TokenBucket.cc

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00006  * 
00007  * Intel Open Source License 
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00009  * Copyright (c) 2006 Intel Corporation. All rights reserved. 
00010  * 
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00018  *   Redistributions in binary form must reproduce the above copyright
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00038 
00039 #include "TokenBucket.h"
00040 
00041 namespace oasys {
00042 
00043 //----------------------------------------------------------------------
00044 TokenBucket::TokenBucket(const char* logpath,
00045                          u_int32_t   depth,   /* in bits */
00046                          u_int32_t   rate     /* in seconds */)
00047     : Logger("TokenBucket", logpath),
00048       depth_(depth),
00049       rate_(rate),
00050       tokens_(depth) // initialize full
00051 {
00052     log_debug("initialized token bucket with depth %u and rate %u",
00053               depth_, rate_);
00054     last_update_.get_time();
00055 }
00056 
00057 //----------------------------------------------------------------------
00058 void
00059 TokenBucket::update()
00060 {
00061     Time now;
00062     now.get_time();
00063 
00064     if (tokens_ == depth_) {
00065         log_debug("update: bucket already full, nothing to update");
00066         last_update_ = now;
00067         return;
00068     }
00069 
00070     u_int32_t elapsed = (now - last_update_).in_milliseconds();
00071     u_int32_t new_tokens = (rate_ * elapsed) / 1000;
00072 
00073     if (new_tokens != 0) {
00074         if ((tokens_ + new_tokens) > depth_) {
00075             new_tokens = depth_ - tokens_;
00076         }
00077 
00078         log_debug("update: filling %u/%u spent tokens after %u milliseconds",
00079                   new_tokens, depth_ - tokens_, elapsed);
00080         tokens_ += new_tokens;
00081         last_update_ = now;
00082         
00083     } else {
00084         // there's a chance that, for a slow rate, that the elapsed
00085         // time isn't enough to fill even a single token. in this
00086         // case, we leave last_update_ to where it was before,
00087         // otherwise we might starve the bucket.
00088         log_debug("update: %u milliseconds elapsed not enough to fill any tokens",
00089                   elapsed);
00090     }
00091 }
00092 
00093 //----------------------------------------------------------------------
00094 bool
00095 TokenBucket::drain(u_int32_t length)
00096 {
00097     update();
00098 
00099     if (length <= tokens_) {
00100         log_debug("drain: draining %u/%u tokens from bucket",
00101                   length, tokens_);
00102         tokens_ -= length;
00103         return true;
00104     } else {
00105         log_debug("drain: not enough tokens (%u) to drain %u from bucket",
00106                   tokens_, length);
00107         return false;
00108     }
00109 }
00110 
00111 //----------------------------------------------------------------------
00112 u_int32_t
00113 TokenBucket::time_to_fill()
00114 {
00115     update();
00116     
00117     u_int32_t t = ((depth_ - tokens_) * 1000) / rate_;
00118 
00119     log_debug("time_to_fill: %u tokens will be full in %u msecs",
00120               (depth_ - tokens_), t);
00121     return t;
00122 }
00123 
00124 //----------------------------------------------------------------------
00125 void
00126 TokenBucket::empty()
00127 {
00128     tokens_      = 0;
00129     last_update_.get_time();
00130 
00131     log_debug("empty: clearing bucket");
00132 }
00133 
00134 } // namespace oasys

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