<!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 8.6.9" />
<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;
}
pre {
white-space: pre-wrap;
}
#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; vertical-align: text-bottom; }
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">
/*<+'])');
// Function that scans the DOM tree for header elements (the DOM2
// nodeIterator API would be a better technique but not supported by all
// browsers).
var iterate = function (el) {
for (var i = el.firstChild; i != null; i = i.nextSibling) {
if (i.nodeType == 1 /* Node.ELEMENT_NODE */) {
var mo = re.exec(i.tagName);
if (mo && (i.getAttribute("class") || i.getAttribute("className")) != "float") {
result[result.length] = new TocEntry(i, getText(i), mo[1]-1);
}
iterate(i);
}
}
}
iterate(el);
return result;
}
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. Members can be used as follows, but should
not be modified directly:
</p>
<div class="paragraph"><p>The <code>size</code> member keeps track of the total number of entries (0 means the
hashmap is empty).</p></div>
<div class="paragraph"><p><code>tablesize</code> is the allocated size of the hash table. A non-0 value indicates
that the hashmap is initialized. It may also be useful for statistical purposes
(i.e. <code>size / tablesize</code> is the current load factor).</p></div>
<div class="paragraph"><p><code>cmpfn</code> stores the comparison function specified in <code>hashmap_init()</code>. In
advanced scenarios, it may be useful to change this, e.g. to switch between
case-sensitive and case-insensitive lookup.</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’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>unsigned int sha1hash(const unsigned char *sha1)</code>
</dt>
<dd>
<p>
Converts a cryptographic hash (e.g. SHA-1) into an int-sized hash code
for use in hash tables. Cryptographic hashes are supposed to have
uniform distribution, so in contrast to <code>memhash()</code>, this just copies
the first <code>sizeof(int)</code> bytes without shuffling any bits. Note that
the results will be different on big-endian and little-endian
platforms, so they should not be stored or transferred over the net.
</p>
</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’s free()).</p></div>
</dd>
<dt class="hdlist1">
<code>void hashmap_entry_init(void *entry, unsigned 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>
<dt class="hdlist1">
<code>const char *strintern(const char *string)</code>
</dt>
<dt class="hdlist1">
<code>const void *memintern(const void *data, size_t len)</code>
</dt>
<dd>
<p>
Returns the unique, interned version of the specified string or data,
similar to the <code>String.intern</code> API in Java and .NET, respectively.
Interned strings remain valid for the entire lifetime of the process.
</p>
<div class="paragraph"><p>Can be used as <code>[x]strdup()</code> or <code>xmemdupz</code> replacement, except that interned
strings / data must not be modified or freed.</p></div>
<div class="paragraph"><p>Interned strings are best used for short strings with high probability of
duplicates.</p></div>
<div class="paragraph"><p>Uses a hashmap to store the pool of interned strings.</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’s a simple usage example that maps long keys to double values.</p></div>
<div class="listingblock">
<div class="content">
<pre><code>struct hashmap map;
struct long2double {
struct hashmap_entry ent; /* must be the first member! */
long key;
double value;
};
static int long2double_cmp(const struct long2double *e1, const struct long2double *e2, const void *unused)
{
return !(e1->key == e2->key);
}
void long2double_init(void)
{
hashmap_init(&map, (hashmap_cmp_fn) long2double_cmp, 0);
}
void long2double_free(void)
{
hashmap_free(&map, 1);
}
static struct long2double *find_entry(long key)
{
struct long2double k;
hashmap_entry_init(&k, memhash(&key, sizeof(long)));
k.key = key;
return hashmap_get(&map, &k, NULL);
}
double get_value(long key)
{
struct long2double *e = find_entry(key);
return e ? e->value : 0;
}
void set_value(long key, double value)
{
struct long2double *e = find_entry(key);
if (!e) {
e = malloc(sizeof(struct long2double));
hashmap_entry_init(e, memhash(&key, sizeof(long)));
e->key = key;
hashmap_add(&map, e);
}
e->value = value;
}</code></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 2016-03-17 20:47:59 UTC
</div>
</div>
</body>
</html>
distrib
>
Mageia
>
5
>
i586
>
media
>
core-updates
>
by-pkgid
>
03fb55f49f638cb73389f6ce84919469
>
files
>
613
