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using System;
using System.Linq;
using System.Reflection;
using System.Runtime.Caching;
namespace StardewModdingAPI.Framework.Reflection
{
/// <summary>Provides helper methods for accessing private game code.</summary>
/// <remarks>This implementation searches up the type hierarchy, and caches the reflected fields and methods with a sliding expiry (to optimise performance without unnecessary memory usage).</remarks>
internal class ReflectionHelper : IReflectionHelper
{
/*********
** Properties
*********/
/// <summary>The cached fields and methods found via reflection.</summary>
private readonly MemoryCache Cache = new MemoryCache(typeof(ReflectionHelper).FullName);
/// <summary>The sliding cache expiration time.</summary>
private readonly TimeSpan SlidingCacheExpiry = TimeSpan.FromMinutes(5);
/*********
** Public methods
*********/
/****
** Fields
****/
/// <summary>Get a private instance field.</summary>
/// <typeparam name="TValue">The field type.</typeparam>
/// <param name="obj">The object which has the field.</param>
/// <param name="name">The field name.</param>
/// <param name="required">Whether to throw an exception if the private field is not found.</param>
/// <returns>Returns the field wrapper, or <c>null</c> if the field doesn't exist and <paramref name="required"/> is <c>false</c>.</returns>
public IPrivateField<TValue> GetPrivateField<TValue>(object obj, string name, bool required = true)
{
// validate
if (obj == null)
throw new ArgumentNullException(nameof(obj), "Can't get a private instance field from a null object.");
// get field from hierarchy
IPrivateField<TValue> field = this.GetFieldFromHierarchy<TValue>(obj.GetType(), obj, name, BindingFlags.Instance | BindingFlags.NonPublic);
if (required && field == null)
throw new InvalidOperationException($"The {obj.GetType().FullName} object doesn't have a private '{name}' instance field.");
return field;
}
/// <summary>Get a private static field.</summary>
/// <typeparam name="TValue">The field type.</typeparam>
/// <param name="type">The type which has the field.</param>
/// <param name="name">The field name.</param>
/// <param name="required">Whether to throw an exception if the private field is not found.</param>
public IPrivateField<TValue> GetPrivateField<TValue>(Type type, string name, bool required = true)
{
// get field from hierarchy
IPrivateField<TValue> field = this.GetFieldFromHierarchy<TValue>(type, null, name, BindingFlags.NonPublic | BindingFlags.Static);
if (required && field == null)
throw new InvalidOperationException($"The {type.FullName} object doesn't have a private '{name}' static field.");
return field;
}
/****
** Field values
** (shorthand since this is the most common case)
****/
/// <summary>Get the value of a private instance field.</summary>
/// <typeparam name="TValue">The field type.</typeparam>
/// <param name="obj">The object which has the field.</param>
/// <param name="name">The field name.</param>
/// <param name="required">Whether to throw an exception if the private field is not found.</param>
/// <remarks>This is a shortcut for <see cref="GetPrivateField{TValue}(object,string,bool)"/> followed by <see cref="IPrivateField{TValue}.GetValue"/>.</remarks>
public TValue GetPrivateValue<TValue>(object obj, string name, bool required = true)
{
return this.GetPrivateField<TValue>(obj, name, required).GetValue();
}
/// <summary>Get the value of a private static field.</summary>
/// <typeparam name="TValue">The field type.</typeparam>
/// <param name="type">The type which has the field.</param>
/// <param name="name">The field name.</param>
/// <param name="required">Whether to throw an exception if the private field is not found.</param>
/// <remarks>This is a shortcut for <see cref="GetPrivateField{TValue}(Type,string,bool)"/> followed by <see cref="IPrivateField{TValue}.GetValue"/>.</remarks>
public TValue GetPrivateValue<TValue>(Type type, string name, bool required = true)
{
return this.GetPrivateField<TValue>(type, name, required).GetValue();
}
/****
** Methods
****/
/// <summary>Get a private instance method.</summary>
/// <param name="obj">The object which has the method.</param>
/// <param name="name">The field name.</param>
/// <param name="required">Whether to throw an exception if the private field is not found.</param>
public IPrivateMethod GetPrivateMethod(object obj, string name, bool required = true)
{
// validate
if (obj == null)
throw new ArgumentNullException(nameof(obj), "Can't get a private instance method from a null object.");
// get method from hierarchy
IPrivateMethod method = this.GetMethodFromHierarchy(obj.GetType(), obj, name, BindingFlags.Instance | BindingFlags.NonPublic);
if (required && method == null)
throw new InvalidOperationException($"The {obj.GetType().FullName} object doesn't have a private '{name}' instance method.");
return method;
}
/// <summary>Get a private static method.</summary>
/// <param name="type">The type which has the method.</param>
/// <param name="name">The field name.</param>
/// <param name="required">Whether to throw an exception if the private field is not found.</param>
public IPrivateMethod GetPrivateMethod(Type type, string name, bool required = true)
{
// get method from hierarchy
IPrivateMethod method = this.GetMethodFromHierarchy(type, null, name, BindingFlags.NonPublic | BindingFlags.Static);
if (required && method == null)
throw new InvalidOperationException($"The {type.FullName} object doesn't have a private '{name}' static method.");
