[PATCH 2/2] xenstore: support XS_DIRECTORY_PART in libxenstore

[Juergen Gross <jgross@suse.com>]

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@suse.com>
---
 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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