[Xen-devel] [PATCH 2/2] xenstore: support XS_DIRECTORY_PART in libxenstore

[Juergen Gross <jgross@xxxxxxxx>]

This will enable all users of libxenstore to handle xenstore nodes
with a huge amount of children.

In order to not depend completely on the XS_DIRECTORY_PART
functionality use it only in case of E2BIG returned by XS_DIRECTORY.

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
 tools/xenstore/xs.c | 74 +++++++++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 66 insertions(+), 8 deletions(-)

diff --git a/tools/xenstore/xs.c b/tools/xenstore/xs.c
index d1e01ba..e64ded8 100644
--- a/tools/xenstore/xs.c
+++ b/tools/xenstore/xs.c
@@ -558,15 +558,10 @@ static bool xs_bool(char *reply)
        return true;
 }
 
-char **xs_directory(struct xs_handle *h, xs_transaction_t t,
-                   const char *path, unsigned int *num)
+static char **xs_directory_common(char *strings, unsigned int len,
+                                 unsigned int *num)
 {
-       char *strings, *p, **ret;
-       unsigned int len;
-
-       strings = xs_single(h, t, XS_DIRECTORY, path, &len);
-       if (!strings)
-               return NULL;
+       char *p, **ret;
 
        /* Count the strings. */
        *num = xs_count_strings(strings, len);
@@ -586,6 +581,69 @@ char **xs_directory(struct xs_handle *h, xs_transaction_t 
t,
        return ret;
 }
 
+static char **xs_directory_part(struct xs_handle *h, xs_transaction_t t,
+                               const char *path, unsigned int *num)
+{
+       char *strings, *p, **ret;
+       unsigned int len, p_len;
+       int saved_errno;
+
+       if (t == XBT_NULL) {
+               for (;;) {
+                       t = xs_transaction_start(h);
+                       if (t == XBT_NULL)
+                               return NULL;
+
+                       ret = xs_directory_part(h, t, path, num);
+                       saved_errno = errno;
+
+                       if (xs_transaction_end(h, t, false) || ret == NULL) {
+                               errno = saved_errno;
+                               return ret;
+                       }
+
+                       free(ret);
+               }
+       }
+
+       strings = xs_single(h, t, XS_DIRECTORY_PART, path, &len);
+       if (!strings) {
+               /* If XS_DIRECTORY_PART is not supported return E2BIG. */
+               if (errno == ENOSYS)
+                       errno = E2BIG;
+               return NULL;
+       }
+
+       while (len > 1 && strings[len - 2] != 0) {
+               p = xs_single(h, t, XS_DIRECTORY_PART, "@", &p_len);
+               if (!p) {
+                       free_no_errno(strings);
+                       return NULL;
+               }
+               strings = realloc(strings, len + p_len);
+               memcpy(strings + len, p, p_len);
+               len += p_len;
+       }
+
+       return xs_directory_common(strings, len - 1, num);
+}
+
+char **xs_directory(struct xs_handle *h, xs_transaction_t t,
+                   const char *path, unsigned int *num)
+{
+       char *strings;
+       unsigned int len;
+
+       strings = xs_single(h, t, XS_DIRECTORY, path, &len);
+       if (!strings) {
+               if (errno != E2BIG)
+                       return NULL;
+               return xs_directory_part(h, t, path, num);
+       }
+
+       return xs_directory_common(strings, len, num);
+}
+
 /* Get the value of a single file, nul terminated.
  * Returns a malloced value: call free() on it after use.
  * len indicates length in bytes, not including the nul.
-- 
2.6.6


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