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diff --git a/lib/nghttp3_ksl.h b/lib/nghttp3_ksl.h
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+/*
+ * nghttp3
+ *
+ * Copyright (c) 2019 nghttp3 contributors
+ * Copyright (c) 2018 ngtcp2 contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+ * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+ * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+#ifndef NGHTTP3_KSL_H
+#define NGHTTP3_KSL_H
+
+#ifdef HAVE_CONFIG_H
+# include <config.h>
+#endif /* HAVE_CONFIG_H */
+
+#include <stdlib.h>
+
+#include <nghttp3/nghttp3.h>
+
+#include "nghttp3_objalloc.h"
+
+/*
+ * Skip List using single key instead of range.
+ */
+
+#define NGHTTP3_KSL_DEGR 16
+/* NGHTTP3_KSL_MAX_NBLK is the maximum number of nodes which a single
+ block can contain. */
+#define NGHTTP3_KSL_MAX_NBLK (2 * NGHTTP3_KSL_DEGR - 1)
+/* NGHTTP3_KSL_MIN_NBLK is the minimum number of nodes which a single
+ block other than root must contains. */
+#define NGHTTP3_KSL_MIN_NBLK (NGHTTP3_KSL_DEGR - 1)
+
+/*
+ * nghttp3_ksl_key represents key in nghttp3_ksl.
+ */
+typedef void nghttp3_ksl_key;
+
+typedef struct nghttp3_ksl_node nghttp3_ksl_node;
+
+typedef struct nghttp3_ksl_blk nghttp3_ksl_blk;
+
+/*
+ * nghttp3_ksl_node is a node which contains either nghttp3_ksl_blk or
+ * opaque data. If a node is an internal node, it contains
+ * nghttp3_ksl_blk. Otherwise, it has data. The key is stored at the
+ * location starting at key.
+ */
+struct nghttp3_ksl_node {
+ union {
+ nghttp3_ksl_blk *blk;
+ void *data;
+ };
+ union {
+ uint64_t align;
+ /* key is a buffer to include key associated to this node.
+ Because the length of key is unknown until nghttp3_ksl_init is
+ called, the actual buffer will be allocated after this
+ field. */
+ uint8_t key[1];
+ };
+};
+
+/*
+ * nghttp3_ksl_blk contains nghttp3_ksl_node objects.
+ */
+struct nghttp3_ksl_blk {
+ union {
+ struct {
+ /* next points to the next block if leaf field is nonzero. */
+ nghttp3_ksl_blk *next;
+ /* prev points to the previous block if leaf field is
+ nonzero. */
+ nghttp3_ksl_blk *prev;
+ /* n is the number of nodes this object contains in nodes. */
+ uint32_t n;
+ /* leaf is nonzero if this block contains leaf nodes. */
+ uint32_t leaf;
+ union {
+ uint64_t align;
+ /* nodes is a buffer to contain NGHTTP3_KSL_MAX_NBLK
+ nghttp3_ksl_node objects. Because nghttp3_ksl_node object
+ is allocated along with the additional variable length key
+ storage, the size of buffer is unknown until
+ nghttp3_ksl_init is called. */
+ uint8_t nodes[1];
+ };
+ };
+
+ nghttp3_opl_entry oplent;
+ };
+};
+
+nghttp3_objalloc_def(ksl_blk, nghttp3_ksl_blk, oplent);
+
+/*
+ * nghttp3_ksl_compar is a function type which returns nonzero if key
+ * |lhs| should be placed before |rhs|. It returns 0 otherwise.
+ */
+typedef int (*nghttp3_ksl_compar)(const nghttp3_ksl_key *lhs,
+ const nghttp3_ksl_key *rhs);
+
+typedef struct nghttp3_ksl nghttp3_ksl;
+
+typedef struct nghttp3_ksl_it nghttp3_ksl_it;
+
+/*
+ * nghttp3_ksl_it is a forward iterator to iterate nodes.
+ */
+struct nghttp3_ksl_it {
+ const nghttp3_ksl *ksl;
+ nghttp3_ksl_blk *blk;
+ size_t i;
+};
+
+/*
+ * nghttp3_ksl is a deterministic paged skip list.
+ */
+struct nghttp3_ksl {
+ nghttp3_objalloc blkalloc;
+ /* head points to the root block. */
+ nghttp3_ksl_blk *head;
+ /* front points to the first leaf block. */
+ nghttp3_ksl_blk *front;
+ /* back points to the last leaf block. */
+ nghttp3_ksl_blk *back;
+ nghttp3_ksl_compar compar;
+ size_t n;
+ /* keylen is the size of key */
+ size_t keylen;
+ /* nodelen is the actual size of nghttp3_ksl_node including key
+ storage. */
+ size_t nodelen;
+};
+
+/*
+ * nghttp3_ksl_init initializes |ksl|. |compar| specifies compare
+ * function. |keylen| is the length of key.
