text: /*
   * Copyright (c) 2007-2009 Niels Provos and Nick Mathewson
   * Copyright (c) 2002-2006 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>
  
  #include "event-config.h"
  
  #ifdef _EVENT_HAVE_SYS_TIME_H
  #include <sys/time.h>
  #endif
  
  #include <errno.h>
  #include <stdio.h>
  #include <stdlib.h>
  #include <string.h>
  #ifdef _EVENT_HAVE_STDARG_H
  #include <stdarg.h>
  #endif
  
  #ifdef WIN32
  #include <winsock2.h>
  #endif
  
  #include "event2/util.h"
  #include "event2/bufferevent.h"
  #include "event2/buffer.h"
  #include "event2/bufferevent_struct.h"
  #include "event2/event.h"
  #include "log-internal.h"
  #include "mm-internal.h"
  #include "bufferevent-internal.h"
  #include "util-internal.h"
  
  /* prototypes */
  static int be_filter_enable(struct bufferevent *, short);
  static int be_filter_disable(struct bufferevent *, short);
  static void be_filter_destruct(struct bufferevent *);
  
  static void be_filter_readcb(struct bufferevent *, void *);
  static void be_filter_writecb(struct bufferevent *, void *);
  static void be_filter_eventcb(struct bufferevent *, short, void *);
  static int be_filter_flush(struct bufferevent *bufev,
      short iotype, enum bufferevent_flush_mode mode);
  static int be_filter_ctrl(struct bufferevent *, enum bufferevent_ctrl_op, union bufferevent_ctrl_data *);
  
  static void bufferevent_filtered_outbuf_cb(struct evbuffer *buf,
      const struct evbuffer_cb_info *info, void *arg);
  
  struct bufferevent_filtered {
  	struct bufferevent_private bev;
  
          /** The bufferevent that we read/write filtered data from/to. */
  	struct bufferevent *underlying;
          /** A callback on our outbuf to notice when somebody adds data */
  	struct evbuffer_cb_entry *outbuf_cb;
          /** True iff we have received an EOF callback from the underlying
           * bufferevent. */
  	unsigned got_eof;
  
          /** Function to free context when we're done. */
  	void (*free_context)(void *);
          /** Input filter */
  	bufferevent_filter_cb process_in;
          /** Output filter */
  	bufferevent_filter_cb process_out;
  
          /** User-supplied argument to the filters. */
  	void *context;
  };
  
  const struct bufferevent_ops bufferevent_ops_filter = {
  	"filter",
  	evutil_offsetof(struct bufferevent_filtered, bev),
  	be_filter_enable,
  	be_filter_disable,
  	be_filter_destruct,
  	_bufferevent_generic_adj_timeouts,
          be_filter_flush,
  	be_filter_ctrl,
  };
  
  /* Given a bufferevent that's really the bev filter of a bufferevent_filtered,
   * return that bufferevent_filtered. Returns NULL otherwise.*/
  static inline struct bufferevent_filtered *
  upcast(struct bufferevent *bev)
  {
  	struct bufferevent_filtered *bev_f;
  	if (bev->be_ops != &bufferevent_ops_filter)
  		return NULL;
  	bev_f = (void*)( ((char*)bev) -
  			 evutil_offsetof(struct bufferevent_filtered, bev.bev));
  	EVUTIL_ASSERT(bev_f->bev.bev.be_ops == &bufferevent_ops_filter);
  	return bev_f;
  }
  
  #define downcast(bev_f) (&(bev_f)->bev.bev)
  
  /** Return 1 iff bevf's underlying bufferevent's output buffer is at or
   * over its high watermark such that we should not write to it in a given
   * flush mode. */
  static int
  be_underlying_writebuf_full(struct bufferevent_filtered *bevf,
      enum bufferevent_flush_mode state)
  {
          struct bufferevent *u = bevf->underlying;
          return state == BEV_NORMAL &&
              u->wm_write.high &&
              evbuffer_get_length(u->output) >= u->wm_write.high;
  }
  
