/// <summary>
/// Searches for the specified object and returns the zero-based virtual index of the first occurrence in a linear list that starts at the specified index and contains the specified number of elements.
/// </summary>
/// <param name="item">The object to locate in the <see cref="Partition{T}"/>. The value can be null for reference types.</param>
/// <param name="startIndex">The zero-based starting index of the search. 0 (zero) is valid in an empty partition.</param>
/// <param name="count">The number of elements in the section to search.</param>
/// <returns>
/// The zero-based virtual index of the first occurrence of <paramref name="item"/> within the range of elements in a linear list that starts at <paramref name="startIndex"/> and contains <paramref name="count"/> number of elements, if found; otherwise, –1.
/// </returns>
public long IndexOf(T item, long startIndex, long count)
{
Debug.Assert(startIndex >= 0 && startIndex <= Count);
Debug.Assert(count >= 0);
Debug.Assert(startIndex + count <= Count);
long Result = -1;
int SegmentIndex;
int ElementStartIndex;
int CacheIndex;
GetPosition(startIndex, out SegmentIndex, out ElementStartIndex, out CacheIndex);
long ItemIndex = startIndex - ElementStartIndex;
long RemainingCount = count;
while (SegmentIndex < SegmentTable.Count && RemainingCount > 0)
{
ISegment <T> Segment = SegmentTable[SegmentIndex];
if (Segment.Count == 0)
{
break;
}
int CompareCount = (Segment.Count - ElementStartIndex <= RemainingCount) ? Segment.Count - ElementStartIndex : (int)RemainingCount;
int ElementIndex = Segment.IndexOf(item, ElementStartIndex, CompareCount);
if (ElementIndex >= 0)
{
Result = ItemIndex + ElementIndex;
break;
}
ElementStartIndex = 0;
RemainingCount -= CompareCount;
ItemIndex += Segment.Count;
SegmentIndex++;
}
Debug.Assert(RemainingCount >= 0);
Debug.Assert(Result == -1 || (Result >= startIndex && Result < startIndex + count && IsItemEqual(Result, item)));
#if DEBUG
AssertInvariant();
#endif
return(Result);
}