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CompiledMapper.cs
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CompiledMapper.cs
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using System;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;
using System.Reflection;
using Velo.Utils;
namespace Velo.Mapping
{
internal sealed class CompiledMapper<TOut> : IMapper<TOut>
{
private readonly Dictionary<Type, Func<object, TOut>> _converters;
private readonly ConstructorInfo _outConstructor;
private readonly Dictionary<string, PropertyInfo> _outProperties;
private readonly Type _outType;
public CompiledMapper()
{
_converters = new Dictionary<Type, Func<object, TOut>>();
_outType = typeof(TOut);
_outProperties = _outType.GetProperties().ToDictionary(p => p.Name);
_outConstructor = ReflectionUtils.GetEmptyConstructor(_outType)
?? throw Error.DefaultConstructorNotFound(_outType);
if (_outConstructor == null) throw Error.DefaultConstructorNotFound(_outType);
}
public TOut Map(object source)
{
var sourceType = source.GetType();
if (_converters.TryGetValue(sourceType, out var existsConverter))
{
return existsConverter(source);
}
var converter = BuildConverter(sourceType);
_converters.Add(sourceType, converter);
return converter(source);
}
private Func<object, TOut> BuildConverter(Type sourceType)
{
var parameter = Expression.Parameter(typeof(object), "source");
var sourceInstance = Expression.Variable(sourceType, "typedSource");
var outInstance = Expression.Variable(_outType, "outInstance");
var expressions = new List<Expression>
{
Expression.Assign(sourceInstance, Expression.Convert(parameter, sourceType)),
Expression.Assign(outInstance, Expression.New(_outConstructor))
};
var sourceProperties = sourceType.GetProperties();
foreach (var sourceProperty in sourceProperties)
{
if (!_outProperties.TryGetValue(sourceProperty.Name, out var outProperty)) continue;
var sourceValue = Expression.Property(sourceInstance, sourceProperty);
var outValue = Expression.Property(outInstance, outProperty);
expressions.Add(Expression.Assign(outValue, sourceValue));
}
expressions.Add(outInstance); // return
var body = Expression.Block(new[] {sourceInstance, outInstance}, expressions);
return Expression.Lambda<Func<object, TOut>>(body, parameter).Compile();
}
}
}