Google

Edit File: api-hashmap.html

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN"
    "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en">
<head>
<meta http-equiv="Content-Type" content="application/xhtml+xml; charset=UTF-8" />
<meta name="generator" content="AsciiDoc 8.6.8" />
<title>hashmap API</title>
<style type="text/css">
/* Shared CSS for AsciiDoc xhtml11 and html5 backends */

/* Default font. */
body {
  font-family: Georgia,serif;
}

/* Title font. */
h1, h2, h3, h4, h5, h6,
div.title, caption.title,
thead, p.table.header,
#toctitle,
#author, #revnumber, #revdate, #revremark,
#footer {
  font-family: Arial,Helvetica,sans-serif;
}

body {
  margin: 1em 5% 1em 5%;
}

a {
  color: blue;
  text-decoration: underline;
}
a:visited {
  color: fuchsia;
}

em {
  font-style: italic;
  color: navy;
}

strong {
  font-weight: bold;
  color: #083194;
}

h1, h2, h3, h4, h5, h6 {
  color: #527bbd;
  margin-top: 1.2em;
  margin-bottom: 0.5em;
  line-height: 1.3;
}

h1, h2, h3 {
  border-bottom: 2px solid silver;
}
h2 {
  padding-top: 0.5em;
}
h3 {
  float: left;
}
h3 + * {
  clear: left;
}
h5 {
  font-size: 1.0em;
}

div.sectionbody {
  margin-left: 0;
}

hr {
  border: 1px solid silver;
}

p {
  margin-top: 0.5em;
  margin-bottom: 0.5em;
}

ul, ol, li > p {
  margin-top: 0;
}
ul > li     { color: #aaa; }
ul > li > * { color: black; }

.monospaced, code, pre {
  font-family: "Courier New", Courier, monospace;
  font-size: inherit;
  color: navy;
  padding: 0;
  margin: 0;
}

#author {
  color: #527bbd;
  font-weight: bold;
  font-size: 1.1em;
}
#email {
}
#revnumber, #revdate, #revremark {
}

#footer {
  font-size: small;
  border-top: 2px solid silver;
  padding-top: 0.5em;
  margin-top: 4.0em;
}
#footer-text {
  float: left;
  padding-bottom: 0.5em;
}
#footer-badges {
  float: right;
  padding-bottom: 0.5em;
}

#preamble {
  margin-top: 1.5em;
  margin-bottom: 1.5em;
}
div.imageblock, div.exampleblock, div.verseblock,
div.quoteblock, div.literalblock, div.listingblock, div.sidebarblock,
div.admonitionblock {
  margin-top: 1.0em;
  margin-bottom: 1.5em;
}
div.admonitionblock {
  margin-top: 2.0em;
  margin-bottom: 2.0em;
  margin-right: 10%;
  color: #606060;
}

div.content { /* Block element content. */
  padding: 0;
}

/* Block element titles. */
div.title, caption.title {
  color: #527bbd;
  font-weight: bold;
  text-align: left;
  margin-top: 1.0em;
  margin-bottom: 0.5em;
}
div.title + * {
  margin-top: 0;
}

td div.title:first-child {
  margin-top: 0.0em;
}
div.content div.title:first-child {
  margin-top: 0.0em;
}
div.content + div.title {
  margin-top: 0.0em;
}

div.sidebarblock > div.content {
  background: #ffffee;
  border: 1px solid #dddddd;
  border-left: 4px solid #f0f0f0;
  padding: 0.5em;
}

div.listingblock > div.content {
  border: 1px solid #dddddd;
  border-left: 5px solid #f0f0f0;
  background: #f8f8f8;
  padding: 0.5em;
}

div.quoteblock, div.verseblock {
  padding-left: 1.0em;
  margin-left: 1.0em;
  margin-right: 10%;
  border-left: 5px solid #f0f0f0;
  color: #888;
}

div.quoteblock > div.attribution {
  padding-top: 0.5em;
  text-align: right;
}

div.verseblock > pre.content {
  font-family: inherit;
  font-size: inherit;
}
div.verseblock > div.attribution {
  padding-top: 0.75em;
  text-align: left;
}
/* DEPRECATED: Pre version 8.2.7 verse style literal block. */
div.verseblock + div.attribution {
  text-align: left;
}

div.admonitionblock .icon {
  vertical-align: top;
  font-size: 1.1em;
  font-weight: bold;
  text-decoration: underline;
  color: #527bbd;
  padding-right: 0.5em;
}
div.admonitionblock td.content {
  padding-left: 0.5em;
  border-left: 3px solid #dddddd;
}

