/// <summary>
/// Construct over an IDictionary instance.
/// </summary>
/// <param name="dictionary"></param>
/// <param name="stringComparer">The string comparer to use.</param>
internal CopyOnWriteHashtable(IDictionary dictionary, StringComparer stringComparer)
{
ErrorUtilities.VerifyThrowArgumentNull(dictionary, "dictionary");
ErrorUtilities.VerifyThrowArgumentNull(stringComparer, "stringComparer");
this.sharedLock = new object();
CopyOnWriteHashtable source = dictionary as CopyOnWriteHashtable;
if (source != null)
{
if (source.stringComparer.GetHashCode() == stringComparer.GetHashCode())
{
// If we're copying another CopyOnWriteHashtable then we can defer the clone until later.
ConstructFrom(source);
return;
}
else
{
// Technically, it would be legal to fall through here and let a new hashtable be constructed.
// However, Engine is supposed to use consistent case comparisons everywhere and so, for us,
// this means a bug in the engine code somewhere.
throw new InternalErrorException("Bug: Changing the case-sensitiveness of a copied hash-table.");
}
}
// Can't defer this because we don't control what gets written to the dictionary exogenously.
writeableData = new Hashtable(dictionary, stringComparer);
readonlyData = null;
this.stringComparer = stringComparer;
}
/// <summary>
/// Implementation of construction logic.
/// </summary>
/// <param name="that"></param>
private void ConstructFrom(CopyOnWriteHashtable that)
{
lock (that.sharedLock)
{
this.writeableData = null;
// If the source it was writeable, need to transform it into
// read-only because we don't want subsequent writes to bleed through.
if (that.writeableData != null)
{
that.readonlyData = that.writeableData;
that.writeableData = null;
}
this.readonlyData = that.readonlyData;
this.stringComparer = that.stringComparer;
}
}
/// <summary>
/// Construct a shallow copy over another instance of this class.
/// </summary>
/// <param name="that"></param>
private CopyOnWriteHashtable(CopyOnWriteHashtable that)
{
this.sharedLock = new object();
ConstructFrom(that);
}