300 lines
9.7 KiB
C++
300 lines
9.7 KiB
C++
/** @file VirtualSchematikaMachine.hpp
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*
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* @author Roland Conybare, Jan 2026
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**/
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#pragma once
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#include "VsmConfig.hpp"
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#include "VsmInstr.hpp"
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#include "VsmFrame.hpp"
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#include "DLocalEnv.hpp"
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#include "DGlobalEnv.hpp"
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#include <xo/object2/RuntimeError.hpp>
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#include <xo/reader2/SchematikaReader.hpp>
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#include <xo/expression2/Expression.hpp>
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#include <xo/gc/GCObject.hpp>
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#include <xo/alloc2/abox.hpp>
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namespace xo {
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namespace scm {
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#ifdef OBSOLETE // see DVsmError
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// TODO: move error to collected space?
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// or special arena?
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//
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struct EvaluationError {
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/** source location (in vsm implementation) at which error identified **/
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std::string_view src_function_;
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/** error description (allocated from ErrorArena) **/
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std::string_view error_description_;
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// TODO: info about location in schematika source
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};
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#endif
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/** similar to @ref xo::scm::ReaderResult **/
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struct VsmResult {
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using AGCObject = xo::mm::AGCObject;
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using span_type = xo::mm::span<const char>;
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VsmResult() = default;
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explicit VsmResult(obj<AGCObject> value) : result_{value} {}
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explicit VsmResult(TokenizerError err) : result_{err} {}
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bool is_value() const { return std::holds_alternative<obj<AGCObject>>(result_); }
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bool is_tk_error() const { return std::holds_alternative<TokenizerError>(result_); }
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bool is_eval_error() const;
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const obj<AGCObject> * value() const { return std::get_if<obj<AGCObject>>(&result_); }
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/** result of evaluating first expression encountered in input **/
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std::variant<obj<AGCObject>, TokenizerError> result_;
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};
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/** vsm result + reamining span **/
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struct VsmResultExt : public VsmResult {
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using span_type = VsmResult::span_type;
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VsmResultExt() = default;
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VsmResultExt(const VsmResult & result, span_type rem) : VsmResult{result}, remaining_{rem} {}
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/** unconsumed portion of input **/
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VsmResult::span_type remaining_;
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};
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/** @class VirtualSchematikaMachine
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* @brief virtual machine for schematika
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**/
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class VirtualSchematikaMachine {
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public:
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// will be DArenaVector<obj<StackFrame>> probably
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using Stack = void *;
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using AAllocator = xo::mm::AAllocator;
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using AGCObject = xo::mm::AGCObject;
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using MemorySizeVisitor = xo::mm::MemorySizeVisitor;
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using span_type = xo::mm::span<const char>;
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public:
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/** @p config. configuration
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* @p aux_mm. Allocator for miscellaneous dataN
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* owned by this VSM.
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**/
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VirtualSchematikaMachine(const VsmConfig & config,
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obj<AAllocator> aux_mm);
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/** non-trivial dtor because of @ref reader_
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* indirect dependency on DGlobalSymtab
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**/
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~VirtualSchematikaMachine() = default;
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/** allocator for schematika data **/
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obj<AAllocator> allocator() const noexcept;
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/** allocator for runtime errors **/
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obj<AAllocator> error_allocator() const noexcept;
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/** visit vsm-owned memory pools; call visitor(info) for each **/
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void visit_pools(const MemorySizeVisitor & visitor) const;
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/** begin interactive session. **/
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void begin_interactive_session();
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/** begin batch session **/
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void begin_batch_session();
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/** consume input @p input_cstr.
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* Require: must first start interactive/batch session
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**/
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VsmResultExt read_eval_print(span_type input_span, bool eof);
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/** evaluate expression @p expr
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* Require: must first start interactive/batch session
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**/
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VsmResult start_eval(obj<AExpression> expr);
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/** borrow calling thread to run indefinitely,
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* until halt instruction
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**/
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void run();
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/** execute vsm instruction in @ref pc_.
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* @retval instruction count. 1 unless pc_ is halt.
