From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michael Haggerty Subject: [PATCH v2 02/18] is_refname_available(): revamp the comments Date: Mon, 11 May 2015 17:25:04 +0200 Message-ID: <1431357920-25090-3-git-send-email-mhagger@alum.mit.edu> References: <1431357920-25090-1-git-send-email-mhagger@alum.mit.edu> Cc: Stefan Beller , Eric Sunshine , Jeff King , git@vger.kernel.org, Michael Haggerty To: Junio C Hamano X-From: git-owner@vger.kernel.org Mon May 11 17:25:38 2015 Return-path: Envelope-to: gcvg-git-2@plane.gmane.org Received: from vger.kernel.org ([209.132.180.67]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1YrpaL-0002PD-QU for gcvg-git-2@plane.gmane.org; Mon, 11 May 2015 17:25:38 +0200 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751314AbbEKPZc (ORCPT ); Mon, 11 May 2015 11:25:32 -0400 Received: from alum-mailsec-scanner-6.mit.edu ([18.7.68.18]:48224 "EHLO alum-mailsec-scanner-6.mit.edu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751138AbbEKPZb (ORCPT ); Mon, 11 May 2015 11:25:31 -0400 X-AuditID: 12074412-f79e46d0000036b4-1d-5550c9eba9a1 Received: from outgoing-alum.mit.edu (OUTGOING-ALUM.MIT.EDU [18.7.68.33]) by alum-mailsec-scanner-6.mit.edu (Symantec Messaging Gateway) with SMTP id 99.B7.14004.BE9C0555; Mon, 11 May 2015 11:25:31 -0400 (EDT) Received: from michael.fritz.box (p5DDB195E.dip0.t-ipconnect.de [93.219.25.94]) (authenticated bits=0) (User authenticated as mhagger@ALUM.MIT.EDU) by outgoing-alum.mit.edu (8.13.8/8.12.4) with ESMTP id t4BFPNnE002156 (version=TLSv1/SSLv3 cipher=AES128-SHA bits=128 verify=NOT); Mon, 11 May 2015 11:25:30 -0400 X-Mailer: git-send-email 2.1.4 In-Reply-To: <1431357920-25090-1-git-send-email-mhagger@alum.mit.edu> X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFnrGIsWRmVeSWpSXmKPExsUixO6iqPv6ZECoQfs7fouuK91MFg29V5gt bq+Yz2zxo6WH2WLz5nYWizNvGhkd2Dz+vv/A5LFgU6nHs949jB4XLyl7LH7g5fF5k1wAWxS3 TVJiSVlwZnqevl0Cd8alX3dZC84qVfzt/crYwPhYsouRk0NCwERi5vxWRghbTOLCvfVsXYxc HEIClxkl7j14yQ7hHGeSWLPgOzNIFZuArsSinmYmEFtEQE1iYtshFpAiZoFdQB1Lp7KAJIQF XCUuXr8FZrMIqEr0974FW8Er4CLRva6JGWKdnMT54z/BbE6g+qVXL4PVCwHVND2+xzKBkXcB I8MqRrnEnNJc3dzEzJzi1GTd4uTEvLzUIl0zvdzMEr3UlNJNjJAwE9rBuP6k3CFGAQ5GJR5e gwv+oUKsiWXFlbmHGCU5mJREeX/tDQgV4kvKT6nMSCzOiC8qzUktPsQowcGsJMKrvAYox5uS WFmVWpQPk5LmYFES5/25WN1PSCA9sSQ1OzW1ILUIJivDwaEkwdt4AqhRsCg1PbUiLTOnBCHN xMEJMpxLSqQ4NS8ltSixtCQjHhQd8cXA+ABJ8QDtrQJp5y0uSMwFikK0nmJUlBLnTQFJCIAk Mkrz4MbCkscrRnGgL4V514NU8QATD1z3K6DBTECDHePABpckIqSkGhiLt29ja+uf2bDoVWmp anlpn/ir6E8iVzabV+nlGkxtmrxCadst812LausL5n9ZzeBd/kAkZEbrhmOSMm8ybrM2n3WJ z/h3PW8t67W6m9sNPotGPeb8teJCjoyKw9y7u4vetJomPDG+H7FXqv1RyNakX7Oy Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org Archived-At: Change the comments to a running example of running the function with refname set to "refs/foo/bar". Add some more explanation of the logic. Signed-off-by: Michael Haggerty --- refs.c | 69 +++++++++++++++++++++++++++++++++++++++++++++--------------------- 1 file changed, 47 insertions(+), 22 deletions(-) diff --git a/refs.c b/refs.c index 47e4e53..776bbce 100644 --- a/refs.c +++ b/refs.c @@ -876,9 +876,9 @@ static void report_refname_conflict(struct ref_entry *entry, * operation). * * Two reference names conflict if one of them exactly matches the - * leading components of the other; e.g., "foo/bar" conflicts with - * both "foo" and with "foo/bar/baz" but