433 	}

   434 

   435 

   436 /**	Allocates a specific range of bit positions.

   437 	

   438 	The specified range must lie within the total range for this allocator but it is

   439 	not necessary that all the positions are currently free.

   440 

   441 	@param	aStart	First position to allocate.

   442 	@param	aLength	Number of consecutive positions to allocate, must be >0.

   443 	@return The number of previously free positions that were allocated.

   444  */

   445 EXPORT_C TUint TBitMapAllocator::SelectiveAlloc(TInt aStart, TInt aLength)

   446 	{

   447 	__ASSERT_ALWAYS(TUint(aStart) < TUint(iSize), TBMA_FAULT());

   448 	__ASSERT_ALWAYS(TUint(aStart + aLength) >= TUint(aStart), TBMA_FAULT());

   449 	__ASSERT_ALWAYS(TUint(aStart + aLength) <= TUint(iSize), TBMA_FAULT());

   450 	TInt wix = aStart >> 5;

   451 	TInt sbit = aStart & 31;

   452 	TUint32* pW = iMap + wix;

   453 	iAvail -= aLength;	// update free count assuming no positions already allocated

   454 	TInt ebit = sbit + aLength;

   455 	if (ebit < 32)

   456 		{

   457 		TUint32 b = ((0xffffffffu >> aLength) >> sbit) | ~(0xffffffffu >> sbit);

   458 		TUint32 w = *pW;

   459 		*pW = w & b;	// mark all positions allocated

   460 		TUint allocated = __e32_bit_count_32(~w & ~b);

   461 		iAvail += allocated;	// increase free count by number of positions already allocated

   462 		return aLength - allocated;

   463 		}

   464 	TUint32 b = ~(0xffffffffu >> sbit);

   465 	while (ebit > 0)

   466 		{

   467 		TUint32 w = *pW;

   468 		*pW++ = w & b;		// mark all positions allocated

   469 		TUint allocated = __e32_bit_count_32(~w & ~b);

   470 		iAvail += allocated;	// increase free count by number of positions already allocated

   471 		aLength -= allocated;

   472 		ebit -= 32;

   473 		b = (ebit >= 32)? 0 : 0xffffffff >> ebit;

   474 		}

   475 	return aLength;