libwbclient: Add wbcAllocateMemory()

This prepares for removing libwbclient's talloc dependency. It is a
non-hierarchical "talloc-lite" that has destructors. It is necessary because we
have the catch-call wbcFreeMemory call. Individual wbcFreeXXX calls for the
different structures wbclient returns would have made this easier, but
wbcFreeMemory is the API we have to live with.

2 files changed, 54 insertions, 2 deletions

diff --git a/nsswitch/libwbclient/wbclient.c b/nsswitch/libwbclient/wbclient.c
index cd5ffa876a..6b076ad499 100644
--- a/nsswitch/libwbclient/wbclient.c
+++ b/nsswitch/libwbclient/wbclient.c
@@ -147,12 +147,61 @@ const char *wbcErrorString(wbcErr error)
 	return "unknown wbcErr value";
 }
 
+#define WBC_MAGIC (0x7a2b0e1e)
+
+struct wbcMemPrefix {
+	uint32_t magic;
+	void (*destructor)(void *ptr);
+};
+
+static size_t wbcPrefixLen(void)
+{
+	size_t result = sizeof(struct wbcMemPrefix);
+	return (result + 15) & ~15;
+}
+
+static struct wbcMemPrefix *wbcMemToPrefix(void *ptr)
+{
+	return (struct wbcMemPrefix *)(((char *)ptr) - wbcPrefixLen());
+}
+
+void *wbcAllocateMemory(size_t nelem, size_t elsize,
+			void (*destructor)(void *ptr))
+{
+	struct wbcMemPrefix *result;
+
+	if (nelem >= (2<<24)/elsize) {
+		/* basic protection against integer wrap */
+		return NULL;
+	}
+
+	result = (struct wbcMemPrefix *)calloc(
+		1, nelem*elsize + wbcPrefixLen());
+	if (result == NULL) {
+		return NULL;
+	}
+	result->magic = WBC_MAGIC;
+	result->destructor = destructor;
+	return ((char *)result) + wbcPrefixLen();
+}
+
 /* Free library allocated memory */
 void wbcFreeMemory(void *p)
 {
-	if (p)
-		talloc_free(p);
+	struct wbcMemPrefix *wbcMem;
 
+	if (p == NULL) {
+		return;
+	}
+	wbcMem = wbcMemToPrefix(p);
+	if (wbcMem->magic != WBC_MAGIC) {
+		talloc_free(p);
+		return;
+	}
+	if (wbcMem->destructor != NULL) {
+		wbcMem->destructor(p);
+	}
+	free(wbcMem);
 	return;
 }
 
diff --git a/nsswitch/libwbclient/wbclient_internal.h b/nsswitch/libwbclient/wbclient_internal.h
index 5ce820785e..6c59be3fef 100644
--- a/nsswitch/libwbclient/wbclient_internal.h
+++ b/nsswitch/libwbclient/wbclient_internal.h
@@ -32,4 +32,7 @@ wbcErr wbcRequestResponsePriv(int cmd,
 			      struct winbindd_request *request,
 			      struct winbindd_response *response);
 
+void *wbcAllocateMemory(size_t nelem, size_t elsize,
+			void (*destructor)(void *ptr));
+
 #endif      /* _WBCLIENT_INTERNAL_H */