CountLeadingZeros.h

Go to the documentation of this file.

// (c) IMT - Information Management Technology AG, CH-9470 Buchs, www.imt.ch.
//
// ActiveParts (AP) and the corresponding Data Flow Framework (DFF) is invented and designed by Jakob Daescher.
// ANY USE OF THIS CODE CONSTITUTES ACCEPTANCE OF THE TERMS OF THE COPYRIGHT NOTICE.
// ===================================================================================================
// COPYRIGHT NOTICE
// ===================================================================================================
// Copyright (C) 2005-2075, IMT Information Management Technology AG, 9470 Buchs, Switzerland
// All rights reserved.
// This code is proprietary software of IMT Information Management Technology AG (hereinafter: "IMT").
// Proprietary software is computer software licensed under exclusive legal right of IMT.
//
// The licensee is given the irrevocable, perpetual, worldwide, non-exclusive right and license to use,
// execute and reproduce the software in binary form within the licensed products.
//
// Redistribution and use in source forms, without modification, are permitted provided that the following conditions are met:
// (1) Copying of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
// (2) Copying of source code is only allowed for regulatory documentation and archiving purposes
// (3) Redistributions in binary form must reproduce the above copyright notice,
//     this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.
//
// IMT provide no reassurances that the source code provided does not infringe
// any patent, copyright, or any other intellectual property rights of third parties.
// IMT disclaim any liability to any recipient for claims brought against
// recipient by any third party for infringement of that parties intellectual property rights.
//
// THIS SOFTWARE IS PROVIDED BY IMT AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
// INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
// IN NO EVENT SHALL IMT OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
// OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCURE-MENT OF SUBSTITUTE GOODS OR SERVICES;
// LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
// WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
// IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
// ===================================================================================================
 
#ifndef IMT_BASE_CORE_PLATFORM_COUNT_LEADING_ZEROS_H
#define IMT_BASE_CORE_PLATFORM_COUNT_LEADING_ZEROS_H
 
#include <cstdint>
 
namespace imt {
namespace base {
namespace core {
namespace platform {
 
inline uint8_t countLeadingZeros(uint32_t const x) {
    uint8_t clz {0U};
    if (x == 0U) {
        constexpr uint8_t maxZeroCount {32U};
        clz = maxZeroCount;
    }
    else {
        constexpr uint32_t mask4 {0xF0000000U};
        constexpr uint32_t mask2 {0xC0000000U};
        constexpr uint32_t mask1 {0x80000000U};
        constexpr uint8_t step4 {4U};
        uint32_t res {x};
        while ((res & mask4) == 0U) {
            clz += step4;
            res <<= step4;
        }
        if ((res & mask2) == 0U) {
            constexpr uint8_t step2 {2U};
            clz += step2;
            res <<= step2;
        }
        if ((res & mask1) == 0U) {
            clz++;
        }
    }
    return clz;
}
 
} // namespace platform
} // namespace core
} // namespace base
} // namespace imt
 
#endif // IMT_BASE_CORE_PLATFORM_COUNT_LEADING_ZEROS_H