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-rw-r--r--fs/btrfs/ulist.h77
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diff --git a/fs/btrfs/ulist.h b/fs/btrfs/ulist.h
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+/*
+ * Copyright (C) 2011 STRATO AG
+ * written by Arne Jansen <sensille@gmx.net>
+ * Distributed under the GNU GPL license version 2.
+ *
+ */
+
+#ifndef __ULIST__
+#define __ULIST__
+
+/*
+ * ulist is a generic data structure to hold a collection of unique u64
+ * values. The only operations it supports is adding to the list and
+ * enumerating it.
+ * It is possible to store an auxiliary value along with the key.
+ *
+ * The implementation is preliminary and can probably be sped up
+ * significantly. A first step would be to store the values in an rbtree
+ * as soon as ULIST_SIZE is exceeded.
+ */
+
+/*
+ * number of elements statically allocated inside struct ulist
+ */
+#define ULIST_SIZE 16
+
+struct ulist_iterator {
+ int i;
+};
+
+/*
+ * element of the list
+ */
+struct ulist_node {
+ u64 val; /* value to store */
+ unsigned long aux; /* auxiliary value saved along with the val */
+};
+
+struct ulist {
+ /*
+ * number of elements stored in list
+ */
+ unsigned long nnodes;
+
+ /*
+ * number of nodes we already have room for
+ */
+ unsigned long nodes_alloced;
+
+ /*
+ * pointer to the array storing the elements. The first ULIST_SIZE
+ * elements are stored inline. In this case the it points to int_nodes.
+ * After exceeding ULIST_SIZE, dynamic memory is allocated.
+ */
+ struct ulist_node *nodes;
+
+ /*
+ * inline storage space for the first ULIST_SIZE entries
+ */
+ struct ulist_node int_nodes[ULIST_SIZE];
+};
+
+void ulist_init(struct ulist *ulist);
+void ulist_fini(struct ulist *ulist);
+void ulist_reinit(struct ulist *ulist);
+struct ulist *ulist_alloc(gfp_t gfp_mask);
+void ulist_free(struct ulist *ulist);
+int ulist_add(struct ulist *ulist, u64 val, unsigned long aux,
+ gfp_t gfp_mask);
+int ulist_add_merge(struct ulist *ulist, u64 val, unsigned long aux,
+ unsigned long *old_aux, gfp_t gfp_mask);
+struct ulist_node *ulist_next(struct ulist *ulist,
+ struct ulist_iterator *uiter);
+
+#define ULIST_ITER_INIT(uiter) ((uiter)->i = 0)
+
+#endif