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// sprit-forth: A portable subroutine-threaded Forth.
// Copyright (C) 2024 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 "executor.hpp"
Executor Exec;
Error Executor::executor(FuncList *list) noexcept
{
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 Executor::execute1(Word *word) noexcept
{
// IP must initially be zero if executing a word at the top level.
ip = nullptr;
return executor(&word->list);
}
[[noreturn]]
void Executor::terminate(Error error) noexcept
{
std::longjmp(jmpbuf, static_cast<int>(error));
}
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