/// <summary>
/// Creates and returns a permission that is the intersection
/// of the current permission and the specified permission.
/// </summary>
/// <param name="target">A permission to intersect with the current permission.
/// It must be of the same type as the current permission.</param>
/// <returns>A new permission that represents the intersection of the current permission
/// and the specified permission. This new permission is null if the intersectionis empty.</returns>
public override System.Security.IPermission Intersect(System.Security.IPermission target)
{
// If 'target' is null, return null.
if (target == null)
{
return(null);
}
// Both objects must be the same type.
FileAccessPermission filePerm = VerifyTypeMatch(target);
// If 'this' and 'target' are unrestricted, return a new unrestricted permission.
if (_specifiedAsUnrestricted && filePerm._specifiedAsUnrestricted)
{
return(Clone(true, PermissionType.Unrestricted));
}
// Calculate the intersected permissions. If there are none, return null.
PermissionType val = (PermissionType)Math.Min((Int32)_permission, (Int32)filePerm._permission);
if (val == 0)
{
return(null);
}
// Get the intersect.
val = new PermissionSource(_permission).Intersect(filePerm._permission);
// Return a new object with the intersected permission value.
return(Clone(false, val));
}
/// <summary>
/// Clone the file access permission.
/// </summary>
/// <param name="specifiedAsUnrestricted">True if unrestricted; else restricted.</param>
/// <param name="flags">The permission flags.</param>
/// <returns>The file access permission clone.</returns>
private FileAccessPermission Clone(Boolean specifiedAsUnrestricted, PermissionType flags)
{
FileAccessPermission filePerm = (FileAccessPermission)Clone();
filePerm._specifiedAsUnrestricted = specifiedAsUnrestricted;
filePerm._permission = specifiedAsUnrestricted ? PermissionType.Unrestricted : _permission;
return(filePerm);
}
/// <summary>
/// Determines whether the current permission
/// is a subset of the specified permission.
/// </summary>
/// <param name="target">A permission that is to be tested for the subset relationship.
/// This permission must be of the same type as the current permission.</param>
/// <returns>True if the current permission is a subset of the specified permission; otherwise, false.</returns>
public override bool IsSubsetOf(System.Security.IPermission target)
{
// If 'target' is null and this permission allows nothing, return true.
if (target == null)
{
return(_permission == 0);
}
// Both objects must be the same type.
FileAccessPermission filePerm = VerifyTypeMatch(target);
// Return true if the permissions of 'this' is a subset of 'target'.
return(new PermissionSource(_permission).IsSubsetOf(filePerm._permission));
}
/// <summary>
/// Creates a permission that is the union of the current permission and the specified permission.
/// </summary>
/// <param name="target">A permission to combine with the current permission. It must be of the same
/// type as the current permission.</param>
/// <returns>A new permission that represents the union of the current permission and
/// the specified permission.</returns>
public override System.Security.IPermission Union(System.Security.IPermission target)
{
// If 'target' is null, then return a copy of 'this'.
if (target == null)
{
return(Copy());
}
// Both objects must be the same type.
FileAccessPermission filePerm = VerifyTypeMatch(target);
// If 'this' or 'target' are unrestricted, return a new unrestricted permission.
if (_specifiedAsUnrestricted || filePerm._specifiedAsUnrestricted)
{
return(Clone(true, PermissionType.Unrestricted));
}
// Return a new object with the calculated, unioned permission value.
return(Clone(false, new PermissionSource(_permission).Union(filePerm._permission)));
}