  /** Return 1 if our input buffer is at or over its high watermark such that we
   * should not write to it in a given flush mode. */
  static int
  be_readbuf_full(struct bufferevent_filtered *bevf,
      enum bufferevent_flush_mode state)
  {
          struct bufferevent *bufev = downcast(bevf);
          return state == BEV_NORMAL &&
              bufev->wm_read.high &&
              evbuffer_get_length(bufev->input) >= bufev->wm_read.high;
  }
  
  
  /* Filter to use when we're created with a NULL filter. */
  static enum bufferevent_filter_result
  be_null_filter(struct evbuffer *src, struct evbuffer *dst, ev_ssize_t lim,
  	       enum bufferevent_flush_mode state, void *ctx)
  {
  	(void)state;
  	if (evbuffer_remove_buffer(src, dst, lim) == 0)
  		return BEV_OK;
  	else
  		return BEV_ERROR;
  }
  
  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)
  {
  	struct bufferevent_filtered *bufev_f;
  	int tmp_options = options & ~BEV_OPT_THREADSAFE;
  
  	if (!input_filter)
  		input_filter = be_null_filter;
  	if (!output_filter)
  		output_filter = be_null_filter;
  
  	bufev_f = mm_calloc(1, sizeof(struct bufferevent_filtered));
  	if (!bufev_f)
  		return NULL;
  
  	if (bufferevent_init_common(&bufev_f->bev, underlying->ev_base,
  				    &bufferevent_ops_filter, tmp_options) < 0) {
  		mm_free(bufev_f);
  		return NULL;
  	}
  	if (options & BEV_OPT_THREADSAFE) {
  		bufferevent_enable_locking(downcast(bufev_f), NULL);
  	}
  
  	bufev_f->underlying = underlying;
  	bufev_f->process_in = input_filter;
  	bufev_f->process_out = output_filter;
  	bufev_f->free_context = free_context;
  	bufev_f->context = ctx;
  
  	bufferevent_setcb(bufev_f->underlying,
              be_filter_readcb, be_filter_writecb, be_filter_eventcb, bufev_f);
  
  	bufev_f->outbuf_cb = evbuffer_add_cb(downcast(bufev_f)->output,
  	   bufferevent_filtered_outbuf_cb, bufev_f);
  
  	_bufferevent_init_generic_timeout_cbs(downcast(bufev_f));
  	bufferevent_incref(underlying);
  
  	return downcast(bufev_f);
  }
  
  static void
  be_filter_destruct(struct bufferevent *bev)
  {
  	struct bufferevent_filtered *bevf = upcast(bev);
  	EVUTIL_ASSERT(bevf);
  	if (bevf->free_context)
  		bevf->free_context(bevf->context);
  
  	if (bevf->bev.options & BEV_OPT_CLOSE_ON_FREE)
  		bufferevent_free(bevf->underlying);
  
  	_bufferevent_del_generic_timeout_cbs(bev);
  }
  
  static int
  be_filter_enable(struct bufferevent *bev, short event)
  {
  	struct bufferevent_filtered *bevf = upcast(bev);
  	_bufferevent_generic_adj_timeouts(bev);
  	return bufferevent_enable(bevf->underlying, event);
  }
  
  static int
  be_filter_disable(struct bufferevent *bev, short event)
  {
  	struct bufferevent_filtered *bevf = upcast(bev);
  	_bufferevent_generic_adj_timeouts(bev);
  	return bufferevent_disable(bevf->underlying, event);
  }
  
  static enum bufferevent_filter_result
  be_filter_process_input(struct bufferevent_filtered *bevf,
  			enum bufferevent_flush_mode state,
  			int *processed_out)
  {
  	enum bufferevent_filter_result res;
  	struct bufferevent *bev = downcast(bevf);
  
