From nobody Sun Feb 8 17:43:38 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 00301EB64DC for ; Tue, 11 Jul 2023 14:34:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233312AbjGKOeA (ORCPT ); Tue, 11 Jul 2023 10:34:00 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43084 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233172AbjGKOdz (ORCPT ); Tue, 11 Jul 2023 10:33:55 -0400 Received: from mail-ed1-x549.google.com (mail-ed1-x549.google.com [IPv6:2a00:1450:4864:20::549]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9BE7F9C for ; Tue, 11 Jul 2023 07:33:53 -0700 (PDT) Received: by mail-ed1-x549.google.com with SMTP id 4fb4d7f45d1cf-50daa85e940so3767500a12.0 for ; Tue, 11 Jul 2023 07:33:53 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20221208; t=1689086032; x=1691678032; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=dufumGN0X5SXjxYpittS7pKflaiJdPliu9At6Sap++c=; b=75uvsIUF8pp1PFh46nfHCG3WKMmvQIBEGMIyyIIHShVAQquW6/g+m+PKuhZ9x6sQji iClp8scbJoKjVEXbhgaKgs8rCWdskSFEIYvo3JSyqpKiPkap0fUB+HL35ZgRzYpA0/CK iE5K9iqwV60CMTAvtPTJl/1mkcJKQKg3m2w+VjR6ju8JEAoevMvbnlXXjIX7t9+e2xEY ZcuxDv+Lb2ZS++s9EWQC4S/MI+LZAjAtZWuUo885GzT68wi616cFcfZ/lsCHwqsE/42r n86Xg5zOdfDTEByAFc8MmPMnUAw7KaxGf2TwZ75eD9yHw1cAySBhvnF16rk6SwZceK5W aa4A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1689086032; x=1691678032; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=dufumGN0X5SXjxYpittS7pKflaiJdPliu9At6Sap++c=; b=ENhMePsbq2WYIMII8NTQp2p4JxYK1hN4ImjweEfbzJayDhdio6LlTz+6vJUKRUDCXl yoc+pSxlbfJS8FkE0PLCWYFqB+U1Gsk2lfkDZUAUyUzrVFigg+CJ9M/+bnl3U1vf+82E KD+jHxQs0MpHll79uQEkQtOklgIA2bHqbGowfAWzg9cAtCjc8mDyOHXobSK8XHMQm0el FLXaNJ937neoIAcvuLI7V9Y2RDoTSBrDgvMH1WjC9lmrhwO4LAXU2o2D/b3EgGcZECIg wK9eBu2gCYILViJhR6/mBZ9kRKooZxWbctxWSz9LJ1x46C5wEWng5S1eC1nRrEzMRf58 1DCg== X-Gm-Message-State: ABy/qLYgWm+N3f5BSv7Zol96rRi3+6RhBEemdOQSuh7B+4uCtMHzzuXz 3Q+Ii4JQOxQKJ5lXPvUaoFtLEGdRVnc= X-Google-Smtp-Source: APBJJlFYz/C1GDAbhGhoPueuxhQix1/9PyVpcPvrmHKitH+djEv3zoQpy4GpjnDGejdwdcFji6DbCjpZTyY= X-Received: from glider.muc.corp.google.com ([2a00:79e0:9c:201:564d:3aaa:6b5f:4419]) (user=glider job=sendgmr) by 2002:a50:d786:0:b0:51e:23bd:df12 with SMTP id w6-20020a50d786000000b0051e23bddf12mr79993edi.7.1689086032177; Tue, 11 Jul 2023 07:33:52 -0700 (PDT) Date: Tue, 11 Jul 2023 16:33:29 +0200 In-Reply-To: <20230711143337.3086664-1-glider@google.com> Mime-Version: 1.0 References: <20230711143337.3086664-1-glider@google.com> X-Mailer: git-send-email 2.41.0.255.g8b1d071c50-goog Message-ID: <20230711143337.3086664-3-glider@google.com> Subject: [PATCH 1/5] linux/bitqueue.h: add the bit queue implementation From: Alexander Potapenko To: glider@google.com, catalin.marinas@arm.com, will@kernel.org, pcc@google.com, andreyknvl@gmail.com Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, eugenis@google.com, yury.norov@gmail.com Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" struct bitq represents a bit queue with external storage. Its purpose is to easily pack sub-byte values, which can be used, for example, to implement RLE algorithms. Signed-off-by: Alexander Potapenko --- include/linux/bitqueue.h | 144 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 144 insertions(+) create mode 100644 include/linux/bitqueue.h diff --git a/include/linux/bitqueue.h b/include/linux/bitqueue.h new file mode 100644 index 0000000000000..c4393f703c697 --- /dev/null +++ b/include/linux/bitqueue.h @@ -0,0 +1,144 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * A simple bit queue which supports enqueueing/dequeueing of sub-byte val= ues. + * + * This can be used to pack complex bitfields into byte arrays. + */ +#ifndef _LINUX_BITQUEUE_H +#define _LINUX_BITQUEUE_H + +#include +#include + +/** + * struct bitq - represents a bit queue with external storage. + * @data: data buffer used by the queue. + * @size: size of @data in bytes. + * @bit_pos: current bit position. + */ +struct bitq { + u8 *data; + int size, bit_pos; +}; + +/** + * bitq_init - initialize an empty bit queue. + * @q: struct bitq to be initialized. + * @data: external data buffer to use. + * @size: capacity in bytes. + * + * Return: 0 in the case of success, -1 if either of the pointers is NULL. + */ +static inline int bitq_init(struct bitq *q, u8 *data, int size) +{ + if (!q || !data) + return -1; + q->data =3D data; + q->size =3D size; + memset(data, 0, size); + q->bit_pos =3D 0; + return 0; +} + +/** + * bitq_init_full - make a bit queue from an initialized byte array. + * @q: struct bitq to be initialized. + * @data: external data buffer to use. + * @size: capacity in bytes. + * + * Return: 0 in the case of success, -1 if either of the pointers is NULL. + */ +static inline int bitq_init_full(struct bitq *q, u8 *data, int size) +{ + if (!q || !data) + return -1; + q->data =3D data; + q->size =3D size; + q->bit_pos =3D q->size * 8; + return 0; +} + +/** + * bitq_enqueue - push up to 8 bits to the end of the queue. + * @q: struct bitq. + * @value: byte containing the value to be pushed. + * @bits: number of bits (1 to 8) to push. + * + * Return: number of bits pushed, or -1 in the case of an error. + */ +static inline int bitq_enqueue(struct bitq *q, u8 value, int bits) +{ + int byte_pos, left_in_byte, max_pos; + u8 hi, lo; + + if (!q || (bits < 1) || (bits > 8)) + return -1; + + max_pos =3D q->size * 8; + if ((max_pos - q->bit_pos) < bits) + return -1; + + left_in_byte =3D 8 - (q->bit_pos % 8); + byte_pos =3D q->bit_pos / 8; + /* Clamp @value. */ + value %=3D (1 << bits); + if (left_in_byte >=3D bits) { + /* @value fits into the current byte. */ + value <<=3D (left_in_byte - bits); + q->data[byte_pos] |=3D value; + } else { + /* + * @value needs to be split between the current and the + * following bytes. + */ + hi =3D value >> (bits - left_in_byte); + q->data[byte_pos] |=3D hi; + byte_pos++; + lo =3D value << (8 - (bits - left_in_byte)); + q->data[byte_pos] |=3D lo; + } + q->bit_pos +=3D bits; + return bits; +} + +/** + * bitq_dequeue - pop up to 8 bits from the beginning of the queue. + * @q: struct bitq. + * @value: u8* to store the popped value (can be NULL). + * @bits: number of bits (1 to 8) to pop. + * + * Return: number of bits popped, or -1 in the case of an error. + */ + +#include +static inline int bitq_dequeue(struct bitq *q, u8 *value, int bits) +{ + int rem_bits =3D 8 - bits, i; + u8 output; + + /* Invalid arguments. */ + if (!q || (bits < 1) || (bits > 8)) + return -1; + /* Not enough space to insert @bits. */ + if (q->bit_pos < bits) + return -1; + /* Take the first @bits bits from the first byte. */ + output =3D q->data[0]; + output >>=3D rem_bits; + if (value) + *value =3D output; + + /* + * Shift every byte in the queue to the left by @bits, carrying over to + * the previous byte. + */ + for (i =3D 0; i < q->size - 1; i++) { + q->data[i] =3D (q->data[i] << bits) | + (q->data[i + 1] >> rem_bits); + } + q->data[q->size - 1] <<=3D bits; + q->bit_pos -=3D bits; + return bits; +} + +#endif // _LINUX_BITQUEUE_H --=20 2.41.0.255.g8b1d071c50-goog