Root/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
11static 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 */
34void argv_free(char **argv)
35{
36    argv--;
37    kfree(argv[0]);
38    kfree(argv);
39}
40EXPORT_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 */
59char **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}
94EXPORT_SYMBOL(argv_split);
95

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