/// <summary>
/// Merges regions in the current list of memory regions using a fast stack based algorithm O(nlogn + n).
/// </summary>
private void MergeAndSortRegions()
{
if (this.SnapshotRegions.IsNullOrEmpty())
{
return;
}
// First, sort by start address
IList <SnapshotRegion> sortedRegions = this.SnapshotRegions.OrderBy(x => x.BaseAddress.ToUInt64()).ToList();
// Create and initialize the stack with the first region
Stack <SnapshotRegion> combinedRegions = new Stack <SnapshotRegion>();
combinedRegions.Push(sortedRegions[0]);
// Build the remaining regions
for (Int32 index = combinedRegions.Count; index < sortedRegions.Count; index++)
{
SnapshotRegion top = combinedRegions.Peek();
if (top.EndAddress.ToUInt64() < sortedRegions[index].BaseAddress.ToUInt64())
{
// If the interval does not overlap, put it on the top of the stack
combinedRegions.Push(sortedRegions[index]);
}
else if (top.EndAddress.ToUInt64() == sortedRegions[index].BaseAddress.ToUInt64())
{
// The regions are adjacent; merge them
top.RegionSize = sortedRegions[index].EndAddress.Subtract(top.BaseAddress).ToInt32();
// Combine values and labels
top.SetElementLabels(top.GetElementLabels()?.Concat(sortedRegions[index].GetElementLabels()));
top.SetCurrentValues(top.GetCurrentValues()?.Concat(sortedRegions[index].GetCurrentValues()));
top.SetPreviousValues(top.GetPreviousValues()?.Concat(sortedRegions[index].GetPreviousValues()));
}
else if (top.EndAddress.ToUInt64() <= sortedRegions[index].EndAddress.ToUInt64())
{
// The regions overlap
top.RegionSize = sortedRegions[index].EndAddress.Subtract(top.BaseAddress).ToInt32();
Int32 overlapSize = unchecked ((Int32)(sortedRegions[index].EndAddress.ToUInt64() - top.EndAddress.ToUInt64()));
// Overlap has conflicting values, so we prioritize the top region and trim the current region
sortedRegions[index].SetElementLabels(sortedRegions[index].GetElementLabels()?.SubArray(overlapSize, sortedRegions[index].RegionSize - overlapSize));
sortedRegions[index].SetCurrentValues(sortedRegions[index].GetCurrentValues()?.SubArray(overlapSize, sortedRegions[index].RegionSize - overlapSize));
sortedRegions[index].SetPreviousValues(sortedRegions[index].GetPreviousValues()?.SubArray(overlapSize, sortedRegions[index].RegionSize - overlapSize));
// Combine values and labels
top.SetElementLabels(top.GetElementLabels()?.Concat(sortedRegions[index].GetElementLabels()));
top.SetCurrentValues(top.GetCurrentValues()?.Concat(sortedRegions[index].GetCurrentValues()));
top.SetPreviousValues(top.GetPreviousValues()?.Concat(sortedRegions[index].GetPreviousValues()));
}
}
this.SnapshotRegions = combinedRegions.ToList().OrderBy(x => x.BaseAddress.ToUInt64()).ToList();
}
/// <summary>
/// Gets the regions in this snapshot with a valid bit set.
/// </summary>
/// <returns>The regions in this snapshot with a valid bit set.</returns>
public IEnumerable <SnapshotRegion> GetValidRegions()
{
List <SnapshotRegion> validRegions = new List <SnapshotRegion>();
if (this.ValidBits == null)
{
return(validRegions);
}
for (Int32 startIndex = 0; startIndex < this.ValidBits.Length; startIndex += this.Alignment)
{
if (!this.ValidBits[startIndex])
{
continue;
}
// Get the length of this valid segment
Int32 validRegionSize = 0;
do
{
// We only care if the aligned elements are valid
validRegionSize += this.Alignment;
}while (startIndex + validRegionSize < this.ValidBits.Length && this.ValidBits[startIndex + validRegionSize]);
// Create new subregion from this valid region
SnapshotRegion subRegion = new SnapshotRegion(this.BaseAddress + startIndex, validRegionSize);
// Ensure region size is worth keeping. This can happen if we grab a misaligned segment
if (subRegion.RegionSize < Conversions.GetTypeSize(this.ElementType))
{
continue;
}
// Copy the current values and labels.