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**/
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bool execute_one();
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private:
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/** Require:
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* - expression in @ref expr_
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**/
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void _do_eval_op();
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/** evaluate a constant expression
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* Require:
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* - expression in @ref expr_
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**/
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void _do_eval_constant_op();
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/** evaluate a define-expression
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* Require:
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* - expression in @ref expr_
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**/
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void _do_eval_define_op();
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/** evaluate a lambda expression
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* Require:
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* - expression in @ref expr_
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**/
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void _do_eval_lambda_op();
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/** evaluate variable expression (definition)
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* Require:
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* - expression in @ref expr_
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**/
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void _do_eval_variable_op();
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/** evaluate a variable reference (use after definition)
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* Require:
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* - expression in @ref expr_
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**/
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void _do_eval_varref_op();
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/** evaluate an apply expression
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* Require:
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* - expression in @ref expr_
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**/
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void _do_eval_apply_op();
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/** evaluate an if-else expression
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* Require:
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* - expression in @ref expr_
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**/
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void _do_eval_if_else_op();
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/** evaluate a sequence expression
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* Require:
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* - expression in @ref expr_
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**/
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void _do_eval_sequence_op();
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/** apply a function to evaluated arguments **/
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void _do_apply_op();
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/** evaluate arguments on behalf of a function call
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* Require:
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* - expression value in @ref value_
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* - stack:
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* [0] VsmEvalArgsFrame
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* [1] VsmApplyFrame
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* ...
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**/
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void _do_evalargs_op();
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/** call closure @ref fn_ with arguments @ref args_ **/
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void _do_call_closure_op();
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/** call primitive @ref fn_ with arguments @ref args_ **/
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void _do_call_primitive_op();
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/** perform assignment after evaluating
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* the rhs of a define-expr
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**/
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void _do_def_cont_op();
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/** restore registers from stack frame
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* (specifically: local_env_, stack_, cont_)
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* after invoking a schematika closure
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**/
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void _do_apply_cont_op();
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/** proceed with if- or else- branch of an if-else expression
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* after evaluating test condition
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**/
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void _do_ifelse_cont_op();
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/** loop continuation after evaluating element of a SequenceExpr **/
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void _do_seq_cont_op();
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private:
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/*
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* Some registers are preserved by evaluation:
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* stack_
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* cont_
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* local_env_
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*
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* Other registers not preserved
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* pc_
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* expr_
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* fn_
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* args_
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* value_
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*/
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/** configuration **/
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VsmConfig config_;
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#ifdef NOT_YET
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/** allocator (likely DArena) for globals.
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* For example DArenaHashMap in global symta.
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**/
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obj<AAllocator> aux_mm_;
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#endif
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/** allocator (likely DX1Collector or similar) for
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* expressions and values. Schemaatika reader will use this also
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**/
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abox<AAllocator> mm_;
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/** Sidecar allocator for error reporting.
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* Separate to mitigate interference with @ref mm_
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* (separate memory so we can for example report
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* an out-of-memory error).
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* Likely DArena or similar
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**/
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abox<AAllocator> error_mm_;
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/** runtime context for this vsm.
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* For example, provides allocator to primitives
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**/
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abox<ARuntimeContext> rcx_;
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// consider separate allocator (which _may_ turn out to be the same)
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// for VM stack. Only works for code that doesn't rely on fancy
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// lexical scoping
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// consider separate allocator for reader (i.e. program code)
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// and data (program execution)
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/** reader: text -> expression **/
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SchematikaReader reader_;
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/** program counter **/
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VsmInstr pc_ = VsmInstr::c_halt;
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/** stack pointer **/
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obj<AGCObject> stack_;
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/** expression register **/
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obj<AExpression> expr_;
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/** environment pointer. Maintains bindings
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* for global variables.
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**/
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DGlobalEnv * global_env_ = nullptr;
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/** environment pointer. Provides bindings
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* for surrounding lexical scope at this point
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* in execution
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**/
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DLocalEnv * local_env_ = nullptr;
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/** evaluated function to call **/
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obj<AGCObject> fn_;
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/** evaluated argument list **/
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DArray * args_;
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/** result register **/
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VsmResult value_;
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/** continuation register **/
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VsmInstr cont_ = VsmInstr::c_halt;
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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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