[Xen-devel] [PATCH 02/10] xenstore: New function xs_path_is_subpath

[Ian Jackson <ian.jackson@xxxxxxxxxxxxx>]

This utility function compares two paths, textually and reports
whether one is a subpath (a child path) of the other.

Signed-off-by: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
---
 tools/xenstore/xs.c |   17 +++++++++++++++++
 tools/xenstore/xs.h |    7 +++++++
 2 files changed, 24 insertions(+), 0 deletions(-)

diff --git a/tools/xenstore/xs.c b/tools/xenstore/xs.c
index 8e54fe0..0a01675 100644
--- a/tools/xenstore/xs.c
+++ b/tools/xenstore/xs.c
@@ -950,6 +950,23 @@ char *xs_get_domain_path(struct xs_handle *h, unsigned int 
domid)
        return xs_single(h, XBT_NULL, XS_GET_DOMAIN_PATH, domid_str, NULL);
 }
 
+bool xs_path_is_subpath(const char *parent, const char *child)
+{
+        size_t childlen = strlen(child);
+        size_t parentlen = strlen(parent);
+
+       if (childlen < parentlen)
+               return false;
+
+       if (memcmp(child, parent, parentlen))
+               return false;
+
+       if (childlen > parentlen && child[parentlen] != '/')
+               return false;
+
+       return true;
+}
+
 bool xs_is_domain_introduced(struct xs_handle *h, unsigned int domid)
 {
        char *domain = single_with_domid(h, XS_IS_DOMAIN_INTRODUCED, domid);
diff --git a/tools/xenstore/xs.h b/tools/xenstore/xs.h
index 63f535d..8d49e50 100644
--- a/tools/xenstore/xs.h
+++ b/tools/xenstore/xs.h
@@ -207,6 +207,13 @@ bool xs_release_domain(struct xs_handle *h, unsigned int 
domid);
  */
 char *xs_get_domain_path(struct xs_handle *h, unsigned int domid);
 
+/* Returns true if child is either equal to parent, or a node underneath
+ * parent; or false otherwise.  Done by string comparison, so relative and
+ * absolute pathnames never in a parent/child relationship by this
+ * definition.  Cannot fail.
+ */
+bool xs_path_is_subpath(const char *parent, const char *child);
+
 /* Return whether the domain specified has been introduced to xenstored.
  */
 bool xs_is_domain_introduced(struct xs_handle *h, unsigned int domid);
-- 
1.7.2.5


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