xref: /freebsd/contrib/ntp/sntp/libevent/evbuffer-internal.h (revision 70bc3f4331a1b6e7045ae5326cbe03428503b612)
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_INCLUDED_
28  #define EVBUFFER_INTERNAL_H_INCLUDED_
29  
30  #ifdef __cplusplus
31  extern "C" {
32  #endif
33  
34  #include "event2/event-config.h"
35  #include "evconfig-private.h"
36  #include "event2/util.h"
37  #include "event2/event_struct.h"
38  #include "util-internal.h"
39  #include "defer-internal.h"
40  
41  /* Experimental cb flag: "never deferred."  Implementation note:
42   * these callbacks may get an inaccurate view of n_del/n_added in their
43   * arguments. */
44  #define EVBUFFER_CB_NODEFER 2
45  
46  #ifdef _WIN32
47  #include <winsock2.h>
48  #endif
49  #include <sys/queue.h>
50  
51  /* Minimum allocation for a chain.  We define this so that we're burning no
52   * more than 5% of each allocation on overhead.  It would be nice to lose even
53   * less space, though. */
54  #if EVENT__SIZEOF_VOID_P < 8
55  #define MIN_BUFFER_SIZE	512
56  #else
57  #define MIN_BUFFER_SIZE	1024
58  #endif
59  
60  /** A single evbuffer callback for an evbuffer. This function will be invoked
61   * when bytes are added to or removed from the evbuffer. */
62  struct evbuffer_cb_entry {
63  	/** Structures to implement a doubly-linked queue of callbacks */
64  	LIST_ENTRY(evbuffer_cb_entry) next;
65  	/** The callback function to invoke when this callback is called.
66  	    If EVBUFFER_CB_OBSOLETE is set in flags, the cb_obsolete field is
67  	    valid; otherwise, cb_func is valid. */
68  	union {
69  		evbuffer_cb_func cb_func;
70  		evbuffer_cb cb_obsolete;
71  	} cb;
72  	/** Argument to pass to cb. */
73  	void *cbarg;
74  	/** Currently set flags on this callback. */
75  	ev_uint32_t flags;
76  };
77  
78  struct bufferevent;
79  struct evbuffer_chain;
80  struct evbuffer {
81  	/** The first chain in this buffer's linked list of chains. */
82  	struct evbuffer_chain *first;
83  	/** The last chain in this buffer's linked list of chains. */
84  	struct evbuffer_chain *last;
85  
86  	/** Pointer to the next pointer pointing at the 'last_with_data' chain.
87  	 *
88  	 * To unpack:
89  	 *
90  	 * The last_with_data chain is the last chain that has any data in it.
91  	 * If all chains in the buffer are empty, it is the first chain.
92  	 * If the buffer has no chains, it is NULL.
93  	 *
94  	 * The last_with_datap pointer points at _whatever 'next' pointer_
95  	 * pointing at the last_with_data chain. If the last_with_data chain
96  	 * is the first chain, or it is NULL, then the last_with_datap pointer
97  	 * is &buf->first.
98  	 */
99  	struct evbuffer_chain **last_with_datap;
100  
101  	/** Total amount of bytes stored in all chains.*/
102  	size_t total_len;
103  
104  	/** Number of bytes we have added to the buffer since we last tried to
105  	 * invoke callbacks. */
106  	size_t n_add_for_cb;
107  	/** Number of bytes we have removed from the buffer since we last
108  	 * tried to invoke callbacks. */
109  	size_t n_del_for_cb;
110  
111  #ifndef EVENT__DISABLE_THREAD_SUPPORT
112  	/** A lock used to mediate access to this buffer. */
113  	void *lock;
114  #endif
115  	/** True iff we should free the lock field when we free this
116  	 * evbuffer. */
117  	unsigned own_lock : 1;
118  	/** True iff we should not allow changes to the front of the buffer
119  	 * (drains or prepends). */
120  	unsigned freeze_start : 1;
121  	/** True iff we should not allow changes to the end of the buffer
122  	 * (appends) */
123  	unsigned freeze_end : 1;
124  	/** True iff this evbuffer's callbacks are not invoked immediately
125  	 * upon a change in the buffer, but instead are deferred to be invoked
126  	 * from the event_base's loop.	Useful for preventing enormous stack
127  	 * overflows when we have mutually recursive callbacks, and for
128  	 * serializing callbacks in a single thread. */
129  	unsigned deferred_cbs : 1;
130  #ifdef _WIN32
131  	/** True iff this buffer is set up for overlapped IO. */
132  	unsigned is_overlapped : 1;
133  #endif
134  	/** Zero or more EVBUFFER_FLAG_* bits */
135  	ev_uint32_t flags;
136  
137  	/** Used to implement deferred callbacks. */
138  	struct event_base *cb_queue;
139  
140  	/** A reference count on this evbuffer.	 When the reference count
141  	 * reaches 0, the buffer is destroyed.	Manipulated with
142  	 * evbuffer_incref and evbuffer_decref_and_unlock and
143  	 * evbuffer_free. */
144  	int refcnt;
145  
146  	/** A struct event_callback handle to make all of this buffer's callbacks
147  	 * invoked from the event loop. */
148  	struct event_callback deferred;
149  
150  	/** A doubly-linked-list of callback functions */
151  	LIST_HEAD(evbuffer_cb_queue, evbuffer_cb_entry) callbacks;
152  
153  	/** The parent bufferevent object this evbuffer belongs to.
