private void OptimizeStarts(OptimizationContext context)
{
Contract.Assert(Lengths.CompressedData == null, "Lengths must be decompressed prior to optimizing starts");
//var starts = Starts.GetReadOnlyList().ToList();
context.Stream.Position = 0;
var startsDataLength = Starts.Data.Length;
context.Stream.Write(Starts.Data, 0, startsDataLength);
var count = Starts.Count;
int priorStart = Starts.MinValue;
int priorLength = 0;
int max = 0;
for (int i = 0; i < count; i++)
{
int start = Starts[i];
int newValue;
if (start == priorStart)
{
newValue = 0;
}
else
{
// If not equal to prior start
// We store the delta from the end of the prior span + 1 (0 is reserved for starting at the same position as the prior segment)
// NOTE: This must be non-negative.
var priorEnd = priorStart + priorLength;
var priorEndOffset = start - priorEnd;
if (priorEndOffset < 0)
{
throw new InvalidOperationException(
$"priorEndOffset: {priorEndOffset} priorStart: {priorStart} priorLength: {priorLength} start: {start}");
}
newValue = priorEndOffset + 1;
}
Starts.SetIndexDirect(i, newValue);
priorStart = start;
priorLength = Lengths[i];
max = Math.Max(newValue, max);
}
var newStartsMinByteWidth = NumberUtils.GetByteWidth(max);
if (newStartsMinByteWidth > Starts.ValueByteWidth)
{
context.Stream.Position = 0;
context.Stream.Read(Starts.Data, 0, startsDataLength);
StartsExpanded = true;
}
}