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/**
* Alee Forth: A portable and concise Forth implementation in modern C++.
* Copyright (C) 2023 Clyne Sullivan <clyne@bitgloo.com>
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
#ifndef ALEEFORTH_STATE_HPP
#define ALEEFORTH_STATE_HPP
#include "dictionary.hpp"
#include "types.hpp"
#include <csetjmp>
#include <cstddef>
#include <tuple>
constexpr unsigned DataStackSize = 16;
constexpr unsigned ReturnStackSize = 16;
class State
{
friend class CoreWords;
public:
Addr ip = 0;
Dictionary& dict;
void (*input)(State&); // User-provided function to collect "stdin" input.
constexpr State(Dictionary& d, void (*i)(State&)):
dict(d), input(i) {}
bool compiling() const;
void compiling(bool);
/**
* Begins execution at the given execution token.
* If the token is a CoreWord, this function exits after its execution.
* Otherwise, execution continues until the word's execution completes.
* Encountering an error will cause this function to exit immediately.
*/
Error execute(Addr);
/**
* Clears the data and return stacks, sets ip to zero, and clears the
* compiling flag.
*/
void reset();
std::size_t size() const noexcept;
std::size_t rsize() const noexcept;
inline void push(Cell value) {
verify(dsp < dstack + DataStackSize, Error::push);
*dsp++ = value;
}
inline Cell pop() {
verify(dsp > dstack, Error::pop);
return *--dsp;
}
inline void pushr(Cell value) {
verify(rsp < rstack + ReturnStackSize, Error::pushr);
*rsp++ = value;
}
inline Cell popr() {
verify(rsp > rstack, Error::popr);
return *--rsp;
}
inline Cell& top() {
verify(dsp > dstack, Error::top);
return *(dsp - 1);
}
inline Cell& pick(std::size_t i) {
verify(dsp - i > dstack, Error::pick);
return *(dsp - i - 1);
}
// Advances the instruction pointer and returns that cell's contents.
inline Cell beyondip() {
ip += sizeof(Cell);
return dict.read(ip);
}
private:
Cell dstack[DataStackSize] = {};
Cell rstack[ReturnStackSize] = {};
Cell *dsp = dstack;
Cell *rsp = rstack;
std::jmp_buf jmpbuf = {}; // Used when catching execution errors.
inline void verify(bool condition, Error error) {
if (!condition)
std::longjmp(jmpbuf, static_cast<int>(error));
}
/**
* Saves execution state so that a new execution can begin.
* Used for EVALUATE.
*/
std::pair<Addr, std::jmp_buf> save();
/**
* Reloads the given execution state.
*/
void load(const std::pair<Addr, std::jmp_buf>&);
};
#endif // ALEEFORTH_STATE_HPP
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