zeek/src/StmtBase.h

// See the file "COPYING" in the main distribution directory for copyright.

#pragma once

// Base class for Zeek statements.  We maintain it separately from
// the bulk of Stmt.h to allow Expr.h to include it, necessary for
// Expr.h to use StmtPtr.

#include "zeek/IntrusivePtr.h"
#include "zeek/Obj.h"
#include "zeek/StmtEnums.h"
#include "zeek/TraverseTypes.h"
#include "zeek/util.h"

namespace zeek
	{

class Val;
using ValPtr = IntrusivePtr<Val>;

namespace run_state
	{
extern double network_time;
	}

namespace detail
	{

class CompositeHash;
class Frame;

class CatchReturnStmt;
class ExprStmt;
class ForStmt;
class IfStmt;
class InitStmt;
class NullStmt;
class PrintStmt;
class ReturnStmt;
class StmtList;
class SwitchStmt;
class WhenStmt;
class WhileStmt;

class EventExpr;
class ListExpr;

using EventExprPtr = IntrusivePtr<EventExpr>;
using ListExprPtr = IntrusivePtr<ListExpr>;

class Inliner;
class Reducer;

class Stmt;
using StmtPtr = IntrusivePtr<Stmt>;

class StmtOptInfo;

class Stmt : public Obj
	{
public:
	StmtTag Tag() const { return tag; }

	~Stmt() override;

	virtual ValPtr Exec(Frame* f, StmtFlowType& flow) = 0;

	Stmt* Ref()
		{
		zeek::Ref(this);
		return this;
		}
	StmtPtr ThisPtr() { return {NewRef{}, this}; }

	bool SetLocationInfo(const Location* loc) override { return Stmt::SetLocationInfo(loc, loc); }
	bool SetLocationInfo(const Location* start, const Location* end) override;

	// True if the statement has no side effects, false otherwise.
	virtual bool IsPure() const;

	StmtList* AsStmtList();
	const StmtList* AsStmtList() const;

	ForStmt* AsForStmt();
	const ForStmt* AsForStmt() const;

	const ExprStmt* AsExprStmt() const;
	const PrintStmt* AsPrintStmt() const;
	const InitStmt* AsInitStmt() const;
	const CatchReturnStmt* AsCatchReturnStmt() const;
	const ReturnStmt* AsReturnStmt() const;
	const IfStmt* AsIfStmt() const;
	const WhileStmt* AsWhileStmt() const;
	const WhenStmt* AsWhenStmt() const;
	const SwitchStmt* AsSwitchStmt() const;
	const NullStmt* AsNullStmt() const;

	void RegisterAccess() const
		{
		last_access = run_state::network_time;
		access_count++;
		}
	void AccessStats(ODesc* d) const;
	uint32_t GetAccessCount() const { return access_count; }

	void Describe(ODesc* d) const final;

	virtual void IncrBPCount() { ++breakpoint_count; }
	virtual void DecrBPCount();

	virtual unsigned int BPCount() const { return breakpoint_count; }

	virtual TraversalCode Traverse(TraversalCallback* cb) const = 0;

	// Returns a duplicate of the statement so that modifications
	// can be made to statements from inlining function bodies - or
	// to the originals - without affecting other instances.
	//
	// It's tempting to think that there are some statements that
	// are safe to share across multiple functions and could just
	// return references to themselves - but since we associate
	// information for script optimization with individual statements
	// nodes, even these need to be duplicated.
	virtual StmtPtr Duplicate() = 0;

	// Recursively traverses the AST to inline eligible function calls.
	virtual void Inline(Inliner* inl) { }

	// True if the statement is in reduced form.
	virtual bool IsReduced(Reducer* c) const;

	// Returns a reduced version of the statement, as managed by
	// the given Reducer.
	StmtPtr Reduce(Reducer* c);
	virtual StmtPtr DoReduce(Reducer* c) { return ThisPtr(); }

	// True if there's definitely no control flow past the statement.
	// The argument governs whether to ignore "break" statements, given
	// they mean two different things depending on whether they're in
	// a loop or a switch.  Also, if we want to know whether flow reaches
	// the *end* of a loop, then we also want to ignore break's, as
	// in that case, they do lead to flow reaching the end.
	virtual bool NoFlowAfter(bool ignore_break) const { return false; }

	// Access to the original statement from which this one is derived,
	// or this one if we don't have an original.  Returns a bare pointer
	// rather than a StmtPtr to emphasize that the access is read-only.
	const Stmt* Original() const { return original ? original->Original() : this; }

	// Designate the given Stmt node as the original for this one.
	void SetOriginal(StmtPtr _orig)
		{
		if ( ! original )
			original = std::move(_orig);
		}

	// A convenience function for taking a newly-created Stmt,
	// making it point to us as the successor, and returning it.
	//
	// Takes a Stmt* rather than a StmtPtr to de-clutter the calling
	// code, which is always passing in "new XyzStmt(...)".  This
	// call, as a convenient side effect, transforms that bare pointer
	// into a StmtPtr.
	virtual StmtPtr SetSucc(Stmt* succ)
		{
		succ->SetOriginal({NewRef{}, this});
		return {AdoptRef{}, succ};
		}

	const detail::Location* GetLocationInfo() const override
		{
		if ( original )
			return original->GetLocationInfo();
		else
			return Obj::GetLocationInfo();
		}

	// Access script optimization information associated with
	// this statement.
	StmtOptInfo* GetOptInfo() const { return opt_info; }

	// Returns the number of statements created since the last reset.
	static int GetNumStmts() { return num_stmts; }

	// Clears the number of statements created.
	static void ResetNumStmts() { num_stmts = 0; }

protected:
	explicit Stmt(StmtTag arg_tag);

	// Helper function called after reductions to perform canonical
	// actions.
	StmtPtr TransformMe(StmtPtr new_me, Reducer* c);

	void AddTag(ODesc* d) const;
	virtual void StmtDescribe(ODesc* d) const;
	void DescribeDone(ODesc* d) const;

	StmtTag tag;
	int breakpoint_count; // how many breakpoints on this statement

	// FIXME: Learn the exact semantics of mutable.
	mutable double last_access; // time of last execution
	mutable uint32_t access_count; // number of executions

	// The original statement from which this statement was
	// derived, if any.  Used as an aid for generating meaningful
	// and correctly-localized error messages.
	StmtPtr original = nullptr;

	// Information associated with the Stmt for purposes of
	// script optimization.
	StmtOptInfo* opt_info;

	// Number of statements created thus far.
	static int num_stmts;
	};

	} // namespace detail
	} // namespace zeek