div.exampleblock > div.content {
  border-left: 3px solid #dddddd;
  padding-left: 0.5em;
}

div.imageblock div.content { padding-left: 0; }
span.image img { border-style: none; }
a.image:visited { color: white; }

dl {
  margin-top: 0.8em;
  margin-bottom: 0.8em;
}
dt {
  margin-top: 0.5em;
  margin-bottom: 0;
  font-style: normal;
  color: navy;
}
dd > *:first-child {
  margin-top: 0.1em;
}

ul, ol {
    list-style-position: outside;
}
ol.arabic {
  list-style-type: decimal;
}
ol.loweralpha {
  list-style-type: lower-alpha;
}
ol.upperalpha {
  list-style-type: upper-alpha;
}
ol.lowerroman {
  list-style-type: lower-roman;
}
ol.upperroman {
  list-style-type: upper-roman;
}

div.compact ul, div.compact ol,
div.compact p, div.compact p,
div.compact div, div.compact div {
  margin-top: 0.1em;
  margin-bottom: 0.1em;
}

tfoot {
  font-weight: bold;
}
td > div.verse {
  white-space: pre;
}

div.hdlist {
  margin-top: 0.8em;
  margin-bottom: 0.8em;
}
div.hdlist tr {
  padding-bottom: 15px;
}
dt.hdlist1.strong, td.hdlist1.strong {
  font-weight: bold;
}
td.hdlist1 {
  vertical-align: top;
  font-style: normal;
  padding-right: 0.8em;
  color: navy;
}
td.hdlist2 {
  vertical-align: top;
}
div.hdlist.compact tr {
  margin: 0;
  padding-bottom: 0;
}

.comment {
  background: yellow;
}

.footnote, .footnoteref {
  font-size: 0.8em;
}

span.footnote, span.footnoteref {
  vertical-align: super;
}

#footnotes {
  margin: 20px 0 20px 0;
  padding: 7px 0 0 0;
}

#footnotes div.footnote {
  margin: 0 0 5px 0;
}

#footnotes hr {
  border: none;
  border-top: 1px solid silver;
  height: 1px;
  text-align: left;
  margin-left: 0;
  width: 20%;
  min-width: 100px;
}

div.colist td {
  padding-right: 0.5em;
  padding-bottom: 0.3em;
  vertical-align: top;
}
div.colist td img {
  margin-top: 0.3em;
}

@media print {
  #footer-badges { display: none; }
}

#toc {
  margin-bottom: 2.5em;
}

#toctitle {
  color: #527bbd;
  font-size: 1.1em;
  font-weight: bold;
  margin-top: 1.0em;
  margin-bottom: 0.1em;
}

div.toclevel0, div.toclevel1, div.toclevel2, div.toclevel3, div.toclevel4 {
  margin-top: 0;
  margin-bottom: 0;
}
div.toclevel2 {
  margin-left: 2em;
  font-size: 0.9em;
}
div.toclevel3 {
  margin-left: 4em;
  font-size: 0.9em;
}
div.toclevel4 {
  margin-left: 6em;
  font-size: 0.9em;
}

span.aqua { color: aqua; }
span.black { color: black; }
span.blue { color: blue; }
span.fuchsia { color: fuchsia; }
span.gray { color: gray; }
span.green { color: green; }
span.lime { color: lime; }
span.maroon { color: maroon; }
span.navy { color: navy; }
span.olive { color: olive; }
span.purple { color: purple; }
span.red { color: red; }
span.silver { color: silver; }
span.teal { color: teal; }
span.white { color: white; }
span.yellow { color: yellow; }

span.aqua-background { background: aqua; }
span.black-background { background: black; }
span.blue-background { background: blue; }
span.fuchsia-background { background: fuchsia; }
span.gray-background { background: gray; }
span.green-background { background: green; }
span.lime-background { background: lime; }
span.maroon-background { background: maroon; }
span.navy-background { background: navy; }
span.olive-background { background: olive; }
span.purple-background { background: purple; }
span.red-background { background: red; }
span.silver-background { background: silver; }
span.teal-background { background: teal; }
span.white-background { background: white; }
span.yellow-background { background: yellow; }

span.big { font-size: 2em; }
span.small { font-size: 0.6em; }

span.underline { text-decoration: underline; }
span.overline { text-decoration: overline; }
span.line-through { text-decoration: line-through; }

div.unbreakable { page-break-inside: avoid; }

/*
 * xhtml11 specific
 *
 * */

div.tableblock {
  margin-top: 1.0em;
  margin-bottom: 1.5em;
}
div.tableblock > table {
  border: 3px solid #527bbd;
}
thead, p.table.header {
  font-weight: bold;
  color: #527bbd;
}
p.table {
  margin-top: 0;
}
/* Because the table frame attribute is overriden by CSS in most browsers. */
div.tableblock > table[frame="void"] {
  border-style: none;
}
div.tableblock > table[frame="hsides"] {
  border-left-style: none;
  border-right-style: none;
}
div.tableblock > table[frame="vsides"] {
  border-top-style: none;
  border-bottom-style: none;
}

