From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Shawn O. Pearce" Subject: [JGIT PATCH v3] Replace inefficient new String(String) constructor to silence FindBugs Date: Fri, 1 May 2009 08:54:32 -0700 Message-ID: <1241193272-20247-1-git-send-email-spearce@spearce.org> Cc: git@vger.kernel.org, Yann Simon , Matthias Sohn To: Robin Rosenberg X-From: git-owner@vger.kernel.org Fri May 01 17:55:15 2009 Return-path: Envelope-to: gcvg-git-2@gmane.org Received: from vger.kernel.org ([209.132.176.167]) by lo.gmane.org with esmtp (Exim 4.50) id 1Lzv4b-0007d5-OH for gcvg-git-2@gmane.org; Fri, 01 May 2009 17:54:50 +0200 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760663AbZEAPyf (ORCPT ); Fri, 1 May 2009 11:54:35 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1760108AbZEAPyf (ORCPT ); Fri, 1 May 2009 11:54:35 -0400 Received: from george.spearce.org ([209.20.77.23]:45533 "EHLO george.spearce.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759484AbZEAPye (ORCPT ); Fri, 1 May 2009 11:54:34 -0400 Received: by george.spearce.org (Postfix, from userid 1000) id D6CE93807E; Fri, 1 May 2009 15:54:34 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.2.4 (2008-01-01) on george.spearce.org X-Spam-Level: X-Spam-Status: No, score=-4.4 required=4.0 tests=ALL_TRUSTED,BAYES_00 autolearn=ham version=3.2.4 Received: from localhost.localdomain (localhost [127.0.0.1]) by george.spearce.org (Postfix) with ESMTP id E45653807B; Fri, 1 May 2009 15:54:32 +0000 (UTC) X-Mailer: git-send-email 1.6.3.rc3.212.g8c698 Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org Archived-At: FindBugs keeps reporting that our usage of new String(String) is not the most efficient way to construct a string. http://thread.gmane.org/gmane.comp.version-control.git/113739/focus=113787 > I had a specific reason for forcing a new String object here. > > The line in question, p, is from the packed-refs file and > contains the entire SHA-1 in hex form at the beginning of it. > We've converted that into binary as an ObjectId, it uses 1/4 the > space of the string portion. > > The Ref object, its ObjectId, and its name string, are going to be > cached in a Map, probably long-term. We're better off shedding the > 80 bytes of memory used to hold the hex SHA-1 then risk substring() > deciding its "faster" to reuse the char[] then to make a copy of it. Another way to force this new unique String instance with its own private char[] is to use a StringBuilder and append onto it the ref name. This shouldn't be a warning for FindBugs, but it would accomplish the same goal of producing 1 clean copy, with no extra transient temporary array. Signed-off-by: Shawn O. Pearce CC: Yann Simon CC: Matthias Sohn --- A less ugly version ? .../src/org/spearce/jgit/lib/RefDatabase.java | 9 ++++++++- 1 files changed, 8 insertions(+), 1 deletions(-) diff --git a/org.spearce.jgit/src/org/spearce/jgit/lib/RefDatabase.java b/org.spearce.jgit/src/org/spearce/jgit/lib/RefDatabase.java index 87f26bf..a865fba 100644 --- a/org.spearce.jgit/src/org/spearce/jgit/lib/RefDatabase.java +++ b/org.spearce.jgit/src/org/spearce/jgit/lib/RefDatabase.java @@ -447,7 +447,7 @@ private synchronized void refreshPackedRefs() { final int sp = p.indexOf(' '); final ObjectId id = ObjectId.fromString(p.substring(0, sp)); - final String name = new String(p.substring(sp + 1)); + final String name = copy(p.substring(sp + 1)); last = new Ref(Ref.Storage.PACKED, name, name, id); newPackedRefs.put(last.getName(), last); } @@ -469,6 +469,13 @@ private synchronized void refreshPackedRefs() { } } + private static String copy(final String src) { + // Force a deep copy of the underlying char[] so that we can + // discard any garbage from any shared char[] within src. + // + return new StringBuilder(src.length()).append(src).toString(); + } + private void lockAndWriteFile(File file, byte[] content) throws IOException { String name = file.getName(); final LockFile lck = new LockFile(file); -- 1.6.3.rc3.212.g8c698