lib/argv_split.c

   1 /*
   2  * Helper function for splitting a string into an argv-like array.
   3  */
   4
   5 #include <linux/kernel.h>
   6 #include <linux/ctype.h>
   7 #include <linux/string.h>
   8 #include <linux/slab.h>
   9 #include <linux/export.h>
  10
  11 static int count_argc(const char *str)
  12 {
  13         int count = 0;
  14         bool was_space;
  15
  16         for (was_space = true; *str; str++) {
  17                 if (isspace(*str)) {
  18                         was_space = true;
  19                 } else if (was_space) {
  20                         was_space = false;
  21                         count++;
  22                 }
  23         }
  24
  25         return count;
  26 }
  27
  28 /**
  29  * argv_free - free an argv
  30  * @argv - the argument vector to be freed
  31  *
  32  * Frees an argv and the strings it points to.
  33  */
  34 void argv_free(char **argv)
  35 {
  36         argv--;
  37         kfree(argv[0]);
  38         kfree(argv);
  39 }
  40 EXPORT_SYMBOL(argv_free);
  41
  42 /**
  43  * argv_split - split a string at whitespace, returning an argv
  44  * @gfp: the GFP mask used to allocate memory
  45  * @str: the string to be split
  46  * @argcp: returned argument count
  47  *
  48  * Returns an array of pointers to strings which are split out from
  49  * @str.  This is performed by strictly splitting on white-space; no
  50  * quote processing is performed.  Multiple whitespace characters are
  51  * considered to be a single argument separator.  The returned array
  52  * is always NULL-terminated.  Returns NULL on memory allocation
  53  * failure.
  54  *
  55  * The source string at `str' may be undergoing concurrent alteration via
  56  * userspace sysctl activity (at least).  The argv_split() implementation
  57  * attempts to handle this gracefully by taking a local copy to work on.
  58  */
  59 char **argv_split(gfp_t gfp, const char *str, int *argcp)
  60 {
  61         char *argv_str;
  62         bool was_space;
  63         char **argv, **argv_ret;
  64         int argc;
  65
  66         argv_str = kstrndup(str, KMALLOC_MAX_SIZE - 1, gfp);
  67         if (!argv_str)
  68                 return NULL;
  69
  70         argc = count_argc(argv_str);
  71         argv = kmalloc(sizeof(*argv) * (argc + 2), gfp);
  72         if (!argv) {
  73                 kfree(argv_str);
  74                 return NULL;
  75         }
  76
  77         *argv = argv_str;
  78         argv_ret = ++argv;
  79         for (was_space = true; *argv_str; argv_str++) {
  80                 if (isspace(*argv_str)) {
  81                         was_space = true;
  82                         *argv_str = 0;
  83                 } else if (was_space) {
  84                         was_space = false;
  85                         *argv++ = argv_str;
  86                 }
  87         }
  88         *argv = NULL;
  89
  90         if (argcp)
  91                 *argcp = argc;
  92         return argv_ret;
  93 }
  94 EXPORT_SYMBOL(argv_split);