+ */
+void nghttp3_ksl_init(nghttp3_ksl *ksl, nghttp3_ksl_compar compar,
+ size_t keylen, const nghttp3_mem *mem);
+
+/*
+ * nghttp3_ksl_free frees resources allocated for |ksl|. If |ksl| is
+ * NULL, this function does nothing. It does not free the memory
+ * region pointed by |ksl| itself.
+ */
+void nghttp3_ksl_free(nghttp3_ksl *ksl);
+
+/*
+ * nghttp3_ksl_insert inserts |key| with its associated |data|. On
+ * successful insertion, the iterator points to the inserted node is
+ * stored in |*it|.
+ *
+ * This function returns 0 if it succeeds, or one of the following
+ * negative error codes:
+ *
+ * NGHTTP3_ERR_NOMEM
+ * Out of memory.
+ * NGHTTP3_ERR_INVALID_ARGUMENT
+ * |key| already exists.
+ */
+int nghttp3_ksl_insert(nghttp3_ksl *ksl, nghttp3_ksl_it *it,
+ const nghttp3_ksl_key *key, void *data);
+
+/*
+ * nghttp3_ksl_remove removes the |key| from |ksl|.
+ *
+ * This function assigns the iterator to |*it|, which points to the
+ * node which is located at the right next of the removed node if |it|
+ * is not NULL. If |key| is not found, no deletion takes place and
+ * the return value of nghttp3_ksl_end(ksl) is assigned to |*it|.
+ *
+ * This function returns 0 if it succeeds, or one of the following
+ * negative error codes:
+ *
+ * NGHTTP3_ERR_INVALID_ARGUMENT
+ * |key| does not exist.
+ */
+int nghttp3_ksl_remove(nghttp3_ksl *ksl, nghttp3_ksl_it *it,
+ const nghttp3_ksl_key *key);
+
+/*
+ * nghttp3_ksl_remove_hint removes the |key| from |ksl|. |hint| must
+ * point to the same node denoted by |key|. |hint| is used to remove
+ * a node efficiently in some cases. Other than that, it behaves
+ * exactly like nghttp3_ksl_remove. |it| and |hint| can point to the
+ * same object.
+ */
+int nghttp3_ksl_remove_hint(nghttp3_ksl *ksl, nghttp3_ksl_it *it,
+ const nghttp3_ksl_it *hint,
+ const nghttp3_ksl_key *key);
+
+/*
+ * nghttp3_ksl_lower_bound returns the iterator which points to the
+ * first node which has the key which is equal to |key| or the last
+ * node which satisfies !compar(&node->key, key). If there is no such
+ * node, it returns the iterator which satisfies nghttp3_ksl_it_end(it)
+ * != 0.
+ */
+nghttp3_ksl_it nghttp3_ksl_lower_bound(nghttp3_ksl *ksl,
+ const nghttp3_ksl_key *key);
+
+/*
+ * nghttp3_ksl_lower_bound_compar works like nghttp3_ksl_lower_bound,
+ * but it takes custom function |compar| to do lower bound search.
+ */
+nghttp3_ksl_it nghttp3_ksl_lower_bound_compar(nghttp3_ksl *ksl,
+ const nghttp3_ksl_key *key,
+ nghttp3_ksl_compar compar);
+
+/*
+ * nghttp3_ksl_update_key replaces the key of nodes which has |old_key|
+ * with |new_key|. |new_key| must be strictly greater than the
+ * previous node and strictly smaller than the next node.
+ */
+void nghttp3_ksl_update_key(nghttp3_ksl *ksl, const nghttp3_ksl_key *old_key,
+ const nghttp3_ksl_key *new_key);
+
+/*
+ * nghttp3_ksl_begin returns the iterator which points to the first
+ * node. If there is no node in |ksl|, it returns the iterator which
+ * satisfies nghttp3_ksl_it_end(it) != 0.
+ */
+nghttp3_ksl_it nghttp3_ksl_begin(const nghttp3_ksl *ksl);
+
+/*
+ * nghttp3_ksl_end returns the iterator which points to the node
+ * following the last node. The returned object satisfies
+ * nghttp3_ksl_it_end(). If there is no node in |ksl|, it returns the
+ * iterator which satisfies nghttp3_ksl_it_begin(it) != 0.
