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Linux/lib/argv_split.c

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  1 // SPDX-License-Identifier: GPL-2.0
  2 /*
  3  * Helper function for splitting a string into an argv-like array.
  4  */
  5 
  6 #include <linux/kernel.h>
  7 #include <linux/ctype.h>
  8 #include <linux/string.h>
  9 #include <linux/slab.h>
 10 #include <linux/export.h>
 11 
 12 static int count_argc(const char *str)
 13 {
 14         int count = 0;
 15         bool was_space;
 16 
 17         for (was_space = true; *str; str++) {
 18                 if (isspace(*str)) {
 19                         was_space = true;
 20                 } else if (was_space) {
 21                         was_space = false;
 22                         count++;
 23                 }
 24         }
 25 
 26         return count;
 27 }
 28 
 29 /**
 30  * argv_free - free an argv
 31  * @argv - the argument vector to be freed
 32  *
 33  * Frees an argv and the strings it points to.
 34  */
 35 void argv_free(char **argv)
 36 {
 37         argv--;
 38         kfree(argv[0]);
 39         kfree(argv);
 40 }
 41 EXPORT_SYMBOL(argv_free);
 42 
 43 /**
 44  * argv_split - split a string at whitespace, returning an argv
 45  * @gfp: the GFP mask used to allocate memory
 46  * @str: the string to be split
 47  * @argcp: returned argument count
 48  *
 49  * Returns an array of pointers to strings which are split out from
 50  * @str.  This is performed by strictly splitting on white-space; no
 51  * quote processing is performed.  Multiple whitespace characters are
 52  * considered to be a single argument separator.  The returned array
 53  * is always NULL-terminated.  Returns NULL on memory allocation
 54  * failure.
 55  *
 56  * The source string at `str' may be undergoing concurrent alteration via
 57  * userspace sysctl activity (at least).  The argv_split() implementation
 58  * attempts to handle this gracefully by taking a local copy to work on.
 59  */
 60 char **argv_split(gfp_t gfp, const char *str, int *argcp)
 61 {
 62         char *argv_str;
 63         bool was_space;
 64         char **argv, **argv_ret;
 65         int argc;
 66 
 67         argv_str = kstrndup(str, KMALLOC_MAX_SIZE - 1, gfp);
 68         if (!argv_str)
 69                 return NULL;
 70 
 71         argc = count_argc(argv_str);
 72         argv = kmalloc_array(argc + 2, sizeof(*argv), gfp);
 73         if (!argv) {
 74                 kfree(argv_str);
 75                 return NULL;
 76         }
 77 
 78         *argv = argv_str;
 79         argv_ret = ++argv;
 80         for (was_space = true; *argv_str; argv_str++) {
 81                 if (isspace(*argv_str)) {
 82                         was_space = true;
 83                         *argv_str = 0;
 84                 } else if (was_space) {
 85                         was_space = false;
 86                         *argv++ = argv_str;
 87                 }
 88         }
 89         *argv = NULL;
 90 
 91         if (argcp)
 92                 *argcp = argc;
 93         return argv_ret;
 94 }
 95 EXPORT_SYMBOL(argv_split);
 96 

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