path: root/lib/erl_interface/doc/src/erl_malloc.xml

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  <header>
    <copyright>
      <year>1996</year><year>2016</year>
      <holder>Ericsson AB. All Rights Reserved.</holder>
    </copyright>
    <legalnotice>
      Licensed under the Apache License, Version 2.0 (the "License");
      you may not use this file except in compliance with the License.
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    </legalnotice>

    <title>erl_malloc</title>
    <prepared>Torbj&ouml;rn T&ouml;rnkvist</prepared>
    <responsible>Torbj&ouml;rn T&ouml;rnkvist</responsible>
    <docno></docno>
    <approved>Bjarne D&auml;cker</approved>
    <checked>Torbj&ouml;rn T&ouml;rnkvist</checked>
    <date>980703</date>
    <rev>A</rev>
    <file>erl_malloc.sgml</file>
  </header>
  <lib>erl_malloc</lib>
  <libsummary>Memory Allocation Functions</libsummary>
  <description>
    <p>This module provides functions for allocating and deallocating
      memory.</p>
  </description>
  <funcs>
    <func>
      <name><ret>ETERM *</ret><nametext>erl_alloc_eterm(etype)</nametext></name>
      <fsummary>Allocates an ETERM structure</fsummary>
      <type>
        <v>unsigned char etype;</v>
      </type>
      <desc>
        <p>This function allocates an <c><![CDATA[(ETERM)]]></c> structure.
          Specify <c><![CDATA[etype]]></c> as one of the following constants:</p>
        <list type="bulleted">
          <item>
            <p>ERL_INTEGER</p>
          </item>
          <item>
            <p>ERL_U_INTEGER <c><![CDATA[/* unsigned integer */]]></c></p>
          </item>
          <item>
            <p>ERL_ATOM</p>
          </item>
          <item>
            <p>ERL_PID <c><![CDATA[/* Erlang process identifier */]]></c></p>
          </item>
          <item>
            <p>ERL_PORT</p>
          </item>
          <item>
            <p>ERL_REF <c><![CDATA[/* Erlang reference */]]></c></p>
          </item>
          <item>
            <p>ERL_LIST</p>
          </item>
          <item>
            <p>ERL_EMPTY_LIST</p>
          </item>
          <item>
            <p>ERL_TUPLE</p>
          </item>
          <item>
            <p>ERL_BINARY</p>
          </item>
          <item>
            <p>ERL_FLOAT</p>
          </item>
          <item>
            <p>ERL_VARIABLE</p>
          </item>
          <item>
            <p>ERL_SMALL_BIG <c><![CDATA[/* bignum */]]></c></p>
          </item>
          <item>
            <p>ERL_U_SMALL_BIG <c><![CDATA[/* bignum */]]></c></p>
          </item>
        </list>
        <p><c><![CDATA[ERL_SMALL_BIG]]></c> and <c><![CDATA[ERL_U_SMALL_BIG]]></c> are for
          creating Erlang <c><![CDATA[bignums]]></c>, which can contain integers of
          arbitrary size. The size of an integer in Erlang is machine
          dependent, but in general any integer larger than 2^28
          requires a bignum.</p>
      </desc>
    </func>
    <func>
      <name><ret>void</ret><nametext>erl_eterm_release(void)</nametext></name>
      <fsummary>Clears the ETERM freelist</fsummary>
      <desc>
        <p>Clears the 
          freelist, where blocks are placed when they are
          released by <c><![CDATA[erl_free_term()]]></c> and
          <c><![CDATA[erl_free_compound()]]></c>. </p>
      </desc>
    </func>
    <func>
      <name><ret>void</ret><nametext>erl_eterm_statistics(allocated, freed)</nametext></name>
      <fsummary>Reports term allocation statistics</fsummary>
      <type>
        <v>long *allocated;</v>
        <v>long *freed;</v>
      </type>
      <desc>
        <p><c><![CDATA[allocated]]></c> and <c><![CDATA[freed]]></c> are initialized to
          contain information about the fix-allocator used to allocate
          ETERM components. <c><![CDATA[allocated]]></c> is the number of blocks
          currently allocated to ETERM objects. <c><![CDATA[freed]]></c> is the
          length of the freelist, where blocks are placed when they are
          released by <c><![CDATA[erl_free_term()]]></c> and
          <c><![CDATA[erl_free_compound()]]></c>. </p>
      </desc>
    </func>
    <func>
      <name><ret>void</ret><nametext>erl_free_array(array, size)</nametext></name>
      <fsummary>Frees an array of ETERM structures</fsummary>
      <type>
        <v>ETERM **array;</v>
        <v>int size;</v>
      </type>
      <desc>
        <p>This function frees an array of Erlang terms.</p>
        <p><c><![CDATA[array]]></c> is an array of ETERM* objects.
          </p>
        <p><c><![CDATA[size]]></c> is the number of terms in the array.</p>
      </desc>
    </func>
    <func>
      <name><ret>void</ret><nametext>erl_free_term(t)</nametext></name>
      <fsummary>Frees an ETERM structure</fsummary>
      <type>
        <v>ETERM *t;</v>
      </type>
      <desc>
        <p>Use this function to free an Erlang term.</p>
      </desc>
    </func>
    <func>
      <name><ret>void</ret><nametext>erl_free_compound(t)</nametext></name>
      <fsummary>Frees an array of ETERM structures</fsummary>
      <type>
        <v>ETERM *t;</v>
      </type>
      <desc>
        <p>Normally it is the programmer's responsibility to free each
          Erlang term that has been returned from any of the
          <c><![CDATA[erl_interface]]></c> functions. However since many of the
          functions that build new Erlang terms in fact share objects
          with other existing terms, it may be difficult for the
          programmer to maintain pointers to all such terms in order to
          free them individually.
          </p>
        <p><c><![CDATA[erl_free_compound()]]></c> will recursively free all of the
          sub-terms associated with a given Erlang term, regardless of
          whether we are still holding pointers to the sub-terms.
          </p>
        <p>There is an example in the User Manual under "Building
          Terms and Patterns"
          </p>
      </desc>
    </func>
    <func>
      <name><ret>void</ret><nametext>erl_malloc(size)</nametext></name>
      <fsummary>Allocates some memory</fsummary>
      <type>
        <v>long size;</v>
      </type>
      <desc>
        <p>This function calls the standard 
          <c><![CDATA[malloc()]]></c> function. </p>
      </desc>
    </func>
    <func>
      <name><ret>void</ret><nametext>erl_free(ptr)</nametext></name>
      <fsummary>Frees some memory</fsummary>
      <type>
        <v>void *ptr;</v>
      </type>
      <desc>
        <p>This function calls the standard 
          <c><![CDATA[free()]]></c> function. </p>
      </desc>
    </func>
  </funcs>
</cref>