From patchwork Sun Oct 6 23:30:33 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Wong X-Patchwork-Id: 11176635 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 81579112B for ; Sun, 6 Oct 2019 23:31:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6B9E120862 for ; Sun, 6 Oct 2019 23:31:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726809AbfJFXbN (ORCPT ); Sun, 6 Oct 2019 19:31:13 -0400 Received: from dcvr.yhbt.net ([64.71.152.64]:39360 "EHLO dcvr.yhbt.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726227AbfJFXbN (ORCPT ); Sun, 6 Oct 2019 19:31:13 -0400 Received: from localhost (dcvr.yhbt.net [127.0.0.1]) by dcvr.yhbt.net (Postfix) with ESMTP id C8C401F4C8; Sun, 6 Oct 2019 23:30:45 +0000 (UTC) From: Eric Wong To: Junio C Hamano Cc: git@vger.kernel.org, Derrick Stolee , Johannes Schindelin , Phillip Wood Subject: [PATCH v3 10/20] introduce container_of macro Date: Sun, 6 Oct 2019 23:30:33 +0000 Message-Id: <20191006233043.3516-11-e@80x24.org> In-Reply-To: <20191006233043.3516-1-e@80x24.org> References: <20191006233043.3516-1-e@80x24.org> MIME-Version: 1.0 Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org This macro is popular within the Linux kernel for supporting intrusive data structures such as linked lists, red-black trees, and chained hash tables while allowing the compiler to do type checking. Later patches will use container_of() to remove the limitation of "hashmap_entry" being location-dependent. This will complete the transition to compile-time type checking for the hashmap API. This macro already exists in our source as "list_entry" in list.h and making "list_entry" an alias to "container_of" as the Linux kernel has done is a possibility. Signed-off-by: Eric Wong Reviewed-by: Derrick Stolee --- git-compat-util.h | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/git-compat-util.h b/git-compat-util.h index 83be89de0a..4cc2c8283a 100644 --- a/git-compat-util.h +++ b/git-compat-util.h @@ -1312,4 +1312,14 @@ void unleak_memory(const void *ptr, size_t len); */ #include "banned.h" +/* + * container_of - Get the address of an object containing a field. + * + * @ptr: pointer to the field. + * @type: type of the object. + * @member: name of the field within the object. + */ +#define container_of(ptr, type, member) \ + ((type *) ((char *)(ptr) - offsetof(type, member))) + #endif