3e3883cfeb
Introduce operation journaling to track how values are read from the binary stream, enabling future write-back of edited fields. New components: - OperationJournal: Records read operations with stream offsets, sizes, byte order, and original values during parsing - ReverseEval: Analyzes expressions for invertibility (e.g., x+5 can be reversed to compute the source field when editing the result) - Recompiler: Infrastructure for recompiling modified values back to binary format Interpreter enhancements: - Add runTypeInternalWithJournal() for journaled parsing - Journal scalar reads, byte reads, strings, skip/seek operations - Add deadrising_lzx() built-in for Dead Rising 2 LZX decompression - Support _deadrising_lzx_stem context variable for nested archives Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
106 lines
3.6 KiB
C++
106 lines
3.6 KiB
C++
#ifndef REVERSEEVAL_H
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#define REVERSEEVAL_H
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#include "operationjournal.h"
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#include "ast.h"
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#include <QVariant>
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/**
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* @brief Analyzes expressions to determine invertibility and compute reverse operations.
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*
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* This is used during parsing to build InverseChain structures that enable
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* editing computed fields. When a user edits a computed field, the inverse
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* chain is used to calculate what the source field's value should be.
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*
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* Invertible operations (single source):
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* - Addition: x = y + c → y = x - c
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* - Subtraction: x = y - c → y = x + c
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* - Multiplication: x = y * c → y = x / c
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* - Division: x = y / c → y = x * c
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* - Left shift: x = y << c → y = x >> c
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* - Right shift: x = y >> c → y = x << c
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* - Negation: x = -y → y = -x
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* - Bitwise XOR: x = y ^ c → y = x ^ c (XOR is self-inverse)
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*
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* Non-invertible operations (information loss):
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* - Bitwise AND: x = y & c (bits masked out are lost)
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* - Bitwise OR: x = y | c (can't determine which bits were originally set)
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* - Modulo: x = y % c (infinite solutions)
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* - Multiple sources: x = a + b (can't determine which to adjust)
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*/
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class ReverseEvaluator {
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public:
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ReverseEvaluator() = default;
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/**
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* @brief Analyze an expression to build an inverse chain.
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* @param expr The expression to analyze
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* @param targetField The field name being assigned to (for context)
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* @return InverseChain with source field and operations, or canInvert=false if not invertible
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*/
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InverseChain analyzeExpression(const Expr& expr, const QString& targetField = QString());
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/**
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* @brief Apply an inverse chain to compute the source value from an edited value.
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* @param chain The inverse chain from analyzeExpression
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* @param editedValue The new value the user entered
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* @return The computed source value
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*/
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qint64 computeInverse(const InverseChain& chain, qint64 editedValue) const;
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/**
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* @brief Apply inverse chain with QVariant (delegates to qint64 version).
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*/
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QVariant computeInverse(const InverseChain& chain, const QVariant& editedValue) const;
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/**
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* @brief Quick check if an expression is invertible.
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* @param expr The expression to check
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* @return true if the expression can be reversed to a single source field
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*/
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bool isInvertible(const Expr& expr) const;
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/**
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* @brief Get human-readable reason why an expression is not invertible.
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* @param expr The expression to check
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* @return Empty string if invertible, otherwise the reason
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*/
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QString whyNotInvertible(const Expr& expr) const;
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private:
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/**
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* @brief Recursively analyze an expression, building up the inverse chain.
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* @param expr The expression to analyze
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* @param chain The chain being built (modified in place)
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* @return true if analysis succeeded and expression is invertible
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*/
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bool analyzeRecursive(const Expr& expr, InverseChain& chain);
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/**
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* @brief Check if an expression is a constant (literal value).
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*/
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bool isConstant(const Expr& expr) const;
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/**
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* @brief Get the constant value from an expression.
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*/
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qint64 getConstantValue(const Expr& expr) const;
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/**
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* @brief Check if an expression is a simple variable reference.
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*/
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bool isVariable(const Expr& expr) const;
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/**
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* @brief Get the variable name from an expression.
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*/
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QString getVariableName(const Expr& expr) const;
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/**
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* @brief Apply a single inverse operation.
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*/
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qint64 applyInverseOp(qint64 value, InvertOp op, qint64 operand) const;
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};
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#endif // REVERSEEVAL_H
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