154  	 * NULL if the evbuffer stands alone. */
155  	struct bufferevent *parent;
156  };
157  
158  #if EVENT__SIZEOF_OFF_T < EVENT__SIZEOF_SIZE_T
159  typedef ev_ssize_t ev_misalign_t;
160  #define EVBUFFER_CHAIN_MAX ((size_t)EV_SSIZE_MAX)
161  #else
162  typedef ev_off_t ev_misalign_t;
163  #if EVENT__SIZEOF_OFF_T > EVENT__SIZEOF_SIZE_T
164  #define EVBUFFER_CHAIN_MAX EV_SIZE_MAX
165  #else
166  #define EVBUFFER_CHAIN_MAX ((size_t)EV_SSIZE_MAX)
167  #endif
168  #endif
169  
170  /** A single item in an evbuffer. */
171  struct evbuffer_chain {
172  	/** points to next buffer in the chain */
173  	struct evbuffer_chain *next;
174  
175  	/** total allocation available in the buffer field. */
176  	size_t buffer_len;
177  
178  	/** unused space at the beginning of buffer or an offset into a
179  	 * file for sendfile buffers. */
180  	ev_misalign_t misalign;
181  
182  	/** Offset into buffer + misalign at which to start writing.
183  	 * In other words, the total number of bytes actually stored
184  	 * in buffer. */
185  	size_t off;
186  
187  	/** Set if special handling is required for this chain */
188  	unsigned flags;
189  #define EVBUFFER_FILESEGMENT	0x0001  /**< A chain used for a file segment */
190  #define EVBUFFER_SENDFILE	0x0002	/**< a chain used with sendfile */
191  #define EVBUFFER_REFERENCE	0x0004	/**< a chain with a mem reference */
192  #define EVBUFFER_IMMUTABLE	0x0008	/**< read-only chain */
193  	/** a chain that mustn't be reallocated or freed, or have its contents
194  	 * memmoved, until the chain is un-pinned. */
195  #define EVBUFFER_MEM_PINNED_R	0x0010
196  #define EVBUFFER_MEM_PINNED_W	0x0020
197  #define EVBUFFER_MEM_PINNED_ANY (EVBUFFER_MEM_PINNED_R|EVBUFFER_MEM_PINNED_W)
198  	/** a chain that should be freed, but can't be freed until it is
199  	 * un-pinned. */
200  #define EVBUFFER_DANGLING	0x0040
201  	/** a chain that is a referenced copy of another chain */
202  #define EVBUFFER_MULTICAST	0x0080
203  
204  	/** number of references to this chain */
205  	int refcnt;
206  
207  	/** Usually points to the read-write memory belonging to this
208  	 * buffer allocated as part of the evbuffer_chain allocation.
209  	 * For mmap, this can be a read-only buffer and
210  	 * EVBUFFER_IMMUTABLE will be set in flags.  For sendfile, it
211  	 * may point to NULL.
212  	 */
213  	unsigned char *buffer;
214  };
215  
216  /** callback for a reference chain; lets us know what to do with it when
217   * we're done with it. Lives at the end of an evbuffer_chain with the
218   * EVBUFFER_REFERENCE flag set */
219  struct evbuffer_chain_reference {
220  	evbuffer_ref_cleanup_cb cleanupfn;
221  	void *extra;
222  };
223  
224  /** File segment for a file-segment chain.  Lives at the end of an
225   * evbuffer_chain with the EVBUFFER_FILESEGMENT flag set.  */
226  struct evbuffer_chain_file_segment {
227  	struct evbuffer_file_segment *segment;
228  #ifdef _WIN32
229  	/** If we're using CreateFileMapping, this is the handle to the view. */
230  	HANDLE view_handle;
231  #endif
232  };
233  
234  /* Declared in event2/buffer.h; defined here. */
235  struct evbuffer_file_segment {
236  	void *lock; /**< lock prevent concurrent access to refcnt */
237  	int refcnt; /**< Reference count for this file segment */
238  	unsigned flags; /**< combination of EVBUF_FS_* flags  */
239  
240  	/** What kind of file segment is this? */
241  	unsigned can_sendfile : 1;
242  	unsigned is_mapping : 1;
243  
244  	/** The fd that we read the data from. */
245  	int fd;
246  	/** If we're using mmap, this is the raw mapped memory. */
247  	void *mapping;
248  #ifdef _WIN32
249  	/** If we're using CreateFileMapping, this is the mapping */
250  	HANDLE mapping_handle;
251  #endif
252  	/** If we're using mmap or IO, this is the content of the file
253  	 * segment. */
254  	char *contents;
255  	/** Position of this segment within the file. */
256  	ev_off_t file_offset;
257  	/** If we're using mmap, this is the offset within 'mapping' where
258  	 * this data segment begins. */
