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Map.html
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Map.html
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<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>
Class: Concurrent::Map
— Concurrent Ruby
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<div id="content"><h1>Class: Concurrent::Map
</h1>
<div class="box_info">
<dl>
<dt>Inherits:</dt>
<dd>
<span class="inheritName"><span class='object_link'>Collection::MapImplementation</span></span>
<ul class="fullTree">
<li>Object</li>
<li class="next">Concurrent::Map</li>
</ul>
<a href="#" class="inheritanceTree">show all</a>
</dd>
</dl>
<dl>
<dt>Defined in:</dt>
<dd>lib/concurrent/map.rb</dd>
</dl>
</div>
<h2>Overview</h2><div class="docstring">
<div class="discussion">
<p><code>Concurrent::Map</code> is a hash-like object and should have much better performance
characteristics, especially under high concurrency, than <code>Concurrent::Hash</code>.
However, <code>Concurrent::Map</code>is not strictly semantically equivalent to a ruby <code>Hash</code>
-- for instance, it does not necessarily retain ordering by insertion time as <code>Hash</code>
does. For most uses it should do fine though, and we recommend you consider
<code>Concurrent::Map</code> instead of <code>Concurrent::Hash</code> for your concurrency-safe hash needs.</p>
</div>
</div>
<div class="tags">
</div>
<h2>
Instance Method Summary
<small><a href="#" class="summary_toggle">collapse</a></small>
</h2>
<ul class="summary">
<li class="public ">
<span class="summary_signature">
<a href="#[]-instance_method" title="#[] (instance method)">#<strong>[]</strong>(key) ⇒ Object </a>
(also: #get)
</span>
<span class="summary_desc"><div class='inline'><p>Get a value with key.</p>
</div></span>
</li>
<li class="public ">
<span class="summary_signature">
<a href="#compute-instance_method" title="#compute (instance method)">#<strong>compute</strong>(key) {|old_value| ... } ⇒ Object<sup>?</sup> </a>
</span>
<span class="summary_desc"><div class='inline'><p>Compute and store new value for key.</p>
</div></span>
</li>
<li class="public ">
<span class="summary_signature">
<a href="#compute_if_absent-instance_method" title="#compute_if_absent (instance method)">#<strong>compute_if_absent</strong>(key) { ... } ⇒ Object </a>
</span>
<span class="summary_desc"><div class='inline'><p>Compute and store new value for key if the key is absent.</p>
</div></span>
</li>
<li class="public ">
<span class="summary_signature">
<a href="#compute_if_present-instance_method" title="#compute_if_present (instance method)">#<strong>compute_if_present</strong>(key) {|old_value| ... } ⇒ Object<sup>?</sup> </a>
</span>
<span class="summary_desc"><div class='inline'><p>Compute and store new value for key if the key is present.</p>
</div></span>
</li>
<li class="public ">
<span class="summary_signature">
<a href="#delete-instance_method" title="#delete (instance method)">#<strong>delete</strong>(key) ⇒ Object<sup>?</sup> </a>
</span>
<span class="summary_desc"><div class='inline'><p>Delete key and its value.</p>
</div></span>
</li>
<li class="public ">
<span class="summary_signature">
<a href="#delete_pair-instance_method" title="#delete_pair (instance method)">#<strong>delete_pair</strong>(key, value) ⇒ true, false </a>
</span>
<span class="summary_desc"><div class='inline'><p>Delete pair and its value if current value equals the provided value.</p>
</div></span>
</li>
<li class="public ">
<span class="summary_signature">
<a href="#each_key-instance_method" title="#each_key (instance method)">#<strong>each_key</strong> {|key| ... } ⇒ self </a>
</span>
<span class="summary_desc"><div class='inline'><p>Iterates over each key.</p>
</div></span>
</li>
<li class="public ">
<span class="summary_signature">
<a href="#each_pair-instance_method" title="#each_pair (instance method)">#<strong>each_pair</strong> {|key, value| ... } ⇒ self </a>
(also: #each)
</span>
<span class="summary_desc"><div class='inline'><p>Iterates over each key value pair.</p>
</div></span>
</li>
<li class="public ">
<span class="summary_signature">
