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alee-forth/libalee/corewords.cpp

268 lines
7.8 KiB
C++

/**
* 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/>.
*/
#include "corewords.hpp"
#include "parser.hpp"
#include <utility>
static void find(State&, Word);
static DoubleCell popd(State&);
static void pushd(State&, DoubleCell);
void CoreWords::run(Cell ins, State& state)
{
Cell cell;
DoubleCell dcell;
Addr index = ins;
auto& ip = state.ip();
execute:
if (index >= Dictionary::Begin) {
// must be calling a defined subroutine
state.pushr(ip);
ip = index;
return;
} else switch (index) {
case token("_lit"): // Execution semantics of `literal`.
state.push(state.beyondip());
break;
case token("drop"):
state.pop();
break;
case token("dup"):
state.push(state.top());
break;
case token("swap"):
std::swap(state.top(), state.pick(1));
break;
case token("pick"):
state.push(state.pick(state.pop()));
break;
case token("sys"): // Calls user-defined "system" handler.
user_sys(state);
break;
case token("+"):
cell = state.pop();
state.top() += cell;
break;
case token("-"):
cell = state.pop();
state.top() -= cell;
break;
case token("m*"): // ( n n -- d )
cell = state.pop();
dcell = state.pop() * cell;
pushd(state, dcell);
break;
case token("_/"): // ( d n -- n )
cell = state.pop();
dcell = popd(state);
state.push(static_cast<Cell>(dcell / cell));
break;
case token("_%"): // ( d n -- n )
cell = state.pop();
dcell = popd(state);
state.push(static_cast<Cell>(dcell % cell));
break;
case token("_@"): // ( addr cell? -- n )
if (state.pop())
state.push(state.dict.read(state.pop()));
else
state.push(state.dict.readbyte(state.pop()));
break;
case token("_!"): // ( n addr cell? -- )
cell = state.pop();
if (auto addr = state.pop(); cell)
state.dict.write(addr, state.pop());
else
state.dict.writebyte(addr, state.pop() & 0xFFu);
break;
case token(">r"):
state.pushr(state.pop());
break;
case token("r>"):
state.push(state.popr());
break;
case token("="):
cell = state.pop();
state.top() = state.top() == cell ? -1 : 0;
break;
case token("<"):
cell = state.pop();
state.top() = state.top() < cell ? -1 : 0;
break;
case token("&"):
cell = state.pop();
state.top() &= cell;
break;
case token("|"):
cell = state.pop();
state.top() |= cell;
break;
case token("^"):
cell = state.pop();
state.top() ^= cell;
break;
case token("<<"):
cell = state.pop();
reinterpret_cast<Addr&>(state.top()) <<= static_cast<Addr>(cell);
break;
case token(">>"):
cell = state.pop();
reinterpret_cast<Addr&>(state.top()) >>= static_cast<Addr>(cell);
break;
case token(":"): // Begins definition/compilation of new word.
state.push(state.dict.alignhere());
state.dict.write(Dictionary::CompToken, state.top());
while (!state.dict.hasInput())
state.input();
state.dict.addDefinition(state.dict.input());
state.compiling(true);
break;
case token("_'"): // Collects input word and finds execution token.
while (!state.dict.hasInput())
state.input();
find(state, state.dict.input());
break;
case token("execute"):
index = state.pop();
goto execute;
case token("exit"):
ip = state.popr();
state.verify(ip != 0, Error::exit);
break;
case token(";"): // Concludes word definition.
state.dict.add(token("exit"));
state.compiling(false);
cell = state.pop();
dcell = cell - state.dict.latest();
if (dcell > (1 << (sizeof(Cell) * 8 - 6)) - 1) {
// Large distance to previous entry: store in dedicated cell.
state.dict.write(static_cast<Addr>(cell) + sizeof(Cell),
static_cast<Cell>(dcell));
dcell = ((1 << (sizeof(Cell) * 8 - 6)) - 1);
}
state.dict.write(cell,
(state.dict.read(cell) & 0x1F) | static_cast<Cell>(dcell << 6));
state.dict.latest(cell);
break;
case token("_jmp0"): // Jump if popped value equals zero.
if (state.pop()) {
state.beyondip();
break;
}
[[fallthrough]];
case token("_jmp"): // Unconditional jump.
ip = state.beyondip();
return;
case token("depth"):
state.push(static_cast<Cell>(state.size()));
break;
case token("_rdepth"):
state.push(static_cast<Cell>(state.rsize()));
break;
case token("_in"): // Fetches more input from the user input source.
state.input();
break;
case token("_ev"): // Evaluates words from current input source.
{
const auto st = state.save();
ip = 0;
Parser::parseSource(state);
state.load(st);
}
break;
case token("find"):
cell = state.pop();
find(state,
Word::fromLength(static_cast<Addr>(cell + 1),
state.dict.readbyte(cell)));
break;
case token("_uma"): // ( d u u -- d ): Unsigned multiply-add.
{
const auto plus = state.pop();
cell = state.pop();
dcell = popd(state);
dcell *= static_cast<Addr>(cell);
dcell += static_cast<Addr>(plus);
pushd(state, dcell);
}
break;
case token("u<"):
cell = state.pop();
state.top() = static_cast<Addr>(state.top()) <
static_cast<Addr>(cell) ? -1 : 0;
break;
case token("um/mod"):
cell = state.pop();
dcell = popd(state);
state.push(static_cast<Cell>(
static_cast<DoubleAddr>(dcell) %
static_cast<Addr>(cell)));
state.push(static_cast<Cell>(
static_cast<DoubleAddr>(dcell) /
static_cast<Addr>(cell)));
break;
default: // Compacted literals (WordCount <= ins < Begin).
state.push(ins - WordCount);
break;
}
ip += sizeof(Cell);
}
Cell CoreWords::findi(State& state, Word word)
{
return findi(word.begin(&state.dict), word.size());
}
void find(State& state, Word word)
{
Cell tok = 0;
Cell imm = 0;
if (auto j = state.dict.find(word); j > 0) {
tok = state.dict.getexec(j);
imm = (state.dict.read(j) & Dictionary::Immediate) ? 1 : -1;
} else if (tok = CoreWords::findi(state, word); tok >= 0) {
imm = (tok == CoreWords::token(";")) ? 1 : -1;
}
state.push(tok);
state.push(imm);
}
DoubleCell popd(State& s)
{
DoubleCell dcell = s.pop();
dcell <<= sizeof(Cell) * 8;
dcell |= static_cast<Addr>(s.pop());
return dcell;
}
void pushd(State& s, DoubleCell d)
{
s.push(static_cast<Cell>(d));
s.push(static_cast<Cell>(d >> (sizeof(Cell) * 8)));
}