1 /*
2 * Copyright (c) 2000-2007 Niels Provos <provos@citi.umich.edu>
3 * Copyright (c) 2007-2012 Niels Provos and Nick Mathewson
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 * 3. The name of the author may not be used to endorse or promote products
14 * derived from this software without specific prior written permission.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
17 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
18 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
19 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
21 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
22 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
23 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
24 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
25 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
26 */
27 #ifndef _EVBUFFER_INTERNAL_H_
28 #define _EVBUFFER_INTERNAL_H_
29
30 #ifdef __cplusplus
31 extern "C" {
32 #endif
33
34 #include "event2/event-config.h"
35 #include "event2/util.h"
36 #include "util-internal.h"
37 #include "defer-internal.h"
38
39 /* Experimental cb flag: "never deferred." Implementation note:
40 * these callbacks may get an inaccurate view of n_del/n_added in their
41 * arguments. */
42 #define EVBUFFER_CB_NODEFER 2
43
44 #ifdef WIN32
45 #include <winsock2.h>
46 #endif
47 #include <sys/queue.h>
48
49 /* Minimum allocation for a chain. We define this so that we're burning no
50 * more than 5% of each allocation on overhead. It would be nice to lose even
51 * less space, though. */
52 #if _EVENT_SIZEOF_VOID_P < 8
53 #define MIN_BUFFER_SIZE 512
54 #else
55 #define MIN_BUFFER_SIZE 1024
56 #endif
57
58 /** A single evbuffer callback for an evbuffer. This function will be invoked
59 * when bytes are added to or removed from the evbuffer. */
60 struct evbuffer_cb_entry {
61 /** Structures to implement a doubly-linked queue of callbacks */
62 TAILQ_ENTRY(evbuffer_cb_entry) next;
63 /** The callback function to invoke when this callback is called.
64 If EVBUFFER_CB_OBSOLETE is set in flags, the cb_obsolete field is
65 valid; otherwise, cb_func is valid. */
66 union {
67 evbuffer_cb_func cb_func;
68 evbuffer_cb cb_obsolete;
69 } cb;
70 /** Argument to pass to cb. */
71 void *cbarg;
72 /** Currently set flags on this callback. */
73 ev_uint32_t flags;
74 };
75
76 struct bufferevent;
77 struct evbuffer_chain;
78 struct evbuffer {
79 /** The first chain in this buffer's linked list of chains. */
80 struct evbuffer_chain *first;
81 /** The last chain in this buffer's linked list of chains. */
82 struct evbuffer_chain *last;
83
84 /** Pointer to the next pointer pointing at the 'last_with_data' chain.
85 *
86 * To unpack:
87 *
88 * The last_with_data chain is the last chain that has any data in it.
89 * If all chains in the buffer are empty, it is the first chain.
90 * If the buffer has no chains, it is NULL.
91 *
92 * The last_with_datap pointer points at _whatever 'next' pointer_
93 * points at the last_with_datap chain. If the last_with_data chain
94 * is the first chain, or it is NULL, then the last_with_datap pointer
95 * is &buf->first.
96 */
97 struct evbuffer_chain **last_with_datap;
98
99 /** Total amount of bytes stored in all chains.*/
100 size_t total_len;
101
102 /** Number of bytes we have added to the buffer since we last tried to
103 * invoke callbacks. */
104 size_t n_add_for_cb;
105 /** Number of bytes we have removed from the buffer since we last
106 * tried to invoke callbacks. */
107 size_t n_del_for_cb;
108
109 #ifndef _EVENT_DISABLE_THREAD_SUPPORT
110 /** A lock used to mediate access to this buffer. */
111 void *lock;
112 #endif
113 /** True iff we should free the lock field when we free this
114 * evbuffer. */
115 unsigned own_lock : 1;
116 /** True iff we should not allow changes to the front of the buffer
117 * (drains or prepends). */
118 unsigned freeze_start : 1;
119 /** True iff we should not allow changes to the end of the buffer
120 * (appends) */
121 unsigned freeze_end : 1;
122 /** True iff this evbuffer's callbacks are not invoked immediately
123 * upon a change in the buffer, but instead are deferred to be invoked
124 * from the event_base's loop. Useful for preventing enormous stack
125 * overflows when we have mutually recursive callbacks, and for
126 * serializing callbacks in a single thread. */
127 unsigned deferred_cbs : 1;
128 #ifdef WIN32
129 /** True iff this buffer is set up for overlapped IO. */
130 unsigned is_overlapped : 1;
131 #endif
132 /** Zero or more EVBUFFER_FLAG_* bits */
133 ev_uint32_t flags;
134
135 /** Used to implement deferred callbacks. */
136 struct deferred_cb_queue *cb_queue;
137
138 /** A reference count on this evbuffer. When the reference count
139 * reaches 0, the buffer is destroyed. Manipulated with
140 * evbuffer_incref and evbuffer_decref_and_unlock and
141 * evbuffer_free. */
142 int refcnt;
143
144 /** A deferred_cb handle to make all of this buffer's callbacks
145 * invoked from the event loop. */
146 struct deferred_cb deferred;
147
148 /** A doubly-linked-list of callback functions */
149 TAILQ_HEAD(evbuffer_cb_queue, evbuffer_cb_entry) callbacks;
150
151 /** The parent bufferevent object this evbuffer belongs to.
152 * NULL if the evbuffer stands alone. */
153 struct bufferevent *parent;
154 };
155
156 #if _EVENT_SIZEOF_OFF_T < _EVENT_SIZEOF_SIZE_T
157 typedef ev_ssize_t ev_misalign_t;
158 #define EVBUFFER_CHAIN_MAX ((size_t)EV_SSIZE_MAX)
159 #else
160 typedef ev_off_t ev_misalign_t;
161 #if _EVENT_SIZEOF_OFF_T > _EVENT_SIZEOF_SIZE_T
162 #define EVBUFFER_CHAIN_MAX EV_SIZE_MAX
163 #else
164 #define EVBUFFER_CHAIN_MAX ((size_t)EV_SSIZE_MAX)
165 #endif
166 #endif
167
168 /** A single item in an evbuffer. */
169 struct evbuffer_chain {
170 /** points to next buffer in the chain */
171 struct evbuffer_chain *next;
172
173 /** total allocation available in the buffer field. */
174 size_t buffer_len;
175
176 /** unused space at the beginning of buffer or an offset into a
177 * file for sendfile buffers. */
178 ev_misalign_t misalign;
179
180 /** Offset into buffer + misalign at which to start writing.
181 * In other words, the total number of bytes actually stored
182 * in buffer. */
183 size_t off;
184
185 /** Set if special handling is required for this chain */
186 unsigned flags;
187 #define EVBUFFER_MMAP 0x0001 /**< memory in buffer is mmaped */
188 #define EVBUFFER_SENDFILE 0x0002 /**< a chain used for sendfile */
189 #define EVBUFFER_REFERENCE 0x0004 /**< a chain with a mem reference */
190 #define EVBUFFER_IMMUTABLE 0x0008 /**< read-only chain */
191 /** a chain that mustn't be reallocated or freed, or have its contents
192 * memmoved, until the chain is un-pinned. */
193 #define EVBUFFER_MEM_PINNED_R 0x0010
194 #define EVBUFFER_MEM_PINNED_W 0x0020
195 #define EVBUFFER_MEM_PINNED_ANY (EVBUFFER_MEM_PINNED_R|EVBUFFER_MEM_PINNED_W)
196 /** a chain that should be freed, but can't be freed until it is
197 * un-pinned. */
198 #define EVBUFFER_DANGLING 0x0040
199
200 /** Usually points to the read-write memory belonging to this
201 * buffer allocated as part of the evbuffer_chain allocation.
202 * For mmap, this can be a read-only buffer and
203 * EVBUFFER_IMMUTABLE will be set in flags. For sendfile, it
204 * may point to NULL.
205 */
206 unsigned char *buffer;
207 };
208
209 /* this is currently used by both mmap and sendfile */
210 /* TODO(niels): something strange needs to happen for Windows here, I am not
211 * sure what that is, but it needs to get looked into.
