qobj_node.nid)
 141 #define QOBJ_ID_0SAFE(ptr)                                                     \
 142         ({                                                                     \
 143                 typeof(ptr) _ptr = (ptr);                                      \
 144                 _ptr ? _ptr->qobj_node.nid : 0ULL;                             \
 145         })
 146
 147 void qobj_init(void);
 148 void qobj_finish(void);
 149
 150 #ifdef __cplusplus
 151 }
 152 #endif
 153
 154 #endif /* _QOBJ_H */