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IdentityField.cs
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IdentityField.cs
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// -----------------------------------------------------------------------------------
// <copyright file="IdentityField.cs" company="NMemory Team">
// Copyright (C) NMemory Team
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
// </copyright>
// -----------------------------------------------------------------------------------
namespace NMemory.Tables
{
using System;
using System.Collections.Generic;
using System.Linq.Expressions;
using System.Reflection;
using System.Threading;
using NMemory.Common;
internal class IdentityField<TEntity>
{
private Func<TEntity, long> identityGetter;
private DynamicPropertySetter<TEntity> identitySetter;
private IdentitySpecification<TEntity> identitySpecification;
private long nextIdentity;
private Type identityType;
internal IdentityField(IdentitySpecification<TEntity> identitySpecification)
{
this.identitySpecification = identitySpecification;
this.nextIdentity = this.identitySpecification.Seed;
MemberExpression member = ExpressionHelper.FindMemberExpression(identitySpecification.IdentityColumn.Body);
PropertyInfo identityInfo = member.Member as PropertyInfo;
this.identityType = identityInfo.PropertyType;
this.identitySetter = DynamicMethodBuilder.CreatePropertySetter<TEntity>(identityInfo);
this.identityGetter = this.identitySpecification.IdentityColumn.Compile();
}
internal void InitializeBasedOnData(IEnumerable<TEntity> initialEntities, bool forceMinValue = false)
{
long? currentNextIdentity = null;
foreach (TEntity entity in initialEntities)
{
long entityIdentity = this.identityGetter(entity);
if (!currentNextIdentity.HasValue ||
(this.identitySpecification.Increment < 0 && entityIdentity < currentNextIdentity.Value) ||
(this.identitySpecification.Increment > 0 && entityIdentity > currentNextIdentity.Value))
{
currentNextIdentity = entityIdentity;
}
}
if (currentNextIdentity.HasValue)
{
var nextValue = currentNextIdentity.Value + this.identitySpecification.Increment;
this.nextIdentity = nextValue > 0 ? nextValue : forceMinValue ? 1 : nextValue;
}
}
internal void Generate(TEntity entity)
{
long nextValue = Interlocked.Add(ref this.nextIdentity, this.identitySpecification.Increment);
long currentValue = nextValue - this.identitySpecification.Increment;
// Int64 to IntX conversion
object currentValueConverted = Convert.ChangeType(currentValue, this.identityType);
this.identitySetter(entity, currentValueConverted);
}
}
}