/*
 * html5 specific
 *
 * */

table.tableblock {
  margin-top: 1.0em;
  margin-bottom: 1.5em;
}
thead, p.tableblock.header {
  font-weight: bold;
  color: #527bbd;
}
p.tableblock {
  margin-top: 0;
}
table.tableblock {
  border-width: 3px;
  border-spacing: 0px;
  border-style: solid;
  border-color: #527bbd;
  border-collapse: collapse;
}
th.tableblock, td.tableblock {
  border-width: 1px;
  padding: 4px;
  border-style: solid;
  border-color: #527bbd;
}

table.tableblock.frame-topbot {
  border-left-style: hidden;
  border-right-style: hidden;
}
table.tableblock.frame-sides {
  border-top-style: hidden;
  border-bottom-style: hidden;
}
table.tableblock.frame-none {
  border-style: hidden;
}

th.tableblock.halign-left, td.tableblock.halign-left {
  text-align: left;
}
th.tableblock.halign-center, td.tableblock.halign-center {
  text-align: center;
}
th.tableblock.halign-right, td.tableblock.halign-right {
  text-align: right;
}

th.tableblock.valign-top, td.tableblock.valign-top {
  vertical-align: top;
}
th.tableblock.valign-middle, td.tableblock.valign-middle {
  vertical-align: middle;
}
th.tableblock.valign-bottom, td.tableblock.valign-bottom {
  vertical-align: bottom;
}

/*
 * manpage specific
 *
 * */

body.manpage h1 {
  padding-top: 0.5em;
  padding-bottom: 0.5em;
  border-top: 2px solid silver;
  border-bottom: 2px solid silver;
}
body.manpage h2 {
  border-style: none;
}
body.manpage div.sectionbody {
  margin-left: 3em;
}

@media print {
  body.manpage div#toc { display: none; }
}

</style>
<script type="text/javascript">
/*<![CDATA[*/
var asciidoc = {  // Namespace.

/////////////////////////////////////////////////////////////////////
// Table Of Contents generator
/////////////////////////////////////////////////////////////////////

/* Author: Mihai Bazon, September 2002
 * http://students.infoiasi.ro/~mishoo
 *
 * Table Of Content generator
 * Version: 0.4
 *
 * Feel free to use this script under the terms of the GNU General Public
 * License, as long as you do not remove or alter this notice.
 */

/* modified by Troy D. Hanson, September 2006. License: GPL */
 /* modified by Stuart Rackham, 2006, 2009. License: GPL */

// toclevels = 1..4.
toc: function (toclevels) {

function getText(el) {
    var text = "";
    for (var i = el.firstChild; i != null; i = i.nextSibling) {
      if (i.nodeType == 3 /* Node.TEXT_NODE */) // IE doesn't speak constants.
        text += i.data;
      else if (i.firstChild != null)
        text += getText(i);
    }
    return text;
  }

function TocEntry(el, text, toclevel) {
    this.element = el;
    this.text = text;
    this.toclevel = toclevel;
  }

var toc = document.getElementById("toc");
  if (!toc) {
    return;
  }

// Delete existing TOC entries in case we're reloading the TOC.
  var tocEntriesToRemove = [];
  var i;
  for (i = 0; i < toc.childNodes.length; i++) {
    var entry = toc.childNodes[i];
    if (entry.nodeName.toLowerCase() == 'div'
     && entry.getAttribute("class")
     && entry.getAttribute("class").match(/^toclevel/))
      tocEntriesToRemove.push(entry);
  }
  for (i = 0; i < tocEntriesToRemove.length; i++) {
    toc.removeChild(tocEntriesToRemove[i]);
  }

// Rebuild TOC entries.
  var entries = tocEntries(document.getElementById("content"), toclevels);
  for (var i = 0; i < entries.length; ++i) {
    var entry = entries[i];
    if (entry.element.id == "")
      entry.element.id = "_toc_" + i;
    var a = document.createElement("a");
    a.href = "#" + entry.element.id;
    a.appendChild(document.createTextNode(entry.text));
    var div = document.createElement("div");
    div.appendChild(a);
    div.className = "toclevel" + entry.toclevel;
    toc.appendChild(div);
  }
  if (entries.length == 0)
    toc.parentNode.removeChild(toc);
},

