<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> <html> <head> <!-- Generated by HsColour, http://www.cs.york.ac.uk/fp/darcs/hscolour/ --> <title>Control/Concurrent/QSemN.hs</title> <link type='text/css' rel='stylesheet' href='hscolour.css' /> </head> <body> <pre><a name="line-1"></a><span class='hs-comment'>-----------------------------------------------------------------------------</span> <a name="line-2"></a><span class='hs-comment'>-- |</span> <a name="line-3"></a><span class='hs-comment'>-- Module : Control.Concurrent.QSemN</span> <a name="line-4"></a><span class='hs-comment'>-- Copyright : (c) The University of Glasgow 2001</span> <a name="line-5"></a><span class='hs-comment'>-- License : BSD-style (see the file libraries/base/LICENSE)</span> <a name="line-6"></a><span class='hs-comment'>-- </span> <a name="line-7"></a><span class='hs-comment'>-- Maintainer : libraries@haskell.org</span> <a name="line-8"></a><span class='hs-comment'>-- Stability : experimental</span> <a name="line-9"></a><span class='hs-comment'>-- Portability : non-portable (concurrency)</span> <a name="line-10"></a><span class='hs-comment'>--</span> <a name="line-11"></a><span class='hs-comment'>-- Quantity semaphores in which each thread may wait for an arbitrary</span> <a name="line-12"></a><span class='hs-comment'>-- \"amount\".</span> <a name="line-13"></a><span class='hs-comment'>--</span> <a name="line-14"></a><span class='hs-comment'>-----------------------------------------------------------------------------</span> <a name="line-15"></a> <a name="line-16"></a><span class='hs-keyword'>module</span> <span class='hs-conid'>Control</span><span class='hs-varop'>.</span><span class='hs-conid'>Concurrent</span><span class='hs-varop'>.</span><span class='hs-conid'>QSemN</span> <a name="line-17"></a> <span class='hs-layout'>(</span> <span class='hs-comment'>-- * General Quantity Semaphores</span> <a name="line-18"></a> <span class='hs-conid'>QSemN</span><span class='hs-layout'>,</span> <span class='hs-comment'>-- abstract</span> <a name="line-19"></a> <span class='hs-varid'>newQSemN</span><span class='hs-layout'>,</span> <span class='hs-comment'>-- :: Int -> IO QSemN</span> <a name="line-20"></a> <span class='hs-varid'>waitQSemN</span><span class='hs-layout'>,</span> <span class='hs-comment'>-- :: QSemN -> Int -> IO ()</span> <a name="line-21"></a> <span class='hs-varid'>signalQSemN</span> <span class='hs-comment'>-- :: QSemN -> Int -> IO ()</span> <a name="line-22"></a> <span class='hs-layout'>)</span> <span class='hs-keyword'>where</span> <a name="line-23"></a> <a name="line-24"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Prelude</span> <a name="line-25"></a> <a name="line-26"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Control</span><span class='hs-varop'>.</span><span class='hs-conid'>Concurrent</span><span class='hs-varop'>.</span><span class='hs-conid'>MVar</span> <a name="line-27"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Control</span><span class='hs-varop'>.</span><span class='hs-conid'>Exception</span> <span class='hs-layout'>(</span> <span class='hs-varid'>mask_</span> <span class='hs-layout'>)</span> <a name="line-28"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>Typeable</span> <a name="line-29"></a> <a name="line-30"></a><span class='hs-cpp'>#include "Typeable.h"</span> <a name="line-31"></a> <a name="line-32"></a><a name="QSemN"></a><span class='hs-comment'>-- |A 'QSemN' is a quantity semaphore, in which the available</span> <a name="line-33"></a><a name="QSemN"></a><span class='hs-comment'>-- \"quantity\" may be signalled or waited for in arbitrary amounts.</span> <a name="line-34"></a><a name="QSemN"></a><span class='hs-keyword'>newtype</span> <span class='hs-conid'>QSemN</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>QSemN</span> <span class='hs-layout'>(</span><span class='hs-conid'>MVar</span> <span class='hs-layout'>(</span><span class='hs-conid'>Int</span><span class='hs-layout'>,</span><span class='hs-keyglyph'>[</span><span class='hs-layout'>(</span><span class='hs-conid'>Int</span><span class='hs-layout'>,</span><span class='hs-conid'>MVar</span> <span class='hs-conid'>()</span><span class='hs-layout'>)</span><span class='hs-keyglyph'>]</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <a name="line-35"></a> <a name="line-36"></a><span class='hs-conid'>INSTANCE_TYPEABLE0</span><span class='hs-layout'>(</span><span class='hs-conid'>QSemN</span><span class='hs-layout'>,</span><span class='hs-varid'>qSemNTc</span><span class='hs-layout'>,</span><span class='hs-str'>"QSemN"</span><span class='hs-layout'>)</span> <a name="line-37"></a> <a name="line-38"></a><a name="newQSemN"></a><span class='hs-comment'>-- |Build a new 'QSemN' with a supplied initial quantity.