protected override Span TrackSpan(ITextVersion targetVersion)
{
// Compute the new span on the requested snapshot.
//
// This method can be called simultaneously from multiple threads, and must be fast.
//
// We are relying on the atomicity of pointer copies (this.cachedSpan might change after we've
// fetched it but we will always get a self-consistent VersionPosition). This ensures we
// have proper behavior when called from multiple threads--multiple threads may all track and update the
// cached value if called at inconvenient times, but they will return consistent results.
// ForwardFidelity spans do not support tracking backward, so consistency is not guaranteed in that case.
VersionSpan cached = this.cachedSpan;
Span targetSpan;
if (targetVersion == cached.Version)
{
targetSpan = cached.Span;
}
else if (targetVersion.VersionNumber > cached.Version.VersionNumber)
{
// Compute the target span by going forward from the cached version
targetSpan = TrackSpanForwardInTime(cached.Span, cached.Version, targetVersion);
// Update the cached value
this.cachedSpan = new VersionSpan(targetVersion, targetSpan);
}
else
{
// Roll backwards from the cached version.
targetSpan = TrackSpanBackwardInTime(cached.Span, cached.Version, targetVersion);
}
return(targetSpan);
}
public ForwardFidelityTrackingSpan(ITextVersion version, Span span, SpanTrackingMode trackingMode)
: base(version, span, trackingMode)
{
this.cachedSpan = new VersionSpan(version, span);
}
public override string ToString()
{
VersionSpan c = this.cachedSpan;
return(ToString(c.Version, c.Span, this.trackingMode));
}