/////////////////////////////////////////////////////////////////////
// Footnotes generator
/////////////////////////////////////////////////////////////////////

/* Based on footnote generation code from:
 * http://www.brandspankingnew.net/archive/2005/07/format_footnote.html
 */

footnotes: function () {
  // Delete existing footnote entries in case we're reloading the footnodes.
  var i;
  var noteholder = document.getElementById("footnotes");
  if (!noteholder) {
    return;
  }
  var entriesToRemove = [];
  for (i = 0; i < noteholder.childNodes.length; i++) {
    var entry = noteholder.childNodes[i];
    if (entry.nodeName.toLowerCase() == 'div' && entry.getAttribute("class") == "footnote")
      entriesToRemove.push(entry);
  }
  for (i = 0; i < entriesToRemove.length; i++) {
    noteholder.removeChild(entriesToRemove[i]);
  }

// Rebuild footnote entries.
  var cont = document.getElementById("content");
  var spans = cont.getElementsByTagName("span");
  var refs = {};
  var n = 0;
  for (i=0; i<spans.length; i++) {
    if (spans[i].className == "footnote") {
      n++;
      var note = spans[i].getAttribute("data-note");
      if (!note) {
        // Use [\s\S] in place of . so multi-line matches work.
        // Because JavaScript has no s (dotall) regex flag.
        note = spans[i].innerHTML.match(/\s*\[([\s\S]*)]\s*/)[1];
        spans[i].innerHTML =
          "[<a id='_footnoteref_" + n + "' href='#_footnote_" + n +
          "' title='View footnote' class='footnote'>" + n + "</a>]";
        spans[i].setAttribute("data-note", note);
      }
      noteholder.innerHTML +=
        "<div class='footnote' id='_footnote_" + n + "'>" +
        "<a href='#_footnoteref_" + n + "' title='Return to text'>" +
        n + "</a>. " + note + "</div>";
      var id =spans[i].getAttribute("id");
      if (id != null) refs["#"+id] = n;
    }
  }
  if (n == 0)
    noteholder.parentNode.removeChild(noteholder);
  else {
    // Process footnoterefs.
    for (i=0; i<spans.length; i++) {
      if (spans[i].className == "footnoteref") {
        var href = spans[i].getElementsByTagName("a")[0].getAttribute("href");
        href = href.match(/#.*/)[0];  // Because IE return full URL.
        n = refs[href];
        spans[i].innerHTML =
          "[<a href='#_footnote_" + n +
          "' title='View footnote' class='footnote'>" + n + "</a>]";
      }
    }
  }
},

install: function(toclevels) {
  var timerId;

function reinstall() {
    asciidoc.footnotes();
    if (toclevels) {
      asciidoc.toc(toclevels);
    }
  }

function reinstallAndRemoveTimer() {
    clearInterval(timerId);
    reinstall();
  }

timerId = setInterval(reinstall, 500);
  if (document.addEventListener)
    document.addEventListener("DOMContentLoaded", reinstallAndRemoveTimer, false);
  else
    window.onload = reinstallAndRemoveTimer;
}

