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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/>.
*/
#include "alee.hpp"
Error (*Parser::customParse)(State&, Word) = nullptr;
LIBALEE_SECTION
Error Parser::parse(State& state, const char *str)
{
auto addr = Dictionary::Input;
// Set source and input length
const auto len = static_cast<Cell>(strlen(str));
state.dict.write(addr, 0);
state.dict.write(Dictionary::SourceLen, len);
// Fill input buffer with string contents
addr += sizeof(Cell);
while (*str)
state.dict.writebyte(addr++, *str++);
// Zero the remaining input buffer
while (addr < Dictionary::Input + Dictionary::InputCells)
state.dict.writebyte(addr++, '\0');
return parseSource(state);
}
LIBALEE_SECTION
Error Parser::parseSource(State& state)
{
auto err = Error::none;
while (err == Error::none && state.dict.hasInput())
err = parseWord(state, state.dict.input());
return err;
}
LIBALEE_SECTION
Error Parser::parseWord(State& state, Word word)
{
bool imm;
Addr ins;
// Search order: dictionary, core word-set, number, custom parse.
ins = state.dict.find(word);
if (ins == 0) {
auto cw = CoreWords::findi(state, word);
if (cw < 0) {
auto r = parseNumber(state, word);
if (r != Error::none)
return customParse ? customParse(state, word) : r;
else
return r;
} else {
ins = cw;
imm = ins == CoreWords::token(";");
}
} 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;
}
LIBALEE_SECTION
Error Parser::parseNumber(State& state, Word word)
{
const auto base = state.dict.read(Dictionary::Base);
DoubleCell result = 0;
auto it = word.begin(&state.dict);
bool inv = *it == '-';
if (inv)
++it;
const auto end = word.end(&state.dict);
for (uint8_t c; it != end; ++it) {
c = *it;
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 (inv)
result *= -1;
processLiteral(state, static_cast<Cell>(result));
return Error::none;
}
LIBALEE_SECTION
void Parser::processLiteral(State& state, Cell value)
{
if (state.compiling()) {
constexpr auto ins = CoreWords::token("_lit");
// Literal compression: opcodes between WordCount and Begin are unused,
// so we assign literals to them to save space. Opcode "WordCount"
// pushes zero to the stack, "WordCount + 1" pushes a one, etc.
const Cell maxlit = Dictionary::Begin - CoreWords::WordCount;
if (value >= 0 && value < maxlit)
value += CoreWords::WordCount;
else
state.dict.add(ins);
state.dict.add(value);
} else {
state.push(value);
}
}
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