libevent  2.2.0
Event notification library
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bufferevent.h File Reference

Functions for buffering data for network sending or receiving. More...

#include <event2/visibility.h>
#include <event2/event-config.h>
#include <event2/util.h>
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Data Structures

struct  bufferevent
 An opaque type for handling buffered IO. More...
 

Macros

#define EV_RATE_LIMIT_MAX   EV_SSIZE_MAX
 Maximum configurable rate- or burst-limit. More...
 
Bufferevent event codes

These flags are passed as arguments to a bufferevent's event callback.

#define BEV_EVENT_READING   0x01
 error encountered while reading
 
#define BEV_EVENT_WRITING   0x02
 error encountered while writing
 
#define BEV_EVENT_EOF   0x10
 eof file reached
 
#define BEV_EVENT_ERROR   0x20
 unrecoverable error encountered
 
#define BEV_EVENT_TIMEOUT   0x40
 user-specified timeout reached
 
#define BEV_EVENT_CONNECTED   0x80
 connect operation finished. More...
 

Typedefs

typedef void(* bufferevent_data_cb )(struct bufferevent *bev, void *ctx)
 A read or write callback for a bufferevent. More...
 
typedef void(* bufferevent_event_cb )(struct bufferevent *bev, short what, void *ctx)
 An event/error callback for a bufferevent. More...
 

Enumerations

enum  bufferevent_flush_mode { BEV_NORMAL = 0, BEV_FLUSH = 1, BEV_FINISHED = 2 }
 Flags that can be passed into filters to let them know how to deal with the incoming data. More...
 
enum  bufferevent_options { BEV_OPT_CLOSE_ON_FREE = (1<<0), BEV_OPT_THREADSAFE = (1<<1), BEV_OPT_DEFER_CALLBACKS = (1<<2), BEV_OPT_UNLOCK_CALLBACKS = (1<<3) }
 Options that can be specified when creating a bufferevent. More...
 
enum  bufferevent_trigger_options { BEV_TRIG_IGNORE_WATERMARKS = (1<<16), BEV_TRIG_DEFER_CALLBACKS = BEV_OPT_DEFER_CALLBACKS }
 Flags for bufferevent_trigger(_event) that modify when and how to trigger the callback. More...
 

Functions

EVENT2_EXPORT_SYMBOL int bufferevent_add_to_rate_limit_group (struct bufferevent *bev, struct bufferevent_rate_limit_group *g)
 Add 'bev' to the list of bufferevents whose aggregate reading and writing is restricted by 'g'. More...
 
EVENT2_EXPORT_SYMBOL int bufferevent_base_set (struct event_base *base, struct bufferevent *bufev)
 Assign a bufferevent to a specific event_base. More...
 
EVENT2_EXPORT_SYMBOL int bufferevent_decref (struct bufferevent *bufev)
 Public interface to manually decrement the reference count of a bufferevent. More...
 
EVENT2_EXPORT_SYMBOL int bufferevent_disable (struct bufferevent *bufev, short event)
 Disable a bufferevent. More...
 
EVENT2_EXPORT_SYMBOL int bufferevent_enable (struct bufferevent *bufev, short event)
 Enable a bufferevent. More...
 
EVENT2_EXPORT_SYMBOL int bufferevent_flush (struct bufferevent *bufev, short iotype, enum bufferevent_flush_mode mode)
 Triggers the bufferevent to produce more data if possible. More...
 
EVENT2_EXPORT_SYMBOL void bufferevent_free (struct bufferevent *bufev)
 Deallocate the storage associated with a bufferevent structure. More...
 
EVENT2_EXPORT_SYMBOL struct
event_base
bufferevent_get_base (struct bufferevent *bev)
 Return the event_base used by a bufferevent.
 
EVENT2_EXPORT_SYMBOL short bufferevent_get_enabled (struct bufferevent *bufev)
 Return the events that are enabled on a given bufferevent. More...
 
EVENT2_EXPORT_SYMBOL struct
evbuffer
bufferevent_get_input (struct bufferevent *bufev)
 Returns the input buffer. More...
 
EVENT2_EXPORT_SYMBOL ev_ssize_t bufferevent_get_max_single_read (struct bufferevent *bev)
 Get the current size limit for single read operation. More...
 
EVENT2_EXPORT_SYMBOL ev_ssize_t bufferevent_get_max_single_write (struct bufferevent *bev)
 Get the current size limit for single write operation. More...
 
EVENT2_EXPORT_SYMBOL ev_ssize_t bufferevent_get_max_to_read (struct bufferevent *bev)
 
EVENT2_EXPORT_SYMBOL ev_ssize_t bufferevent_get_max_to_write (struct bufferevent *bev)
 
EVENT2_EXPORT_SYMBOL struct
evbuffer
bufferevent_get_output (struct bufferevent *bufev)
 Returns the output buffer. More...
 
EVENT2_EXPORT_SYMBOL int bufferevent_get_priority (const struct bufferevent *bufev)
 Return the priority of a bufferevent. More...
 
EVENT2_EXPORT_SYMBOL const
struct ev_token_bucket_cfg * 
bufferevent_get_token_bucket_cfg (const struct bufferevent *bev)
 
EVENT2_EXPORT_SYMBOL struct
bufferevent
bufferevent_get_underlying (struct bufferevent *bufev)
 Returns the underlying bufferevent associated with a bufferevent (if the bufferevent is a wrapper), or NULL if there is no underlying bufferevent.
 
