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// sprit-forth: A portable subroutine-threaded Forth.
// Copyright (C) 2023 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.
#include "core.hpp"
#include "state.hpp"
#include <csetjmp>
#include <cstring>
FuncList IP = nullptr;
std::array<Cell, DictSize> DICT;
Cell& BASE = DICT[DIdxBase];
Cell& HERE = DICT[DIdxHere];
Cell& LATEST = DICT[DIdxLatest];
Cell& STATE = DICT[DIdxState];
static std::jmp_buf jmpbuf;
static Cell *SP = DICT.data() + DICT.size() - DS;
static Cell *RP = DICT.data() + DICT.size() - DS - RS;
void push(Cell value) {
if (SP >= DICT.data() + DICT.size())
std::longjmp(jmpbuf, static_cast<int>(Error::push));
*++SP = value;
}
Cell pop() {
if (SP - 1 < DICT.data() + DICT.size() - DS)
std::longjmp(jmpbuf, static_cast<int>(Error::pop));
return *SP--;
}
Cell *sp() {
return SP;
}
void rpush(Cell value) {
if (RP >= DICT.data() + DICT.size() - DS)
std::longjmp(jmpbuf, static_cast<int>(Error::rpush));
*++RP = value;
}
Cell rpop() {
if (RP - 1 < DICT.data() + DICT.size() - DS - RS)
std::longjmp(jmpbuf, static_cast<int>(Error::rpop));
return *RP--;
}
Cell *rp() {
return RP;
}
Error executor(FuncList *list)
{
auto result = static_cast<Error>(setjmp(jmpbuf));
FuncList body;
if (static_cast<int>(result) == 0) {
result = Error::none;
// We are given the pointer to a list of function pointers.
// Dereference once to retrieve the function pointer list.
// We do not work with IP initially since it needs to be set to zero if
// this is a top-level call/execution.
body = *list;
// Enter the execution loop.
goto entry;
// Execution continues so long as IP is not zero.
// If this is a top-level execution of a pre-defined word, then IP will
// remain zero'd and the loop will immediately exit.
// If this is a defined word's execution, then its "call" will overwrite
// IP (and push the initial zero-IP to the return stack); execution will
// continue until we return to the zero-IP.
while (IP) {
// Retrieve next function pointer list.
body = (FuncList)*++IP;
entry:
// Dereference `body` to get the first function in the list.
// This is casted to take a FuncList as an argument since defined
// words need to know their addresses so that they can perform
// their "calls".
// If the word is pre-defined then the argument will simply be
// ignored.
auto func = (void (*)(FuncList))*body;
func(body);
}
}
return result;
}
Error execute1(Word *word)
{
// IP must initially be zero if executing a word at the top level.
IP = 0;
return executor(&word->list);
}
Word *find(const char *s, int len)
{
for (auto w = (Word *)LATEST; w; w = w->link) {
if (len == (int)strlen(w->name) && strncmp(s, w->name, len) == 0)
return w;
}
return nullptr;
}
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