bitmask.cpp

来自「这个文件是windows mysql源码」· C++ 代码 · 共 118 行

/* Copyright (C) 2004-2005 MySQL AB

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; version 2 of the License.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA */

#include <Bitmask.hpp>
#include <NdbOut.hpp>

void
BitmaskImpl::getFieldImpl(const Uint32 src[],
			  unsigned shiftL, unsigned len, Uint32 dst[])
{
  /* Copy whole words of src to dst, shifting src left
   * by shiftL.  Undefined bits of the last written dst word
   * should be zeroed.
   */
  assert(shiftL < 32);

  unsigned shiftR = 32 - shiftL;
  unsigned undefined = shiftL ? ~0 : 0;

  /* Merge first word with previously set bits if there's a shift */
  * dst = shiftL ? * dst : 0;

  /* Treat the zero-shift case separately to avoid
   * trampling or reading past the end of src
   */
  if (shiftL == 0)
  {
    while(len >= 32)
    {
      * dst++ = * src++;
      len -=32;
    }

    if (len != 0)
    {
      /* Last word has some bits set */
      Uint32 mask= ((1 << len) -1); // 0000111
      * dst = (* src) & mask;
    }
  }
  else // shiftL !=0, need to build each word from two words shifted
  {
    while(len >= 32)
    {
      * dst++ |= (* src) << shiftL;
      * dst = ((* src++) >> shiftR) & undefined;
      len -= 32;
    }

    /* Have space for shiftR more bits in the current dst word
     * is that enough?
     */
    if(len <= shiftR)
    {
      /* Fit the remaining bits in the current dst word */
      * dst |= ((* src) & ((1 << len) - 1)) << shiftL;
    }
    else
    {
      /* Need to write to two dst words */
      * dst++ |= ((* src) << shiftL);
      * dst = ((* src) >> shiftR) & ((1 << (len - shiftR)) - 1) & undefined;
    }
  }
}

void
BitmaskImpl::setFieldImpl(Uint32 dst[],
			  unsigned shiftL, unsigned len, const Uint32 src[])
{
  /**
   *
   * abcd ef00
   * 00ab cdef
   */
  assert(shiftL < 32);
  unsigned shiftR = 32 - shiftL;
  unsigned undefined = shiftL ? ~0 : 0;  
  while(len >= 32)
  {
    * dst = (* src++) >> shiftL;
    * dst++ |= ((* src) << shiftR) & undefined;
    len -= 32;
  }
  
  /* Copy last bits */
  Uint32 mask = ((1 << len) -1);
  * dst = (* dst & ~mask);
  if(len <= shiftR)
  {
    /* Remaining bits fit in current word */
    * dst |= ((* src++) >> shiftL) & mask;
  }
  else
  {
    /* Remaining bits update 2 words */
    * dst |= ((* src++) >> shiftL);
    * dst |= ((* src) & ((1 << (len - shiftR)) - 1)) << shiftR ;
  }
}

/* Bitmask testcase code moved from here to
 * storage/ndb/test/ndbapi/testBitfield.cpp
 * to get coverage from automated testing
 */