EVENT2_EXPORT_SYMBOL void bufferevent_getcb (struct bufferevent *bufev, bufferevent_data_cb *readcb_ptr, bufferevent_data_cb *writecb_ptr, bufferevent_event_cb *eventcb_ptr, void **cbarg_ptr)
 Retrieves the callbacks for a bufferevent. More...
 
EVENT2_EXPORT_SYMBOL
evutil_socket_t 
bufferevent_getfd (struct bufferevent *bufev)
 Returns the file descriptor associated with a bufferevent, or -1 if no file descriptor is associated with the bufferevent.
 
EVENT2_EXPORT_SYMBOL int bufferevent_getwatermark (struct bufferevent *bufev, short events, size_t *lowmark, size_t *highmark)
 Retrieves the watermarks for read or write events. More...
 
EVENT2_EXPORT_SYMBOL void bufferevent_incref (struct bufferevent *bufev)
 Public interface to manually increase the reference count of a bufferevent this is useful in situations where a user may reference the bufferevent somewhere else (unknown to libevent) More...
 
EVENT2_EXPORT_SYMBOL void bufferevent_lock (struct bufferevent *bufev)
 Acquire the lock on a bufferevent. More...
 
EVENT2_EXPORT_SYMBOL struct
bufferevent
bufferevent_pair_get_partner (struct bufferevent *bev)
 Given one bufferevent returned by bufferevent_pair_new(), returns the other one if it still exists. More...
 
EVENT2_EXPORT_SYMBOL int bufferevent_pair_new (struct event_base *base, int options, struct bufferevent *pair[2])
 Allocate a pair of linked bufferevents. More...
 
EVENT2_EXPORT_SYMBOL int bufferevent_priority_set (struct bufferevent *bufev, int pri)
 Assign a priority to a bufferevent. More...
 
EVENT2_EXPORT_SYMBOL void bufferevent_rate_limit_group_free (struct bufferevent_rate_limit_group *)
 Free a rate-limiting group. More...
 
EVENT2_EXPORT_SYMBOL void bufferevent_rate_limit_group_get_totals (struct bufferevent_rate_limit_group *grp, ev_uint64_t *total_read_out, ev_uint64_t *total_written_out)
 Inspect the total bytes read/written on a group. More...
 
EVENT2_EXPORT_SYMBOL struct
bufferevent_rate_limit_group * 
bufferevent_rate_limit_group_new (struct event_base *base, const struct ev_token_bucket_cfg *cfg)
 Create a new rate-limit group for bufferevents. More...
 
EVENT2_EXPORT_SYMBOL void bufferevent_rate_limit_group_reset_totals (struct bufferevent_rate_limit_group *grp)
 Reset the total bytes read/written on a group. More...
 
EVENT2_EXPORT_SYMBOL int bufferevent_rate_limit_group_set_cfg (struct bufferevent_rate_limit_group *, const struct ev_token_bucket_cfg *)
 Change the rate-limiting settings for a given rate-limiting group. More...
 
EVENT2_EXPORT_SYMBOL int bufferevent_rate_limit_group_set_min_share (struct bufferevent_rate_limit_group *, size_t)
 Change the smallest quantum we're willing to allocate to any single bufferevent in a group for reading or writing at a time. More...
 
EVENT2_EXPORT_SYMBOL size_t bufferevent_read (struct bufferevent *bufev, void *data, size_t size)
 Read data from a bufferevent buffer. More...
 
EVENT2_EXPORT_SYMBOL int bufferevent_read_buffer (struct bufferevent *bufev, struct evbuffer *buf)
 Read data from a bufferevent buffer into an evbuffer. More...
 
EVENT2_EXPORT_SYMBOL int bufferevent_remove_from_rate_limit_group (struct bufferevent *bev)
 Remove 'bev' from its current rate-limit group (if any). More...
 
EVENT2_EXPORT_SYMBOL int bufferevent_set_max_single_read (struct bufferevent *bev, size_t size)
 Set the size limit for single read operation. More...
 
EVENT2_EXPORT_SYMBOL int bufferevent_set_max_single_write (struct bufferevent *bev, size_t size)
 Set the size limit for single write operation. More...
 
EVENT2_EXPORT_SYMBOL int bufferevent_set_rate_limit (struct bufferevent *bev, struct ev_token_bucket_cfg *cfg)
 Set the rate-limit of a the bufferevent 'bev' to the one specified in 'cfg'. More...
 
EVENT2_EXPORT_SYMBOL int bufferevent_set_timeouts (struct bufferevent *bufev, const struct timeval *timeout_read, const struct timeval *timeout_write)
 Set the read and write timeout for a bufferevent. More...
 
EVENT2_EXPORT_SYMBOL void bufferevent_setcb (struct bufferevent *bufev, bufferevent_data_cb readcb, bufferevent_data_cb writecb, bufferevent_event_cb eventcb, void *cbarg)
 Changes the callbacks for a bufferevent. More...
 
EVENT2_EXPORT_SYMBOL int bufferevent_setfd (struct bufferevent *bufev, evutil_socket_t fd)
 Changes the file descriptor on which the bufferevent operates. More...
 
EVENT2_EXPORT_SYMBOL void bufferevent_setwatermark (struct bufferevent *bufev, short events, size_t lowmark, size_t highmark)
 Sets the watermarks for read and write events. More...
 
EVENT2_EXPORT_SYMBOL int bufferevent_socket_connect (struct bufferevent *bufev, const struct sockaddr *addr, int socklen)
 Launch a connect() attempt with a socket-based bufferevent. More...
 
