57 lines
1.9 KiB
C++
57 lines
1.9 KiB
C++
/** @file ParserStack.hpp
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*
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* @author Roland Conybeare, Jan 2026
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**/
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#pragma once
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#include "SyntaxStateMachine.hpp"
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#include <xo/arena/DArena.hpp>
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#include <xo/facet/obj.hpp>
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namespace xo {
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namespace scm {
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/** @brief A stack of expression state machines
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*
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* Each state machine is dedicated to a particular syntax instance.
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* The innermost machine is in xsm; machines for surrounding expressions
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* are in progressively removed frames reached via parent links.
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**/
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class ParserStack {
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public:
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using DArena = xo::mm::DArena;
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public:
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ParserStack(DArena::Checkpoint ckp,
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obj<ASyntaxStateMachine> ssm,
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ParserStack * parent);
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/** create new top of stack for syntax @p ssm, using memory from @p mm.
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* previous stack given by @p parent
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**/
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static ParserStack * push(ParserStack * stack,
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DArena & mm,
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obj<ASyntaxStateMachine> ssm);
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/** unwind effect of last call to @ref push **/
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static ParserStack * pop(ParserStack * stack,
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DArena & mm);
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DArena::Checkpoint ckp() const noexcept { return ckp_; }
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obj<ASyntaxStateMachine> top() const noexcept { return ssm_; }
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ParserStack * parent() const noexcept { return parent_; }
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private:
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/** stack pointer: top of stack just before this instance created **/
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DArena::Checkpoint ckp_;
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/** top of parsing stack: always non-null **/
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obj<ASyntaxStateMachine> ssm_;
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/** remainder of parsing stack excluding top **/
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ParserStack * parent_ = nullptr;
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};
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} /*namespace scm*/
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} /*namespace xo*/
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/* end ParserStack.hpp */
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