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138 lines
3.4 KiB
C++
138 lines
3.4 KiB
C++
/**
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* Alee Forth: A portable and concise Forth implementation in modern C++.
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* Copyright (C) 2023 Clyne Sullivan <clyne@bitgloo.com>
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Lesser General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public License
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* along with this program. If not, see <https://www.gnu.org/licenses/>.
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*/
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#ifndef ALEEFORTH_STATE_HPP
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#define ALEEFORTH_STATE_HPP
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#include "dictionary.hpp"
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#include "types.hpp"
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#include <csetjmp>
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#include <cstddef>
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constexpr unsigned DataStackSize = 64;
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constexpr unsigned ReturnStackSize = 64;
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class State
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{
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using InputFunc = void (*)(State&);
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struct Context {
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Addr ip = 0;
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std::jmp_buf jmpbuf = {};
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};
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public:
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Dictionary& dict;
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constexpr State(Dictionary& d, InputFunc i):
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dict(d), inputfunc(i), context() {}
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/**
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* Begins execution at the given execution token.
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* If the token is a CoreWord, this function exits after its execution.
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* Otherwise, execution continues until the word's execution completes.
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* Encountering an error will cause this function to exit immediately.
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*/
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Error execute(Addr);
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/**
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* Clears the data and return stacks, sets ip to zero, and clears the
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* compiling flag.
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*/
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void reset();
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Addr& ip() noexcept {
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return context.ip;
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}
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void input() noexcept {
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inputfunc(*this);
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}
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bool compiling() const;
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void compiling(bool);
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std::size_t size() const noexcept;
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std::size_t rsize() const noexcept;
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/**
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* Saves execution state so that a new execution can begin.
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* Used for EVALUATE.
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*/
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Context save();
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/**
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* Reloads the given execution state.
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*/
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void load(const Context&);
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inline void push(Cell value) {
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verify(dsp < dstack + DataStackSize, Error::push);
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*dsp++ = value;
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}
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inline Cell pop() {
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verify(dsp > dstack, Error::pop);
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return *--dsp;
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}
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inline void pushr(Cell value) {
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verify(rsp < rstack + ReturnStackSize, Error::pushr);
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*rsp++ = value;
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}
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inline Cell popr() {
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verify(rsp > rstack, Error::popr);
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return *--rsp;
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}
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inline Cell& top() {
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verify(dsp > dstack, Error::top);
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return *(dsp - 1);
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}
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inline Cell& pick(std::size_t i) {
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verify(dsp - i > dstack, Error::pick);
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return *(dsp - i - 1);
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}
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// Advances the instruction pointer and returns that cell's contents.
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inline Cell beyondip() {
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context.ip += sizeof(Cell);
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return dict.read(context.ip);
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}
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inline void verify(bool condition, Error error) {
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if (!condition)
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std::longjmp(context.jmpbuf, static_cast<int>(error));
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}
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private:
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InputFunc inputfunc; // User-provided function to collect "stdin" input.
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Context context;
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Cell dstack[DataStackSize] = {};
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Cell rstack[ReturnStackSize] = {};
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Cell *dsp = dstack;
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Cell *rsp = rstack;
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};
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#endif // ALEEFORTH_STATE_HPP
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