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/ctype.h"
  15 #include "qemu/id.h"
  16
  17 bool id_wellformed(const char *id)
  18 {
  19     int i;
  20
  21     if (!qemu_isalpha(id[0])) {
  22         return false;
  23     }
  24     for (i = 1; id[i]; i++) {
  25         if (!qemu_isalnum(id[i]) && !strchr("-._", id[i])) {
  26             return false;
  27         }
  28     }
  29     return true;
  30 }
  31
  32 #define ID_SPECIAL_CHAR '#'
  33
  34 static const char *const id_subsys_str[ID_MAX] = {
  35     [ID_QDEV]  = "qdev",
  36     [ID_BLOCK] = "block",
  37     [ID_CHR] = "chr",
  38     [ID_NET] = "net",
  39 };
  40
  41 /*
  42  *  Generates an ID of the form PREFIX SUBSYSTEM NUMBER
  43  *  where:
  44  *
  45  *  - PREFIX is the reserved character '#'
  46  *  - SUBSYSTEM identifies the subsystem creating the ID
  47  *  - NUMBER is a decimal number unique within SUBSYSTEM.
  48  *
  49  *    Example: "#block146"
  50  *
  51  * Note that these IDs do not satisfy id_wellformed().
  52  *
  53  * The caller is responsible for freeing the returned string with g_free()
  54  */
  55 char *id_generate(IdSubSystems id)
  56 {
  57     static uint64_t id_counters[ID_MAX];
  58     uint32_t rnd;
  59
  60     assert(id < ARRAY_SIZE(id_subsys_str));
  61     assert(id_subsys_str[id]);
  62
  63     rnd = g_random_int_range(0, 100);
  64
  65     return g_strdup_printf("%c%s%" PRIu64 "%02" PRId32, ID_SPECIAL_CHAR,
  66                                                         id_subsys_str[id],
  67                                                         id_counters[id]++,
  68                                                         rnd);
  69 }