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 { int dummy; };
  51 #endif
  52
  53 #ifndef HAVE_QOBJ_NODETYPE_CAPNP
  54 #define HAVE_QOBJ_NODETYPE_CAPNP -1
  55 struct qobj_nodetype_capnp { int dummy; };
  56 #endif
  57
  58 /* each different kind of object will have a global variable of this type,
  59  * which can be used by various other pieces to store type-related bits.
  60  * type equality can be tested as pointer equality. (cf. QOBJ_GET_TYPESAFE)
  61  */
  62 struct qobj_nodetype {
  63         ptrdiff_t node_member_offset;
  64         RESERVED_SPACE_STRUCT(qobj_nodetype_cli, cli, 256)
  65         RESERVED_SPACE_STRUCT(qobj_nodetype_capnp, capnp, 256)
  66 };
  67
  68 /* anchor to be embedded somewhere in the object's struct */
  69 struct qobj_node {
  70         uint64_t nid;
  71         struct qobj_nodetype *type;
  72 };
  73
  74 #define QOBJ_FIELDS \
  75         struct qobj_node qobj_node;
  76
  77 /* call these at the end of any _create function (QOBJ_REG)
  78  * and beginning of any _destroy function (QOBJ_UNREG) */
  79 #define QOBJ_REG(n, structname) \
  80         qobj_reg(&n->qobj_node, &qobj_t_ ## structname)
  81 #define QOBJ_UNREG(n) \
  82         qobj_unreg(&n->qobj_node)
  83
  84 /* internals - should not be directly used without a good reason*/
  85 void qobj_reg(struct qobj_node *node, struct qobj_nodetype *type);
  86 void qobj_unreg(struct qobj_node *node);
  87 struct qobj_node *qobj_get(uint64_t id);
  88 void *qobj_get_typed(uint64_t id, struct qobj_nodetype *type);
  89
  90 /* type declarations */
  91 #define DECLARE_QOBJ_TYPE(structname) \
  92         extern struct qobj_nodetype qobj_t_ ## structname;
  93 #define DEFINE_QOBJ_TYPE(structname) \
  94         struct qobj_nodetype qobj_t_ ## structname = { \
  95                 .node_member_offset = \
  96                         (ptrdiff_t)offsetof(struct structname, qobj_node) \
  97         };
  98 #define DEFINE_QOBJ_TYPE_INIT(structname, ...) \
  99         struct qobj_nodetype qobj_t_ ## structname = { \
 100                 .node_member_offset = \
 101                         (ptrdiff_t)offsetof(struct structname, qobj_node), \
 102                 __VA_ARGS__ \
 103         };
 104
 105 /* ID dereference with typecheck.
 106  * will return NULL if id not found or wrong type. */
 107 #define QOBJ_GET_TYPESAFE(id, structname) \
 108         ((struct structname *)qobj_get_typed((id), &qobj_t_ ## structname))
 109
 110 #define QOBJ_ID(ptr) \
 111         ((ptr)->qobj_node.nid)
 112 #define QOBJ_ID_0SAFE(ptr) \
 113         ({ typeof (ptr) _ptr = (ptr); _ptr ? _ptr->qobj_node.nid : 0ULL; })
 114
 115 void qobj_init(void);
 116 void qobj_finish(void);
 117
 118 #endif /* _QOBJ_H */