<a href="#each_value-instance_method" title="#each_value (instance method)">#<strong>each_value</strong> {|value| ... } ⇒ self </a>
</span>
<span class="summary_desc"><div class='inline'><p>Iterates over each value.</p>
</div></span>
</li>
<li class="public ">
<span class="summary_signature">
<a href="#empty%3F-instance_method" title="#empty? (instance method)">#<strong>empty?</strong> ⇒ true, false </a>
</span>
<span class="summary_desc"><div class='inline'><p>Is map empty?.</p>
</div></span>
</li>
<li class="public ">
<span class="summary_signature">
<a href="#fetch-instance_method" title="#fetch (instance method)">#<strong>fetch</strong>(key, default_value = NULL) {|key| ... } ⇒ Object </a>
</span>
<span class="summary_desc"><div class='inline'><p>Get a value with key, or default_value when key is absent, or fail when no default_value is given.</p>
</div></span>
</li>
<li class="public ">
<span class="summary_signature">
<a href="#fetch_or_store-instance_method" title="#fetch_or_store (instance method)">#<strong>fetch_or_store</strong>(key, default_value = NULL) {|key| ... } ⇒ Object </a>
</span>
<span class="summary_desc"><div class='inline'><p>Fetch value with key, or store default value when key is absent, or fail when no default_value is given.</p>
</div></span>
</li>
<li class="public ">
<span class="summary_signature">
<a href="#get_and_set-instance_method" title="#get_and_set (instance method)">#<strong>get_and_set</strong>(key, value) ⇒ Object<sup>?</sup> </a>
</span>
<span class="summary_desc"><div class='inline'><p>Get the current value under key and set new value.</p>
</div></span>
</li>
<li class="public ">
<span class="summary_signature">
<a href="#initialize-instance_method" title="#initialize (instance method)">#<strong>initialize</strong>(options = nil, &block) ⇒ Map </a>
</span>
<span class="note title constructor">constructor</span>
<span class="summary_desc"><div class='inline'><p>A new instance of Map.</p>
</div></span>
</li>
<li class="public ">
<span class="summary_signature">
<a href="#key-instance_method" title="#key (instance method)">#<strong>key</strong>(value) ⇒ Object<sup>?</sup> </a>
(also: #index)
</span>
<span class="summary_desc"><div class='inline'><p>Find key of a value.</p>
</div></span>
</li>
<li class="public ">
<span class="summary_signature">
<a href="#keys-instance_method" title="#keys (instance method)">#<strong>keys</strong> ⇒ ::Array<Object> </a>
</span>
<span class="summary_desc"><div class='inline'><p>All keys.</p>
</div></span>
</li>
<li class="public ">
<span class="summary_signature">
<a href="#merge_pair-instance_method" title="#merge_pair (instance method)">#<strong>merge_pair</strong>(key, value) {|old_value| ... } ⇒ Object<sup>?</sup> </a>
</span>
<span class="summary_desc"><div class='inline'><p>If the key is absent, the value is stored, otherwise new value is computed with a block.</p>
</div></span>
</li>
<li class="public ">
<span class="summary_signature">
<a href="#put_if_absent-instance_method" title="#put_if_absent (instance method)">#<strong>put_if_absent</strong>(key, value) ⇒ Object<sup>?</sup> </a>
</span>
<span class="summary_desc"><div class='inline'><p>Insert value into map with key if key is absent in one atomic step.</p>
</div></span>
</li>
<li class="public ">
<span class="summary_signature">
<a href="#replace_if_exists-instance_method" title="#replace_if_exists (instance method)">#<strong>replace_if_exists</strong>(key, new_value) ⇒ Object<sup>?</sup> </a>
</span>
<span class="summary_desc"><div class='inline'><p>Replaces current value with new_value if key exists This method is atomic.</p>
</div></span>
</li>
<li class="public ">
<span class="summary_signature">
<a href="#replace_pair-instance_method" title="#replace_pair (instance method)">#<strong>replace_pair</strong>(key, old_value, new_value) ⇒ true, false </a>
</span>
<span class="summary_desc"><div class='inline'><p>Replaces old_value with new_value if key exists and current value matches old_value This method is atomic.</p>
</div></span>
</li>
<li class="public ">
<span class="summary_signature">
<a href="#size-instance_method" title="#size (instance method)">#<strong>size</strong> ⇒ Integer </a>
