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using System;
using System.Reflection;
using StardewModdingAPI.Framework.Reflection;
namespace StardewModdingAPI.Framework.ModHelpers
{
/// <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 : BaseHelper, IReflectionHelper
{
/*********
** Fields
*********/
/// <summary>The underlying reflection helper.</summary>
private readonly Reflector Reflector;
/// <summary>The mod name for error messages.</summary>
private readonly string ModName;
/*********
** Public methods
*********/
/// <summary>Construct an instance.</summary>
/// <param name="modID">The unique ID of the relevant mod.</param>
/// <param name="modName">The mod name for error messages.</param>
/// <param name="reflector">The underlying reflection helper.</param>
public ReflectionHelper(string modID, string modName, Reflector reflector)
: base(modID)
{
this.ModName = modName;
this.Reflector = reflector;
}
/// <summary>Get an 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 field is not found.</param>
public IReflectedField<TValue> GetField<TValue>(object obj, string name, bool required = true)
{
return this.AssertAccessAllowed(
this.Reflector.GetField<TValue>(obj, name, required)
);
}
/// <summary>Get a 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 field is not found.</param>
public IReflectedField<TValue> GetField<TValue>(Type type, string name, bool required = true)
{
return this.AssertAccessAllowed(
this.Reflector.GetField<TValue>(type, name, required)
);
}
/// <summary>Get an instance property.</summary>
/// <typeparam name="TValue">The property type.</typeparam>
/// <param name="obj">The object which has the property.</param>
/// <param name="name">The property name.</param>
/// <param name="required">Whether to throw an exception if the property is not found.</param>
public IReflectedProperty<TValue> GetProperty<TValue>(object obj, string name, bool required = true)
{
return this.AssertAccessAllowed(
this.Reflector.GetProperty<TValue>(obj, name, required)
);
}
/// <summary>Get a static property.</summary>
/// <typeparam name="TValue">The property type.</typeparam>
/// <param name="type">The type which has the property.</param>
/// <param name="name">The property name.</param>
/// <param name="required">Whether to throw an exception if the property is not found.</param>
public IReflectedProperty<TValue> GetProperty<TValue>(Type type, string name, bool required = true)
{
return this.AssertAccessAllowed(
this.Reflector.GetProperty<TValue>(type, name, required)
);
}
/// <summary>Get an 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 field is not found.</param>
public IReflectedMethod GetMethod(object obj, string name, bool required = true)
{
return this.AssertAccessAllowed(
this.Reflector.GetMethod(obj, name, required)
);
}
/// <summary>Get a 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 field is not found.</param>
public IReflectedMethod GetMethod(Type type, string name, bool required = true)
{
return this.AssertAccessAllowed(
this.Reflector.GetMethod(type, name, required)
);
}
/*********
** Private methods
*********/
/// <summary>Assert that mods can use the reflection helper to access the given member.</summary>
/// <typeparam name="T">The field value type.</typeparam>
/// <param name="field">The field being accessed.</param>
/// <returns>Returns the same field instance for convenience.</returns>
private IReflectedField<T> AssertAccessAllowed<T>(IReflectedField<T> field)
{
this.AssertAccessAllowed(field?.FieldInfo);
return field;
}
/// <summary>Assert that mods can use the reflection helper to access the given member.</summary>
/// <typeparam name="T">The property value type.</typeparam>
/// <param name="property">The property being accessed.</param>
/// <returns>Returns the same property instance for convenience.</returns>
private IReflectedProperty<T> AssertAccessAllowed<T>(IReflectedProperty<T> property)
{
this.AssertAccessAllowed(property?.PropertyInfo);
return property;
}
/// <summary>Assert that mods can use the reflection helper to access the given member.</summary>
/// <param name="method">The method being accessed.</param>
/// <returns>Returns the same method instance for convenience.</returns>
private IReflectedMethod AssertAccessAllowed(IReflectedMethod method)
{
this.AssertAccessAllowed(method?.MethodInfo);
return method;
}
/// <summary>Assert that mods can use the reflection helper to access the given member.</summary>
/// <param name="member">The member being accessed.</param>
private void AssertAccessAllowed(MemberInfo member)
{
if (member == null)
return;
// get type which defines the member
Type declaringType = member.DeclaringType;
if (declaringType == null)
throw new InvalidOperationException($"Can't validate access to {member.MemberType} {member.Name} because it has no declaring type."); // should never happen
// validate access
string rootNamespace = typeof(Program).Namespace;
if (declaringType.Namespace == rootNamespace || declaringType.Namespace?.StartsWith(rootNamespace + ".") == true)
throw new InvalidOperationException($"SMAPI blocked access by {this.ModName} to its internals through the reflection API. Accessing the SMAPI internals is strongly discouraged since they're subject to change, which means the mod can break without warning. (Detected access to {declaringType.FullName}.{member.Name}.)");
}
}
}
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