misc.d

/*****************************************************************************
*
*                      Higgs JavaScript Virtual Machine
*
*  This file is part of the Higgs project. The project is distributed at:
*  https://github.com/maximecb/Higgs
*
*  Copyright (c) 2013, Maxime Chevalier-Boisvert. All rights reserved.
*
*  This software is licensed under the following license (Modified BSD
*  License):
*
*  Redistribution and use in source and binary forms, with or without
*  modification, are permitted provided that the following conditions are
*  met:
*   1. Redistributions of source code must retain the above copyright
*      notice, this list of conditions and the following disclaimer.
*   2. 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.
*   3. The name of the author may not be used to endorse or promote
*      products derived from this software without specific prior written
*      permission.
*
*  THIS SOFTWARE IS PROVIDED ``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 THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
*  INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
*  NOT LIMITED TO PROCUREMENT 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.
*
*****************************************************************************/

module util.misc;

/// Pointer size on this platform
immutable size_t PTR_SIZE = (void*).sizeof;

/**
Align a pointer to a specified number of bytes
*/
auto alignPtr(ubyte* ptr, size_t alignBytes = PTR_SIZE)
{
    // Compute the pointer modulo the given alignment boundary
    auto rem = (cast(size_t)ptr) % alignBytes;

    // If the pointer is already aligned, return it
    if (rem == 0)
        return ptr;

    // Pad the pointer by the necessary amount to align it
    auto pad = alignBytes - rem;
    ptr += pad;

    // Return the aligned pointer
    return ptr;
}

/**
Test if a positive integer value is a power of 2
*/
bool isPow2(long x)
{
    return (x & (x-1)) == 0;
}

/**
Return the index of the lowest bit set to 1
*/
int lowestBitIdx(long x)
{
    for (uint idx = 0; idx < 64; ++idx)
        if (x & (1 << idx))
            return idx;

    return -1;
}