1 /*
2  * nghttp2 - HTTP/2 C Library
3  *
4  * Copyright (c) 2012 Tatsuhiro Tsujikawa
5  *
6  * Permission is hereby granted, free of charge, to any person obtaining
7  * a copy of this software and associated documentation files (the
8  * "Software"), to deal in the Software without restriction, including
9  * without limitation the rights to use, copy, modify, merge, publish,
10  * distribute, sublicense, and/or sell copies of the Software, and to
11  * permit persons to whom the Software is furnished to do so, subject to
12  * the following conditions:
13  *
14  * The above copyright notice and this permission notice shall be
15  * included in all copies or substantial portions of the Software.
16  *
17  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
18  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
19  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
20  * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
21  * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
22  * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
23  * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
24  */
25 #ifndef NGHTTP2_PQ_H
26 #define NGHTTP2_PQ_H
27 
28 #ifdef HAVE_CONFIG_H
29 #include <config.h>
30 #endif /* HAVE_CONFIG_H */
31 
32 #include "nghttp2.h"
33 #include "nghttp2_int.h"
34 #include "nghttp2_mem.h"
35 
36 /* Implementation of priority queue */
37 
38 typedef struct {
39     size_t index;
40 } nghttp2_pq_entry;
41 
42 typedef struct {
43     /* The pointer to the pointer to the item stored */
44     nghttp2_pq_entry **q;
45     /* Memory allocator */
46     nghttp2_mem *mem;
47     /* The number of items stored */
48     size_t length;
49     /* The maximum number of items this pq can store. This is
50        automatically extended when length is reached to this value. */
51     size_t capacity;
52     /* The less function between items */
53     nghttp2_less less;
54 } nghttp2_pq;
55 
56 /*
57  * Initializes priority queue |pq| with compare function |cmp|.
58  *
59  * This function returns 0 if it succeeds, or one of the following
60  * negative error codes:
61  *
62  * NGHTTP2_ERR_NOMEM
63  *     Out of memory.
64  */
65 int nghttp2_pq_init(nghttp2_pq *pq, nghttp2_less less, nghttp2_mem *mem);
66 
67 /*
68  * Deallocates any resources allocated for |pq|.  The stored items are
69  * not freed by this function.
70  */
71 void nghttp2_pq_free(nghttp2_pq *pq);
72 
73 /*
74  * Adds |item| to the priority queue |pq|.
75  *
76  * This function returns 0 if it succeeds, or one of the following
77  * negative error codes:
78  *
79  * NGHTTP2_ERR_NOMEM
80  *     Out of memory.
81  */
82 int nghttp2_pq_push(nghttp2_pq *pq, nghttp2_pq_entry *item);
83 
84 /*
85  * Returns item at the top of the queue |pq|. If the queue is empty,
86  * this function returns NULL.
87  */
88 nghttp2_pq_entry *nghttp2_pq_top(nghttp2_pq *pq);
89 
90 /*
91  * Pops item at the top of the queue |pq|. The popped item is not
92  * freed by this function.
93  */
94 void nghttp2_pq_pop(nghttp2_pq *pq);
95 
96 /*
97  * Returns nonzero if the queue |pq| is empty.
98  */
99 int nghttp2_pq_empty(nghttp2_pq *pq);
100 
101 /*
102  * Returns the number of items in the queue |pq|.
103  */
104 size_t nghttp2_pq_size(nghttp2_pq *pq);
105 
106 typedef int (*nghttp2_pq_item_cb)(nghttp2_pq_entry *item, void *arg);
107 
108 /*
109  * Updates each item in |pq| using function |fun| and re-construct
110  * priority queue. The |fun| must return non-zero if it modifies the
111  * item in a way that it affects ordering in the priority queue. The
112  * |arg| is passed to the 2nd parameter of |fun|.
113  */
114 void nghttp2_pq_update(nghttp2_pq *pq, nghttp2_pq_item_cb fun, void *arg);
115 
116 /*
117  * Applys |fun| to each item in |pq|.  The |arg| is passed as arg
118  * parameter to callback function.  This function must not change the
119  * ordering key.  If the return value from callback is nonzero, this
120  * function returns 1 immediately without iterating remaining items.
121  * Otherwise this function returns 0.
122  */
123 int nghttp2_pq_each(nghttp2_pq *pq, nghttp2_pq_item_cb fun, void *arg);
124 
125 /*
126  * Removes |item| from priority queue.
127  */
128 void nghttp2_pq_remove(nghttp2_pq *pq, nghttp2_pq_entry *item);
129 
130 #endif /* NGHTTP2_PQ_H */
131