EVENT2_EXPORT_SYMBOL int bufferevent_socket_connect_hostname (struct bufferevent *bufev, struct evdns_base *evdns_base, int family, const char *hostname, int port)
 Resolve the hostname 'hostname' and connect to it as with bufferevent_socket_connect(). More...
 
EVENT2_EXPORT_SYMBOL int bufferevent_socket_connect_hostname_hints (struct bufferevent *bufev, struct evdns_base *evdns_base, const struct evutil_addrinfo *hints_in, const char *hostname, int port)
 Resolve the hostname 'hostname' and connect to it as with bufferevent_socket_connect(). More...
 
EVENT2_EXPORT_SYMBOL int bufferevent_socket_get_dns_error (struct bufferevent *bev)
 Return the error code for the last failed DNS lookup attempt made by bufferevent_socket_connect_hostname(). More...
 
EVENT2_EXPORT_SYMBOL struct
bufferevent
bufferevent_socket_new (struct event_base *base, evutil_socket_t fd, int options)
 Create a new socket bufferevent over an existing socket. More...
 
EVENT2_EXPORT_SYMBOL void bufferevent_trigger (struct bufferevent *bufev, short iotype, int options)
 Triggers bufferevent data callbacks. More...
 
EVENT2_EXPORT_SYMBOL void bufferevent_trigger_event (struct bufferevent *bufev, short what, int options)
 Triggers the bufferevent event callback. More...
 
EVENT2_EXPORT_SYMBOL void bufferevent_unlock (struct bufferevent *bufev)
 Release the lock on a bufferevent. More...
 
EVENT2_EXPORT_SYMBOL int bufferevent_write (struct bufferevent *bufev, const void *data, size_t size)
 Write data to a bufferevent buffer. More...
 
EVENT2_EXPORT_SYMBOL int bufferevent_write_buffer (struct bufferevent *bufev, struct evbuffer *buf)
 Write data from an evbuffer to a bufferevent buffer. More...
 
EVENT2_EXPORT_SYMBOL void ev_token_bucket_cfg_free (struct ev_token_bucket_cfg *cfg)
 Free all storage held in 'cfg'. More...
 
EVENT2_EXPORT_SYMBOL struct
ev_token_bucket_cfg * 
ev_token_bucket_cfg_new (size_t read_rate, size_t read_burst, size_t write_rate, size_t write_burst, const struct timeval *tick_len)
 Initialize and return a new object to configure the rate-limiting behavior of bufferevents. More...
 
Rate limit inspection

Return the current read or write bucket size for a bufferevent.

If it is not configured with a per-bufferevent ratelimit, return EV_SSIZE_MAX. This function does not inspect the group limit, if any. Note that it can return a negative value if the bufferevent has been made to read or write more than its limit.

EVENT2_EXPORT_SYMBOL ev_ssize_t bufferevent_get_read_limit (struct bufferevent *bev)
 
EVENT2_EXPORT_SYMBOL ev_ssize_t bufferevent_get_write_limit (struct bufferevent *bev)
 
Group Rate limit inspection

Return the read or write bucket size for a bufferevent rate limit group.

Note that it can return a negative value if bufferevents in the group have been made to read or write more than their limits.

EVENT2_EXPORT_SYMBOL ev_ssize_t bufferevent_rate_limit_group_get_read_limit (struct bufferevent_rate_limit_group *)
 
EVENT2_EXPORT_SYMBOL ev_ssize_t bufferevent_rate_limit_group_get_write_limit (struct bufferevent_rate_limit_group *)
 
Rate limit manipulation

Subtract a number of bytes from a bufferevent's read or write bucket.

The decrement value can be negative, if you want to manually refill the bucket. If the change puts the bucket above or below zero, the bufferevent will resume or suspend reading writing as appropriate. These functions make no change in the buckets for the bufferevent's group, if any.

Returns 0 on success, -1 on internal error.

EVENT2_EXPORT_SYMBOL int bufferevent_decrement_read_limit (struct bufferevent *bev, ev_ssize_t decr)
 
EVENT2_EXPORT_SYMBOL int bufferevent_decrement_write_limit (struct bufferevent *bev, ev_ssize_t decr)
 
Group rate limit manipulation

Subtract a number of bytes from a bufferevent rate-limiting group's read or write bucket.

The decrement value can be negative, if you want to manually refill the bucket. If the change puts the bucket above or below zero, the bufferevents in the group will resume or suspend reading writing as appropriate.

Returns 0 on success, -1 on internal error.

EVENT2_EXPORT_SYMBOL int bufferevent_rate_limit_group_decrement_read (struct bufferevent_rate_limit_group *, ev_ssize_t)
 
EVENT2_EXPORT_SYMBOL int bufferevent_rate_limit_group_decrement_write (struct bufferevent_rate_limit_group *, ev_ssize_t)
 

Filtering support

enum  bufferevent_filter_result { BEV_OK = 0, BEV_NEED_MORE = 1, BEV_ERROR = 2 }
 Values that filters can return. More...
 
typedef enum
bufferevent_filter_result(* 
bufferevent_filter_cb )(struct evbuffer *src, struct evbuffer *dst, ev_ssize_t dst_limit, enum bufferevent_flush_mode mode, void *ctx)
 A callback function to implement a filter for a bufferevent. More...
 
EVENT2_EXPORT_SYMBOL struct
bufferevent
bufferevent_filter_new (struct bufferevent *underlying, bufferevent_filter_cb input_filter, bufferevent_filter_cb output_filter, int options, void(*free_context)(void *), void *ctx)
 Allocate a new filtering bufferevent on top of an existing bufferevent. More...
 

Detailed Description

Functions for buffering data for network sending or receiving.

Bufferevents are higher level than evbuffers: each has an underlying evbuffer for reading and one for writing, and callbacks that are invoked under certain circumstances.

A bufferevent provides input and output buffers that get filled and drained automatically. The user of a bufferevent no longer deals directly with the I/O, but instead is reading from input and writing to output buffers.

Once initialized, the bufferevent structure can be used repeatedly with bufferevent_enable() and bufferevent_disable().

When reading is enabled, the bufferevent will try to read from the file descriptor onto its input buffer, and call the read callback. When writing is enabled, the bufferevent will try to write data onto its file descriptor when the output buffer has enough data, and call the write callback when the output buffer is sufficiently drained.

Bufferevents come in several flavors, including:

Socket-based bufferevents

A bufferevent that reads and writes data onto a network socket. Created with bufferevent_socket_new().

Paired bufferevents

A pair of bufferevents that send and receive data to one another without touching the network. Created with bufferevent_pair_new().

Filtering bufferevents

A bufferevent that transforms data, and sends or receives it over another underlying bufferevent. Created with bufferevent_filter_new().

SSL-backed bufferevents
A bufferevent that uses the openssl library to send and receive data over an encrypted connection. Created with bufferevent_openssl_socket_new() or bufferevent_openssl_filter_new().

Macro Definition Documentation

#define BEV_EVENT_CONNECTED   0x80

connect operation finished.

#define EV_RATE_LIMIT_MAX   EV_SSIZE_MAX

Maximum configurable rate- or burst-limit.

Typedef Documentation

typedef void(* bufferevent_data_cb)(struct bufferevent *bev, void *ctx)

A read or write callback for a bufferevent.

The read callback is triggered when new data arrives in the input buffer and the amount of readable data exceed the low watermark which is 0 by default.

The write callback is triggered if the write buffer has been exhausted or fell below its low watermark.

Parameters
bevthe bufferevent that triggered the callback
ctxthe user-specified context for this bufferevent
typedef void(* bufferevent_event_cb)(struct bufferevent *bev, short what, void *ctx)

An event/error callback for a bufferevent.

The event callback is triggered if either an EOF condition or another unrecoverable error was encountered.

For bufferevents with deferred callbacks, this is a bitwise OR of all errors that have happened on the bufferevent since the last callback invocation.

Parameters
bevthe bufferevent for which the error condition was reached
whata conjunction of flags: BEV_EVENT_READING or BEV_EVENT_WRITING to indicate if the error was encountered on the read or write path, and one of the following flags: BEV_EVENT_EOF, BEV_EVENT_ERROR, BEV_EVENT_TIMEOUT, BEV_EVENT_CONNECTED.
ctxthe user-specified context for this bufferevent
typedef enum bufferevent_filter_result(* bufferevent_filter_cb)(struct evbuffer *src, struct evbuffer *dst, ev_ssize_t dst_limit, enum bufferevent_flush_mode mode, void *ctx)

A callback function to implement a filter for a bufferevent.

Parameters
srcAn evbuffer to drain data from.
dstAn evbuffer to add data to.
limitA suggested upper bound of bytes to write to dst. The filter may ignore this value, but doing so means that it will overflow the high-water mark associated with dst. -1 means "no limit".
modeWhether we should write data as may be convenient (BEV_NORMAL), or flush as much data as we can (BEV_FLUSH), or flush as much as we can, possibly including an end-of-stream marker (BEV_FINISH).
ctxA user-supplied pointer.
Returns
BEV_OK if we wrote some data; BEV_NEED_MORE if we can't produce any more output until we get some input; and BEV_ERROR on an error.

Enumeration Type Documentation

Values that filters can return.

Enumerator
BEV_OK 

everything is okay

BEV_NEED_MORE 

the filter needs to read more data before output

BEV_ERROR 

the filter encountered a critical error, no further data can be processed.

Flags that can be passed into filters to let them know how to deal with the incoming data.

Enumerator
BEV_NORMAL 

usually set when processing data

BEV_FLUSH 

want to checkpoint all data sent.

BEV_FINISHED 

encountered EOF on read or done sending data

Options that can be specified when creating a bufferevent.

Enumerator
BEV_OPT_CLOSE_ON_FREE 

If set, we close the underlying file descriptor/bufferevent/whatever when this bufferevent is freed.

BEV_OPT_THREADSAFE 

If set, and threading is enabled, operations on this bufferevent are protected by a lock.

BEV_OPT_DEFER_CALLBACKS 

If set, callbacks are run deferred in the event loop.

BEV_OPT_UNLOCK_CALLBACKS 

If set, callbacks are executed without locks being held on the bufferevent.

This option currently requires that BEV_OPT_DEFER_CALLBACKS also be set; a future version of Libevent might remove the requirement.

Flags for bufferevent_trigger(_event) that modify when and how to trigger the callback.

Enumerator
BEV_TRIG_IGNORE_WATERMARKS 

trigger the callback regardless of the watermarks

BEV_TRIG_DEFER_CALLBACKS 

defer even if the callbacks are not

Function Documentation

EVENT2_EXPORT_SYMBOL int bufferevent_add_to_rate_limit_group ( struct bufferevent bev,
struct bufferevent_rate_limit_group *  g 
)

Add 'bev' to the list of bufferevents whose aggregate reading and writing is restricted by 'g'.

If 'g' is NULL, remove 'bev' from its current group.

A bufferevent may belong to no more than one rate-limit group at a time. If 'bev' is already a member of a group, it will be removed from its old group before being added to 'g'.

