evbuffer.c

/*
 * Copyright (c) 2002-2004 Niels Provos <provos@citi.umich.edu>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <sys/types.h>

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#ifdef HAVE_SYS_TIME_H
#include <sys/time.h>
#endif

#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#ifdef HAVE_STDARG_H
#include <stdarg.h>
#endif

#ifdef WIN32
#include <winsock2.h>
#endif

#include "evutil.h"
#include "event.h"

/* prototypes */

void bufferevent_read_pressure_cb(struct evbuffer *, size_t, size_t, void *);

static int
bufferevent_add(struct event *ev, int timeout)
{
        struct timeval tv, *ptv = NULL;

        if (timeout) {
                evutil_timerclear(&tv);
                tv.tv_sec = timeout;
                ptv = &tv;
        }

        return (event_add(ev, ptv));
}

/* 
 * This callback is executed when the size of the input buffer changes.
 * We use it to apply back pressure on the reading side.
 */

void
bufferevent_read_pressure_cb(struct evbuffer *buf, size_t old, size_t now,
    void *arg) {
        struct bufferevent *bufev = arg;
        /* 
         * If we are below the watermark then reschedule reading if it's
         * still enabled.
         */
        if (bufev->wm_read.high == 0 || now < bufev->wm_read.high) {
                evbuffer_setcb(buf, NULL, NULL);

                if (bufev->enabled & EV_READ)
                        bufferevent_add(&bufev->ev_read, bufev->timeout_read);
        }
}

static void
bufferevent_readcb(int fd, short event, void *arg)
{
        struct bufferevent *bufev = arg;
        int res = 0;
        short what = EVBUFFER_READ;
        size_t len;
        int howmuch = -1;

        if (event == EV_TIMEOUT) {
                what |= EVBUFFER_TIMEOUT;
                goto error;
        }

        /*
         * 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_LENGTH(bufev->input);
                /* we might have lowered the watermark, stop reading */
                if (howmuch <= 0) {
                        struct evbuffer *buf = bufev->input;
                        event_del(&bufev->ev_read);
                        evbuffer_setcb(buf,
                            bufferevent_read_pressure_cb, bufev);
                        return;
                }
        }

        res = evbuffer_read(bufev->input, fd, howmuch);
        if (res == -1) {
                if (errno == EAGAIN || errno == EINTR)
                        goto reschedule;
                /* error case */
                what |= EVBUFFER_ERROR;
        } else if (res == 0) {
                /* eof case */
                what |= EVBUFFER_EOF;
        }

        if (res <= 0)
                goto error;

        bufferevent_add(&bufev->ev_read, bufev->timeout_read);

        /* See if this callbacks meets the water marks */
        len = EVBUFFER_LENGTH(bufev->input);
        if (bufev->wm_read.low != 0 && len < bufev->wm_read.low)
                return;
        if (bufev->wm_read.high != 0 && len >= bufev->wm_read.high) {
                struct evbuffer *buf = bufev->input;
                event_del(&bufev->ev_read);

                /* Now schedule a callback for us when the buffer changes */
                evbuffer_setcb(buf, bufferevent_read_pressure_cb, bufev);
        }

        /* Invoke the user callback - must always be called last */
        if (bufev->readcb != NULL)
                (*bufev->readcb)(bufev, bufev->cbarg);
        return;

 reschedule:
        bufferevent_add(&bufev->ev_read, bufev->timeout_read);
        return;

 error:
        (*bufev->errorcb)(bufev, what, bufev->cbarg);
}

static void
bufferevent_writecb(int fd, short event, void *arg)
{
        struct bufferevent *bufev = arg;
        int res = 0;
        short what = EVBUFFER_WRITE;

        if (event == EV_TIMEOUT) {
                what |= EVBUFFER_TIMEOUT;
                goto error;
        }

        if (EVBUFFER_LENGTH(bufev->output)) {
            res = evbuffer_write(bufev->output, fd);
            if (res == -1) {
#ifndef WIN32
/*todo. evbuffer uses WriteFile when WIN32 is set. WIN32 system calls do not
 *set errno. thus this error checking is not portable*/
                    if (errno == EAGAIN ||
                        errno == EINTR ||
                        errno == EINPROGRESS)
                            goto reschedule;
                    /* error case */
                    what |= EVBUFFER_ERROR;

#else
                                goto reschedule;
#endif

            } else if (res == 0) {
                    /* eof case */
                    what |= EVBUFFER_EOF;
            }
            if (res <= 0)
                    goto error;
        }

        if (EVBUFFER_LENGTH(bufev->output) != 0)
                bufferevent_add(&bufev->ev_write, bufev->timeout_write);

        /*
         * Invoke the user callback if our buffer is drained or below the
         * low watermark.
         */
        if (bufev->writecb != NULL &&
            EVBUFFER_LENGTH(bufev->output) <= bufev->wm_write.low)
                (*bufev->writecb)(bufev, bufev->cbarg);

        return;

 reschedule:
        if (EVBUFFER_LENGTH(bufev->output) != 0)
                bufferevent_add(&bufev->ev_write, bufev->timeout_write);
        return;

 error:
        (*bufev->errorcb)(bufev, what, bufev->cbarg);
}

/*
 * Create a new buffered event object.
 *
 * The read callback is invoked whenever we read new data.
 * The write callback is invoked whenever the output buffer is drained.
 * The error callback is invoked on a write/read error or on EOF.
 *
 * Both read and write callbacks maybe NULL.  The error callback is not
 * allowed to be NULL and have to be provided always.
 */

struct bufferevent *
bufferevent_new(int fd, evbuffercb readcb, evbuffercb writecb,
    everrorcb errorcb, void *cbarg)
{
        struct bufferevent *bufev;

        if ((bufev = calloc(1, sizeof(struct bufferevent))) == NULL)
                return (NULL);

        if ((bufev->input = evbuffer_new()) == NULL) {
                free(bufev);
                return (NULL);
        }

        if ((bufev->output = evbuffer_new()) == NULL) {
                evbuffer_free(bufev->input);
                free(bufev);
                return (NULL);
        }

        event_set(&bufev->ev_read, fd, EV_READ, bufferevent_readcb, bufev);
        event_set(&bufev->ev_write, fd, EV_WRITE, bufferevent_writecb, bufev);

        bufferevent_setcb(bufev, readcb, writecb, errorcb, cbarg);

