xapian-core/common/proc_uuid.cc

   1 /** @file proc_uuid.cc
   2  * @brief Generate UUIDs by reading from a pseudo-file under /proc
   3  *
   4  * Especially useful when building for Android, as it avoids having to
   5  * cross-build a UUID library.
   6  */
   7 /* Copyright (C) 2008 Lemur Consulting Ltd
   8  * Copyright (C) 2013,2015,2016,2017 Olly Betts
   9  *
  10  * This program is free software; you can redistribute it and/or modify
  11  * it under the terms of the GNU General Public License as published by
  12  * the Free Software Foundation; either version 2 of the License, or
  13  * (at your option) any later version.
  14  *
  15  * This program is distributed in the hope that it will be useful,
  16  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  17  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18  * GNU General Public License for more details.
  19  *
  20  * You should have received a copy of the GNU General Public License
  21  * along with this program; if not, write to the Free Software
  22  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
  23  */
  24
  25 #include <config.h>
  26
  27 #include "proc_uuid.h"
  28
  29 #include "xapian/error.h"
  30
  31 #include <cstring>
  32 #include "stringutils.h"
  33
  34 #include <sys/types.h>
  35 #include "safesysstat.h"
  36 #include "safeerrno.h"
  37 #include "safefcntl.h"
  38 #include "safeunistd.h"
  39
  40 using namespace std;
  41
  42 /// The size of a UUID in bytes.
  43 const size_t UUID_SIZE = 16;
  44
  45 /// The size of a UUID string in bytes (not including trailing '\0').
  46 const size_t UUID_STRING_SIZE = 36;
  47
  48 void
  49 uuid_generate(uuid_t uu)
  50 {
  51     char buf[UUID_STRING_SIZE];
  52     int fd = open("/proc/sys/kernel/random/uuid", O_RDONLY);
  53     if (rare(fd == -1)) {
  54         throw Xapian::DatabaseCreateError("Opening UUID generator failed", errno);
  55     }
  56     if (read(fd, buf, UUID_STRING_SIZE) != UUID_STRING_SIZE) {
  57         close(fd);
  58         throw Xapian::DatabaseCreateError("Generating UUID failed");
  59     }
  60     close(fd);
  61     uuid_parse(buf, uu);
  62 }
  63
  64 int
  65 uuid_parse(const char * in, uuid_t uu)
  66 {
  67     for (unsigned i = 0; i != UUID_SIZE; ++i) {
  68         uu[i] = hex_digit(in[0]) << 4 | hex_digit(in[1]);
  69         in += ((0x2a8 >> i) & 1) | 2;
  70     }
  71     return 0;
  72 }
  73
  74 void uuid_unparse_lower(const uuid_t uu, char * out)
  75 {
  76     for (unsigned i = 0; i != UUID_SIZE; ++i) {
  77         unsigned char ch = uu[i];
  78         *out++ = "0123456789abcdef"[ch >> 4];
  79         *out++ = "0123456789abcdef"[ch & 0x0f];
  80         if ((0x2a8 >> i) & 1)
  81            *out++ = '-';
  82     }
  83     *out = '\0';
  84 }
  85
  86 void uuid_clear(uuid_t uu)
  87 {
  88     memset(uu, 0, UUID_SIZE);
  89 }
  90
  91 int uuid_is_null(const uuid_t uu)
  92 {
  93     unsigned i = 0;
  94     while (i < UUID_SIZE) {
  95         if (uu[i++])
  96             return 0;
  97     }
  98     return 1;
  99 }