}
asciidoc.install();
/*]]>*/
</script>
</head>
<body class="article">
<div id="header">
<h1>hashmap API</h1>
</div>
<div id="content">
<div id="preamble">
<div class="sectionbody">
<div class="paragraph"><p>The hashmap API is a generic implementation of hash-based key-value mappings.</p></div>
</div>
</div>
<div class="sect1">
<h2 id="_data_structures">Data Structures</h2>
<div class="sectionbody">
<div class="dlist"><dl>
<dt class="hdlist1">
<code>struct hashmap</code>
</dt>
<dd>
<p>
        The hash table structure.
</p>
<div class="paragraph"><p>The <code>size</code> member keeps track of the total number of entries. The <code>cmpfn</code>
member is a function used to compare two entries for equality. The <code>table</code> and
<code>tablesize</code> members store the hash table and its size, respectively.</p></div>
</dd>
<dt class="hdlist1">
<code>struct hashmap_entry</code>
</dt>
<dd>
<p>
        An opaque structure representing an entry in the hash table, which must
        be used as first member of user data structures. Ideally it should be
        followed by an int-sized member to prevent unused memory on 64-bit
        systems due to alignment.
</p>
<div class="paragraph"><p>The <code>hash</code> member is the entry&#8217;s hash code and the <code>next</code> member points to the
next entry in case of collisions (i.e. if multiple entries map to the same
bucket).</p></div>
</dd>
<dt class="hdlist1">
<code>struct hashmap_iter</code>
</dt>
<dd>
<p>
        An iterator structure, to be used with hashmap_iter_* functions.
</p>
</dd>
</dl></div>
</div>
</div>
<div class="sect1">
<h2 id="_types">Types</h2>
<div class="sectionbody">
<div class="dlist"><dl>
<dt class="hdlist1">
<code>int (*hashmap_cmp_fn)(const void *entry, const void *entry_or_key, const void *keydata)</code>
</dt>
<dd>
<p>
        User-supplied function to test two hashmap entries for equality. Shall
        return 0 if the entries are equal.
</p>
<div class="paragraph"><p>This function is always called with non-NULL <code>entry</code> / <code>entry_or_key</code>
parameters that have the same hash code. When looking up an entry, the <code>key</code>
and <code>keydata</code> parameters to hashmap_get and hashmap_remove are always passed
as second and third argument, respectively. Otherwise, <code>keydata</code> is NULL.</p></div>
</dd>
</dl></div>
</div>
</div>
<div class="sect1">
<h2 id="_functions">Functions</h2>
<div class="sectionbody">
<div class="dlist"><dl>
<dt class="hdlist1">
<code>unsigned int strhash(const char *buf)</code>
</dt>
<dt class="hdlist1">
<code>unsigned int strihash(const char *buf)</code>
</dt>
<dt class="hdlist1">
<code>unsigned int memhash(const void *buf, size_t len)</code>
</dt>
<dt class="hdlist1">
<code>unsigned int memihash(const void *buf, size_t len)</code>
</dt>
<dd>
<p>
        Ready-to-use hash functions for strings, using the FNV-1 algorithm (see
        <a href="http://www.isthe.com/chongo/tech/comp/fnv">http://www.isthe.com/chongo/tech/comp/fnv</a>).
</p>
<div class="paragraph"><p><code>strhash</code> and <code>strihash</code> take 0-terminated strings, while <code>memhash</code> and
<code>memihash</code> operate on arbitrary-length memory.</p></div>
<div class="paragraph"><p><code>strihash</code> and <code>memihash</code> are case insensitive versions.</p></div>
</dd>
<dt class="hdlist1">
<code>void hashmap_init(struct hashmap *map, hashmap_cmp_fn equals_function, size_t initial_size)</code>
</dt>
<dd>
<p>
        Initializes a hashmap structure.
</p>
<div class="paragraph"><p><code>map</code> is the hashmap to initialize.</p></div>
<div class="paragraph"><p>The <code>equals_function</code> can be specified to compare two entries for equality.
If NULL, entries are considered equal if their hash codes are equal.</p></div>
<div class="paragraph"><p>If the total number of entries is known in advance, the <code>initial_size</code>
parameter may be used to preallocate a sufficiently large table and thus
prevent expensive resizing. If 0, the table is dynamically resized.</p></div>
</dd>
<dt class="hdlist1">
<code>void hashmap_free(struct hashmap *map, int free_entries)</code>
</dt>
<dd>
<p>
        Frees a hashmap structure and allocated memory.
</p>
<div class="paragraph"><p><code>map</code> is the hashmap to free.</p></div>
<div class="paragraph"><p>If <code>free_entries</code> is true, each hashmap_entry in the map is freed as well
(using stdlib&#8217;s free()).</p></div>
</dd>
<dt class="hdlist1">
<code>void hashmap_entry_init(void *entry, int hash)</code>
</dt>
<dd>
<p>
        Initializes a hashmap_entry structure.
</p>
<div class="paragraph"><p><code>entry</code> points to the entry to initialize.</p></div>
<div class="paragraph"><p><code>hash</code> is the hash code of the entry.</p></div>
</dd>
<dt class="hdlist1">
<code>void *hashmap_get(const struct hashmap *map, const void *key, const void *keydata)</code>
</dt>
<dd>
<p>
        Returns the hashmap entry for the specified key, or NULL if not found.
