[PATCH v4 17/19] tools/xenstore: introduce get_node_const()

[Juergen Gross <jgross@xxxxxxxx>]

Add a variant of get_node() returning a const struct node pointer.

Note that all callers of this new variant don't supply a pointer where
to store the canonical node name, while all callers needing a non-const
node do supply this pointer. This results in an asymmetric
simplification of the two variants.

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
V3:
- new approach (Julien Grall)
---
 tools/xenstore/xenstored_core.c | 35 ++++++++++++++++++++++-----------
 1 file changed, 24 insertions(+), 11 deletions(-)

diff --git a/tools/xenstore/xenstored_core.c b/tools/xenstore/xenstored_core.c
index 9098b7eee2..7de4df2f28 100644
--- a/tools/xenstore/xenstored_core.c
+++ b/tools/xenstore/xenstored_core.c
@@ -1301,11 +1301,8 @@ static struct node *get_node(struct connection *conn, 
const void *ctx,
                             const char *name, const char **canonical_name,
                             unsigned int perm, bool allow_special)
 {
-       const char *tmp_name;
        struct node *node;
 
-       if (!canonical_name)
-               canonical_name = &tmp_name;
        *canonical_name = canonicalize(conn, ctx, name, allow_special);
        if (!*canonical_name)
                return NULL;
@@ -1316,12 +1313,28 @@ static struct node *get_node(struct connection *conn, 
const void *ctx,
               ? node : NULL;
 }
 
+static const struct node *get_node_const(struct connection *conn,
+                                        const void *ctx, const char *name,
+                                        unsigned int perm, bool allow_special)
+{
+       const char *tmp_name;
+       const struct node *node;
+
+       tmp_name = canonicalize(conn, ctx, name, allow_special);
+       if (!tmp_name)
+               return NULL;
+
+       node = read_node_const(conn, ctx, tmp_name);
+
+       return get_node_chk_perm(conn, ctx, node, tmp_name, perm) ? node : NULL;
+}
+
 static int send_directory(const void *ctx, struct connection *conn,
                          struct buffered_data *in)
 {
-       struct node *node;
+       const struct node *node;
 
-       node = get_node(conn, ctx, onearg(in), NULL, XS_PERM_READ, false);
+       node = get_node_const(conn, ctx, onearg(in), XS_PERM_READ, false);
        if (!node)
                return errno;
 
@@ -1335,14 +1348,14 @@ static int send_directory_part(const void *ctx, struct 
connection *conn,
 {
        unsigned int off, len, maxlen, genlen;
        char *child, *data;
-       struct node *node;
+       const struct node *node;
        char gen[24];
 
        if (xenstore_count_strings(in->buffer, in->used) != 2)
                return EINVAL;
 
        /* First arg is node name. */
-       node = get_node(conn, ctx, in->buffer, NULL, XS_PERM_READ, false);
+       node = get_node_const(conn, ctx, in->buffer, XS_PERM_READ, false);
        if (!node)
                return errno;
 
@@ -1389,9 +1402,9 @@ static int send_directory_part(const void *ctx, struct 
connection *conn,
 static int do_read(const void *ctx, struct connection *conn,
                   struct buffered_data *in)
 {
-       struct node *node;
+       const struct node *node;
 
-       node = get_node(conn, ctx, onearg(in), NULL, XS_PERM_READ, false);
+       node = get_node_const(conn, ctx, onearg(in), XS_PERM_READ, false);
        if (!node)
                return errno;
 
@@ -1799,11 +1812,11 @@ static int do_rm(const void *ctx, struct connection 
*conn,
 static int do_get_perms(const void *ctx, struct connection *conn,
                        struct buffered_data *in)
 {
-       struct node *node;
+       const struct node *node;
        char *strings;
        unsigned int len;
 
-       node = get_node(conn, ctx, onearg(in), NULL, XS_PERM_READ, true);
+       node = get_node_const(conn, ctx, onearg(in), XS_PERM_READ, true);
        if (!node)
                return errno;
 
-- 
2.35.3