108 lines
3.7 KiB
C++
108 lines
3.7 KiB
C++
/** @file VirtualSchematikaMachine.hpp **/
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#pragma once
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#include "VsmInstr.hpp"
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#include "SchematikaError.hpp"
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#include "Env.hpp"
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#include "xo/expression/Expression.hpp"
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#include "xo/object/ObjectConverter.hpp"
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#include "xo/alloc/Object.hpp"
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namespace xo {
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namespace scm {
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/** @brief state that may be shared across VirtualSchematikaMachine instances **/
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struct VirtualSchematikaMachineFlyweight {
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explicit VirtualSchematikaMachineFlyweight(gc::IAlloc * mm,
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gp<Env> env);
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/** memory allocator for interpreter operation. **/
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gc::IAlloc * object_mm_ = nullptr;
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/** global environment **/
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gp<Env> toplevel_env_;
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/** convert TaggedPtr->Object **/
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xo::obj::ObjectConverter object_converter_;
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};
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/** @class VirtualSchematikaMachine
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* @brief Virtual machine implementing a Schematika interpreter
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*
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**/
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class VirtualSchematikaMachine {
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public:
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using IAlloc = xo::gc::IAlloc;
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public:
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VirtualSchematikaMachine(IAlloc * mm, gp<Env> toplevel_env);
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~VirtualSchematikaMachine();
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/** evaluate expression @p expr.
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* borrows calling thread until completion
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* return [value, error]. error ignored unless value is nullptr.
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* conversely when value is nullptr, error gives details of original
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* error.
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*
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* Evaluate schematika expression @p expr in environment @p env
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**/
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std::pair<gp<Object>, SchematikaError> eval(bp<Expression> expr, gp<Env> env);
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/** evaluate expression @p expr in toplevel environment **/
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std::pair<gp<Object>, SchematikaError> toplevel_eval(bp<Expression> expr);
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private:
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/** Not moveable or copyable.
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* One constraint is member variables added to flyweight_.object_mm_
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* as GC roots, with no provision for unwinding later.
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**/
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VirtualSchematikaMachine(const VirtualSchematikaMachine &) = delete;
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VirtualSchematikaMachine(VirtualSchematikaMachine &&) = delete;
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/** borrow calling thread to run schematika machine
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* indefinitely, or until null continuation
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**/
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void run();
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/** execute vsm instruction in program counter.
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* Note: may possibly be able to replace with just opcode
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**/
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void execute_one();
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/** interpret literal constant expression **/
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void constant_op();
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/** goto error state with message @p err **/
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void report_error(const std::string & err);
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/** implementation class; contains instruction implementations **/
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friend struct VsmOps;
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private:
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/** program counter.
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* (Perhaps replace with VsmInstr::Opcode ?)
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**/
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const VsmInstr * pc_ = nullptr;
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/** expression **/
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rp<Expression> expr_;
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/** holds bindings for all schematika variables **/
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gp<Env> env_;
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/** non-error result value from eval() / apply() **/
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gp<Object> value_;
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/** error result value from eval() / apply() **/
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SchematikaError error_;
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/** continuation
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* (Perhaps replace with VsmInstr::Opcode ?)
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**/
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const VsmInstr * cont_ = nullptr;
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/** possibly-shared data **/
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VirtualSchematikaMachineFlyweight flyweight_;
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};
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} /*namespace scm*/
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} /*namespace xo*/
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/* end VirtualSchematikaMachine.hpp */
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