kernel/eka/klib/bma.cpp
branchRCL_3
changeset 26 c734af59ce98
parent 0 a41df078684a
child 28 5b5d147c7838
--- a/kernel/eka/klib/bma.cpp	Tue Apr 27 18:02:57 2010 +0300
+++ b/kernel/eka/klib/bma.cpp	Tue May 11 17:28:22 2010 +0300
@@ -762,6 +762,49 @@
 	}
 
 
+/**	Allocates a specific range of bit positions.
+	
+	The specified range must lie within the total range for this allocator but it is
+	not necessary that all the positions are currently free.
+
+	@param	aStart	First position to allocate.
+	@param	aLength	Number of consecutive positions to allocate, must be >0.
+	@return The number of previously free positions that were allocated.
+ */
+EXPORT_C TUint TBitMapAllocator::SelectiveAlloc(TInt aStart, TInt aLength)
+	{
+	__ASSERT_ALWAYS(TUint(aStart) < TUint(iSize), TBMA_FAULT());
+	__ASSERT_ALWAYS(TUint(aStart + aLength) >= TUint(aStart), TBMA_FAULT());
+	__ASSERT_ALWAYS(TUint(aStart + aLength) <= TUint(iSize), TBMA_FAULT());
+	TInt wix = aStart >> 5;
+	TInt sbit = aStart & 31;
+	TUint32* pW = iMap + wix;
+	iAvail -= aLength;	// update free count assuming no positions already allocated
+	TInt ebit = sbit + aLength;
+	if (ebit < 32)
+		{
+		TUint32 b = ((0xffffffffu >> aLength) >> sbit) | ~(0xffffffffu >> sbit);
+		TUint32 w = *pW;
+		*pW = w & b;	// mark all positions allocated
+		TUint allocated = __e32_bit_count_32(~w & ~b);
+		iAvail += allocated;	// increase free count by number of positions already allocated
+		return aLength - allocated;
+		}
+	TUint32 b = ~(0xffffffffu >> sbit);
+	while (ebit > 0)
+		{
+		TUint32 w = *pW;
+		*pW++ = w & b;		// mark all positions allocated
+		TUint allocated = __e32_bit_count_32(~w & ~b);
+		iAvail += allocated;	// increase free count by number of positions already allocated
+		aLength -= allocated;
+		ebit -= 32;
+		b = (ebit >= 32)? 0 : 0xffffffff >> ebit;
+		}
+	return aLength;
+	}
+
+
 /** Copies a range from another allocator, mark remainder as occupied.
 
 	Values of bit positions from aFirst to aFirst+aLen-1 inclusive in allocator