+ */
+nghttp3_ksl_it nghttp3_ksl_end(const nghttp3_ksl *ksl);
+
+/*
+ * nghttp3_ksl_len returns the number of elements stored in |ksl|.
+ */
+size_t nghttp3_ksl_len(nghttp3_ksl *ksl);
+
+/*
+ * nghttp3_ksl_clear removes all elements stored in |ksl|.
+ */
+void nghttp3_ksl_clear(nghttp3_ksl *ksl);
+
+/*
+ * nghttp3_ksl_nth_node returns the |n|th node under |blk|.
+ */
+#define nghttp3_ksl_nth_node(KSL, BLK, N) \
+ ((nghttp3_ksl_node *)(void *)((BLK)->nodes + (KSL)->nodelen * (N)))
+
+/*
+ * nghttp3_ksl_print prints its internal state in stderr. It assumes
+ * that the key is of type int64_t. This function should be used for
+ * the debugging purpose only.
+ */
+void nghttp3_ksl_print(nghttp3_ksl *ksl);
+
+/*
+ * nghttp3_ksl_it_init initializes |it|.
+ */
+void nghttp3_ksl_it_init(nghttp3_ksl_it *it, const nghttp3_ksl *ksl,
+ nghttp3_ksl_blk *blk, size_t i);
+
+/*
+ * nghttp3_ksl_it_get returns the data associated to the node which
+ * |it| points to. It is undefined to call this function when
+ * nghttp3_ksl_it_end(it) returns nonzero.
+ */
+#define nghttp3_ksl_it_get(IT) \
+ nghttp3_ksl_nth_node((IT)->ksl, (IT)->blk, (IT)->i)->data
+
+/*
+ * nghttp3_ksl_it_next advances the iterator by one. It is undefined
+ * if this function is called when nghttp3_ksl_it_end(it) returns
+ * nonzero.
+ */
+#define nghttp3_ksl_it_next(IT) \
+ (++(IT)->i == (IT)->blk->n && (IT)->blk->next \
+ ? ((IT)->blk = (IT)->blk->next, (IT)->i = 0) \
+ : 0)
+
+/*
+ * nghttp3_ksl_it_prev moves backward the iterator by one. It is
+ * undefined if this function is called when nghttp3_ksl_it_begin(it)
+ * returns nonzero.
+ */
+void nghttp3_ksl_it_prev(nghttp3_ksl_it *it);
+
+/*
+ * nghttp3_ksl_it_end returns nonzero if |it| points to the beyond the
+ * last node.
+ */
+#define nghttp3_ksl_it_end(IT) \
+ ((IT)->blk->n == (IT)->i && (IT)->blk->next == NULL)
+
+/*
+ * nghttp3_ksl_it_begin returns nonzero if |it| points to the first
+ * node. |it| might satisfy both nghttp3_ksl_it_begin(&it) and
+ * nghttp3_ksl_it_end(&it) if the skip list has no node.
+ */
+int nghttp3_ksl_it_begin(const nghttp3_ksl_it *it);
+
+/*
+ * nghttp3_ksl_key returns the key of the node which |it| points to.
+ * It is undefined to call this function when nghttp3_ksl_it_end(it)
+ * returns nonzero.
+ */
+#define nghttp3_ksl_it_key(IT) \
+ ((nghttp3_ksl_key *)nghttp3_ksl_nth_node((IT)->ksl, (IT)->blk, (IT)->i)->key)
+
+/*
+ * nghttp3_ksl_range_compar is an implementation of
+ * nghttp3_ksl_compar. lhs->ptr and rhs->ptr must point to
+ * nghttp3_range object and the function returns nonzero if (const
+ * nghttp3_range *)(lhs->ptr)->begin < (const nghttp3_range
+ * *)(rhs->ptr)->begin.
+ */
+int nghttp3_ksl_range_compar(const nghttp3_ksl_key *lhs,
+ const nghttp3_ksl_key *rhs);
+
+/*
+ * nghttp3_ksl_range_exclusive_compar is an implementation of
+ * nghttp3_ksl_compar. lhs->ptr and rhs->ptr must point to
+ * nghttp3_range object and the function returns nonzero if (const
+ * nghttp3_range *)(lhs->ptr)->begin < (const nghttp3_range
+ * *)(rhs->ptr)->begin and the 2 ranges do not intersect.
+ */
+int nghttp3_ksl_range_exclusive_compar(const nghttp3_ksl_key *lhs,
+ const nghttp3_ksl_key *rhs);
+
+#endif /* NGHTTP3_KSL_H */