</p>
<div class="paragraph"><p><code>map</code> is the hashmap structure.</p></div>
<div class="paragraph"><p><code>key</code> is a hashmap_entry structure (or user data structure that starts with
hashmap_entry) that has at least been initialized with the proper hash code
(via <code>hashmap_entry_init</code>).</p></div>
<div class="paragraph"><p>If an entry with matching hash code is found, <code>key</code> and <code>keydata</code> are passed
to <code>hashmap_cmp_fn</code> to decide whether the entry matches the key.</p></div>
</dd>
<dt class="hdlist1">
<code>void *hashmap_get_from_hash(const struct hashmap *map, unsigned int hash, const void *keydata)</code>
</dt>
<dd>
<p>
        Returns the hashmap entry for the specified hash code and key data,
        or NULL if not found.
</p>
<div class="paragraph"><p><code>map</code> is the hashmap structure.</p></div>
<div class="paragraph"><p><code>hash</code> is the hash code of the entry to look up.</p></div>
<div class="paragraph"><p>If an entry with matching hash code is found, <code>keydata</code> is passed to
<code>hashmap_cmp_fn</code> to decide whether the entry matches the key. The
<code>entry_or_key</code> parameter points to a bogus hashmap_entry structure that
should not be used in the comparison.</p></div>
</dd>
<dt class="hdlist1">
<code>void *hashmap_get_next(const struct hashmap *map, const void *entry)</code>
</dt>
<dd>
<p>
        Returns the next equal hashmap entry, or NULL if not found. This can be
        used to iterate over duplicate entries (see <code>hashmap_add</code>).
</p>
<div class="paragraph"><p><code>map</code> is the hashmap structure.</p></div>
<div class="paragraph"><p><code>entry</code> is the hashmap_entry to start the search from, obtained via a previous
call to <code>hashmap_get</code> or <code>hashmap_get_next</code>.</p></div>
</dd>
<dt class="hdlist1">
<code>void hashmap_add(struct hashmap *map, void *entry)</code>
</dt>
<dd>
<p>
        Adds a hashmap entry. This allows to add duplicate entries (i.e.
        separate values with the same key according to hashmap_cmp_fn).
</p>
<div class="paragraph"><p><code>map</code> is the hashmap structure.</p></div>
<div class="paragraph"><p><code>entry</code> is the entry to add.</p></div>
</dd>
<dt class="hdlist1">
<code>void *hashmap_put(struct hashmap *map, void *entry)</code>
</dt>
<dd>
<p>
        Adds or replaces a hashmap entry. If the hashmap contains duplicate
        entries equal to the specified entry, only one of them will be replaced.
</p>
<div class="paragraph"><p><code>map</code> is the hashmap structure.</p></div>
<div class="paragraph"><p><code>entry</code> is the entry to add or replace.</p></div>
<div class="paragraph"><p>Returns the replaced entry, or NULL if not found (i.e. the entry was added).</p></div>
</dd>
<dt class="hdlist1">
<code>void *hashmap_remove(struct hashmap *map, const void *key, const void *keydata)</code>
</dt>
<dd>
<p>
        Removes a hashmap entry matching the specified key. If the hashmap
        contains duplicate entries equal to the specified key, only one of
        them will be removed.
</p>
<div class="paragraph"><p><code>map</code> is the hashmap structure.</p></div>
<div class="paragraph"><p><code>key</code> is a hashmap_entry structure (or user data structure that starts with
hashmap_entry) that has at least been initialized with the proper hash code
(via <code>hashmap_entry_init</code>).</p></div>
<div class="paragraph"><p>If an entry with matching hash code is found, <code>key</code> and <code>keydata</code> are
passed to <code>hashmap_cmp_fn</code> to decide whether the entry matches the key.</p></div>
<div class="paragraph"><p>Returns the removed entry, or NULL if not found.</p></div>
</dd>
<dt class="hdlist1">
<code>void hashmap_iter_init(struct hashmap *map, struct hashmap_iter *iter)</code>
</dt>
<dt class="hdlist1">
<code>void *hashmap_iter_next(struct hashmap_iter *iter)</code>
</dt>
<dt class="hdlist1">
<code>void *hashmap_iter_first(struct hashmap *map, struct hashmap_iter *iter)</code>
</dt>
<dd>
<p>
        Used to iterate over all entries of a hashmap.
</p>
<div class="paragraph"><p><code>hashmap_iter_init</code> initializes a <code>hashmap_iter</code> structure.</p></div>
<div class="paragraph"><p><code>hashmap_iter_next</code> returns the next hashmap_entry, or NULL if there are no
more entries.</p></div>
<div class="paragraph"><p><code>hashmap_iter_first</code> is a combination of both (i.e. initializes the iterator
and returns the first entry, if any).</p></div>
</dd>
</dl></div>
</div>
</div>
<div class="sect1">
<h2 id="_usage_example">Usage example</h2>
<div class="sectionbody">
<div class="paragraph"><p>Here&#8217;s a simple usage example that maps long keys to double values.</p></div>
<div class="listingblock">
<div class="content">
<pre><tt><span style="font-weight: bold"><span style="color: #0000FF">struct</span></span> <span style="color: #008080">hashmap</span> map<span style="color: #990000">;</span>

