<?xml version="1.0" encoding="iso-8859-1"?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html> <head> <title>get (CacheManager)</title> <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" /> <link rel="stylesheet" href="../.././rdoc-style.css" type="text/css" media="screen" /> </head> <body class="standalone-code"> <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> </body> </html>