</span>
<span class="summary_desc"><div class='inline'><p>The size of map.</p>
</div></span>
</li>
<li class="public ">
<span class="summary_signature">
<a href="#value%3F-instance_method" title="#value? (instance method)">#<strong>value?</strong>(value) ⇒ true, false </a>
</span>
<span class="summary_desc"><div class='inline'><p>Is the value stored in the map.</p>
</div></span>
</li>
<li class="public ">
<span class="summary_signature">
<a href="#values-instance_method" title="#values (instance method)">#<strong>values</strong> ⇒ ::Array<Object> </a>
</span>
<span class="summary_desc"><div class='inline'><p>All values.</p>
</div></span>
</li>
</ul>
<div id="constructor_details" class="method_details_list">
<h2>Constructor Details</h2>
<div class="method_details first">
<h3 class="signature first" id="initialize-instance_method">
#<strong>initialize</strong>(options = nil, &block) ⇒ <tt><span class='object_link'><a href="" title="Concurrent::Map (class)">Map</a></span></tt>
</h3><div class="docstring">
<div class="discussion">
<p>Returns a new instance of Map</p>
</div>
</div>
<div class="tags">
</div><table class="source_code">
<tr>
<td>
<pre class="lines">
118
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127</pre>
</td>
<td>
<pre class="code"><span class="info file"># File 'lib/concurrent/map.rb', line 118</span>
<span class='kw'>def</span> <span class='id identifier rubyid_initialize'>initialize</span><span class='lparen'>(</span><span class='id identifier rubyid_options'>options</span> <span class='op'>=</span> <span class='kw'>nil</span><span class='comma'>,</span> <span class='op'>&</span><span class='id identifier rubyid_block'>block</span><span class='rparen'>)</span>
<span class='kw'>if</span> <span class='id identifier rubyid_options'>options</span><span class='period'>.</span><span class='id identifier rubyid_kind_of?'>kind_of?</span><span class='lparen'>(</span><span class='op'>::</span><span class='const'>Hash</span><span class='rparen'>)</span>
<span class='id identifier rubyid_validate_options_hash!'>validate_options_hash!</span><span class='lparen'>(</span><span class='id identifier rubyid_options'>options</span><span class='rparen'>)</span>
<span class='kw'>else</span>
<span class='id identifier rubyid_options'>options</span> <span class='op'>=</span> <span class='kw'>nil</span>
<span class='kw'>end</span>
<span class='kw'>super</span><span class='lparen'>(</span><span class='id identifier rubyid_options'>options</span><span class='rparen'>)</span>
<span class='ivar'>@default_proc</span> <span class='op'>=</span> <span class='id identifier rubyid_block'>block</span>
<span class='kw'>end</span></pre>
</td>
</tr>
</table>
</div>
</div>
<div id="instance_method_details" class="method_details_list">
<h2>Instance Method Details</h2>
<div class="method_details first">
<h3 class="signature first" id="[]-instance_method">
#<strong>[]</strong>(key) ⇒ <tt>Object</tt>
<span class="aliases">Also known as:
<span class="names"><span id='get-instance_method'>get</span></span>
</span>
</h3><div class="docstring">
<div class="discussion">
<p>Get a value with key</p>
</div>
</div>
<div class="tags">
<p class="tag_title">Parameters:</p>
<ul class="param">
<li>
<span class='name'>key</span>
<span class='type'>(<tt>Object</tt>)</span>
</li>
</ul>
<p class="tag_title">Returns:</p>
<ul class="return">
<li>
<span class='type'>(<tt>Object</tt>)</span>
—
<div class='inline'><p>the value</p>
</div>
</li>
</ul>
</div><table class="source_code">
<tr>
<td>
<pre class="lines">
132
133
134
135
136
137
138
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140
141
142
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144</pre>
</td>
<td>
<pre class="code"><span class="info file"># File 'lib/concurrent/map.rb', line 132</span>
<span class='kw'>def</span> <span class='op'>[]</span><span class='lparen'>(</span><span class='id identifier rubyid_key'>key</span><span class='rparen'>)</span>
<span class='kw'>if</span> <span class='id identifier rubyid_value'>value</span> <span class='op'>=</span> <span class='kw'>super</span> <span class='comment'># non-falsy value is an existing mapping, return it right away