Return 0 on success and -1 on failure.

EVENT2_EXPORT_SYMBOL int bufferevent_base_set ( struct event_base base,
struct bufferevent bufev 
)

Assign a bufferevent to a specific event_base.

NOTE that only socket bufferevents support this function.

Parameters
basean event_base returned by event_init()
bufeva bufferevent struct returned by bufferevent_new() or bufferevent_socket_new()
Returns
0 if successful, or -1 if an error occurred
See Also
bufferevent_new()
EVENT2_EXPORT_SYMBOL int bufferevent_decref ( struct bufferevent bufev)

Public interface to manually decrement the reference count of a bufferevent.

Warning: make sure you know what you're doing. This is mainly used in conjunction with bufferevent_incref(). This will free up all data associated with a bufferevent if the reference count hits 0.

Parameters
bufevthe bufferevent to decrement the refcount on
Returns
1 if the bufferevent was freed, otherwise 0 (still referenced)
EVENT2_EXPORT_SYMBOL int bufferevent_disable ( struct bufferevent bufev,
short  event 
)

Disable a bufferevent.

Parameters
bufevthe bufferevent to be disabled
eventany combination of EV_READ | EV_WRITE.
Returns
0 if successful, or -1 if an error occurred
See Also
bufferevent_enable()
EVENT2_EXPORT_SYMBOL int bufferevent_enable ( struct bufferevent bufev,
short  event 
)

Enable a bufferevent.

Parameters
bufevthe bufferevent to be enabled
eventany combination of EV_READ | EV_WRITE.
Returns
0 if successful, or -1 if an error occurred
See Also
bufferevent_disable()
EVENT2_EXPORT_SYMBOL struct bufferevent* bufferevent_filter_new ( struct bufferevent underlying,
bufferevent_filter_cb  input_filter,
bufferevent_filter_cb  output_filter,
int  options,
void(*)(void *)  free_context,
void *  ctx 
)

Allocate a new filtering bufferevent on top of an existing bufferevent.

Parameters
underlyingthe underlying bufferevent.
input_filterThe filter to apply to data we read from the underlying bufferevent
output_filterThe filer to apply to data we write to the underlying bufferevent
optionsA bitfield of bufferevent options.
free_contextA function to use to free the filter context when this bufferevent is freed.
ctxA context pointer to pass to the filter functions.
EVENT2_EXPORT_SYMBOL int bufferevent_flush ( struct bufferevent bufev,
short  iotype,
enum bufferevent_flush_mode  mode 
)

Triggers the bufferevent to produce more data if possible.

Parameters
bufevthe bufferevent object
iotypeeither EV_READ or EV_WRITE or both.
modeeither BEV_NORMAL or BEV_FLUSH or BEV_FINISHED
Returns
-1 on failure, 0 if no data was produces, 1 if data was produced
EVENT2_EXPORT_SYMBOL void bufferevent_free ( struct bufferevent bufev)

Deallocate the storage associated with a bufferevent structure.

If there is pending data to write on the bufferevent, it probably won't be flushed before the bufferevent is freed.

Parameters
bufevthe bufferevent structure to be freed.
EVENT2_EXPORT_SYMBOL short bufferevent_get_enabled ( struct bufferevent bufev)

Return the events that are enabled on a given bufferevent.

Parameters
bufevthe bufferevent to inspect
Returns
A combination of EV_READ | EV_WRITE
EVENT2_EXPORT_SYMBOL struct evbuffer* bufferevent_get_input ( struct bufferevent bufev)

Returns the input buffer.

The user MUST NOT set the callback on this buffer.

Parameters
bufevthe bufferevent from which to get the evbuffer
Returns
the evbuffer object for the input buffer
EVENT2_EXPORT_SYMBOL ev_ssize_t bufferevent_get_max_single_read ( struct bufferevent bev)

Get the current size limit for single read operation.

EVENT2_EXPORT_SYMBOL ev_ssize_t bufferevent_get_max_single_write ( struct bufferevent bev)

Get the current size limit for single write operation.

EVENT2_EXPORT_SYMBOL struct evbuffer* bufferevent_get_output ( struct bufferevent bufev)

Returns the output buffer.

The user MUST NOT set the callback on this buffer.

When filters are being used, the filters need to be manually triggered if the output buffer was manipulated.

Parameters
bufevthe bufferevent from which to get the evbuffer
Returns
the evbuffer object for the output buffer
EVENT2_EXPORT_SYMBOL int bufferevent_get_priority ( const struct bufferevent bufev)

Return the priority of a bufferevent.

Only supported for socket bufferevents

EVENT2_EXPORT_SYMBOL void bufferevent_getcb ( struct bufferevent bufev,
bufferevent_data_cb readcb_ptr,
bufferevent_data_cb writecb_ptr,
bufferevent_event_cb eventcb_ptr,
void **  cbarg_ptr 
)

Retrieves the callbacks for a bufferevent.

Parameters
bufevthe bufferevent to examine.
readcb_ptrif readcb_ptr is nonnull, *readcb_ptr is set to the current read callback for the bufferevent.
writecb_ptrif writecb_ptr is nonnull, *writecb_ptr is set to the current write callback for the bufferevent.
eventcb_ptrif eventcb_ptr is nonnull, *eventcb_ptr is set to the current event callback for the bufferevent.
cbarg_ptrif cbarg_ptr is nonnull, *cbarg_ptr is set to the current callback argument for the bufferevent.
See Also
buffervent_setcb()
EVENT2_EXPORT_SYMBOL int bufferevent_getwatermark ( struct bufferevent bufev,
short  events,
size_t *  lowmark,
size_t *  highmark 
)

Retrieves the watermarks for read or write events.

