util/id.c

   1 /*
   2  * Dealing with identifiers
   3  *
   4  * Copyright (C) 2014 Red Hat, Inc.
   5  *
   6  * Authors:
   7  *  Markus Armbruster <armbru@redhat.com>,
   8  *
   9  * This work is licensed under the terms of the GNU LGPL, version 2.1
  10  * or later.  See the COPYING.LIB file in the top-level directory.
  11  */
  12
  13 #include "qemu-common.h"
  14
  15 bool id_wellformed(const char *id)
  16 {
  17     int i;
  18
  19     if (!qemu_isalpha(id[0])) {
  20         return false;
  21     }
  22     for (i = 1; id[i]; i++) {
  23         if (!qemu_isalnum(id[i]) && !strchr("-._", id[i])) {
  24             return false;
  25         }
  26     }
  27     return true;
  28 }
  29
  30 #define ID_SPECIAL_CHAR '#'
  31
  32 static const char *const id_subsys_str[ID_MAX] = {
  33     [ID_QDEV]  = "qdev",
  34     [ID_BLOCK] = "block",
  35 };
  36
  37 /*
  38  *  Generates an ID of the form PREFIX SUBSYSTEM NUMBER
  39  *  where:
  40  *
  41  *  - PREFIX is the reserved character '#'
  42  *  - SUBSYSTEM identifies the subsystem creating the ID
  43  *  - NUMBER is a decimal number unique within SUBSYSTEM.
  44  *
  45  *    Example: "#block146"
  46  *
  47  * Note that these IDs do not satisfy id_wellformed().
  48  *
  49  * The caller is responsible for freeing the returned string with g_free()
  50  */
  51 char *id_generate(IdSubSystems id)
  52 {
  53     static uint64_t id_counters[ID_MAX];
  54     uint32_t rnd;
  55
  56     assert(id < ARRAY_SIZE(id_subsys_str));
  57     assert(id_subsys_str[id]);
  58
  59     rnd = g_random_int_range(0, 100);
  60
  61     return g_strdup_printf("%c%s%" PRIu64 "%02" PRId32, ID_SPECIAL_CHAR,
  62                                                         id_subsys_str[id],
  63                                                         id_counters[id]++,
  64                                                         rnd);
  65 }