        /*
         * Set to EV_WRITE so that using bufferevent_write is going to
         * trigger a callback.  Reading needs to be explicitly enabled
         * because otherwise no data will be available.
         */
        bufev->enabled = EV_WRITE;

        return (bufev);
}

void
bufferevent_setcb(struct bufferevent *bufev,
    evbuffercb readcb, evbuffercb writecb, everrorcb errorcb, void *cbarg)
{
        bufev->readcb = readcb;
        bufev->writecb = writecb;
        bufev->errorcb = errorcb;

        bufev->cbarg = cbarg;
}

void
bufferevent_setfd(struct bufferevent *bufev, int fd)
{
        event_del(&bufev->ev_read);
        event_del(&bufev->ev_write);

        event_set(&bufev->ev_read, fd, EV_READ, bufferevent_readcb, bufev);
        event_set(&bufev->ev_write, fd, EV_WRITE, bufferevent_writecb, bufev);
        if (bufev->ev_base != NULL) {
                event_base_set(bufev->ev_base, &bufev->ev_read);
                event_base_set(bufev->ev_base, &bufev->ev_write);
        }

        /* might have to manually trigger event registration */
}

int
bufferevent_priority_set(struct bufferevent *bufev, int priority)
{
        if (event_priority_set(&bufev->ev_read, priority) == -1)
                return (-1);
        if (event_priority_set(&bufev->ev_write, priority) == -1)
                return (-1);

        return (0);
}

/* Closing the file descriptor is the responsibility of the caller */

void
bufferevent_free(struct bufferevent *bufev)
{
        event_del(&bufev->ev_read);
        event_del(&bufev->ev_write);

        evbuffer_free(bufev->input);
        evbuffer_free(bufev->output);

        free(bufev);
}

/*
 * Returns 0 on success;
 *        -1 on failure.
 */

int
bufferevent_write(struct bufferevent *bufev, const void *data, size_t size)
{
        int res;

        res = evbuffer_add(bufev->output, data, size);

        if (res == -1)
                return (res);

        /* If everything is okay, we need to schedule a write */
        if (size > 0 && (bufev->enabled & EV_WRITE))
                bufferevent_add(&bufev->ev_write, bufev->timeout_write);

        return (res);
}

int
bufferevent_write_buffer(struct bufferevent *bufev, struct evbuffer *buf)
{
        int res;

        res = bufferevent_write(bufev, buf->buffer, buf->off);
        if (res != -1)
                evbuffer_drain(buf, buf->off);

        return (res);
}

size_t
bufferevent_read(struct bufferevent *bufev, void *data, size_t size)
{
        struct evbuffer *buf = bufev->input;

        if (buf->off < size)
                size = buf->off;

        /* Copy the available data to the user buffer */
        memcpy(data, buf->buffer, size);

        if (size)
                evbuffer_drain(buf, size);

        return (size);
}

int
bufferevent_enable(struct bufferevent *bufev, short event)
{
        if (event & EV_READ) {
                if (bufferevent_add(&bufev->ev_read, bufev->timeout_read) == -1)
                        return (-1);
        }
        if (event & EV_WRITE) {
                if (bufferevent_add(&bufev->ev_write, bufev->timeout_write) == -1)
                        return (-1);
        }

        bufev->enabled |= event;
        return (0);
}

int
bufferevent_disable(struct bufferevent *bufev, short event)
{
        if (event & EV_READ) {
                if (event_del(&bufev->ev_read) == -1)
                        return (-1);
        }
        if (event & EV_WRITE) {
                if (event_del(&bufev->ev_write) == -1)
                        return (-1);
        }

        bufev->enabled &= ~event;
        return (0);
}

/*
 * Sets the read and write timeout for a buffered event.
 */

void
bufferevent_settimeout(struct bufferevent *bufev,
    int timeout_read, int timeout_write) {
        bufev->timeout_read = timeout_read;
        bufev->timeout_write = timeout_write;

        if (event_pending(&bufev->ev_read, EV_READ, NULL))
                bufferevent_add(&bufev->ev_read, timeout_read);
        if (event_pending(&bufev->ev_write, EV_WRITE, NULL))
                bufferevent_add(&bufev->ev_write, timeout_write);
}

/*
 * Sets the water marks
 */

void
bufferevent_setwatermark(struct bufferevent *bufev, short events,
    size_t lowmark, size_t highmark)
{
        if (events & EV_READ) {
                bufev->wm_read.low = lowmark;
                bufev->wm_read.high = highmark;
        }

        if (events & EV_WRITE) {
                bufev->wm_write.low = lowmark;
                bufev->wm_write.high = highmark;
        }

        /* If the watermarks changed then see if we should call read again */
        bufferevent_read_pressure_cb(bufev->input,
            0, EVBUFFER_LENGTH(bufev->input), bufev);
}

int
bufferevent_base_set(struct event_base *base, struct bufferevent *bufev)
{
        int res;

        bufev->ev_base = base;

        res = event_base_set(base, &bufev->ev_read);
        if (res == -1)
                return (res);

        res = event_base_set(base, &bufev->ev_write);
        return (res);
}