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[2620:137:e000::1:20]) by mx.google.com with ESMTP id u11-20020aa7d88b000000b0046a279823d6si6050610edq.298.2022.12.02.08.18.56; Fri, 02 Dec 2022 08:19:21 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@kernel.org header.s=k20201202 header.b=eZA4rWwQ; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233979AbiLBQRg (ORCPT + 99 others); Fri, 2 Dec 2022 11:17:36 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53764 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233937AbiLBQQs (ORCPT ); Fri, 2 Dec 2022 11:16:48 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C34DDBE6A1; Fri, 2 Dec 2022 08:16:27 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 7C22BB821EF; Fri, 2 Dec 2022 16:16:26 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0B1C9C433D6; Fri, 2 Dec 2022 16:16:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1669997785; bh=lNOFPVRbAKVrfjnVGGlh1mHXRjctVq4x9YbdvqaJ5Pc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=eZA4rWwQlLf/QhcBhrlLCwVeLdG0tbiNvtMljCe5GPUaS1snLGeCqEF0fOQBXL7lc O2Ou8zvs6Vta595iqoUkxn4qyPgwQuNC5GP2RciAUllOKsi6dtrrQYCKCo9U0jkxh+ sxWfFO04JADRtp9ZcKcTKc7ap54ysr+Z8tjDdc+I1gtNedTFaZU7/OHjDSQdVfGCl5 xhAkSvQCowbAgvVNgnOAehjsD8GEYd/OPcBMJIl5vfBqi7Nm3LBbA9yDFVqDVTKnFT 1+SBvnDxZ77h5m0ZRF2lCbhdTzUhYh1tR7kSG4rMVVbTib/D3BnZcwOWS/UJ/C1Hq6 lqzZKBgD4TMFg== From: ojeda@kernel.org To: Miguel Ojeda , Wedson Almeida Filho , Alex Gaynor , Boqun Feng , Gary Guo , =?utf-8?q?Bj=C3=B6rn_Roy_Baron?= Cc: rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org, patches@lists.linux.dev, Adam Bratschi-Kaye Subject: [PATCH v2 20/28] rust: str: add `Formatter` type Date: Fri, 2 Dec 2022 17:14:51 +0100 Message-Id: <20221202161502.385525-21-ojeda@kernel.org> In-Reply-To: <20221202161502.385525-1-ojeda@kernel.org> References: <20221202161502.385525-1-ojeda@kernel.org> MIME-Version: 1.0 X-Spam-Status: No, score=-7.1 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_HI, SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1751119782429416579?= X-GMAIL-MSGID: =?utf-8?q?1751119782429416579?= From: Wedson Almeida Filho Add the `Formatter` type, which leverages `RawFormatter`, but fails if callers attempt to write more than will fit in the buffer. In order to so, implement the `RawFormatter::from_buffer()` constructor as well. Co-developed-by: Adam Bratschi-Kaye Signed-off-by: Adam Bratschi-Kaye Signed-off-by: Wedson Almeida Filho Reviewed-by: Gary Guo [Reworded, adapted for upstream and applied latest changes] Signed-off-by: Miguel Ojeda --- rust/kernel/str.rs | 57 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 57 insertions(+) diff --git a/rust/kernel/str.rs b/rust/kernel/str.rs index a995db36486f..ce207d1b3d2a 100644 --- a/rust/kernel/str.rs +++ b/rust/kernel/str.rs @@ -406,6 +406,23 @@ impl RawFormatter { } } + /// Creates a new instance of [`RawFormatter`] with the given buffer. + /// + /// # Safety + /// + /// The memory region starting at `buf` and extending for `len` bytes must be valid for writes + /// for the lifetime of the returned [`RawFormatter`]. + pub(crate) unsafe fn from_buffer(buf: *mut u8, len: usize) -> Self { + let pos = buf as usize; + // INVARIANT: We ensure that `end` is never less then `buf`, and the safety requirements + // guarantees that the memory region is valid for writes. + Self { + pos, + beg: pos, + end: pos.saturating_add(len), + } + } + /// Returns the current insert position. /// /// N.B. It may point to invalid memory. @@ -439,3 +456,43 @@ impl fmt::Write for RawFormatter { Ok(()) } } + +/// Allows formatting of [`fmt::Arguments`] into a raw buffer. +/// +/// Fails if callers attempt to write more than will fit in the buffer. +pub(crate) struct Formatter(RawFormatter); + +impl Formatter { + /// Creates a new instance of [`Formatter`] with the given buffer. + /// + /// # Safety + /// + /// The memory region starting at `buf` and extending for `len` bytes must be valid for writes + /// for the lifetime of the returned [`Formatter`]. + #[allow(dead_code)] + pub(crate) unsafe fn from_buffer(buf: *mut u8, len: usize) -> Self { + // SAFETY: The safety requirements of this function satisfy those of the callee. + Self(unsafe { RawFormatter::from_buffer(buf, len) }) + } +} + +impl Deref for Formatter { + type Target = RawFormatter; + + fn deref(&self) -> &Self::Target { + &self.0 + } +} + +impl fmt::Write for Formatter { + fn write_str(&mut self, s: &str) -> fmt::Result { + self.0.write_str(s)?; + + // Fail the request if we go past the end of the buffer. + if self.0.pos > self.0.end { + Err(fmt::Error) + } else { + Ok(()) + } + } +}