/**
 * Myext lock (aka binary semaphore aka mutex)
 *
 * Copyright (C) 2021 Wojtek Kosior
 * Redistribution terms are gathered in the `copyright' file.
 */

/*
 * Javascript runs single-threaded, with an event loop. Because of that,
 * explicit synchronization is often not needed. An exception is when we use
 * an API function that must wait. Ajax is an example. Callback passed to ajax
 * call doesn't get called immediately, but after some time. In the meantime
 * some other piece of code might get to execute and modify some variables.
 * Access to WebExtension local storage is another situation where this problem
 * can occur.
 *
 * This is a solution. A lock object, that can be used to delay execution of
 * some code until other code finishes its critical work. Locking is wrapped
 * in a promise.
 */

"use strict";

(() => {
    function make_lock() {
	return {free: true, queue: []};
    }

    function _lock(lock, cb) {
	if (lock.free) {
	    lock.free = false;
	    setTimeout(cb);
	} else {
	    lock.queue.push(cb);
	}
    }

    function lock(lock) {
	return new Promise((resolve, reject) => _lock(lock, resolve));
    }

    function unlock(lock) {
	if (lock.free)
	    throw new Exception("Attempting to release a free lock");

	if (lock.queue.length === 0) {
	    lock.free = true;
	} else {
	    let cb = lock.queue[0];
	    lock.queue.splice(0, 1);
	    setTimeout(cb);
	}
    }

    window.make_lock = make_lock;
    window.lock = lock;
    window.unlock = unlock;
})();
2068c94ba828a04559007d4b957be83b'>diff</a></td><td class='form'><form class='right' method='get' action='/guix/log/gnu/packages/man.scm'>
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<div class='path'>path: <a href='/guix/log/?id=24a23bea2068c94ba828a04559007d4b957be83b'>root</a>/<a href='/guix/log/gnu?id=24a23bea2068c94ba828a04559007d4b957be83b'>gnu</a>/<a href='/guix/log/gnu/packages?id=24a23bea2068c94ba828a04559007d4b957be83b'>packages</a>/<a href='/guix/log/gnu/packages/man.scm?id=24a23bea2068c94ba828a04559007d4b957be83b'>man.scm</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/gnu/packages/man.scm?id=24a23bea2068c94ba828a04559007d4b957be83b&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2018-12-20 08:59:36 +0100'>2018-12-20</span></td><td><a href='/guix/commit/gnu/packages/man.scm?id=e2dd54c09035aadce8a363c3b1faf703f025d62d'>gnu: Add scdoc.</a><span class='msg-avail'>...</span></td><td>Rutger Helling</td></tr>
<tr><td><span title='2018-11-19 09:59:08 +0100'>2018-11-19</span></td><td><a href='/guix/commit/gnu/packages/man.scm?id=5e9ce98af74d96bc4f2caf965de3bcd4aa8d8d2a'>gnu: help2man: Add 1.47.8.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2018-05-08 18:45:39 -0400'>2018-05-08</span></td><td><a href='/guix/commit/gnu/packages/man.scm?id=aedc6e9fc952665e666f2febfc0b37235ad850ff'>Merge branch 'master' into core-updates</a></td><td>Mark H Weaver</td></tr>
<tr><td><span title='2018-05-06 23:55:50 +0200'>2018-05-06</span></td><td><a href='/guix/commit/gnu/packages/man.scm?id=ccb15b343e35d76a5c7c693f4c00d3f5b5a4cc39'>Revert "gnu: man-db: Embed absolute reference to 'preconv'."</a><span class='msg-avail'>...</span></td><td>Marius Bakke</td></tr>
<tr><td><span title='2018-05-06 15:56:24 +0200'>2018-05-06</span></td><td><a href='/guix/commit/gnu/packages/man.scm?id=12bd588346f8b2fb3709acfe0ee89d153da2db34'>Merge branch 'master' into core-updates</a></td><td>Marius Bakke</td></tr>
<tr><td><span title='2018-05-06 15:47:20 +0200'>2018-05-06</span></td><td><a href='/guix/commit/gnu/packages/man.scm?id=296551a2e9310d4a030ee49530e9367e73aaeecf'>gnu: man-db: Embed absolute reference to 'preconv'.</a><span class='msg-avail'>...</span></td><td>Marius Bakke</td></tr>
<tr><td><span title='2018-05-02 14:40:14 +0200'>2018-05-02</span></td><td><a href='/guix/commit/gnu/packages/man.scm?id=0ef3c023852799bfe2e5b6a6779568262087b152'>gnu: man-pages: Update to 4.16.</a><span class='msg-avail'>...</span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2018-04-21 05:02:52 -0400'>2018-04-21</span></td><td><a href='/guix/commit/gnu/packages/man.scm?id=c52872bfc418c6b2273f973dff8003ca9e062792'>Merge branch 'master' into core-updates</a></td><td>Mark H Weaver</td></tr>
<tr><td><span title='2018-04-17 04:02:13 +0200'>2018-04-17</span></td><td><a href='/guix/commit/gnu/packages/man.scm?id=c33a27ceb8388cf918716fe1729d640594504c67'>gnu: man-db: Update to 2.8.3.</a><span class='msg-avail'>...</span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2018-03-23 04:42:53 -0400'>2018-03-23</span></td><td><a href='/guix/commit/gnu/packages/man.scm?id=ff57d5b18e675abe2f9a437b7eb7487f1df33e44'>gnu: man-db: Return #t from all phases.</a><span class='msg-avail'>...</span></td><td>Mark H Weaver</td></tr>
<tr><td><span title='2018-03-14 17:37:20 +0100'>2018-03-14</span></td><td><a href='/guix/commit/gnu/packages/man.scm?id=8c72ed923d77ee55989965bb02628043799b9548'>Merge branch 'master' into core-updates</a></td><td>Ricardo Wurmus</td></tr>
<tr><td><span title='2018-03-14 16:48:04 +0100'>2018-03-14</span></td><td><a href='/guix/commit/gnu/packages/man.scm?id=880e2170b7ef53399d9989d9895e6ea102a0c7ed'>gnu: man-db: Update to 2.8.2.</a><span class='msg-avail'>...</span></td><td>Marius Bakke</td></tr>