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alee-forth/libalee/parser.cpp

132 lines
3.3 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 "ctype.hpp"
#include "parser.hpp"
Error Parser::parse(State& state, const char *str)
{
auto addr = Dictionary::Input;
Cell len = 0;
for (auto ptr = str; *ptr; ++ptr)
++len;
state.dict.write(addr, 0);
state.dict.write(Dictionary::SourceLen, len);
addr += sizeof(Cell);
while (*str)
state.dict.writebyte(addr++, *str++);
while (addr < Dictionary::Input + Dictionary::InputCells)
state.dict.writebyte(addr++, '\0');
return parseSource(state);
}
Error Parser::parseSource(State& state)
{
auto word = state.dict.input();
while (word.size() > 0) {
if (auto ret = parseWord(state, word); ret != Error::none)
return ret;
word = state.dict.input();
}
return Error::none;
}
Error Parser::parseWord(State& state, Word word)
{
bool imm;
Addr ins = state.dict.find(word);
if (ins == 0) {
auto cw = CoreWords::findi(state, word);
if (cw < 0) {
return parseNumber(state, word);
} else {
ins = cw;
imm = ins == CoreWords::Semicolon;
}
} else {
imm = state.dict.read(ins) & Dictionary::Immediate;
ins = state.dict.getexec(ins);
}
if (state.compiling() && !imm)
state.dict.add(ins);
else if (auto stat = state.execute(ins); stat != Error::none)
return stat;
return Error::none;
}
Error Parser::parseNumber(State& state, Word word)
{
const auto base = state.dict.read(Dictionary::Base);
DoubleCell result = 0;
auto i = word.start;
bool inv;
char c;
c = state.dict.readbyte(i);
if (inv = c == '-'; inv)
c = state.dict.readbyte(++i);
do {
if (isdigit(c)) {
result *= base;
result += c - '0';
} else if (isalpha(c) && base > 10) {
result *= base;
result += 10 + c - (isupper(c) ? 'A' : 'a');
} else {
return Error::noword;
}
if (++i < word.wend)
c = state.dict.readbyte(i);
} while (i < word.wend);
if (inv)
result *= -1;
auto value = static_cast<Cell>(result);
if (state.compiling()) {
auto ins = CoreWords::findi("_lit");
const Cell maxlit = Dictionary::Begin - CoreWords::WordCount;
if (value >= 0 && value < maxlit) {
state.dict.add(value + CoreWords::WordCount);
} else {
state.dict.add(ins);
state.dict.add(value);
}
} else {
state.push(value);
}
return Error::none;
}