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/* ****************************************************************************
*
* Copyright (c) Microsoft Corporation. All rights reserved.
*
* This software is subject to the Microsoft Public License (Ms-PL).
* A copy of the license can be found in the license.htm file included
* in this distribution.
*
* You must not remove this notice, or any other, from this software.
*
* ***************************************************************************/
namespace System.Web.Mvc.ExpressionUtil {
using System;
using System.Linq.Expressions;
internal static class CachedExpressionCompiler {
// This is the entry point to the cached expression tree compiler. The processor will perform a series of checks
// and optimizations in order to return a fully-compiled func as quickly as possible to the caller. If the
// input expression is particularly obscure, the system will fall back to a slow but correct compilation step.
public static Func<TModel, TValue> Process<TModel, TValue>(Expression<Func<TModel, TValue>> lambdaExpression) {
return Processor<TModel, TValue>.GetFunc(lambdaExpression);
}
private static class Processor<TModel, TValue> {
private static readonly Cache _cache = new Cache();
public static Func<TModel, TValue> GetFunc(Expression<Func<TModel, TValue>> lambdaExpression) {
// look for common patterns that don't need to be fingerprinted
Func<TModel, TValue> func = GetFuncFastTrack(lambdaExpression);
if (func != null) {
return func;
}
// not a common pattern, so try fingerprinting (slower, but cached)
func = GetFuncFingerprinted(lambdaExpression);
if (func != null) {
return func;
}
// pattern not recognized by fingerprinting routine, so compile directly (slowest)
return GetFuncSlow(lambdaExpression);
}
private static Func<TModel, TValue> GetFuncFastTrack(Expression<Func<TModel, TValue>> lambdaExpression) {
ParameterExpression modelParameter = lambdaExpression.Parameters[0];
Expression body = lambdaExpression.Body;
return FastTrack<TModel, TValue>.GetFunc(modelParameter, body);
}
private static Func<TModel, TValue> GetFuncFingerprinted(Expression<Func<TModel, TValue>> lambdaExpression) {
ParserContext context = ExpressionParser.Parse(lambdaExpression);
if (context.Fingerprint == null) {
// fingerprinting failed
return null;
}
object[] hoistedValues = context.HoistedValues.ToArray();
var del = _cache.GetDelegate(context);
return model => del(model, hoistedValues);
}
private static Func<TModel, TValue> GetFuncSlow(Expression<Func<TModel, TValue>> lambdaExpression) {
Func<TModel, TValue> del = lambdaExpression.Compile();
return del;
}
private sealed class Cache : ReaderWriterCache<ExpressionFingerprint, CompiledExpressionDelegate<TModel, TValue>> {
private static CompiledExpressionDelegate<TModel, TValue> CreateDelegate(ParserContext context) {
var bodyExpr = context.Fingerprint.ToExpression(context);
var lambdaExpr = Expression.Lambda<CompiledExpressionDelegate<TModel, TValue>>(bodyExpr, context.ModelParameter, ParserContext.HoistedValuesParameter);
var del = lambdaExpr.Compile();
return del;
}
public CompiledExpressionDelegate<TModel, TValue> GetDelegate(ParserContext context) {
return FetchOrCreateItem(context.Fingerprint, () => CreateDelegate(context));
}
}
}
}
}
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