<span style="font-weight: bold"><span style="color: #0000FF">struct</span></span> <span style="color: #008080">long2double</span> <span style="color: #FF0000">{</span>
        <span style="font-weight: bold"><span style="color: #0000FF">struct</span></span> <span style="color: #008080">hashmap_entry</span> ent<span style="color: #990000">;</span> <span style="font-style: italic"><span style="color: #9A1900">/* must be the first member! */</span></span>
        <span style="color: #009900">long</span> key<span style="color: #990000">;</span>
        <span style="color: #009900">double</span> value<span style="color: #990000">;</span>
<span style="color: #FF0000">}</span><span style="color: #990000">;</span>

<span style="font-weight: bold"><span style="color: #0000FF">static</span></span> <span style="color: #009900">int</span> <span style="font-weight: bold"><span style="color: #000000">long2double_cmp</span></span><span style="color: #990000">(</span><span style="font-weight: bold"><span style="color: #0000FF">const</span></span> <span style="font-weight: bold"><span style="color: #0000FF">struct</span></span> <span style="color: #008080">long2double</span> <span style="color: #990000">*</span>e1<span style="color: #990000">,</span> <span style="font-weight: bold"><span style="color: #0000FF">const</span></span> <span style="font-weight: bold"><span style="color: #0000FF">struct</span></span> <span style="color: #008080">long2double</span> <span style="color: #990000">*</span>e2<span style="color: #990000">,</span> <span style="font-weight: bold"><span style="color: #0000FF">const</span></span> <span style="color: #009900">void</span> <span style="color: #990000">*</span>unused<span style="color: #990000">)</span>
<span style="color: #FF0000">{</span>
        <span style="font-weight: bold"><span style="color: #0000FF">return</span></span> <span style="color: #990000">!(</span>e1<span style="color: #990000">-&gt;</span>key <span style="color: #990000">==</span> e2<span style="color: #990000">-&gt;</span>key<span style="color: #990000">);</span>
<span style="color: #FF0000">}</span>

<span style="color: #009900">void</span> <span style="font-weight: bold"><span style="color: #000000">long2double_init</span></span><span style="color: #990000">(</span><span style="color: #009900">void</span><span style="color: #990000">)</span>
<span style="color: #FF0000">{</span>
        <span style="font-weight: bold"><span style="color: #000000">hashmap_init</span></span><span style="color: #990000">(&amp;</span>map<span style="color: #990000">,</span> <span style="color: #990000">(</span>hashmap_cmp_fn<span style="color: #990000">)</span> long2double_cmp<span style="color: #990000">,</span> <span style="color: #993399">0</span><span style="color: #990000">);</span>
<span style="color: #FF0000">}</span>

<span style="color: #009900">void</span> <span style="font-weight: bold"><span style="color: #000000">long2double_free</span></span><span style="color: #990000">(</span><span style="color: #009900">void</span><span style="color: #990000">)</span>
<span style="color: #FF0000">{</span>
        <span style="font-weight: bold"><span style="color: #000000">hashmap_free</span></span><span style="color: #990000">(&amp;</span>map<span style="color: #990000">,</span> <span style="color: #993399">1</span><span style="color: #990000">);</span>
<span style="color: #FF0000">}</span>

<span style="font-weight: bold"><span style="color: #0000FF">static</span></span> <span style="font-weight: bold"><span style="color: #0000FF">struct</span></span> <span style="color: #008080">long2double</span> <span style="color: #990000">*</span><span style="font-weight: bold"><span style="color: #000000">find_entry</span></span><span style="color: #990000">(</span><span style="color: #009900">long</span> key<span style="color: #990000">)</span>
<span style="color: #FF0000">{</span>
        <span style="font-weight: bold"><span style="color: #0000FF">struct</span></span> <span style="color: #008080">long2double</span> k<span style="color: #990000">;</span>
        <span style="font-weight: bold"><span style="color: #000000">hashmap_entry_init</span></span><span style="color: #990000">(&amp;</span>k<span style="color: #990000">,</span> <span style="font-weight: bold"><span style="color: #000000">memhash</span></span><span style="color: #990000">(&amp;</span>key<span style="color: #990000">,</span> <span style="font-weight: bold"><span style="color: #0000FF">sizeof</span></span><span style="color: #990000">(</span><span style="color: #009900">long</span><span style="color: #990000">)));</span>
        k<span style="color: #990000">.</span>key <span style="color: #990000">=</span> key<span style="color: #990000">;</span>
        <span style="font-weight: bold"><span style="color: #0000FF">return</span></span> <span style="font-weight: bold"><span style="color: #000000">hashmap_get</span></span><span style="color: #990000">(&amp;</span>map<span style="color: #990000">,</span> <span style="color: #990000">&amp;</span>k<span style="color: #990000">,</span> NULL<span style="color: #990000">);</span>
<span style="color: #FF0000">}</span>

