From mboxrd@z Thu Jan 1 00:00:00 1970 Delivery-date: Thu, 27 Oct 2022 09:25:57 +0200 Received: from metis.ext.pengutronix.de ([2001:67c:670:201:290:27ff:fe1d:cc33]) by lore.white.stw.pengutronix.de with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1onxH3-003p59-7G for lore@lore.pengutronix.de; Thu, 27 Oct 2022 09:25:57 +0200 Received: from bombadil.infradead.org ([2607:7c80:54:3::133]) by metis.ext.pengutronix.de with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1onxH2-00082E-4y for lore@pengutronix.de; Thu, 27 Oct 2022 09:25:56 +0200 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=GxHSEqx/AawGPtPLrQcCZ0TjD4AOTavv0wzXg8/D05E=; b=E0RCwbON87dk+YRwyqomhhH5aV c2A0nduVXnhpNRl7Fj2/fcNl3x/Kg+5x8Rb+L/EyIP6IQDejYMu2slqDXvKp1eeJX7nrK+KTCo6Jn JXbtDH3NTNYUqDMZeD9PnP+SeABU/ChoCyoXri4ecN04caLwO0fudhwWDTaphYquEehW2uQsGg6di lNglETnyAKMFIJwgCj0jgZ06zx4Rito/v+nmUnQ7LHW8FO/a/hty/DI/98urdkFzhbP4kTcU20jyr Q6KSp6T++E+/hgLDhRuIlwgO8+3jELnBBhL0dZn5gIeU01ERUWiRT0GotvRnqZfDIELAeHlhc3TfE i6fzRDvw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1onxFd-00CA4m-3P; Thu, 27 Oct 2022 07:24:29 +0000 Received: from metis.ext.pengutronix.de ([2001:67c:670:201:290:27ff:fe1d:cc33]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1onxFY-00CA3m-JM for barebox@lists.infradead.org; Thu, 27 Oct 2022 07:24:26 +0000 Received: from ptz.office.stw.pengutronix.de ([2a0a:edc0:0:900:1d::77] helo=[127.0.0.1]) by metis.ext.pengutronix.de with esmtp (Exim 4.92) (envelope-from ) id 1onxFV-0007qa-0A; Thu, 27 Oct 2022 09:24:21 +0200 Message-ID: Date: Thu, 27 Oct 2022 09:24:20 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.12.0 Content-Language: en-US To: Sascha Hauer Cc: barebox@lists.infradead.org References: <20221026064205.2360041-1-a.fatoum@pengutronix.de> <20221026064205.2360041-3-a.fatoum@pengutronix.de> <20221027065651.GQ6702@pengutronix.de> From: Ahmad Fatoum In-Reply-To: <20221027065651.GQ6702@pengutronix.de> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20221027_002424_683567_2428E108 X-CRM114-Status: GOOD ( 22.10 ) X-BeenThere: barebox@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "barebox" X-SA-Exim-Connect-IP: 2607:7c80:54:3::133 X-SA-Exim-Mail-From: barebox-bounces+lore=pengutronix.de@lists.infradead.org X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on metis.ext.pengutronix.de X-Spam-Level: X-Spam-Status: No, score=-4.9 required=4.0 tests=AWL,BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,NICE_REPLY_A,RCVD_IN_DNSWL_MED,SPF_HELO_NONE, SPF_NONE,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.2 Subject: Re: [PATCH 3/6] string: reduce strjoin runtime, drop trailing separator X-SA-Exim-Version: 4.2.1 (built Wed, 08 May 2019 21:11:16 +0000) X-SA-Exim-Scanned: Yes (on metis.ext.pengutronix.de) Hi, On 27.10.22 08:56, Sascha Hauer wrote: > On Wed, Oct 26, 2022 at 08:42:02AM +0200, Ahmad Fatoum wrote: >> The implementation of strjoin is a bit suboptimal. The destination >> string is traversed from the beginning due to strcat and we have a >> left-over separator at the end, while it should only be in-between. >> >> Fix this. > > Rather than fixing a just introduced function I would expect a patch > introducing strjoin() and then another one converting the time command > over to use it. What difference does it make? >> +void *mempcpy(void *dest, const void *src, size_t count) >> +{ >> + return memcpy(dest, src, count) + count; >> +} >> +EXPORT_SYMBOL(mempcpy); >> >> #ifndef __HAVE_ARCH_MEMMOVE >> /** >> @@ -943,7 +948,7 @@ char *strjoin(const char *separator, char **arr, size_t arrlen) >> { >> size_t separatorlen; >> int len = 1; /* '\0' */ >> - char *buf; >> + char *buf, *p; >> int i; >> >> separatorlen = strlen(separator); >> @@ -951,12 +956,14 @@ char *strjoin(const char *separator, char **arr, size_t arrlen) >> for (i = 0; i < arrlen; i++) >> len += strlen(arr[i]) + separatorlen; >> >> - buf = xzalloc(len); >> + p = buf = xmalloc(len); >> >> for (i = 0; i < arrlen; i++) { >> - strcat(buf, arr[i]); >> - strcat(buf, separator); >> + p = stpcpy(p, arr[i]); >> + p = mempcpy(p, separator, separatorlen); >> } >> >> + p[-separatorlen] = '\0'; > > That's a bit hard to read. How about: > > for (i = 0; i < arrlen; i++) { > p = stpcpy(p, arr[i]); > if (i < arrlen - 1) > p = stpcpy(p, separator); > } > > That would also allow you to optimize the allocated buffer size above. I like my version more. I dislike these once-only checks inside loops. Cheers, Ahmad > > Sascha > -- Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |