From nobody Sun Feb 8 21:46:18 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 E0D94EB64DC for ; Tue, 11 Jul 2023 14:42:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232127AbjGKOmp (ORCPT ); Tue, 11 Jul 2023 10:42:45 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51218 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231898AbjGKOmm (ORCPT ); Tue, 11 Jul 2023 10:42:42 -0400 Received: from mail-yw1-x114a.google.com (mail-yw1-x114a.google.com [IPv6:2607:f8b0:4864:20::114a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 47210BC for ; Tue, 11 Jul 2023 07:42:41 -0700 (PDT) Received: by mail-yw1-x114a.google.com with SMTP id 00721157ae682-57320c10635so63070157b3.3 for ; Tue, 11 Jul 2023 07:42:41 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20221208; t=1689086560; x=1691678560; 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=dLRkccixklYYXR2WU6Ln/pjVdN3Qd9Ec+IRQSqKyylEED1pH7A8wD4Qv2myKG/RfLD Jmz7qFSWO5vQZdgvSSTVF0jfpbFG+iIWCuI73GkGjsLdmmFtHeaEXarEarzKRxLo3Bbu Oa7iNom8QaPEKsXkrFwKbZwche58tepyDYMn2uuFlCkTDLEMqryEOghFXXF/Xr3QtaQA O9v+M21PEGqtdr36HSBveJlshivuqQkleC6reypNk8f7QOeE59/oCbcDig3awR0KcPbJ GOVy7GA+6yaCuScu0UfAVfJfq/ycqEaCCA0f2JkINq5xfGn+SvqCQktRwaRosZt61X7s 6FDw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1689086560; x=1691678560; 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=jbWyCw0gm32sqLV6q/bag/3DoyNaCVJ+AZYIhuaszxJRoD2vSYV8ZPFQkNSHyF/lI8 xro4BC/7qmbeEn9zq4fpGbki1QX4qj57HfBkOdoAZmVBaAjnXAPZvKJWGeuGRepo0RZX HKZVUHaEFVMQuflCHzeJhZskqVYooBGEe6cPYii/bdZzKyXSHzai7+UBIANfFXJs5/Za YgRHAONUplBj1qvz+Bk9hMxkOG9+dnySc2lmsDk8IpmTip2GZqgToLQuZ8z4J6HwhDAC D/OkKx5D3mhL3SSSxq48ovqHMrREMmy03hQBdvx0aiYVfS9fESAi94JbVepHWoKLSUj0 SWgQ== X-Gm-Message-State: ABy/qLYBzpOS1bHdtInqcmRYFHusUvds/IsIskfA2RFrkhjdZ1ZpVKDP nwEP0llwQVQC3TKX8dfr6y9b78APywA= X-Google-Smtp-Source: APBJJlFIZz3CqK9sHFiNkuXlFYUZxhErF6A+cY/vC/nVCEfDRQwrtiXHgvzlHG6TlEhbEb3LNYtF3wh57Bs= X-Received: from glider.muc.corp.google.com ([2a00:79e0:9c:201:564d:3aaa:6b5f:4419]) (user=glider job=sendgmr) by 2002:a05:690c:705:b0:565:a42c:79fe with SMTP id bs5-20020a05690c070500b00565a42c79femr126547ywb.1.1689086560587; Tue, 11 Jul 2023 07:42:40 -0700 (PDT) Date: Tue, 11 Jul 2023 16:42:29 +0200 In-Reply-To: <20230711144233.3129207-1-glider@google.com> Mime-Version: 1.0 References: <20230711144233.3129207-1-glider@google.com> X-Mailer: git-send-email 2.41.0.255.g8b1d071c50-goog Message-ID: <20230711144233.3129207-2-glider@google.com> Subject: [Resend v1 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