text: /*
   * Copyright (c) 2009-2012 Niels Provos and Nick Mathewson
   *
   * 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.
   */
  #ifndef RATELIM_INTERNAL_H_INCLUDED_
  #define RATELIM_INTERNAL_H_INCLUDED_
  
  #ifdef __cplusplus
  extern "C" {
  #endif
  
  #include "event2/util.h"
  
  /** A token bucket is an internal structure that tracks how many bytes we are
   * currently willing to read or write on a given bufferevent or group of
   * bufferevents */
  struct ev_token_bucket {
  	/** How many bytes are we willing to read or write right now? These
  	 * values are signed so that we can do "defecit spending" */
  	ev_ssize_t read_limit, write_limit;
  	/** When was this bucket last updated?  Measured in abstract 'ticks'
  	 * relative to the token bucket configuration. */
  	ev_uint32_t last_updated;
  };
  
  /** Configuration info for a token bucket or set of token buckets. */
  // 用于限制单个或者一组 bufferevent 速率的一对记号存储器的配置值
  struct ev_token_bucket_cfg {
  	/** How many bytes are we willing to read on average per tick? */
  	size_t read_rate;
  	/** How many bytes are we willing to read at most in any one tick? */
  	size_t read_maximum;
  	/** How many bytes are we willing to write on average per tick? */
  	size_t write_rate;
  	/** How many bytes are we willing to write at most in any one tick? */
  	size_t write_maximum;
  
  	/* How long is a tick?  Note that fractions of a millisecond are
  	 * ignored. */
  	struct timeval tick_timeout;
  
  	/* How long is a tick, in milliseconds?  Derived from tick_timeout. */
  	unsigned msec_per_tick;
  };
  
  /** The current tick is 'current_tick': add bytes to 'bucket' as specified in
   * 'cfg'. */
  int ev_token_bucket_update_(struct ev_token_bucket *bucket,
      const struct ev_token_bucket_cfg *cfg,
      ev_uint32_t current_tick);
  
  /** In which tick does 'tv' fall according to 'cfg'?  Note that ticks can
   * overflow easily; your code needs to handle this. */
  ev_uint32_t ev_token_bucket_get_tick_(const struct timeval *tv,
      const struct ev_token_bucket_cfg *cfg);
  
  /** Adjust 'bucket' to respect 'cfg', and note that it was last updated in
   * 'current_tick'.  If 'reinitialize' is true, we are changing the
   * configuration of 'bucket'; otherwise, we are setting it up for the first
   * time.
   */
  int ev_token_bucket_init_(struct ev_token_bucket *bucket,
      const struct ev_token_bucket_cfg *cfg,
      ev_uint32_t current_tick,
      int reinitialize);
  
  int bufferevent_remove_from_rate_limit_group_internal_(struct bufferevent *bev,
      int unsuspend);
  
  /** Decrease the read limit of 'b' by 'n' bytes */
  #define ev_token_bucket_decrement_read(b,n)	\
  	do {					\
  		(b)->read_limit -= (n);		\
  	} while (0)
  /** Decrease the write limit of 'b' by 'n' bytes */
  #define ev_token_bucket_decrement_write(b,n)	\
  	do {					\
  		(b)->write_limit -= (n);	\
  	} while (0)
  
  #ifdef __cplusplus
  }
  #endif
  
  #endif
  