          if (state == BEV_NORMAL) {
                  /* If we're in 'normal' mode, don't urge data on the filter
                   * unless we're reading data and under our high-water mark.*/
                  if (!(bev->enabled & EV_READ) ||
                      be_readbuf_full(bevf, state))
                          return BEV_OK;
          }
  
  	do {
                  ev_ssize_t limit = -1;
                  if (state == BEV_NORMAL && bev->wm_read.high)
                          limit = bev->wm_read.high -
                              evbuffer_get_length(bev->input);
  
  		res = bevf->process_in(bevf->underlying->input,
                      bev->input, limit, state, bevf->context);
  
  		if (res == BEV_OK)
  			*processed_out = 1;
  	} while (res == BEV_OK &&
  		 (bev->enabled & EV_READ) &&
  		 evbuffer_get_length(bevf->underlying->input) &&
    		 !be_readbuf_full(bevf, state));
  
  	if (*processed_out)
  		BEV_RESET_GENERIC_READ_TIMEOUT(bev);
  
  	return res;
  }
  
  
  static enum bufferevent_filter_result
  be_filter_process_output(struct bufferevent_filtered *bevf,
  			 enum bufferevent_flush_mode state,
  			 int *processed_out)
  {
  	/* Requires references and lock: might call writecb */
  	enum bufferevent_filter_result res = BEV_OK;
          struct bufferevent *bufev = downcast(bevf);
          int again = 0;
  
          if (state == BEV_NORMAL) {
                  /* If we're in 'normal' mode, don't urge data on the
                   * filter unless we're writing data, and the underlying
                   * bufferevent is accepting data, and we have data to
                   * give the filter.  If we're in 'flush' or 'finish',
                   * call the filter no matter what. */
                  if (!(bufev->enabled & EV_WRITE) ||
                      be_underlying_writebuf_full(bevf, state) ||
                      !evbuffer_get_length(bufev->output))
                          return BEV_OK;
          }
  
          /* disable the callback that calls this function
             when the user adds to the output buffer. */
          evbuffer_cb_set_flags(bufev->output, bevf->outbuf_cb, 0);
  
          do {
                  int processed = 0;
                  again = 0;
  
                  do {
                          ev_ssize_t limit = -1;
                          if (state == BEV_NORMAL &&
                              bevf->underlying->wm_write.high)
                                  limit = bevf->underlying->wm_write.high -
                                      evbuffer_get_length(bevf->underlying->output);
  
                          res = bevf->process_out(downcast(bevf)->output,
                              bevf->underlying->output,
                              limit,
                              state,
                              bevf->context);
  
                          if (res == BEV_OK)
                                  processed = *processed_out = 1;
                  } while (/* Stop if the filter wasn't successful...*/
                          res == BEV_OK &&
                          /* Or if we aren't writing any more. */
                          (bufev->enabled & EV_WRITE) &&
                          /* Of if we have nothing more to write and we are
                           * not flushing. */
                          evbuffer_get_length(bufev->output) &&
                          /* Or if we have filled the underlying output buffer. */
                          !be_underlying_writebuf_full(bevf,state));
  
                  if (processed &&
                      evbuffer_get_length(bufev->output) <= bufev->wm_write.low) {
                          /* call the write callback.*/
                          _bufferevent_run_writecb(bufev);
  
                          if (res == BEV_OK &&
                              (bufev->enabled & EV_WRITE) &&
                              evbuffer_get_length(bufev->output) &&
                              !be_underlying_writebuf_full(bevf, state)) {
                                  again = 1;
                          }
                  }
          } while (again);
  
