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using System;
using Mono.Cecil;
using Mono.Cecil.Cil;
using StardewModdingAPI.Framework.ModLoading.Framework;
namespace StardewModdingAPI.Framework.ModLoading.Rewriters
{
/// <summary>Rewrites static field references into constant values.</summary>
/// <typeparam name="TValue">The constant value type.</typeparam>
internal class StaticFieldToConstantRewriter<TValue> : BaseInstructionHandler
{
/*********
** Fields
*********/
/// <summary>The type containing the field to which references should be rewritten.</summary>
private readonly Type Type;
/// <summary>The field name to which references should be rewritten.</summary>
private readonly string FromFieldName;
/// <summary>The constant value to replace with.</summary>
private readonly TValue Value;
/*********
** Public methods
*********/
/// <summary>Construct an instance.</summary>
/// <param name="type">The type whose field to which references should be rewritten.</param>
/// <param name="fieldName">The field name to rewrite.</param>
/// <param name="value">The constant value to replace with.</param>
public StaticFieldToConstantRewriter(Type type, string fieldName, TValue value)
: base(defaultPhrase: $"{type.FullName}.{fieldName} field")
{
this.Type = type;
this.FromFieldName = fieldName;
this.Value = value;
}
/// <summary>Rewrite a CIL instruction reference if needed.</summary>
/// <param name="module">The assembly module containing the instruction.</param>
/// <param name="cil">The CIL processor.</param>
/// <param name="instruction">The CIL instruction to handle.</param>
/// <param name="replaceWith">Replaces the CIL instruction with a new one.</param>
/// <returns>Returns whether the instruction was changed.</returns>
public override bool Handle(ModuleDefinition module, ILProcessor cil, Instruction instruction, Action<Instruction> replaceWith)
{
// get field reference
FieldReference fieldRef = RewriteHelper.AsFieldReference(instruction);
if (!RewriteHelper.IsFieldReferenceTo(fieldRef, this.Type.FullName, this.FromFieldName))
return false;
// rewrite to constant
replaceWith(this.CreateConstantInstruction(cil, this.Value));
return this.MarkRewritten();
}
/*********
** Private methods
*********/
/// <summary>Create a CIL constant value instruction.</summary>
/// <param name="cil">The CIL processor.</param>
/// <param name="value">The constant value to set.</param>
private Instruction CreateConstantInstruction(ILProcessor cil, object value)
{
if (typeof(TValue) == typeof(int))
return cil.Create(OpCodes.Ldc_I4, (int)value);
if (typeof(TValue) == typeof(string))
return cil.Create(OpCodes.Ldstr, (string)value);
throw new NotSupportedException($"Rewriting to constant values of type {typeof(TValue)} isn't currently supported.");
}
}
}
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