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/osdep.h"
  14 #include "qemu-common.h"
  15
  16 bool id_wellformed(const char *id)
  17 {
  18     int i;
  19
  20     if (!qemu_isalpha(id[0])) {
  21         return false;
  22     }
  23     for (i = 1; id[i]; i++) {
  24         if (!qemu_isalnum(id[i]) && !strchr("-._", id[i])) {
  25             return false;
  26         }
  27     }
  28     return true;
  29 }
  30
  31 #define ID_SPECIAL_CHAR '#'
  32
  33 static const char *const id_subsys_str[ID_MAX] = {
  34     [ID_QDEV]  = "qdev",
  35     [ID_BLOCK] = "block",
  36 };
  37
  38 /*
  39  *  Generates an ID of the form PREFIX SUBSYSTEM NUMBER
  40  *  where:
  41  *
  42  *  - PREFIX is the reserved character '#'
  43  *  - SUBSYSTEM identifies the subsystem creating the ID
  44  *  - NUMBER is a decimal number unique within SUBSYSTEM.
  45  *
  46  *    Example: "#block146"
  47  *
  48  * Note that these IDs do not satisfy id_wellformed().
  49  *
  50  * The caller is responsible for freeing the returned string with g_free()
  51  */
  52 char *id_generate(IdSubSystems id)
  53 {
  54     static uint64_t id_counters[ID_MAX];
  55     uint32_t rnd;
  56
  57     assert(id < ARRAY_SIZE(id_subsys_str));
  58     assert(id_subsys_str[id]);
  59
  60     rnd = g_random_int_range(0, 100);
  61
  62     return g_strdup_printf("%c%s%" PRIu64 "%02" PRId32, ID_SPECIAL_CHAR,
  63                                                         id_subsys_str[id],
  64                                                         id_counters[id]++,
  65                                                         rnd);
  66 }