sysdeps/unix/sysv/linux/procutils.c

   1 /* Utilities functions to read/parse Linux procfs and sysfs.
   2    Copyright (C) 2023 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 #include <assert.h>
  20 #include <not-cancel.h>
  21 #include <procutils.h>
  22 #include <string.h>
  23
  24 static int
  25 next_line (char **r, int fd, char *const buffer, char **cp, char **re,
  26            char *const buffer_end)
  27 {
  28   char *res = *cp;
  29   char *nl = memchr (*cp, '\n', *re - *cp);
  30   if (nl == NULL)
  31     {
  32       if (*cp != buffer)
  33         {
  34           if (*re == buffer_end)
  35             {
  36               memmove (buffer, *cp, *re - *cp);
  37               *re = buffer + (*re - *cp);
  38               *cp = buffer;
  39
  40               ssize_t n = TEMP_FAILURE_RETRY (
  41                 __read_nocancel (fd, *re, buffer_end - *re));
  42               if (n < 0)
  43                 return -1;
  44
  45               *re += n;
  46
  47               nl = memchr (*cp, '\n', *re - *cp);
  48               if (nl == NULL)
  49                 /* Line too long.  */
  50                 return 0;
  51             }
  52           else
  53             nl = memchr (*cp, '\n', *re - *cp);
  54
  55           res = *cp;
  56         }
  57
  58       if (nl == NULL)
  59         nl = *re - 1;
  60     }
  61
  62   *nl = '\0';
  63   *cp = nl + 1;
  64   assert (*cp <= *re);
  65
  66   if (res == *re)
  67     return 0;
  68
  69   *r = res;
  70   return 1;
  71 }
  72
  73 bool
  74 procutils_read_file (const char *filename, procutils_closure_t closure,
  75                      void *arg)
  76 {
  77   enum { buffer_size = PROCUTILS_MAX_LINE_LEN };
  78   char buffer[buffer_size];
  79   char *buffer_end = buffer + buffer_size;
  80   char *cp = buffer_end;
  81   char *re = buffer_end;
  82
  83   int fd = TEMP_FAILURE_RETRY (
  84     __open64_nocancel (filename, O_RDONLY | O_CLOEXEC));
  85   if (fd == -1)
  86     return false;
  87
  88   char *l;
  89   int r;
  90   while ((r = next_line (&l, fd, buffer, &cp, &re, buffer_end)) > 0)
  91     if (closure (l, arg) != 0)
  92       break;
  93
  94   __close_nocancel_nostatus (fd);
  95
  96   return r == 1;
  97 }