<span style="color: #009900">double</span> <span style="font-weight: bold"><span style="color: #000000">get_value</span></span><span style="color: #990000">(</span><span style="color: #009900">long</span> key<span style="color: #990000">)</span>
<span style="color: #FF0000">{</span>
        <span style="font-weight: bold"><span style="color: #0000FF">struct</span></span> <span style="color: #008080">long2double</span> <span style="color: #990000">*</span>e <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">find_entry</span></span><span style="color: #990000">(</span>key<span style="color: #990000">);</span>
        <span style="font-weight: bold"><span style="color: #0000FF">return</span></span> e <span style="color: #990000">?</span> e<span style="color: #990000">-&gt;</span>value <span style="color: #990000">:</span> <span style="color: #993399">0</span><span style="color: #990000">;</span>
<span style="color: #FF0000">}</span>

<span style="color: #009900">void</span> <span style="font-weight: bold"><span style="color: #000000">set_value</span></span><span style="color: #990000">(</span><span style="color: #009900">long</span> key<span style="color: #990000">,</span> <span style="color: #009900">double</span> value<span style="color: #990000">)</span>
<span style="color: #FF0000">{</span>
        <span style="font-weight: bold"><span style="color: #0000FF">struct</span></span> <span style="color: #008080">long2double</span> <span style="color: #990000">*</span>e <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">find_entry</span></span><span style="color: #990000">(</span>key<span style="color: #990000">);</span>
        <span style="font-weight: bold"><span style="color: #0000FF">if</span></span> <span style="color: #990000">(!</span>e<span style="color: #990000">)</span> <span style="color: #FF0000">{</span>
                e <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">malloc</span></span><span style="color: #990000">(</span><span style="font-weight: bold"><span style="color: #0000FF">sizeof</span></span><span style="color: #990000">(</span><span style="font-weight: bold"><span style="color: #0000FF">struct</span></span> <span style="color: #008080">long2double</span><span style="color: #990000">));</span>
                <span style="font-weight: bold"><span style="color: #000000">hashmap_entry_init</span></span><span style="color: #990000">(</span>e<span style="color: #990000">,</span> <span style="font-weight: bold"><span style="color: #000000">memhash</span></span><span style="color: #990000">(&amp;</span>key<span style="color: #990000">,</span> <span style="font-weight: bold"><span style="color: #0000FF">sizeof</span></span><span style="color: #990000">(</span><span style="color: #009900">long</span><span style="color: #990000">)));</span>
                e<span style="color: #990000">-&gt;</span>key <span style="color: #990000">=</span> key<span style="color: #990000">;</span>
                <span style="font-weight: bold"><span style="color: #000000">hashmap_add</span></span><span style="color: #990000">(&amp;</span>map<span style="color: #990000">,</span> e<span style="color: #990000">);</span>
        <span style="color: #FF0000">}</span>
        e<span style="color: #990000">-&gt;</span>value <span style="color: #990000">=</span> value<span style="color: #990000">;</span>
<span style="color: #FF0000">}</span></tt></pre></div></div>
</div>
</div>
<div class="sect1">
<h2 id="_using_variable_sized_keys">Using variable-sized keys</h2>
<div class="sectionbody">
<div class="paragraph"><p>The <code>hashmap_entry_get</code> and <code>hashmap_entry_remove</code> functions expect an ordinary
<code>hashmap_entry</code> structure as key to find the correct entry. If the key data is
variable-sized (e.g. a FLEX_ARRAY string) or quite large, it is undesirable
to create a full-fledged entry structure on the heap and copy all the key data
into the structure.</p></div>
<div class="paragraph"><p>In this case, the <code>keydata</code> parameter can be used to pass
variable-sized key data directly to the comparison function, and the <code>key</code>
parameter can be a stripped-down, fixed size entry structure allocated on the
stack.</p></div>
<div class="paragraph"><p>See test-hashmap.c for an example using arbitrary-length strings as keys.</p></div>
</div>
</div>
</div>
<div id="footnotes"><hr /></div>
<div id="footer">
<div id="footer-text">
Last updated 2023-05-23 15:02:26 UTC
</div>
</div>
</body>
</html>