From patchwork Tue Sep 24 22:02:56 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andreas Rheinhardt X-Patchwork-Id: 15263 Return-Path: X-Original-To: patchwork@ffaux-bg.ffmpeg.org Delivered-To: patchwork@ffaux-bg.ffmpeg.org Received: from ffbox0-bg.mplayerhq.hu (ffbox0-bg.ffmpeg.org [79.124.17.100]) by ffaux.localdomain (Postfix) with ESMTP id 92D78449BE7 for ; Wed, 25 Sep 2019 01:03:40 +0300 (EEST) Received: from [127.0.1.1] (localhost [127.0.0.1]) by ffbox0-bg.mplayerhq.hu (Postfix) with ESMTP id 828B5689DC4; Wed, 25 Sep 2019 01:03:40 +0300 (EEST) X-Original-To: ffmpeg-devel@ffmpeg.org Delivered-To: ffmpeg-devel@ffmpeg.org Received: from mail-wm1-f65.google.com (mail-wm1-f65.google.com [209.85.128.65]) by ffbox0-bg.mplayerhq.hu (Postfix) with ESMTPS id 65B66689DA5 for ; Wed, 25 Sep 2019 01:03:34 +0300 (EEST) Received: by mail-wm1-f65.google.com with SMTP id r19so531179wmh.2 for ; Tue, 24 Sep 2019 15:03:34 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=Mm3aPuvHiJJafWL+FdWiJ7H5L10S04jw6IkVuPrHgy8=; b=HmUN9VeXRgbFa39l380R/hj0Wq3BsFM3807VvT4pIr1iRUHzO2LW7yx9MXuwdyPrlG x8qDE0Wz8Lu0rUmFBLAEGqDKtMAUDqpAtvObPxW+I4QTO4n/fNjoS0yfv9wzTz53CtXK L8wixcmKBBIu1nDsw/fPh4jQNLwcttkbTD9XhDI39mmXfWLiv3Vtwa/ST8JsVeAel9ZR l2K6r1nPOysYimYnflzfSygnxyk0HNuVMiS86oIGHBbqp28F6YBq4pCBQYokYo/r4GNU vPAkgY5dz+OPxWhfN31MzRGRZhDZtx7Nfd7N5fo1zdobcnsFAXnirLAKCdCfcP/ERT8V zOzQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=Mm3aPuvHiJJafWL+FdWiJ7H5L10S04jw6IkVuPrHgy8=; b=Y2UrX27/x7QgHxnIkkvOAy1/4qed5PmofC4CeoRtz0GGlFeYElb7bHCBkkmlFHZrQz 4TTDIyX1Y3Oegr9ynElE2cG/rt5qDkK7mM++9JCoUmdEnAfNY5cd/Dx7c/UicJgVCRZi 5wVU/W1hdiQ+InJ7+e16tvpv0/L/AygRSP7m7on7nxCN4fAbSlDeGPGv6Q0q9IW39Udp xkbc4ClsnzU8LwskquS0cUrt9s8EyNylAs1gUr1sgEIbyAuKyERIlTVeDLdthZiuOtqA hUZ6C3Nb3ZiV50VE0rRkfU9YaBfcwK4rdBjUTZc2NpQOTKhurr5GBtqu/GjRyNbbzK4K v0sA== X-Gm-Message-State: APjAAAX9akdXtI/D+ZsSN2+bRvj426OlAyRDTfA3dovRdllpk8LxCcOU ka8ipKLnvKYmaQtqgKEApZdRZGBi X-Google-Smtp-Source: APXvYqxaicDFvJ39vPK/fpe1wY7jmrd3nyBeg78vEYFOqxZ8DEfukcV0ll+ZZv5PAoL1M48E8fxLAg== X-Received: by 2002:a7b:c4c9:: with SMTP id g9mr3042923wmk.150.1569362613664; Tue, 24 Sep 2019 15:03:33 -0700 (PDT) Received: from sblaptop.fritz.box ([188.192.248.87]) by smtp.gmail.com with ESMTPSA id l1sm3023808wrb.1.2019.09.24.15.03.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 24 Sep 2019 15:03:33 -0700 (PDT) From: Andreas Rheinhardt To: ffmpeg-devel@ffmpeg.org Date: Wed, 25 Sep 2019 00:02:56 +0200 Message-Id: <20190924220310.31157-2-andreas.rheinhardt@gmail.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190924220310.31157-1-andreas.rheinhardt@gmail.com> References: <20190924220310.31157-1-andreas.rheinhardt@gmail.com> MIME-Version: 1.0 Subject: [FFmpeg-devel] [PATCH 01/15] avutil/common: Add macro for left-shifting X-BeenThere: ffmpeg-devel@ffmpeg.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: FFmpeg development discussions and patches List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: FFmpeg development discussions and patches Cc: Andreas Rheinhardt Errors-To: ffmpeg-devel-bounces@ffmpeg.org Sender: "ffmpeg-devel" Left shifting a negative integer is undefined, yet often needed. Therefore add a macro that internally uses multiplication by powers of two to make it clear that a shift is intended. Signed-off-by: Andreas Rheinhardt --- I don't insist on this macro. I only added it so that one can easily see that shifting was intended. I initially wanted to use "FFLS", but eventually chose FFLSHIFT because it is self-explanatory. libavutil/common.h | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/libavutil/common.h b/libavutil/common.h index af35397eb9..93c5dd0af7 100644 --- a/libavutil/common.h +++ b/libavutil/common.h @@ -60,6 +60,14 @@ /* Backwards compat. */ #define FF_CEIL_RSHIFT AV_CEIL_RSHIFT +/** + * Left shift macro designed to tackle the undefinedness + * of left-shifting negative numbers. + * + * Note: Still undefined if the multiplication overflows. + */ +#define FFLSHIFT(a,b) ((a) * (1 << (b))) + #define FFUDIV(a,b) (((a)>0 ?(a):(a)-(b)+1) / (b)) #define FFUMOD(a,b) ((a)-(b)*FFUDIV(a,b))