212 */
213 struct evbuffer_chain_fd {
214 int fd; /**< the fd associated with this chain */
215 };
216
217 /** callback for a reference buffer; lets us know what to do with it when
218 * we're done with it. */
219 struct evbuffer_chain_reference {
220 evbuffer_ref_cleanup_cb cleanupfn;
221 void *extra;
222 };
223
224 #define EVBUFFER_CHAIN_SIZE sizeof(struct evbuffer_chain)
225 /** Return a pointer to extra data allocated along with an evbuffer. */
226 #define EVBUFFER_CHAIN_EXTRA(t, c) (t *)((struct evbuffer_chain *)(c) + 1)
227
228 /** Assert that we are holding the lock on an evbuffer */
229 #define ASSERT_EVBUFFER_LOCKED(buffer) \
230 EVLOCK_ASSERT_LOCKED((buffer)->lock)
231
232 #define EVBUFFER_LOCK(buffer) \
233 do { \
234 EVLOCK_LOCK((buffer)->lock, 0); \
235 } while (0)
236 #define EVBUFFER_UNLOCK(buffer) \
237 do { \
238 EVLOCK_UNLOCK((buffer)->lock, 0); \
239 } while (0)
240 #define EVBUFFER_LOCK2(buffer1, buffer2) \
241 do { \
242 EVLOCK_LOCK2((buffer1)->lock, (buffer2)->lock, 0, 0); \
243 } while (0)
244 #define EVBUFFER_UNLOCK2(buffer1, buffer2) \
245 do { \
246 EVLOCK_UNLOCK2((buffer1)->lock, (buffer2)->lock, 0, 0); \
247 } while (0)
248
249 /** Increase the reference count of buf by one. */
250 void _evbuffer_incref(struct evbuffer *buf);
251 /** Increase the reference count of buf by one and acquire the lock. */
252 void _evbuffer_incref_and_lock(struct evbuffer *buf);
253 /** Pin a single buffer chain using a given flag. A pinned chunk may not be
254 * moved or freed until it is unpinned. */
255 void _evbuffer_chain_pin(struct evbuffer_chain *chain, unsigned flag);
256 /** Unpin a single buffer chain using a given flag. */
257 void _evbuffer_chain_unpin(struct evbuffer_chain *chain, unsigned flag);
258 /** As evbuffer_free, but requires that we hold a lock on the buffer, and
259 * releases the lock before freeing it and the buffer. */
260 void _evbuffer_decref_and_unlock(struct evbuffer *buffer);
261
262 /** As evbuffer_expand, but does not guarantee that the newly allocated memory
263 * is contiguous. Instead, it may be split across two or more chunks. */
264 int _evbuffer_expand_fast(struct evbuffer *, size_t, int);
265
266 /** Helper: prepares for a readv/WSARecv call by expanding the buffer to
267 * hold enough memory to read 'howmuch' bytes in possibly noncontiguous memory.
268 * Sets up the one or two iovecs in 'vecs' to point to the free memory and its
269 * extent, and *chainp to point to the first chain that we'll try to read into.
270 * Returns the number of vecs used.
271 */
272 int _evbuffer_read_setup_vecs(struct evbuffer *buf, ev_ssize_t howmuch,
273 struct evbuffer_iovec *vecs, int n_vecs, struct evbuffer_chain ***chainp,
274 int exact);
275
276 /* Helper macro: copies an evbuffer_iovec in ei to a win32 WSABUF in i. */
277 #define WSABUF_FROM_EVBUFFER_IOV(i,ei) do { \
278 (i)->buf = (ei)->iov_base; \
279 (i)->len = (unsigned long)(ei)->iov_len; \
280 } while (0)
281 /* XXXX the cast above is safe for now, but not if we allow mmaps on win64.
282 * See note in buffer_iocp's launch_write function */
283
284 /** Set the parent bufferevent object for buf to bev */
285 void evbuffer_set_parent(struct evbuffer *buf, struct bufferevent *bev);
286
287 void evbuffer_invoke_callbacks(struct evbuffer *buf);
288
289 #ifdef __cplusplus
290 }
291 #endif
292
293 #endif /* _EVBUFFER_INTERNAL_H_ */