txlyre
/
avram


			
				
					
						
						
							12345678910111213141516171819202122232425262728293031323334353637383940414243444546474849505152535455565758596061626364656667686970717273747576777879808182838485868788899091
							<html lang="en">
<head>
<title>Lists of Pairs of Ports - avram - a virtual machine code interpreter</title>
<meta http-equiv="Content-Type" content="text/html">
<meta name="description" content="avram - a virtual machine code interpreter">
<meta name="generator" content="makeinfo 4.13">
<link title="Top" rel="start" href="index.html#Top">
<link rel="up" href="Emulation-Primitives.html#Emulation-Primitives" title="Emulation Primitives">
<link rel="prev" href="Emulation-Primitives.html#Emulation-Primitives" title="Emulation Primitives">
<link rel="next" href="Ports-and-Packets.html#Ports-and-Packets" title="Ports and Packets">
<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
<meta http-equiv="Content-Style-Type" content="text/css">
<style type="text/css"><!--
  pre.display { font-family:inherit }
  pre.format  { font-family:inherit }
  pre.smalldisplay { font-family:inherit; font-size:smaller }
  pre.smallformat  { font-family:inherit; font-size:smaller }
  pre.smallexample { font-size:smaller }
  pre.smalllisp    { font-size:smaller }
  span.sc    { font-variant:small-caps }
  span.roman { font-family:serif; font-weight:normal; } 
  span.sansserif { font-family:sans-serif; font-weight:normal; } 
--></style>
</head>
<body>
<div class="node">
<a name="Lists-of-Pairs-of-Ports"></a>
<p>
Next:&nbsp;<a rel="next" accesskey="n" href="Ports-and-Packets.html#Ports-and-Packets">Ports and Packets</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="Emulation-Primitives.html#Emulation-Primitives">Emulation Primitives</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="Emulation-Primitives.html#Emulation-Primitives">Emulation Primitives</a>
<hr>
</div>

<h4 class="subsection">3.8.1 Lists of Pairs of Ports</h4>

<p><a name="index-g_t_0040code_007bport_007d-628"></a>A <code>port</code> is the name given to a type of pointer used in the library
as the address of a place where a computational result yet to be
evaluated will be sent. Ports are discussed further in <a href="Ports-and-Packets.html#Ports-and-Packets">Ports and Packets</a>,
but are mentioned here because it is sometimes necessary to employ a
list of pairs of them. A pointer to such a list is declared as a
<code>portal</code> type. It refers to a structure of the form
<a name="index-g_t_0040code_007bportal_007d-629"></a><a name="index-g_t_0040code_007bport_005fpair_007d-630"></a>
<pre class="example">     struct port_pair
     {
       port left;
       port right;
       portal alters;
     }
</pre>
   <p>A small selection of functions for <code>portal</code> memory management is
declared as follows in the header file <samp><span class="file">portals.h</span></samp>. For reasons of
C-ness, the type declarations themselves are forced to be in
<samp><span class="file">lists.h</span></samp>.

<div class="defun">
&mdash; Function: portal <b>avm_new_portal</b> (<var>portal alters</var>)<var><a name="index-avm_005fnew_005fportal-631"></a></var><br>
<blockquote><p>This function is used to create storage for a new <code>port_pair</code>
structure, and returns a <code>portal</code> pointer to it if successful. If
the storage can't be allocated, a <code>NULL</code> pointer is returned. 
The <code>alters</code> field of the result is initialized as the given
parameter supplied by the caller. All other fields are filled with zeros. 
</p></blockquote></div>

<div class="defun">
&mdash; Function: void <b>avm_seal</b> (<var>portal fate</var>)<var><a name="index-avm_005fseal-632"></a></var><br>
<blockquote><p>This function performs the reclamation of storage associated with
<code>portal</code> pointers, either by freeing them or by consigning them
temporarily to a local cache for performance reasons. Client programs
should use only this function for disposing of <code>portal</code> storage
rather than using <code>free</code> directly, so as to allow accurate record
keeping. 
</p></blockquote></div>

<div class="defun">
&mdash; Function: void <b>avm_initialize_portals</b> ()<var><a name="index-avm_005finitialize_005fportals-633"></a></var><br>
<blockquote><p>This function should be called by a client program prior to calling
either of the above memory management functions in order to initialize
some local variables. Anomalous results are possible otherwise. 
</p></blockquote></div>

<div class="defun">
&mdash; Function: void <b>avm_count_portals</b> ()<var><a name="index-avm_005fcount_005fportals-634"></a></var><br>
<blockquote><p>This function should be called at the end of a run or after the last
call to any of the other functions in this section as a way of detecting
memory leaks associated with <code>portal</code> pointers. A warning message
will be written to standard error if any remains unreclaimed. 
</p></blockquote></div>

   </body></html>