</span> <span class='id identifier rubyid_value'>value</span>
<span class='comment'># re-check is done with get_or_default(key, NULL) instead of a simple !key?(key) in order to avoid a race condition, whereby by the time the current thread gets to the key?(key) call
</span> <span class='comment'># a key => value mapping might have already been created by a different thread (key?(key) would then return true, this elsif branch wouldn't be taken and an incorrent +nil+ value
</span> <span class='comment'># would be returned)
</span> <span class='comment'># note: nil == value check is not technically necessary
</span> <span class='kw'>elsif</span> <span class='ivar'>@default_proc</span> <span class='op'>&&</span> <span class='kw'>nil</span> <span class='op'>==</span> <span class='id identifier rubyid_value'>value</span> <span class='op'>&&</span> <span class='const'>NULL</span> <span class='op'>==</span> <span class='lparen'>(</span><span class='id identifier rubyid_value'>value</span> <span class='op'>=</span> <span class='id identifier rubyid_get_or_default'>get_or_default</span><span class='lparen'>(</span><span class='id identifier rubyid_key'>key</span><span class='comma'>,</span> <span class='const'>NULL</span><span class='rparen'>)</span><span class='rparen'>)</span>
<span class='ivar'>@default_proc</span><span class='period'>.</span><span class='id identifier rubyid_call'>call</span><span class='lparen'>(</span><span class='kw'>self</span><span class='comma'>,</span> <span class='id identifier rubyid_key'>key</span><span class='rparen'>)</span>
<span class='kw'>else</span>
<span class='id identifier rubyid_value'>value</span>
<span class='kw'>end</span>
<span class='kw'>end</span></pre>
</td>
</tr>
</table>
</div>
<div class="method_details ">
<h3 class="signature " id="compute-instance_method">
#<strong>compute</strong>(key) {|old_value| ... } ⇒ <tt>Object</tt><sup>?</sup>
</h3><div class="docstring">
<div class="discussion">
<div class="note notetag">
<strong>Note:</strong>
<div class='inline'><p>Atomic methods taking a block do not allow the <code>self</code> instance
to be used within the block. Doing so will cause a deadlock.</p>
</div>
</div>
<p>Compute and store new value for key.
This method is atomic.</p>
</div>
</div>
<div class="tags">
<p class="tag_title">Parameters:</p>
<ul class="param">
<li>
<span class='name'>key</span>
<span class='type'>(<tt>Object</tt>)</span>
</li>
</ul>
<p class="tag_title">Yields:</p>
<ul class="yield">
<li>
<span class='type'></span>
<div class='inline'><p>compute new value from old one</p>
</div>
</li>
</ul>
<p class="tag_title">Yield Parameters:</p>
<ul class="yieldparam">
<li>
<span class='name'>old_value</span>
<span class='type'>(<tt>Object</tt>, <tt>nil</tt>)</span>
—
<div class='inline'><p>old_value, or nil when key is absent</p>
</div>
</li>
</ul>
<p class="tag_title">Yield Returns:</p>
<ul class="yieldreturn">
<li>
<span class='type'>(<tt>Object</tt>, <tt>nil</tt>)</span>
—
<div class='inline'><p>new value, when nil the key is removed</p>
</div>
</li>
</ul>
<p class="tag_title">Returns:</p>
<ul class="return">
<li>
<span class='type'>(<tt>Object</tt>, <tt>nil</tt>)</span>
—
<div class='inline'><p>new value or nil</p>
</div>
</li>
</ul>
</div><table class="source_code">
<tr>
<td>
<pre class="lines">
</pre>
</td>
<td>
<pre class="code"><span class="info file"># File 'lib/concurrent/map.rb', line 61</span>
</pre>
</td>
</tr>
</table>
</div>
<div class="method_details ">
<h3 class="signature " id="compute_if_absent-instance_method">
#<strong>compute_if_absent</strong>(key) { ... } ⇒ <tt>Object</tt>
</h3><div class="docstring">
<div class="discussion">
<div class="note notetag">
<strong>Note:</strong>
<div class='inline'><p>Atomic methods taking a block do not allow the <code>self</code> instance
to be used within the block. Doing so will cause a deadlock.</p>
</div>
</div>
<p>Compute and store new value for key if the key is absent.
This method is atomic.</p>
</div>
</div>
<div class="tags">
<p class="tag_title">Parameters:</p>
<ul class="param">
<li>
<span class='name'>key</span>
<span class='type'>(<tt>Object</tt>)</span>
</li>