From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:53949) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UDR2F-0007wT-9r for qemu-devel@nongnu.org; Wed, 06 Mar 2013 21:58:26 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1UDR2C-0000XD-EK for qemu-devel@nongnu.org; Wed, 06 Mar 2013 21:58:23 -0500 Received: from mail-ie0-x233.google.com ([2607:f8b0:4001:c03::233]:48542) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UDR2C-0000X9-A7 for qemu-devel@nongnu.org; Wed, 06 Mar 2013 21:58:20 -0500 Received: by mail-ie0-f179.google.com with SMTP id k11so10387395iea.38 for ; Wed, 06 Mar 2013 18:58:19 -0800 (PST) MIME-Version: 1.0 In-Reply-To: <5136FD98.3030901@redhat.com> References: <1362554857-3896-1-git-send-email-dantesu@gmail.com> <1362554857-3896-18-git-send-email-dantesu@gmail.com> <5136FD98.3030901@redhat.com> Date: Thu, 7 Mar 2013 10:58:19 +0800 Message-ID: From: Kuo-Jung Su Content-Type: text/plain; charset=UTF-8 Subject: Re: [Qemu-devel] [PATCH v6 17/24] qemu/bitops.h: add the bit ordering reversal functions stolen from linux List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paolo Bonzini Cc: Peter Maydell , Igor Mitsyanko , qemu-devel@nongnu.org, Blue Swirl , Paul Brook , Andreas , fred konrad 2013/3/6 Paolo Bonzini : > Il 06/03/2013 08:27, Kuo-Jung Su ha scritto: >> Signed-off-by: Kuo-Jung Su >> --- >> include/qemu/bitops.h | 63 ++++++++++++++++++++++++++++++++++++++++++++++++- >> 1 file changed, 62 insertions(+), 1 deletion(-) >> >> diff --git a/include/qemu/bitops.h b/include/qemu/bitops.h >> index affcc96..920d028 100644 >> --- a/include/qemu/bitops.h >> +++ b/include/qemu/bitops.h >> @@ -3,7 +3,8 @@ >> * >> * Copyright (C) 2010 Corentin Chary >> * >> - * Mostly inspired by (stolen from) linux/bitmap.h and linux/bitops.h >> + * Mostly inspired by (stolen from) linux/bitmap.h, linux/bitops.h >> + * and linux/bitrev.h >> * >> * This work is licensed under the terms of the GNU LGPL, version 2.1 or later. >> * See the COPYING.LIB file in the top-level directory. >> @@ -273,4 +274,64 @@ static inline uint64_t deposit64(uint64_t value, int start, int length, >> return (value & ~mask) | ((fieldval << start) & mask); >> } >> >> +/** >> + * bitrev8: >> + * @value: the value to reverse bit ordering from >> + * >> + * Reverse the 8 bit input @value >> + * >> + * Returns: the input @value with reversed bit ordering >> + */ >> +static inline uint8_t bitrev8(uint8_t value) >> +{ >> + int i; >> + uint8_t ret = 0; >> + for (i = 0; i < 8; ++i) { >> + if (value & BIT(i)) { >> + ret |= BIT(7 - i); >> + } >> + } > > Please use instead > > value = ((value & 0xAA) >> 1) | ((value & 0x55) << 1); > value = ((value & 0xCC) >> 2) | ((value & 0x33) << 2); > value = ((value & 0xF0) >> 4) | ((value & 0x0F) << 4); > return value; > > Paolo > Got it, thanks >> + return ret; >> +} >> + >> +/** >> + * bitrev16: >> + * @value: the value to reverse bit ordering from >> + * >> + * Reverse the 16 bit input @value >> + * >> + * Returns: the input @value with reversed bit ordering >> + */ >> +static inline uint16_t bitrev16(uint16_t value) >> +{ >> + return (bitrev8(value & 0xff) << 8) | bitrev8(value >> 8); >> +} >> + >> +/** >> + * bitrev32: >> + * @value: the value to reverse bit ordering from >> + * >> + * Reverse the 32 bit input @value >> + * >> + * Returns: the input @value with reversed bit ordering >> + */ >> +static inline uint32_t bitrev32(uint32_t value) >> +{ >> + return (bitrev16(value & 0xffff) << 16) | bitrev16(value >> 16); >> +} >> + >> +/** >> + * bitrev64: >> + * @value: the value to reverse bit ordering from >> + * >> + * Reverse the 64 bit input @value >> + * >> + * Returns: the input @value with reversed bit ordering >> + */ >> +static inline uint64_t bitrev64(uint64_t value) >> +{ >> + return ((uint64_t)bitrev32(value & 0xffffffffULL) << 32) >> + | (uint64_t)bitrev32(value >> 32); >> +} >> + >> #endif >> > -- Best wishes, Kuo-Jung Su