259  	ev_off_t mmap_offset;
260  	/** The length of this segment. */
261  	ev_off_t length;
262  	/** Cleanup callback function */
263  	evbuffer_file_segment_cleanup_cb cleanup_cb;
264  	/** Argument to be pass to cleanup callback function */
265  	void *cleanup_cb_arg;
266  };
267  
268  /** Information about the multicast parent of a chain.  Lives at the
269   * end of an evbuffer_chain with the EVBUFFER_MULTICAST flag set.  */
270  struct evbuffer_multicast_parent {
271  	/** source buffer the multicast parent belongs to */
272  	struct evbuffer *source;
273  	/** multicast parent for this chain */
274  	struct evbuffer_chain *parent;
275  };
276  
277  #define EVBUFFER_CHAIN_SIZE sizeof(struct evbuffer_chain)
278  /** Return a pointer to extra data allocated along with an evbuffer. */
279  #define EVBUFFER_CHAIN_EXTRA(t, c) (t *)((struct evbuffer_chain *)(c) + 1)
280  
281  /** Assert that we are holding the lock on an evbuffer */
282  #define ASSERT_EVBUFFER_LOCKED(buffer)			\
283  	EVLOCK_ASSERT_LOCKED((buffer)->lock)
284  
285  #define EVBUFFER_LOCK(buffer)						\
286  	do {								\
287  		EVLOCK_LOCK((buffer)->lock, 0);				\
288  	} while (0)
289  #define EVBUFFER_UNLOCK(buffer)						\
290  	do {								\
291  		EVLOCK_UNLOCK((buffer)->lock, 0);			\
292  	} while (0)
293  #define EVBUFFER_LOCK2(buffer1, buffer2)				\
294  	do {								\
295  		EVLOCK_LOCK2((buffer1)->lock, (buffer2)->lock, 0, 0);	\
296  	} while (0)
297  #define EVBUFFER_UNLOCK2(buffer1, buffer2)				\
298  	do {								\
299  		EVLOCK_UNLOCK2((buffer1)->lock, (buffer2)->lock, 0, 0);	\
300  	} while (0)
301  
302  /** Increase the reference count of buf by one. */
303  void evbuffer_incref_(struct evbuffer *buf);
304  /** Increase the reference count of buf by one and acquire the lock. */
305  void evbuffer_incref_and_lock_(struct evbuffer *buf);
306  /** Pin a single buffer chain using a given flag. A pinned chunk may not be
307   * moved or freed until it is unpinned. */
308  void evbuffer_chain_pin_(struct evbuffer_chain *chain, unsigned flag);
309  /** Unpin a single buffer chain using a given flag. */
310  void evbuffer_chain_unpin_(struct evbuffer_chain *chain, unsigned flag);
311  /** As evbuffer_free, but requires that we hold a lock on the buffer, and
312   * releases the lock before freeing it and the buffer. */
313  void evbuffer_decref_and_unlock_(struct evbuffer *buffer);
314  
315  /** As evbuffer_expand, but does not guarantee that the newly allocated memory
316   * is contiguous.  Instead, it may be split across two or more chunks. */
317  int evbuffer_expand_fast_(struct evbuffer *, size_t, int);
318  
319  /** Helper: prepares for a readv/WSARecv call by expanding the buffer to
320   * hold enough memory to read 'howmuch' bytes in possibly noncontiguous memory.
321   * Sets up the one or two iovecs in 'vecs' to point to the free memory and its
322   * extent, and *chainp to point to the first chain that we'll try to read into.
323   * Returns the number of vecs used.
324   */
325  int evbuffer_read_setup_vecs_(struct evbuffer *buf, ev_ssize_t howmuch,
326      struct evbuffer_iovec *vecs, int n_vecs, struct evbuffer_chain ***chainp,
327      int exact);
328  
329  /* Helper macro: copies an evbuffer_iovec in ei to a win32 WSABUF in i. */
330  #define WSABUF_FROM_EVBUFFER_IOV(i,ei) do {		\
331  		(i)->buf = (ei)->iov_base;		\
332  		(i)->len = (unsigned long)(ei)->iov_len;	\
333  	} while (0)
334  /* XXXX the cast above is safe for now, but not if we allow mmaps on win64.
335   * See note in buffer_iocp's launch_write function */
336  
337  /** Set the parent bufferevent object for buf to bev */
338  void evbuffer_set_parent_(struct evbuffer *buf, struct bufferevent *bev);
339  
340  void evbuffer_invoke_callbacks_(struct evbuffer *buf);
341  
342  
343  int evbuffer_get_callbacks_(struct evbuffer *buffer,
344      struct event_callback **cbs,
345      int max_cbs);
346  
347  #ifdef __cplusplus
348  }
349  #endif
350  
351  #endif /* EVBUFFER_INTERNAL_H_INCLUDED_ */
352