[Xen-devel] [patch 02/44] add argv_split()

[Jeremy Fitzhardinge <jeremy@xxxxxxxxxxxxx>]

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@xxxxxxxxxxxxx>
Signed-off-by: Chris Wright <chrisw@xxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Randy Dunlap <randy.dunlap@xxxxxxxxxx>

---
 include/linux/string.h |    3 +
 lib/Makefile           |    2 
 lib/argv_split.c       |  106 ++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 110 insertions(+), 1 deletion(-)

===================================================================
--- a/include/linux/string.h
+++ b/include/linux/string.h
@@ -108,6 +108,9 @@ extern char *kstrndup(const char *s, siz
 extern char *kstrndup(const char *s, size_t len, gfp_t gfp);
 extern void *kmemdup(const void *src, size_t len, gfp_t gfp);
 
+extern char **argv_split(gfp_t gfp, const char *str, int *argcp);
+extern void argv_free(char **argv);
+
 #ifdef __cplusplus
 }
 #endif
===================================================================
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -5,7 +5,7 @@ lib-y := ctype.o string.o vsprintf.o cmd
 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
===================================================================
--- /dev/null
+++ b/lib/argv_split.c
@@ -0,0 +1,106 @@
+/*
+ * 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);

-- 


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