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using System.Collections.Generic;
using System.Linq;
using Mono.Cecil;
using Mono.Cecil.Cil;
using StardewModdingAPI.Framework.ModLoading.Framework;
namespace StardewModdingAPI.Framework.ModLoading.Rewriters
{
/// <summary>Automatically fix references to fields that have been replaced by a property or const field.</summary>
internal class HeuristicFieldRewriter : BaseInstructionHandler
{
/*********
** Fields
*********/
/// <summary>The assembly names to which to rewrite broken references.</summary>
private readonly ISet<string> RewriteReferencesToAssemblies;
/*********
** Public methods
*********/
/// <summary>Construct an instance.</summary>
/// <param name="rewriteReferencesToAssemblies">The assembly names to which to rewrite broken references.</param>
public HeuristicFieldRewriter(ISet<string> rewriteReferencesToAssemblies)
: base(defaultPhrase: "field changed to property") // ignored since we specify phrases
{
this.RewriteReferencesToAssemblies = rewriteReferencesToAssemblies;
}
/// <inheritdoc />
public override bool Handle(ModuleDefinition module, ILProcessor cil, Instruction instruction)
{
// get field ref
FieldReference fieldRef = RewriteHelper.AsFieldReference(instruction);
if (fieldRef == null || !this.ShouldValidate(fieldRef.DeclaringType))
return false;
// skip if not broken
FieldDefinition fieldDefinition = fieldRef.Resolve();
if (fieldDefinition?.HasConstant == false)
return false;
// rewrite if possible
TypeDefinition declaringType = fieldRef.DeclaringType.Resolve();
bool isRead = instruction.OpCode == OpCodes.Ldsfld || instruction.OpCode == OpCodes.Ldfld;
return
this.TryRewriteToProperty(module, instruction, fieldRef, declaringType, isRead)
|| this.TryRewriteToConstField(instruction, fieldDefinition);
}
/*********
** Private methods
*********/
/// <summary>Whether references to the given type should be validated.</summary>
/// <param name="type">The type reference.</param>
private bool ShouldValidate(TypeReference type)
{
return type != null && this.RewriteReferencesToAssemblies.Contains(type.Scope.Name);
}
/// <summary>Try rewriting the field into a matching property.</summary>
/// <param name="module">The assembly module containing the instruction.</param>
/// <param name="instruction">The CIL instruction to rewrite.</param>
/// <param name="fieldRef">The field reference.</param>
/// <param name="declaringType">The type on which the field was defined.</param>
/// <param name="isRead">Whether the field is being read; else it's being written to.</param>
private bool TryRewriteToProperty(ModuleDefinition module, Instruction instruction, FieldReference fieldRef, TypeDefinition declaringType, bool isRead)
{
// get equivalent property
PropertyDefinition property = declaringType?.Properties.FirstOrDefault(p => p.Name == fieldRef.Name);
MethodDefinition method = isRead ? property?.GetMethod : property?.SetMethod;
if (method == null)
return false;
// rewrite field to property
instruction.OpCode = OpCodes.Call;
instruction.Operand = module.ImportReference(method);
this.Phrases.Add($"{fieldRef.DeclaringType.Name}.{fieldRef.Name} (field => property)");
return this.MarkRewritten();
}
/// <summary>Try rewriting the field into a matching const field.</summary>
/// <param name="instruction">The CIL instruction to rewrite.</param>
/// <param name="field">The field definition.</param>
private bool TryRewriteToConstField(Instruction instruction, FieldDefinition field)
{
// must have been a static field read, and the new field must be const
if (instruction.OpCode != OpCodes.Ldsfld || field?.HasConstant != true)
return false;
// get opcode for value type
Instruction loadInstruction = RewriteHelper.GetLoadValueInstruction(field.Constant);
if (loadInstruction == null)
return false;
// rewrite to constant
instruction.OpCode = loadInstruction.OpCode;
instruction.Operand = loadInstruction.Operand;
this.Phrases.Add($"{field.DeclaringType.Name}.{field.Name} (field => const)");
return this.MarkRewritten();
}
}
}
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