sprit-forth/source/state.hpp

// sprit-forth: A portable subroutine-threaded Forth.
// Copyright (C) 2024  Clyne Sullivan <clyne@bitgloo.com>
//
// This library is free software; you can redistribute it and/or modify it
// under the terms of the GNU Library General Public License as published by
// the Free Software Foundation; either version 2 of the License, or (at your
// option) any later version.
//
// This library 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 Library General Public License for
// more details.
//
// You should have received a copy of the GNU Library General Public License
// along with this library; if not, write to the Free Software Foundation, Inc.,
// 51 Franklin St, Fifth Floor, Boston, MA  02110-1301, USA.

#ifndef STATE_HPP
#define STATE_HPP

#include "types.hpp"

constexpr Addr DS = 16; /** Data stack size */
constexpr Addr RS = 16; /** Return stack size */
constexpr auto DictSize = 2048u; /** Dictionary size */

constexpr Addr DIdxBase   = 0;
constexpr Addr DIdxHere   = 1;
constexpr Addr DIdxLatest = 2;
constexpr Addr DIdxState  = 3;
constexpr Addr DIdxCompXt = 4;
constexpr Addr DIdxSource = 5;
constexpr Addr DIdxSrcLen = 6;
constexpr Addr DIdxInBuf  = 7;
constexpr Addr DIdxBegin  = DIdxInBuf + 80 * sizeof(char);

class State
{
    /**
     * Memory chunk used to store the dictoinary and stacks.
     */
    std::array<Cell, DictSize> dict;
    std::array<Cell, DS> ds;
    std::array<Cell, RS> rs;

public:
    Cell *sp        = ds.begin();
    Cell *rp        = rs.begin();
    Cell& base      = dict[DIdxBase];
    Cell& here      = dict[DIdxHere];
    Word *& latest  = *(Word **)&dict[DIdxLatest];
    Cell& state     = dict[DIdxState];
    Cell& compxt    = dict[DIdxCompXt];
    Cell& source    = dict[DIdxSource];
    Cell& sourceu   = dict[DIdxSrcLen];
    unsigned char& sourcei = *(unsigned char *)&dict[DIdxInBuf];

    State() {
        dict[DIdxBase]   = 10;
        dict[DIdxHere]   = (Cell)&dict[DIdxBegin];
        dict[DIdxLatest] = 0;//(Cell)&wordset.back();
        dict[DIdxState]  = 0;
    }

    void add(Word& word) noexcept {
        word.link = latest;
        latest = &word;
    }

    auto dictdata() noexcept {
        return dict.data();
    }

    void push(Cell);
    [[nodiscard]] Cell pop();

    void rpush(Cell);
    [[nodiscard]] Cell rpop();

    /**
     * Looks up the definition of the given word.
     * @param s The name of the word to find
     * @param len The character count of the word's name
     * @return Pointer to the word's definition or nullptr if not found
     */
    [[nodiscard]]
    Word *find(const char *s, int len);
};

extern State Forth;

#endif // STATE_HPP