lib/registry.c

   1 /*
   2  * BabelTrace
   3  *
   4  * Format Registry
   5  *
   6  * Copyright 2010-2011 EfficiOS Inc. and Linux Foundation
   7  *
   8  * Author: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   9  *
  10  * Permission is hereby granted, free of charge, to any person obtaining a copy
  11  * of this software and associated documentation files (the "Software"), to deal
  12  * in the Software without restriction, including without limitation the rights
  13  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  14  * copies of the Software, and to permit persons to whom the Software is
  15  * furnished to do so, subject to the following conditions:
  16  *
  17  * The above copyright notice and this permission notice shall be included in
  18  * all copies or substantial portions of the Software.
  19  *
  20  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  21  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  22  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  23  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  24  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  25  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  26  * SOFTWARE.
  27  */
  28
  29 #include <babeltrace/format.h>
  30 #include <glib.h>
  31 #include <errno.h>
  32 #include <stdio.h>
  33 #include <assert.h>
  34
  35 struct walk_data {
  36         FILE *fp;
  37         int iter;
  38 };
  39
  40 /*
  41  * Format registry hash table contains the registered formats. Format
  42  * registration is typically performed by a format plugin.
  43  */
  44 static GHashTable *format_registry;
  45 static int format_refcount;
  46 static int init_done;
  47
  48 static __attribute__((constructor)) void format_init(void);
  49
  50 static
  51 void format_refcount_inc(void)
  52 {
  53         format_refcount++;
  54 }
  55
  56 static
  57 void format_cleanup(void)
  58 {
  59         if (format_registry)
  60                 g_hash_table_destroy(format_registry);
  61 }
  62
  63 static
  64 void format_refcount_dec(void)
  65 {
  66         if (!--format_refcount)
  67                 format_cleanup();
  68 }
  69
  70 struct bt_format *bt_lookup_format(bt_intern_str name)
  71 {
  72         if (!init_done)
  73                 return NULL;
  74
  75         return g_hash_table_lookup(format_registry,
  76                                    (gconstpointer) GUINT_TO_POINTER(name));
  77 }
  78
  79 static void show_format(gpointer key, gpointer value, gpointer user_data)
  80 {
  81         struct walk_data *data = user_data;
  82
  83         fprintf(data->fp, "%s%s", data->iter ? ", " : "",
  84                 g_quark_to_string((GQuark) GPOINTER_TO_UINT(key)));
  85         data->iter++;
  86 }
  87
  88 void bt_fprintf_format_list(FILE *fp)
  89 {
  90         struct walk_data data;
  91
  92         assert(fp);
  93
  94         data.fp = fp;
  95         data.iter = 0;
  96
  97         fprintf(fp, "Formats available: ");
  98         if (!init_done)
  99                 return;
 100         g_hash_table_foreach(format_registry, show_format, &data);
 101         if (data.iter == 0)
 102                 fprintf(fp, "<none>");
 103         fprintf(fp, ".\n");
 104 }
 105
 106 int bt_register_format(struct bt_format *format)
 107 {
 108         if (!format)
 109                 return -EINVAL;
 110
 111         if (!init_done)
 112                 format_init();
 113
 114         if (bt_lookup_format(format->name))
 115                 return -EEXIST;
 116
 117         format_refcount_inc();
 118         g_hash_table_insert(format_registry,
 119                             GUINT_TO_POINTER(format->name),
 120                             format);
 121         return 0;
 122 }
 123
 124 void bt_unregister_format(struct bt_format *format)
 125 {
 126         assert(bt_lookup_format(format->name));
 127         g_hash_table_remove(format_registry,
 128                             GUINT_TO_POINTER(format->name));
 129         format_refcount_dec();
 130 }
 131
 132 /*
 133  * We cannot assume that the constructor and destructor order will be
 134  * right: another library might be loaded before us, and initialize us
 135  * from bt_register_format(). This is why we use a reference count to
 136  * handle cleanup of this module. The format_finalize destructor
 137  * refcount decrement matches format_init refcount increment.
 138  */
 139 static __attribute__((constructor))
 140 void format_init(void)
 141 {
 142         if (init_done)
 143                 return;
 144         format_refcount_inc();
 145         format_registry = g_hash_table_new(g_direct_hash, g_direct_equal);
 146         assert(format_registry);
 147         init_done = 1;
 148 }
 149
 150 static __attribute__((destructor))
 151 void format_finalize(void)
 152 {
 153         format_refcount_dec();
 154 }