Re: [RFC PATCH] hashmap API: introduce for_each_hashmap_entry() helper macro

From: Karsten Blees <karsten.blees@gmail.com>
Date: Mar 16, 2016, 23:47 UTC
Message-ID: <56E9F0A8.5080308@gmail.com>
In-Reply-To: <1458146346-27959-1-git-send-email-kuleshovmail@gmail.com>

Am 16.03.2016 um 17:39 schrieb Alexander Kuleshov:

Show 6 quoted lines

> There is common pattern to traverse a hashmap in git source code:
> 
>         hashmap_iter_init(map, &iter);
>         while ((entry = hashmap_iter_next(&iter)))
>              // do something with entry
>

The hashmap_iter_first() function allows you to do this instead:

	for (entry = hashmap_iter_first(map, &iter); entry; entry = hashmap_iter_next(&iter))
		doSomething(entry);

With an appropriate macro definition, this could be simplified to:

	#define hashmap_for_each(map, iter, entry) for (entry = hashmap_iter_first(map, iter); entry; entry = hashmap_iter_next(iter))
	...
	hashmap_for_each(map, &iter, entry)
		doSomething(entry);

You would still need to declare the 'iter' and 'entry' variables, but there is no danger of decl-after-statement or variable shadowing mentioned by Junio. That is, you can do this:

	hashmap_for_each(map, &iter, entry)
		if (checkCondition(entry))
			break;
	// work with found entry

Or even this:

	hashmap_for_each(map, &iter1, entry1)
		hashmap_for_each(map, &iter2, entry2)
			doSomething(entry1, entry2);