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alee-forth/parser.cpp

113 lines
3.0 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 <charconv>
#include <cstring>
int Parser::parse(State& state, const char *str)
{
auto addr = Dictionary::Input;
state.dict.write(addr, 0);
state.dict.write(Dictionary::SourceLen, std::strlen(str));
addr += sizeof(Cell);
while (*str)
state.dict.writebyte(addr++, *str++);
while (addr < Dictionary::Input + Dictionary::InputCells)
state.dict.writebyte(addr++, '\0');
return parseSource(state);
}
int Parser::parseSource(State& state)
{
auto word = state.dict.input();
while (word.size() > 0) {
if (auto ret = parseWord(state, word); ret)
return ret;
word = state.dict.input();
}
return 0;
}
int Parser::parseWord(State& state, Word word)
{
int ins, imm;
ins = state.dict.find(word);
if (ins <= 0) {
ins = CoreWords::findi(state, word);
if (ins < 0)
return parseNumber(state, word);
else
imm = ins == CoreWords::Semicolon;
} else {
imm = state.dict.read(ins) & CoreWords::Immediate;
ins = state.dict.getexec(ins);
}
if (state.compiling() && !imm)
state.dict.add(ins);
else if (auto stat = state.execute(ins); stat != State::Error::none)
return static_cast<int>(stat);
return 0;
}
int Parser::parseNumber(State& state, Word word)
{
char buf[MaxCellNumberChars + 1];
unsigned i;
for (i = 0; i < std::min(MaxCellNumberChars, word.size()); ++i)
buf[i] = state.dict.readbyte(word.start + i);
buf[i] = '\0';
auto base = state.dict.read(0);
DoubleCell dl;
auto [ptr, ec] = std::from_chars(buf, buf + i, dl, base);
Cell l = static_cast<Cell>(dl);
if (ec == std::errc() && ptr == buf + i) {
if (state.compiling()) {
auto ins = CoreWords::findi("_lit");
//if (l >= 0 && l < 0xFF) {
// state.dict.add(ins | ((l + 1) << 8));
//} else {
state.dict.add(ins);
state.dict.add(l);
//}
} else {
state.push(l);
}
return 0;
} else {
return UnknownWord;
}
}