subRegion.SetCurrentValues(this.CurrentValues.LargestSubArray(startIndex, subRegion.RegionSize));
subRegion.SetPreviousValues(this.PreviousValues.LargestSubArray(startIndex, subRegion.RegionSize));
subRegion.SetElementLabels(this.ElementLabels.LargestSubArray(startIndex, subRegion.RegionSize));
validRegions.Add(subRegion);
startIndex += validRegionSize;
}
this.ValidBits = null;
return(validRegions);
}
/// <summary>
/// Masks the given memory regions against the given memory regions, keeping the common elements of the two in O(n).
/// </summary>
/// <param name="groundTruth">The snapshot regions to mask the target regions against.</param>
public void MaskRegions(IEnumerable <NormalizedRegion> groundTruth)
{
List <SnapshotRegion> resultRegions = new List <SnapshotRegion>();
groundTruth = this.MergeAndSortRegions(groundTruth);
// if (this.SnapshotRegions == null || groundTruth == null || this.SnapshotRegions.Count <= 0 || groundTruth.Count() <= 0)
{
// this.SnapshotRegions = resultRegions;
// return;
}
this.MergeAndSortRegions();
// TODO: Resolve the masking issues below:
return;
// Initialize stacks with regions and masking regions
Queue <SnapshotRegion> candidateRegions = new Queue <SnapshotRegion>();
Queue <NormalizedRegion> maskingRegions = new Queue <NormalizedRegion>();
// Build candidate region queue from target region array
foreach (SnapshotRegion region in this.SnapshotRegions.OrderBy(x => x.BaseAddress.ToUInt64()))
{
candidateRegions.Enqueue(region);
}
// Build masking region queue from snapshot
foreach (NormalizedRegion maskRegion in groundTruth.OrderBy(x => x.BaseAddress.ToUInt64()))
{
maskingRegions.Enqueue(maskRegion);
}
if (candidateRegions.Count <= 0 || maskingRegions.Count <= 0)
{
this.SnapshotRegions = resultRegions;
return;
}
SnapshotRegion currentRegion;
NormalizedRegion currentMask = maskingRegions.Dequeue();
while (candidateRegions.Count > 0)
{
// Grab next region
currentRegion = candidateRegions.Dequeue();
// Grab the next mask following the current region
while (currentMask.EndAddress.ToUInt64() < currentRegion.BaseAddress.ToUInt64() && maskingRegions.Count > 0)
{
currentMask = maskingRegions.Dequeue();
}
// Check for mask completely removing this region
if (currentMask.EndAddress.ToUInt64() < currentRegion.BaseAddress.ToUInt64() || currentMask.BaseAddress.ToUInt64() > currentRegion.EndAddress.ToUInt64())
{
continue;
}
// Mask completely overlaps, just use the original region
if (currentMask.BaseAddress == currentRegion.BaseAddress && currentMask.EndAddress == currentRegion.EndAddress)
{
resultRegions.Add(currentRegion);
continue;
}
// Mask is within bounds; Grab the masked portion of this region
Int32 baseOffset = currentMask.BaseAddress.ToUInt64() <= currentRegion.BaseAddress.ToUInt64() ? 0 : currentMask.BaseAddress.Subtract(currentRegion.BaseAddress).ToInt32();
SnapshotRegion newRegion = new SnapshotRegion(currentRegion as NormalizedRegion);
newRegion.BaseAddress = currentRegion.BaseAddress + baseOffset;
newRegion.BaseAddress = Math.Min(currentMask.EndAddress.ToUInt64(), currentRegion.EndAddress.ToUInt64()).ToIntPtr();
newRegion.SetCurrentValues(currentRegion.GetCurrentValues().LargestSubArray(baseOffset, newRegion.RegionSize));
newRegion.SetPreviousValues(currentRegion.GetPreviousValues().LargestSubArray(baseOffset, newRegion.RegionSize));
newRegion.SetElementLabels(currentRegion.GetElementLabels().LargestSubArray(baseOffset, newRegion.RegionSize));
newRegion.ElementType = currentRegion.ElementType;
newRegion.Alignment = currentRegion.Alignment;
resultRegions.Add(newRegion);
}
this.SnapshotRegions = resultRegions;
}