          /* reenable the outbuf_cb */
          evbuffer_cb_set_flags(bufev->output,bevf->outbuf_cb,
              EVBUFFER_CB_ENABLED);
  
  	if (*processed_out)
  		BEV_RESET_GENERIC_WRITE_TIMEOUT(bufev);
  
  	return res;
  }
  
  /* Called when the size of our outbuf changes. */
  static void
  bufferevent_filtered_outbuf_cb(struct evbuffer *buf,
      const struct evbuffer_cb_info *cbinfo, void *arg)
  {
  	struct bufferevent_filtered *bevf = arg;
  	struct bufferevent *bev = downcast(bevf);
  
  	if (cbinfo->n_added) {
  		int processed_any = 0;
  		/* Somebody added more data to the output buffer. Try to
  		 * process it, if we should. */
  		_bufferevent_incref_and_lock(bev);
                  be_filter_process_output(bevf, BEV_NORMAL, &processed_any);
  		_bufferevent_decref_and_unlock(bev);
  	}
  }
  
  /* Called when the underlying socket has read. */
  static void
  be_filter_readcb(struct bufferevent *underlying, void *_me)
  {
  	struct bufferevent_filtered *bevf = _me;
  	enum bufferevent_filter_result res;
  	enum bufferevent_flush_mode state;
  	struct bufferevent *bufev = downcast(bevf);
  	int processed_any = 0;
  
  	_bufferevent_incref_and_lock(bufev);
  
  	if (bevf->got_eof)
  		state = BEV_FINISHED;
  	else
  		state = BEV_NORMAL;
  
  	res = be_filter_process_input(bevf, state, &processed_any);
  
  	/* XXX This should be in process_input, not here.  There are
  	 * other places that can call process-input, and they should
  	 * force readcb calls as needed. */
  	if (processed_any &&
  	    evbuffer_get_length(bufev->input) >= bufev->wm_read.low)
  		_bufferevent_run_readcb(bufev);
  
  	_bufferevent_decref_and_unlock(bufev);
  }
  
  /* Called when the underlying socket has drained enough that we can write to
     it. */
  static void
  be_filter_writecb(struct bufferevent *underlying, void *_me)
  {
  	struct bufferevent_filtered *bevf = _me;
  	struct bufferevent *bev = downcast(bevf);
          int processed_any = 0;
  
  	_bufferevent_incref_and_lock(bev);
          be_filter_process_output(bevf, BEV_NORMAL, &processed_any);
  	_bufferevent_decref_and_unlock(bev);
  }
  
  /* Called when the underlying socket has given us an error */
  static void
  be_filter_eventcb(struct bufferevent *underlying, short what, void *_me)
  {
  	struct bufferevent_filtered *bevf = _me;
  	struct bufferevent *bev = downcast(bevf);
  
  	_bufferevent_incref_and_lock(bev);
  	/* All we can really to is tell our own eventcb. */
  	_bufferevent_run_eventcb(bev, what);
  	_bufferevent_decref_and_unlock(bev);
  }
  
  static int
  be_filter_flush(struct bufferevent *bufev,
      short iotype, enum bufferevent_flush_mode mode)
  {
  	struct bufferevent_filtered *bevf = upcast(bufev);
  	int processed_any = 0;
  	EVUTIL_ASSERT(bevf);
  
  	_bufferevent_incref_and_lock(bufev);
  
  	if (iotype & EV_READ) {
  		be_filter_process_input(bevf, mode, &processed_any);
  	}
  	if (iotype & EV_WRITE) {
  		be_filter_process_output(bevf, mode, &processed_any);
  	}
          /* XXX check the return value? */
          /* XXX does this want to recursively call lower-level flushes? */
          bufferevent_flush(bevf->underlying, iotype, mode);
  
  	_bufferevent_decref_and_unlock(bufev);
  
  	return processed_any;
  }
  
  static int
  be_filter_ctrl(struct bufferevent *bev, enum bufferevent_ctrl_op op,
      union bufferevent_ctrl_data *data)
  {
  	struct bufferevent_filtered *bevf;
  	switch(op) {
  	case BEV_CTRL_GET_UNDERLYING:
  		bevf = upcast(bev);
  		data->ptr = bevf->underlying;
  		return 0;
  	case BEV_CTRL_GET_FD:
  	case BEV_CTRL_SET_FD:
  	default:
  		return -1;
  	}
  }
  