Returns non-zero if events contains not only EV_READ or EV_WRITE. Returns zero if events equal EV_READ or EV_WRITE

Parameters
bufevthe bufferevent to be examined
eventsEV_READ or EV_WRITE
lowmarkreceives the lower watermark if not NULL
highmarkreceives the high watermark if not NULL
EVENT2_EXPORT_SYMBOL void bufferevent_incref ( struct bufferevent bufev)

Public interface to manually increase the reference count of a bufferevent this is useful in situations where a user may reference the bufferevent somewhere else (unknown to libevent)

Parameters
bufevthe bufferevent to increase the refcount on
EVENT2_EXPORT_SYMBOL void bufferevent_lock ( struct bufferevent bufev)

Acquire the lock on a bufferevent.

Has no effect if locking was not enabled with BEV_OPT_THREADSAFE.

EVENT2_EXPORT_SYMBOL struct bufferevent* bufferevent_pair_get_partner ( struct bufferevent bev)

Given one bufferevent returned by bufferevent_pair_new(), returns the other one if it still exists.

Otherwise returns NULL.

EVENT2_EXPORT_SYMBOL int bufferevent_pair_new ( struct event_base base,
int  options,
struct bufferevent pair[2] 
)

Allocate a pair of linked bufferevents.

The bufferevents behave as would two bufferevent_sock instances connected to opposite ends of a socketpair(), except that no internal socketpair is allocated.

Parameters
baseThe event base to associate with the socketpair.
optionsA set of options for this bufferevent
pairA pointer to an array to hold the two new bufferevent objects.
Returns
0 on success, -1 on failure.
EVENT2_EXPORT_SYMBOL int bufferevent_priority_set ( struct bufferevent bufev,
int  pri 
)

Assign a priority to a bufferevent.

Only supported for socket bufferevents.

Parameters
bufeva bufferevent struct
prithe priority to be assigned
Returns
0 if successful, or -1 if an error occurred
EVENT2_EXPORT_SYMBOL void bufferevent_rate_limit_group_free ( struct bufferevent_rate_limit_group *  )

Free a rate-limiting group.

The group must have no members when this function is called.

EVENT2_EXPORT_SYMBOL void bufferevent_rate_limit_group_get_totals ( struct bufferevent_rate_limit_group *  grp,
ev_uint64_t *  total_read_out,
ev_uint64_t *  total_written_out 
)

Inspect the total bytes read/written on a group.

Set the variable pointed to by total_read_out to the total number of bytes ever read on grp, and the variable pointed to by total_written_out to the total number of bytes ever written on grp.

EVENT2_EXPORT_SYMBOL struct bufferevent_rate_limit_group* bufferevent_rate_limit_group_new ( struct event_base base,
const struct ev_token_bucket_cfg *  cfg 
)

Create a new rate-limit group for bufferevents.

A rate-limit group constrains the maximum number of bytes sent and received, in toto, by all of its bufferevents.

Parameters
baseAn event_base to run any necessary timeouts for the group. Note that all bufferevents in the group do not necessarily need to share this event_base.
cfgThe rate-limit for this group.

Note that all rate-limits hare are currently best-effort: future versions of Libevent may implement them more tightly.

Note also that only some bufferevent types currently respect rate-limiting. They are: socket-based bufferevents (normal and IOCP-based), and SSL-based bufferevents.

EVENT2_EXPORT_SYMBOL void bufferevent_rate_limit_group_reset_totals ( struct bufferevent_rate_limit_group *  grp)

Reset the total bytes read/written on a group.

Reset the number of bytes read or written on grp as given by bufferevent_rate_limit_group_reset_totals().

EVENT2_EXPORT_SYMBOL int bufferevent_rate_limit_group_set_cfg ( struct bufferevent_rate_limit_group *  ,
const struct ev_token_bucket_cfg *   
)

Change the rate-limiting settings for a given rate-limiting group.

Return 0 on success, -1 on failure.

EVENT2_EXPORT_SYMBOL int bufferevent_rate_limit_group_set_min_share ( struct bufferevent_rate_limit_group *  ,
size_t   
)

Change the smallest quantum we're willing to allocate to any single bufferevent in a group for reading or writing at a time.

The rationale is that, because of TCP/IP protocol overheads and kernel behavior, if a rate-limiting group is so tight on bandwidth that you're only willing to send 1 byte per tick per bufferevent, you might instead want to batch up the reads and writes so that you send N bytes per 1/N of the bufferevents (chosen at random) each tick, so you still wind up send 1 byte per tick per bufferevent on average, but you don't send so many tiny packets.

The default min-share is currently 64 bytes.

Returns 0 on success, -1 on failure.

EVENT2_EXPORT_SYMBOL size_t bufferevent_read ( struct bufferevent bufev,
void *  data,
size_t  size 
)

Read data from a bufferevent buffer.

The bufferevent_read() function is used to read data from the input buffer.

Parameters
bufevthe bufferevent to be read from
datapointer to a buffer that will store the data
sizethe size of the data buffer, in bytes
Returns
the amount of data read, in bytes.
EVENT2_EXPORT_SYMBOL int bufferevent_read_buffer ( struct bufferevent bufev,
struct evbuffer buf 
)

Read data from a bufferevent buffer into an evbuffer.

This avoids memory copies.