</span> <a name="line-39"></a><span class='hs-comment'>-- The initial quantity must be at least 0.</span> <a name="line-40"></a><span class='hs-definition'>newQSemN</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Int</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>IO</span> <span class='hs-conid'>QSemN</span> <a name="line-41"></a><span class='hs-definition'>newQSemN</span> <span class='hs-varid'>initial</span> <span class='hs-keyglyph'>=</span> <a name="line-42"></a> <span class='hs-keyword'>if</span> <span class='hs-varid'>initial</span> <span class='hs-varop'><</span> <span class='hs-num'>0</span> <a name="line-43"></a> <span class='hs-keyword'>then</span> <span class='hs-varid'>fail</span> <span class='hs-str'>"newQSemN: Initial quantity must be non-negative"</span> <a name="line-44"></a> <span class='hs-keyword'>else</span> <span class='hs-keyword'>do</span> <span class='hs-varid'>sem</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>newMVar</span> <span class='hs-layout'>(</span><span class='hs-varid'>initial</span><span class='hs-layout'>,</span> <span class='hs-conid'>[]</span><span class='hs-layout'>)</span> <a name="line-45"></a> <span class='hs-varid'>return</span> <span class='hs-layout'>(</span><span class='hs-conid'>QSemN</span> <span class='hs-varid'>sem</span><span class='hs-layout'>)</span> <a name="line-46"></a> <a name="line-47"></a><a name="waitQSemN"></a><span class='hs-comment'>-- |Wait for the specified quantity to become available</span> <a name="line-48"></a><span class='hs-definition'>waitQSemN</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>QSemN</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Int</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>IO</span> <span class='hs-conid'>()</span> <a name="line-49"></a><span class='hs-definition'>waitQSemN</span> <span class='hs-layout'>(</span><span class='hs-conid'>QSemN</span> <span class='hs-varid'>sem</span><span class='hs-layout'>)</span> <span class='hs-varid'>sz</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>mask_</span> <span class='hs-varop'>$</span> <span class='hs-keyword'>do</span> <a name="line-50"></a> <span class='hs-layout'>(</span><span class='hs-varid'>avail</span><span class='hs-layout'>,</span><span class='hs-varid'>blocked</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>takeMVar</span> <span class='hs-varid'>sem</span> <span class='hs-comment'>-- gain ex. access</span> <a name="line-51"></a> <span class='hs-keyword'>let</span> <span class='hs-varid'>remaining</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>avail</span> <span class='hs-comment'>-</span> <span class='hs-varid'>sz</span> <a name="line-52"></a> <span class='hs-keyword'>if</span> <span class='hs-varid'>remaining</span> <span class='hs-varop'>>=</span> <span class='hs-num'>0</span> <span class='hs-keyword'>then</span> <a name="line-53"></a> <span class='hs-comment'>-- discharging 'sz' still leaves the semaphore</span> <a name="line-54"></a> <span class='hs-comment'>-- in an 'unblocked' state.</span> <a name="line-55"></a> <span class='hs-varid'>putMVar</span> <span class='hs-varid'>sem</span> <span class='hs-layout'>(</span><span class='hs-varid'>remaining</span><span class='hs-layout'>,</span><span class='hs-varid'>blocked</span><span class='hs-layout'>)</span> <a name="line-56"></a> <span class='hs-keyword'>else</span> <span class='hs-keyword'>do</span> <a name="line-57"></a> <span class='hs-varid'>b</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>newEmptyMVar</span> <a name="line-58"></a> <span class='hs-varid'>putMVar</span> <span class='hs-varid'>sem</span> <span class='hs-layout'>(</span><span class='hs-varid'>avail</span><span class='hs-layout'>,</span> <span class='hs-varid'>blocked</span><span class='hs-varop'>++</span><span class='hs-keyglyph'>[</span><span class='hs-layout'>(</span><span class='hs-varid'>sz</span><span class='hs-layout'>,</span><span class='hs-varid'>b</span><span class='hs-layout'>)</span><span class='hs-keyglyph'>]</span><span class='hs-layout'>)</span> <a name="line-59"></a> <span class='hs-varid'>takeMVar</span> <span class='hs-varid'>b</span> <a name="line-60"></a> <a name="line-61"></a><a name="signalQSemN"></a><span class='hs-comment'>-- |Signal that a given quantity is now available from the 'QSemN'.