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<title>get (CacheManager)</title>
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<pre><span class="ruby-comment cmt"># File lib/storage/cache.rb, line 151</span>
<span class="ruby-keyword kw">def</span> <span class="ruby-identifier">get</span>(<span class="ruby-identifier">oid</span>)
<span class="ruby-keyword kw">return</span> <span class="ruby-keyword kw">nil</span> <span class="ruby-keyword kw">if</span> <span class="ruby-identifier">oid</span>.<span class="ruby-identifier">nil?</span>
<span class="ruby-ivar">@st</span>.<span class="ruby-identifier">inc</span>(<span class="ruby-identifier">:reads</span>)
<span class="ruby-identifier">hv</span> = <span class="ruby-identifier">hash</span>(<span class="ruby-identifier">oid</span>)
<span class="ruby-comment cmt"># search the cache
</span>
<span class="ruby-ivar">@cache</span>[<span class="ruby-identifier">hv</span>].<span class="ruby-identifier">each</span> <span class="ruby-keyword kw">do</span> <span class="ruby-operator">|</span><span class="ruby-identifier">ce</span><span class="ruby-operator">|</span>
<span class="ruby-keyword kw">if</span> <span class="ruby-identifier">ce</span>.<span class="ruby-identifier">oid</span> <span class="ruby-operator">==</span> <span class="ruby-identifier">oid</span>
<span class="ruby-ivar">@st</span>.<span class="ruby-identifier">inc</span>(<span class="ruby-identifier">:cache_read_hits</span>)
<span class="ruby-comment cmt"># need to try putting hot hit to the head of the list?
</span>
<span class="ruby-keyword kw">return</span> <span class="ruby-identifier">ce</span>.<span class="ruby-identifier">obj</span>
<span class="ruby-keyword kw">end</span>
<span class="ruby-keyword kw">end</span>
<span class="ruby-comment cmt"># cache miss - search the database
</span>
<span class="ruby-keyword kw">if</span> <span class="ruby-ivar">@db</span>.<span class="ruby-identifier">has_key?</span> <span class="ruby-identifier">oid</span>.<span class="ruby-identifier">to_s</span>
<span class="ruby-identifier">ret</span> = <span class="ruby-constant">Utility</span>.<span class="ruby-identifier">decode</span>(<span class="ruby-ivar">@db</span>[<span class="ruby-identifier">oid</span>.<span class="ruby-identifier">to_s</span>])
<span class="ruby-keyword kw">else</span>
<span class="ruby-ivar">@st</span>.<span class="ruby-identifier">inc</span>(<span class="ruby-identifier">:database_read_fails</span>)
<span class="ruby-keyword kw">return</span> <span class="ruby-keyword kw">nil</span>
<span class="ruby-keyword kw">end</span>
<span class="ruby-ivar">@st</span>.<span class="ruby-identifier">inc</span>(<span class="ruby-identifier">:database_reads</span>)
<span class="ruby-comment cmt"># get and remove the last entry off this list
</span>
<span class="ruby-identifier">ch</span> = <span class="ruby-ivar">@cache</span>[<span class="ruby-identifier">hv</span>].<span class="ruby-identifier">pop</span>
<span class="ruby-comment cmt"># if its dirty we write it to the database
</span>
<span class="ruby-keyword kw">if</span> <span class="ruby-identifier">ch</span>.<span class="ruby-identifier">dirty?</span> <span class="ruby-operator">&&</span> <span class="ruby-operator">!</span><span class="ruby-identifier">ch</span>.<span class="ruby-identifier">dead?</span>
<span class="ruby-ivar">@db</span>[<span class="ruby-identifier">ch</span>.<span class="ruby-identifier">oid</span>.<span class="ruby-identifier">to_s</span>] = <span class="ruby-constant">Utility</span>.<span class="ruby-identifier">encode</span>(<span class="ruby-identifier">ch</span>.<span class="ruby-identifier">obj</span>)
<span class="ruby-ivar">@st</span>.<span class="ruby-identifier">inc</span>(<span class="ruby-identifier">:database_writes</span>)
<span class="ruby-keyword kw">if</span> <span class="ruby-identifier">ch</span>.<span class="ruby-identifier">noswap?</span> <span class="ruby-comment cmt"># here we have a problem we can't use this
</span>
<span class="ruby-comment cmt"># first push it back onto the list
</span>
<span class="ruby-ivar">@cache</span>[<span class="ruby-identifier">hv</span>].<span class="ruby-identifier">unshift</span> <span class="ruby-identifier">ch</span>
<span class="ruby-comment cmt"># get ourselves a brand new
</span>
<span class="ruby-identifier">ch</span> = <span class="ruby-constant">CacheEntry</span>.<span class="ruby-identifier">new</span>
<span class="ruby-comment cmt"># problem solved
</span>
<span class="ruby-comment cmt"># the depth of any list chains will be cache_depth + # noswap entries
</span>
<span class="ruby-keyword kw">end</span>
<span class="ruby-keyword kw">end</span>
<span class="ruby-comment cmt"># assign our new object to the cache entry
</span>
<span class="ruby-identifier">ch</span>.<span class="ruby-identifier">obj</span> = <span class="ruby-identifier">ret</span>
<span class="ruby-identifier">ch</span>.<span class="ruby-identifier">oid</span> = <span class="ruby-identifier">oid</span>
<span class="ruby-identifier">ch</span>.<span class="ruby-identifier">clean!</span>
<span class="ruby-comment cmt"># push it to the head of the list
</span>
<span class="ruby-ivar">@cache</span>[<span class="ruby-identifier">hv</span>].<span class="ruby-identifier">unshift</span> <span class="ruby-identifier">ch</span>
<span class="ruby-identifier">ret</span>
<span class="ruby-keyword kw">end</span></pre>
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