Parameters
bufevthe bufferevent to be read from
bufthe evbuffer to which to add data
Returns
0 if successful, or -1 if an error occurred.
EVENT2_EXPORT_SYMBOL int bufferevent_remove_from_rate_limit_group ( struct bufferevent bev)

Remove 'bev' from its current rate-limit group (if any).

EVENT2_EXPORT_SYMBOL int bufferevent_set_max_single_read ( struct bufferevent bev,
size_t  size 
)

Set the size limit for single read operation.

Set to 0 for a reasonable default.

Return 0 on success and -1 on failure.

See Also
evbuffer_set_max_read()
EVENT2_EXPORT_SYMBOL int bufferevent_set_max_single_write ( struct bufferevent bev,
size_t  size 
)

Set the size limit for single write operation.

Set to 0 for a reasonable default.

Return 0 on success and -1 on failure.

EVENT2_EXPORT_SYMBOL int bufferevent_set_rate_limit ( struct bufferevent bev,
struct ev_token_bucket_cfg *  cfg 
)

Set the rate-limit of a the bufferevent 'bev' to the one specified in 'cfg'.

If 'cfg' is NULL, disable any per-bufferevent rate-limiting on 'bev'.

Note that only some bufferevent types currently respect rate-limiting. They are: socket-based bufferevents (normal and IOCP-based), and SSL-based bufferevents.

Return 0 on success, -1 on failure.

EVENT2_EXPORT_SYMBOL int bufferevent_set_timeouts ( struct bufferevent bufev,
const struct timeval *  timeout_read,
const struct timeval *  timeout_write 
)

Set the read and write timeout for a bufferevent.

A bufferevent's timeout will fire the first time that the indicated amount of time has elapsed since a successful read or write operation, during which the bufferevent was trying to read or write.

(In other words, if reading or writing is disabled, or if the bufferevent's read or write operation has been suspended because there's no data to write, or not enough bandwidth, or so on, the timeout isn't active. The timeout only becomes active when we we're willing to actually read or write.)

Calling bufferevent_enable or setting a timeout for a bufferevent whose timeout is already pending resets its timeout.

If the timeout elapses, the corresponding operation (EV_READ or EV_WRITE) becomes disabled until you re-enable it again. The bufferevent's event callback is called with the BEV_EVENT_TIMEOUT|BEV_EVENT_READING or BEV_EVENT_TIMEOUT|BEV_EVENT_WRITING.

Parameters
bufevthe bufferevent to be modified
timeout_readthe read timeout, or NULL
timeout_writethe write timeout, or NULL
EVENT2_EXPORT_SYMBOL void bufferevent_setcb ( struct bufferevent bufev,
bufferevent_data_cb  readcb,
bufferevent_data_cb  writecb,
bufferevent_event_cb  eventcb,
void *  cbarg 
)

Changes the callbacks for a bufferevent.

Parameters
bufevthe bufferevent object for which to change callbacks
readcbcallback to invoke when there is data to be read, or NULL if no callback is desired
writecbcallback to invoke when the file descriptor is ready for writing, or NULL if no callback is desired
eventcbcallback to invoke when there is an event on the file descriptor
cbargan argument that will be supplied to each of the callbacks (readcb, writecb, and errorcb)
See Also
bufferevent_new()
EVENT2_EXPORT_SYMBOL int bufferevent_setfd ( struct bufferevent bufev,
evutil_socket_t  fd 
)

Changes the file descriptor on which the bufferevent operates.

Not supported for all bufferevent types.

Parameters
bufevthe bufferevent object for which to change the file descriptor
fdthe file descriptor to operate on
EVENT2_EXPORT_SYMBOL void bufferevent_setwatermark ( struct bufferevent bufev,
short  events,
size_t  lowmark,
size_t  highmark 
)

Sets the watermarks for read and write events.

On input, a bufferevent does not invoke the user read callback unless there is at least low watermark data in the buffer. If the read buffer is beyond the high watermark, the bufferevent stops reading from the network. But be aware that bufferevent input/read buffer can overrun high watermark limit (typical example is openssl bufferevent), so you should not relay in this.

On output, the user write callback is invoked whenever the buffered data falls below the low watermark. Filters that write to this bufev will try not to write more bytes to this buffer than the high watermark would allow, except when flushing.

Parameters
bufevthe bufferevent to be modified
eventsEV_READ, EV_WRITE or both
lowmarkthe lower watermark to set
highmarkthe high watermark to set
EVENT2_EXPORT_SYMBOL int bufferevent_socket_connect ( struct bufferevent bufev,
const struct sockaddr *  addr,
int  socklen 
)

Launch a connect() attempt with a socket-based bufferevent.

When the connect succeeds, the eventcb will be invoked with BEV_EVENT_CONNECTED set.

If the bufferevent does not already have a socket set, we allocate a new socket here and make it nonblocking before we begin.

If no address is provided, we assume that the socket is already connecting, and configure the bufferevent so that a BEV_EVENT_CONNECTED event will be yielded when it is done connecting.

Parameters
bufevan existing bufferevent allocated with bufferevent_socket_new().
addrthe address we should connect to
socklenThe length of the address
Returns
0 on success, -1 on failure.
EVENT2_EXPORT_SYMBOL int bufferevent_socket_connect_hostname ( struct bufferevent bufev,
struct evdns_base *  evdns_base,
int  family,
const char *  hostname,
int  port 
)

Resolve the hostname 'hostname' and connect to it as with bufferevent_socket_connect().