return method;
}
/****
** Methods by signature
****/
/// <summary>Get a private instance method.</summary>
/// <param name="obj">The object which has the method.</param>
/// <param name="name">The field name.</param>
/// <param name="argumentTypes">The argument types of the method signature to find.</param>
/// <param name="required">Whether to throw an exception if the private field is not found.</param>
public IPrivateMethod GetPrivateMethod(object obj, string name, Type[] argumentTypes, bool required = true)
{
// validate parent
if (obj == null)
throw new ArgumentNullException(nameof(obj), "Can't get a private instance method from a null object.");
// get method from hierarchy
PrivateMethod method = this.GetMethodFromHierarchy(obj.GetType(), obj, name, BindingFlags.Instance | BindingFlags.NonPublic, argumentTypes);
if (required && method == null)
throw new InvalidOperationException($"The {obj.GetType().FullName} object doesn't have a private '{name}' instance method with that signature.");
return method;
}
/// <summary>Get a private static method.</summary>
/// <param name="type">The type which has the method.</param>
/// <param name="name">The field name.</param>
/// <param name="argumentTypes">The argument types of the method signature to find.</param>
/// <param name="required">Whether to throw an exception if the private field is not found.</param>
public IPrivateMethod GetPrivateMethod(Type type, string name, Type[] argumentTypes, bool required = true)
{
// get field from hierarchy
PrivateMethod method = this.GetMethodFromHierarchy(type, null, name, BindingFlags.NonPublic | BindingFlags.Static, argumentTypes);
if (required && method == null)
throw new InvalidOperationException($"The {type.FullName} object doesn't have a private '{name}' static method with that signature.");
return method;
}
/*********
** Private methods
*********/
/// <summary>Get a field from the type hierarchy.</summary>
/// <typeparam name="TValue">The expected field type.</typeparam>
/// <param name="type">The type which has the field.</param>
/// <param name="obj">The object which has the field.</param>
/// <param name="name">The field name.</param>
/// <param name="bindingFlags">The reflection binding which flags which indicates what type of field to find.</param>
private IPrivateField<TValue> GetFieldFromHierarchy<TValue>(Type type, object obj, string name, BindingFlags bindingFlags)
{
bool isStatic = bindingFlags.HasFlag(BindingFlags.Static);
FieldInfo field = this.GetCached<FieldInfo>($"field::{isStatic}::{type.FullName}::{name}", () =>
{
FieldInfo fieldInfo = null;
for (; type != null && fieldInfo == null; type = type.BaseType)
fieldInfo = type.GetField(name, bindingFlags);
return fieldInfo;
});
return field != null
? new PrivateField<TValue>(type, obj, field, isStatic)
: null;
}
/// <summary>Get a method from the type hierarchy.</summary>
/// <param name="type">The type which has the method.</param>
/// <param name="obj">The object which has the method.</param>
/// <param name="name">The method name.</param>
/// <param name="bindingFlags">The reflection binding which flags which indicates what type of method to find.</param>
private IPrivateMethod GetMethodFromHierarchy(Type type, object obj, string name, BindingFlags bindingFlags)
{
bool isStatic = bindingFlags.HasFlag(BindingFlags.Static);
MethodInfo method = this.GetCached($"method::{isStatic}::{type.FullName}::{name}", () =>
{
MethodInfo methodInfo = null;
for (; type != null && methodInfo == null; type = type.BaseType)
methodInfo = type.GetMethod(name, bindingFlags);
return methodInfo;
});
return method != null
? new PrivateMethod(type, obj, method, isStatic: bindingFlags.HasFlag(BindingFlags.Static))
: null;
}
/// <summary>Get a method from the type hierarchy.</summary>
/// <param name="type">The type which has the method.</param>
/// <param name="obj">The object which has the method.</param>
/// <param name="name">The method name.</param>
/// <param name="bindingFlags">The reflection binding which flags which indicates what type of method to find.</param>
/// <param name="argumentTypes">The argument types of the method signature to find.</param>
private PrivateMethod GetMethodFromHierarchy(Type type, object obj, string name, BindingFlags bindingFlags, Type[] argumentTypes)
{
bool isStatic = bindingFlags.HasFlag(BindingFlags.Static);
MethodInfo method = this.GetCached($"method::{isStatic}::{type.FullName}::{name}({string.Join(",", argumentTypes.Select(p => p.FullName))})", () =>
{
MethodInfo methodInfo = null;
for (; type != null && methodInfo == null; type = type.BaseType)
methodInfo = type.GetMethod(name, bindingFlags, null, argumentTypes, null);
return methodInfo;
});
return method != null
? new PrivateMethod(type, obj, method, isStatic)
: null;
}
/// <summary>Get a method or field through the cache.</summary>
/// <typeparam name="TMemberInfo">The expected <see cref="MemberInfo"/> type.</typeparam>
/// <param name="key">The cache key.</param>
/// <param name="fetch">Fetches a new value to cache.</param>
private TMemberInfo GetCached<TMemberInfo>(string key, Func<TMemberInfo> fetch) where TMemberInfo : MemberInfo
{
// get from cache
if (this.Cache.Contains(key))
return (TMemberInfo)this.Cache[key];
// fetch & cache new value
TMemberInfo result = fetch();
this.Cache.Add(key, result, new CacheItemPolicy { SlidingExpiration = this.SlidingCacheExpiry });
return result;
}
}
}
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