</span> <a name="line-62"></a><span class='hs-definition'>signalQSemN</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>QSemN</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Int</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>IO</span> <span class='hs-conid'>()</span> <a name="line-63"></a><span class='hs-definition'>signalQSemN</span> <span class='hs-layout'>(</span><span class='hs-conid'>QSemN</span> <span class='hs-varid'>sem</span><span class='hs-layout'>)</span> <span class='hs-varid'>n</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>mask_</span> <span class='hs-varop'>$</span> <span class='hs-keyword'>do</span> <a name="line-64"></a> <span class='hs-layout'>(</span><span class='hs-varid'>avail</span><span class='hs-layout'>,</span><span class='hs-varid'>blocked</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>takeMVar</span> <span class='hs-varid'>sem</span> <a name="line-65"></a> <span class='hs-layout'>(</span><span class='hs-varid'>avail'</span><span class='hs-layout'>,</span><span class='hs-varid'>blocked'</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>free</span> <span class='hs-layout'>(</span><span class='hs-varid'>avail</span><span class='hs-varop'>+</span><span class='hs-varid'>n</span><span class='hs-layout'>)</span> <span class='hs-varid'>blocked</span> <a name="line-66"></a> <span class='hs-varid'>avail'</span> <span class='hs-varop'>`seq`</span> <span class='hs-varid'>putMVar</span> <span class='hs-varid'>sem</span> <span class='hs-layout'>(</span><span class='hs-varid'>avail'</span><span class='hs-layout'>,</span><span class='hs-varid'>blocked'</span><span class='hs-layout'>)</span> <a name="line-67"></a> <span class='hs-keyword'>where</span> <a name="line-68"></a> <span class='hs-varid'>free</span> <span class='hs-varid'>avail</span> <span class='hs-conid'>[]</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>return</span> <span class='hs-layout'>(</span><span class='hs-varid'>avail</span><span class='hs-layout'>,</span><span class='hs-conid'>[]</span><span class='hs-layout'>)</span> <a name="line-69"></a> <span class='hs-varid'>free</span> <span class='hs-varid'>avail</span> <span class='hs-layout'>(</span><span class='hs-layout'>(</span><span class='hs-varid'>req</span><span class='hs-layout'>,</span><span class='hs-varid'>b</span><span class='hs-layout'>)</span><span class='hs-conop'>:</span><span class='hs-varid'>blocked</span><span class='hs-layout'>)</span> <a name="line-70"></a> <span class='hs-keyglyph'>|</span> <span class='hs-varid'>avail</span> <span class='hs-varop'>>=</span> <span class='hs-varid'>req</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>do</span> <a name="line-71"></a> <span class='hs-varid'>putMVar</span> <span class='hs-varid'>b</span> <span class='hs-conid'>()</span> <a name="line-72"></a> <span class='hs-varid'>free</span> <span class='hs-layout'>(</span><span class='hs-varid'>avail</span><span class='hs-comment'>-</span><span class='hs-varid'>req</span><span class='hs-layout'>)</span> <span class='hs-varid'>blocked</span> <a name="line-73"></a> <span class='hs-keyglyph'>|</span> <span class='hs-varid'>otherwise</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>do</span> <a name="line-74"></a> <span class='hs-layout'>(</span><span class='hs-varid'>avail'</span><span class='hs-layout'>,</span><span class='hs-varid'>blocked'</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>free</span> <span class='hs-varid'>avail</span> <span class='hs-varid'>blocked</span> <a name="line-75"></a> <span class='hs-varid'>return</span> <span class='hs-layout'>(</span><span class='hs-varid'>avail'</span><span class='hs-layout'>,</span><span class='hs-layout'>(</span><span class='hs-varid'>req</span><span class='hs-layout'>,</span><span class='hs-varid'>b</span><span class='hs-layout'>)</span><span class='hs-conop'>:</span><span class='hs-varid'>blocked'</span><span class='hs-layout'>)</span> </pre></body> </html>
