add argv_split()

argv_split() is a helper function which takes a string, splits it at
whitespace, and returns a NULL-terminated argv vector.  This is
deliberately simple - it does no quote processing of any kind.

[ Seems to me that this is something which is already being done in
  the kernel, but I couldn't find any other implementations, either to
  steal or replace.  Keep an eye out. ]

Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Randy Dunlap <randy.dunlap@oracle.com>

2 files changed, 106 insertions, 1 deletions

diff --git a/lib/Makefile b/lib/Makefile
index da68b2ca0606..614966387402 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -5,7 +5,7 @@
 lib-y := ctype.o string.o vsprintf.o cmdline.o \
          rbtree.o radix-tree.o dump_stack.o \
          idr.o int_sqrt.o bitmap.o extable.o prio_tree.o \
-         sha1.o irq_regs.o reciprocal_div.o
+         sha1.o irq_regs.o reciprocal_div.o argv_split.o
 
 lib-$(CONFIG_MMU) += ioremap.o
 lib-$(CONFIG_SMP) += cpumask.o
diff --git a/lib/argv_split.c b/lib/argv_split.c
new file mode 100644
index 000000000000..4096ed42f490
--- /dev/null
+++ b/lib/argv_split.c
@@ -0,0 +1,105 @@
+/*
+ * Helper function for splitting a string into an argv-like array.
+ */
+
+#include <linux/kernel.h>
+#include <linux/ctype.h>
+#include <linux/bug.h>
+
+static const char *skip_sep(const char *cp)
+{
+        while (*cp && isspace(*cp))
+                cp++;
+
+        return cp;
+}
+
+static const char *skip_arg(const char *cp)
+{
+        while (*cp && !isspace(*cp))
+                cp++;
+
+        return cp;
+}
+
+static int count_argc(const char *str)
+{
+        int count = 0;
+
+        while (*str) {
+                str = skip_sep(str);
+                if (*str) {
+                        count++;
+                        str = skip_arg(str);
+                }
+        }
+
+        return count;
+}
+
+/**
+ * argv_free - free an argv
+ * @argv - the argument vector to be freed
+ *
+ * Frees an argv and the strings it points to.
+ */
+void argv_free(char **argv)
+{
+        char **p;
+        for (p = argv; *p; p++)
+                kfree(*p);
+
+        kfree(argv);
+}
+EXPORT_SYMBOL(argv_free);
+
+/**
+ * argv_split - split a string at whitespace, returning an argv
+ * @gfp: the GFP mask used to allocate memory
+ * @str: the string to be split
+ * @argcp: returned argument count
+ *
+ * Returns an array of pointers to strings which are split out from
+ * @str.  This is performed by strictly splitting on white-space; no
+ * quote processing is performed.  Multiple whitespace characters are
+ * considered to be a single argument separator.  The returned array
+ * is always NULL-terminated.  Returns NULL on memory allocation
+ * failure.
+ */
+char **argv_split(gfp_t gfp, const char *str, int *argcp)
+{
+        int argc = count_argc(str);
+        char **argv = kzalloc(sizeof(*argv) * (argc+1), gfp);
+        char **argvp;
+
+        if (argv == NULL)
+                goto out;
+
+        *argcp = argc;
+        argvp = argv;
+
+        while (*str) {
+                str = skip_sep(str);
+
+                if (*str) {
+                        const char *p = str;
+                        char *t;
+
+                        str = skip_arg(str);
+
+                        t = kstrndup(p, str-p, gfp);
+                        if (t == NULL)
+                                goto fail;
+                        *argvp++ = t;
+                }
+        }
+        *argvp = NULL;
+
+  out:
+        return argv;
+
+  fail:
+        argv_free(argv);
+        return NULL;
+}
+EXPORT_SYMBOL(argv_split);