static void
bev_async_consider_reading(struct bufferevent_async *beva)
{
size_t cur_size;
size_t read_high;
size_t at_most;
int limit;
struct bufferevent *bev = &beva->bev.bev;
/* Don't read if there is a read in progress, or we do not
* want to read. */
if (beva->read_in_progress || beva->bev.connecting)
return;
if (!beva->ok || !(bev->enabled&EV_READ)) {
bev_async_del_read(beva);
return;
}
/* Don't read if we're full */
cur_size = evbuffer_get_length(bev->input);
read_high = bev->wm_read.high;
if (read_high) {
if (cur_size >= read_high) {
bev_async_del_read(beva);
return;
}
at_most = read_high - cur_size;
} else {
at_most = 16384; /* FIXME totally magic. */
}
/* XXXX This over-commits. */
/* XXXX see also not above on cast on _bufferevent_get_write_max() */
limit = (int)_bufferevent_get_read_max(&beva->bev);
if (at_most >= (size_t)limit && limit >= 0)
at_most = limit;
if (beva->bev.read_suspended) {
bev_async_del_read(beva);
return;
}
bufferevent_incref(bev);
if (evbuffer_launch_read(bev->input, at_most, &beva->read_overlapped)) {
beva->ok = 0;
_bufferevent_run_eventcb(bev, BEV_EVENT_ERROR);
bufferevent_decref(bev);
} else {
beva->read_in_progress = at_most;
_bufferevent_decrement_read_buckets(&beva->bev, at_most);
bev_async_add_read(beva);
}
return;
}
static void
bev_async_consider_reading(struct bufferevent_async *b)
{
size_t cur_size;
size_t read_high;
size_t at_most;
int limit;
/* Don't read if there is a read in progress, or we do not
* want to read. */
if (!b->ok || b->read_in_progress || !(b->bev.bev.enabled&EV_READ))
return;
/* Don't read if we're full */
cur_size = evbuffer_get_length(b->bev.bev.input);
read_high = b->bev.bev.wm_read.high;
if (read_high) {
if (cur_size >= read_high)
return;
at_most = read_high - cur_size;
} else {
at_most = 16384; /* FIXME totally magic. */
}
/* XXXX This over-commits. */
limit = _bufferevent_get_read_max(&b->bev);
if (at_most >= limit)
at_most = limit;
if (b->bev.read_suspended)
return;
if (evbuffer_launch_read(b->bev.bev.input, at_most,
&b->read_overlapped)) {
EVUTIL_ASSERT(0);
} else {
b->read_in_progress = 1;
}
}
static void
bufferevent_readcb(evutil_socket_t fd, short event, void *arg)
{
struct bufferevent *bufev = arg;
struct bufferevent_private *bufev_p =
EVUTIL_UPCAST(bufev, struct bufferevent_private, bev);
struct evbuffer *input;
int res = 0;
short what = BEV_EVENT_READING;
ev_ssize_t howmuch = -1, readmax=-1;
_bufferevent_incref_and_lock(bufev);
if (event == EV_TIMEOUT) {
/* Note that we only check for event==EV_TIMEOUT. If
* event==EV_TIMEOUT|EV_READ, we can safely ignore the
* timeout, since a read has occurred */
what |= BEV_EVENT_TIMEOUT;
goto error;
}
input = bufev->input;
/*
* If we have a high watermark configured then we don't want to
* read more data than would make us reach the watermark.
*/
if (bufev->wm_read.high != 0) {
howmuch = bufev->wm_read.high - evbuffer_get_length(input);
/* 缓冲区超过高水位，挂起读。 */
if (howmuch <= 0) {
bufferevent_wm_suspend_read(bufev);
goto done;
}
}
//因为用户可以限速，所以这么要检测最大的可读大小。
//如果没有限速的话，那么将返回16384字节，即16K
//默认情况下是没有限速的。
readmax = _bufferevent_get_read_max(bufev_p);
if (howmuch < 0 || howmuch > readmax) /* The use of -1 for "unlimited"
* uglifies this code. XXXX */
howmuch = readmax;
if (bufev_p->read_suspended)
goto done;
evbuffer_unfreeze(input, 0);
res = evbuffer_read(input, fd, (int)howmuch); /* XXXX evbuffer_read would do better to take and return ev_ssize_t */
evbuffer_freeze(input, 0);
if (res == -1) {
int err = evutil_socket_geterror(fd);
if (EVUTIL_ERR_RW_RETRIABLE(err)) //EINTER or EAGAIN
goto reschedule;
/* error case */
what |= BEV_EVENT_ERROR;
} else if (res == 0) {
/* eof case */
what |= BEV_EVENT_EOF;
}
if (res <= 0)
goto error;
_bufferevent_decrement_read_buckets(bufev_p, res);
/* 数据大于低水平，调用用户设置的回调。 */
if (evbuffer_get_length(input) >= bufev->wm_read.low)
_bufferevent_run_readcb(bufev);
goto done;
reschedule:
goto done;
error:
bufferevent_disable(bufev, EV_READ);
_bufferevent_run_eventcb(bufev, what);
done:
_bufferevent_decref_and_unlock(bufev);
}
static void
bufferevent_readcb(evutil_socket_t fd, short event, void *arg)
{
struct bufferevent *bufev = arg;
struct bufferevent_private *bufev_p =
EVUTIL_UPCAST(bufev, struct bufferevent_private, bev);
struct evbuffer *input;
int res = 0;
short what = BEV_EVENT_READING;
int howmuch = -1, readmax=-1;
_bufferevent_incref_and_lock(bufev);
if (event == EV_TIMEOUT) {
what |= BEV_EVENT_TIMEOUT;
goto error;
}
input = bufev->input;
/*
* If we have a high watermark configured then we don't want to
* read more data than would make us reach the watermark.
*/
if (bufev->wm_read.high != 0) {
howmuch = bufev->wm_read.high - evbuffer_get_length(input);
/* we somehow lowered the watermark, stop reading */
if (howmuch <= 0) {
bufferevent_wm_suspend_read(bufev);
goto done;
}
}
readmax = _bufferevent_get_read_max(bufev_p);
if (howmuch < 0 || howmuch > readmax) /* The use of -1 for "unlimited"
* uglifies this code. */
howmuch = readmax;
if (bufev_p->read_suspended)
goto done;
evbuffer_unfreeze(input, 0);
res = evbuffer_read(input, fd, howmuch);
evbuffer_freeze(input, 0);
if (res == -1) {
int err = evutil_socket_geterror(fd);
if (EVUTIL_ERR_RW_RETRIABLE(err))
goto reschedule;
/* error case */
what |= BEV_EVENT_ERROR;
} else if (res == 0) {
/* eof case */
what |= BEV_EVENT_EOF;
}
if (res <= 0)
goto error;
_bufferevent_decrement_read_buckets(bufev_p, res);
/* Invoke the user callback - must always be called last */
if (evbuffer_get_length(input) >= bufev->wm_read.low)
_bufferevent_run_readcb(bufev);
goto done;
reschedule:
goto done;
error:
bufferevent_disable(bufev, EV_READ);
_bufferevent_run_eventcb(bufev, what);
done:
_bufferevent_decref_and_unlock(bufev);
}
