/// <summary>
/// Given a single item function that should be a static method, this builds a serialized version of
/// that method that should be enough to "recover" it, assuming it is a "recoverable" method (recoverable
/// here is a loose definition, meaning that <see cref="DeserializeStaticDelegateOrNull"/> is capable
/// of creating it, which includes among other things that it's static, non-lambda, accessible to
/// this assembly, etc.).
/// </summary>
/// <param name="func">The method that should be "recoverable"</param>
/// <returns>A string array describing the input method</returns>
public static byte[] GetSerializedStaticDelegate(ExtLambdaTransform.LoadDelegate func)
{
Contracts.CheckValue(func, nameof(func));
Contracts.CheckParam(func.Target == null, nameof(func), "The load delegate must be static");
Contracts.CheckParam(Utils.Size(func.GetInvocationList()) <= 1, nameof(func),
"The load delegate must not be a multicast delegate");
var meth = func.GetMethodInfo();
using (var ms = new MemoryStream())
{
var formatter = new BinaryFormatter();
#if CORECLR
var m = new CoreHackMethodInfo();
m.AssemblyName = meth.Module.Assembly.FullName;
m.MethodName = meth.Name;
m.ClassName = meth.DeclaringType.ToString();
formatter.Serialize(ms, m);
#else
formatter.Serialize(ms, meth);
#endif
var result = ms.ToArray();
// I assume it must be impossible to serialize in 0 bytes.
Contracts.Assert(Utils.Size(result) > 0);
return(result);
}
}
/// <summary>
/// Create a filter transform that is savable iff <paramref name="saveAction"/> and <paramref name="loadFunc"/> are
/// not null.
/// </summary>
/// <param name="env">The host environment</param>
/// <param name="source">The dataview upon which we construct the transform</param>
/// <param name="filterFunc">The function by which we transform source to destination columns and decide whether
/// to keep the row.</param>
/// <param name="initStateAction">The function that is called once per cursor to initialize state. Can be null.</param>
/// <param name="saveAction">An action that allows us to save state to the serialization stream. May be
/// null simultaneously with <paramref name="loadFunc"/>.</param>
/// <param name="loadFunc">A function that given the serialization stream and a data view, returns
/// an <see cref="ITransformTemplate"/>. The intent is, this returned object should itself be a
/// <see cref="CustomMappingTransformer{TSrc,TDst}"/>, but this is not strictly necessary. This delegate should be
/// a static non-lambda method that this assembly can legally call. May be null simultaneously with
/// <paramref name="saveAction"/>.</param>
/// <param name="inputSchemaDefinition">The schema definition overrides for <typeparamref name="TSrc"/></param>
/// <param name="outputSchemaDefinition">The schema definition overrides for <typeparamref name="TDst"/></param>
public ExtStatefulFilterTransform(IHostEnvironment env, IDataView source, Func <TSrc, TDst, TState, bool> filterFunc,
Action <TState> initStateAction,
Action <BinaryWriter> saveAction, ExtLambdaTransform.LoadDelegate loadFunc,
SchemaDefinition inputSchemaDefinition = null, SchemaDefinition outputSchemaDefinition = null)
: base(env, RegistrationName, saveAction, loadFunc)
{
Host.AssertValue(source, "source");
Host.AssertValue(filterFunc, "filterFunc");
Host.AssertValueOrNull(initStateAction);
Host.AssertValueOrNull(inputSchemaDefinition);
Host.AssertValueOrNull(outputSchemaDefinition);
_source = source;
_filterFunc = filterFunc;
_initStateAction = initStateAction;
_inputSchemaDefinition = inputSchemaDefinition;
_typedSource = TypedCursorable <TSrc> .Create(Host, Source, false, inputSchemaDefinition);
var outSchema = InternalSchemaDefinition.Create(typeof(TDst), outputSchemaDefinition);
_addedSchema = outSchema;
_bindings = new ColumnBindings(Source.Schema, DataViewConstructionUtils.GetSchemaColumns(outSchema));
}
protected ExtLambdaTransformBase(IHostEnvironment env, string name, Action <BinaryWriter> saveAction, ExtLambdaTransform.LoadDelegate loadFunc)
{
Contracts.AssertValue(env);
env.AssertNonWhiteSpace(name);
Host = env.Register(name);
Host.Assert((saveAction == null) == (loadFunc == null));
if (saveAction != null)
{
_saveAction = saveAction;
// First, verify as best we can, that we can recover the function, by attempting to do it once.
_loadFuncBytes = SerializableExtLambdaTransform.GetSerializedStaticDelegate(loadFunc);
Exception error;
var recoveredLoadFunc = SerializableExtLambdaTransform.DeserializeStaticDelegateOrNull(Host, _loadFuncBytes, out error);
if (recoveredLoadFunc == null)
{
Host.AssertValue(error);
throw Host.Except(error, "Load function does not appear recoverable");
}
}
AssertConsistentSerializable();
}