not with "foo/bar" or - * "foo/barbados". + * leading components of the other; e.g., "refs/foo/bar" conflicts + * with both "refs/foo" and with "refs/foo/bar/baz" but not with + * "refs/foo/bar" or "refs/foo/barbados". * * skip must be sorted. */ @@ -891,19 +891,39 @@ static int is_refname_available(const char *refname, int pos; char *dirname; + /* + * For the sake of comments in this function, suppose that + * refname is "refs/foo/bar". + */ + for (slash = strchr(refname, '/'); slash; slash = strchr(slash + 1, '/')) { /* - * We are still at a leading dir of the refname; we are - * looking for a conflict with a leaf entry. - * - * If we find one, we still must make sure it is - * not in "skip". + * We are still at a leading dir of the refname (e.g., + * "refs/foo"; if there is a reference with that name, + * it is a conflict, *unless* it is in skip. */ pos = search_ref_dir(dir, refname, slash - refname); if (pos >= 0) { + /* + * We found a reference whose name is a proper + * prefix of refname; e.g., "refs/foo". + */ struct ref_entry *entry = dir->entries[pos]; - if (entry_matches(entry, skip)) + if (entry_matches(entry, skip)) { + /* + * The reference we just found, e.g., + * "refs/foo", is also in skip, so it + * is not considered a conflict. + * Moreover, the fact that "refs/foo" + * exists means that there cannot be + * any references anywhere under the + * "refs/foo/" namespace (because they + * would have conflicted with + * "refs/foo"). So we can stop looking + * now and return true. + */ return 1; + } report_refname_conflict(entry, refname); return 0; } @@ -911,19 +931,29 @@ static int is_refname_available(const char *refname, /* * Otherwise, we can try to continue our search with - * the next component; if we come up empty, we know - * there is nothing under this whole prefix. + * the next component. So try to look up the + * directory, e.g., "refs/foo/". */ pos = search_ref_dir(dir, refname, slash + 1 - refname); - if (pos < 0) + if (pos < 0) { + /* + * There was no directory "refs/foo/", so + * there is nothing under this whole prefix, + * and we are OK. + */ return 1; + } dir = get_ref_dir(dir->entries[pos]); } /* - * We are at the leaf of our refname; we want to - * make sure there are no directories which match it. + * We are at the leaf of our refname (e.g., "refs/foo/bar"). + * There is no point in searching for a reference with that + * name, because a refname isn't considered to conflict with + * itself. But we still need to check for references whose + * names are in the "refs/foo/bar/" namespace, because they + * *do* conflict. */ len = strlen(refname); dirname = xmallocz(len + 1); @@ -933,9 +963,9 @@ static int is_refname_available(const char *refname, if (pos >= 0) { /* - * We found a directory named "refname". It is a - * problem iff it contains any ref that is not - * in "skip". + * We found a directory named "$refname/" (e.g., + * "refs/foo/bar/"). It is a problem iff it contains + * any ref that is not in "skip". */ struct ref_entry *entry = dir->entries[pos]; struct ref_dir *dir = get_ref_dir(entry); @@ -950,11 +980,6 @@ static int is_refname_available(const char *refname, return 0; } - /* - * There is no point in searching for another leaf - * node which matches it; such an entry would be the - * ref we are looking for, not a conflict. - */ return 1; } -- 2.1.4