Modified source engine (2017) developed by valve and leaked in 2020. Not for commercial purporses
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//===== Copyright © 1996-2006, Valve Corporation, All rights reserved. ======//
//
// Purpose: ExprSimplifier builds a binary tree from an infix expression (in the
// form of a character array).
//
//===========================================================================//
#ifndef EXPREVALUATOR_H
#define EXPREVALUATOR_H
#if defined( _WIN32 )
#pragma once
#endif
static const char OR_OP = '|';
static const char AND_OP = '&';
static const char NOT_OP = '!';
#define MAX_IDENTIFIER_LEN 128
enum Kind {CONDITIONAL, NOT, LITERAL};
struct ExprNode
{
ExprNode *left; // left sub-expression
ExprNode *right; // right sub-expression
Kind kind; // kind of node this is
union
{
char cond; // the conditional
bool value; // the value
} data;
};
typedef ExprNode *ExprTree;
// callback to evaluate a $<symbol> during evaluation, return true or false
typedef bool (*GetSymbolProc_t)( const char *pKey );
typedef void (*SyntaxErrorProc_t)( const char *pReason );
class CExpressionEvaluator
{
public:
CExpressionEvaluator();
~CExpressionEvaluator();
bool Evaluate( bool &result, const char *pInfixExpression, GetSymbolProc_t pGetSymbolProc = 0, SyntaxErrorProc_t pSyntaxErrorProc = 0 );
private:
CExpressionEvaluator( CExpressionEvaluator& ); // prevent copy constructor being used
char GetNextToken( void );
void FreeNode( ExprNode *pNode );
ExprNode *AllocateNode( void );
void FreeTree( ExprTree &node );
bool IsConditional( bool &bCondition, const char token );
bool IsNotOp( const char token );
bool IsIdentifierOrConstant( const char token );
bool MakeExprNode( ExprTree &tree, char token, Kind kind, ExprTree left, ExprTree right );
bool MakeFactor( ExprTree &tree );
bool MakeTerm( ExprTree &tree );
bool MakeExpression( ExprTree &tree );
bool BuildExpression( void );
bool SimplifyNode( ExprTree &node );
ExprTree m_ExprTree; // Tree representation of the expression
char m_CurToken; // Current token read from the input expression
const char *m_pExpression; // Array of the expression characters
int m_CurPosition; // Current position in the input expression
char m_Identifier[MAX_IDENTIFIER_LEN]; // Stores the identifier string
GetSymbolProc_t m_pGetSymbolProc;
SyntaxErrorProc_t m_pSyntaxErrorProc;
bool m_bSetup;
};
#endif