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
  21 #include <babeltrace/format.h>
  22 #include <glib.h>
  23 #include <errno.h>
  24 #include <stdio.h>
  25 #include <assert.h>
  26
  27 struct walk_data {
  28         FILE *fp;
  29         int iter;
  30 };
  31
  32 /*
  33  * Format registry hash table contains the registered formats. Format
  34  * registration is typically performed by a format plugin.
  35  */
  36 static GHashTable *format_registry;
  37 static int format_refcount;
  38 static int init_done;
  39
  40 static __attribute__((constructor)) void format_init(void);
  41
  42 static
  43 void format_refcount_inc(void)
  44 {
  45         format_refcount++;
  46 }
  47
  48 static
  49 void format_cleanup(void)
  50 {
  51         if (format_registry)
  52                 g_hash_table_destroy(format_registry);
  53 }
  54
  55 static
  56 void format_refcount_dec(void)
  57 {
  58         if (!--format_refcount)
  59                 format_cleanup();
  60 }
  61
  62 struct format *bt_lookup_format(bt_intern_str name)
  63 {
  64         if (!init_done)
  65                 return NULL;
  66
  67         return g_hash_table_lookup(format_registry,
  68                                    (gconstpointer) (unsigned long) name);
  69 }
  70
  71 static void show_format(gpointer key, gpointer value, gpointer user_data)
  72 {
  73         struct walk_data *data = user_data;
  74
  75         fprintf(data->fp, "%s%s", data->iter ? ", " : "",
  76                 g_quark_to_string((GQuark) (unsigned long) key));
  77         data->iter++;
  78 }
  79
  80 void bt_fprintf_format_list(FILE *fp)
  81 {
  82         struct walk_data data;
  83
  84         assert(fp);
  85
  86         data.fp = fp;
  87         data.iter = 0;
  88
  89         fprintf(fp, "Formats available: ");
  90         if (!init_done)
  91                 return;
  92         g_hash_table_foreach(format_registry, show_format, &data);
  93         if (data.iter == 0)
  94                 fprintf(fp, "<none>");
  95         fprintf(fp, ".\n");
  96 }
  97
  98 int bt_register_format(struct format *format)
  99 {
 100         if (!format)
 101                 return -EINVAL;
 102
 103         if (!init_done)
 104                 format_init();
 105
 106         if (bt_lookup_format(format->name))
 107                 return -EEXIST;
 108
 109         format_refcount_inc();
 110         g_hash_table_insert(format_registry,
 111                             (gpointer) (unsigned long) format->name,
 112                             format);
 113         return 0;
 114 }
 115
 116 void bt_unregister_format(struct format *format)
 117 {
 118         assert(bt_lookup_format(format->name));
 119         g_hash_table_remove(format_registry,
 120                             (gpointer) (unsigned long) format->name);
 121         format_refcount_dec();
 122 }
 123
 124 /*
 125  * We cannot assume that the constructor and destructor order will be
 126  * right: another library might be loaded before us, and initialize us
 127  * from bt_register_format(). This is why we use a reference count to
 128  * handle cleanup of this module. The format_finalize destructor
 129  * refcount decrement matches format_init refcount increment.
 130  */
 131 static __attribute__((constructor))
 132 void format_init(void)
 133 {
 134         if (init_done)
 135                 return;
 136         format_refcount_inc();
 137         format_registry = g_hash_table_new(g_direct_hash, g_direct_equal);
 138         assert(format_registry);
 139         init_done = 1;
 140 }
 141
 142 static __attribute__((destructor))
 143 void format_finalize(void)
 144 {
 145         format_refcount_dec();
 146 }