Parameters
bufevAn existing bufferevent allocated with bufferevent_socket_new()
evdns_baseOptionally, an evdns_base to use for resolving hostnames asynchronously. May be set to NULL for a blocking resolve.
familyA preferred address family to resolve addresses to, or AF_UNSPEC for no preference. Only AF_INET, AF_INET6, and AF_UNSPEC are supported.
hostnameThe hostname to resolve; see below for notes on recognized formats
portThe port to connect to on the resolved address.
Returns
0 if successful, -1 on failure.
See Also
bufferevent_socket_connect_hostname_hints()
EVENT2_EXPORT_SYMBOL int bufferevent_socket_connect_hostname_hints ( struct bufferevent bufev,
struct evdns_base *  evdns_base,
const struct evutil_addrinfo hints_in,
const char *  hostname,
int  port 
)

Resolve the hostname 'hostname' and connect to it as with bufferevent_socket_connect().

Parameters
bufevAn existing bufferevent allocated with bufferevent_socket_new()
evdns_baseOptionally, an evdns_base to use for resolving hostnames asynchronously. May be set to NULL for a blocking resolve.
hints_inpoints to an addrinfo structure that specifies criteria for selecting the socket address structures to be used
hostnameThe hostname to resolve; see below for notes on recognized formats
portThe port to connect to on the resolved address.
Returns
0 if successful, -1 on failure.

Recognized hostname formats are:

www.example.com (hostname)
1.2.3.4     (ipv4address)
::1     (ipv6address)
[::1]       ([ipv6address])

Performance note: If you do not provide an evdns_base, this function may block while it waits for a DNS response. This is probably not what you want.

EVENT2_EXPORT_SYMBOL int bufferevent_socket_get_dns_error ( struct bufferevent bev)

Return the error code for the last failed DNS lookup attempt made by bufferevent_socket_connect_hostname().

Parameters
bevThe bufferevent object.
Returns
DNS error code.
See Also
evutil_gai_strerror()
EVENT2_EXPORT_SYMBOL struct bufferevent* bufferevent_socket_new ( struct event_base base,
evutil_socket_t  fd,
int  options 
)

Create a new socket bufferevent over an existing socket.

Parameters
basethe event base to associate with the new bufferevent.
fdthe file descriptor from which data is read and written to. This file descriptor is not allowed to be a pipe(2). It is safe to set the fd to -1, so long as you later set it with bufferevent_setfd or bufferevent_socket_connect().
optionsZero or more BEV_OPT_* flags
Returns
a pointer to a newly allocated bufferevent struct, or NULL if an error occurred
See Also
bufferevent_free()
EVENT2_EXPORT_SYMBOL void bufferevent_trigger ( struct bufferevent bufev,
short  iotype,
int  options 
)

Triggers bufferevent data callbacks.

The function will honor watermarks unless options contain BEV_TRIG_IGNORE_WATERMARKS. If the options contain BEV_OPT_DEFER_CALLBACKS, the callbacks are deferred.

Parameters
bufevthe bufferevent object
iotypeeither EV_READ or EV_WRITE or both.
options
EVENT2_EXPORT_SYMBOL void bufferevent_trigger_event ( struct bufferevent bufev,
short  what,
int  options 
)

Triggers the bufferevent event callback.

If the options contain BEV_OPT_DEFER_CALLBACKS, the callbacks are deferred.

Parameters
bufevthe bufferevent object
whatthe flags to pass onto the event callback
options
EVENT2_EXPORT_SYMBOL void bufferevent_unlock ( struct bufferevent bufev)

Release the lock on a bufferevent.

Has no effect if locking was not enabled with BEV_OPT_THREADSAFE.

EVENT2_EXPORT_SYMBOL int bufferevent_write ( struct bufferevent bufev,
const void *  data,
size_t  size 
)

Write data to a bufferevent buffer.

The bufferevent_write() function can be used to write data to the file descriptor. The data is appended to the output buffer and written to the descriptor automatically as it becomes available for writing.

Parameters
bufevthe bufferevent to be written to
dataa pointer to the data to be written
sizethe length of the data, in bytes
Returns
0 if successful, or -1 if an error occurred
See Also
bufferevent_write_buffer()
EVENT2_EXPORT_SYMBOL int bufferevent_write_buffer ( struct bufferevent bufev,
struct evbuffer buf 
)

Write data from an evbuffer to a bufferevent buffer.

The evbuffer is being drained as a result.

Parameters
bufevthe bufferevent to be written to
bufthe evbuffer to be written
Returns
0 if successful, or -1 if an error occurred
See Also
bufferevent_write()
EVENT2_EXPORT_SYMBOL void ev_token_bucket_cfg_free ( struct ev_token_bucket_cfg *  cfg)

Free all storage held in 'cfg'.

Note: 'cfg' is not currently reference-counted; it is not safe to free it until no bufferevent is using it.

EVENT2_EXPORT_SYMBOL struct ev_token_bucket_cfg* ev_token_bucket_cfg_new ( size_t  read_rate,
size_t  read_burst,
size_t  write_rate,
size_t  write_burst,
const struct timeval *  tick_len 
)

Initialize and return a new object to configure the rate-limiting behavior of bufferevents.

Parameters
read_rateThe maximum number of bytes to read per tick on average.
read_burstThe maximum number of bytes to read in any single tick.
write_rateThe maximum number of bytes to write per tick on average.
write_burstThe maximum number of bytes to write in any single tick.
tick_lenThe length of a single tick. Defaults to one second. Any fractions of a millisecond are ignored.

Note that all rate-limits hare are currently best-effort: future versions of Libevent may implement them more tightly.