cont.h

/*
 cont.h - continuations support for Xtensa call0 ABI
 Copyright (c) 2014 Ivan Grokhotkov. All rights reserved.
 This file is part of the esp8266 core for Arduino environment.

 This library 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 2.1 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
 Lesser General Public License for more details.

 You should have received a copy of the GNU Lesser 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
 */

#ifndef CONT_H_
#define CONT_H_

#include <stdbool.h>

#ifndef CONT_STACKSIZE
#define CONT_STACKSIZE 4096
#endif

typedef struct cont_ {
        void (*pc_ret)(void);
        unsigned* sp_ret;

        void (*pc_yield)(void);
        unsigned* sp_yield;

        unsigned* stack_end;
        unsigned unused1;
        unsigned unused2;
        unsigned stack_guard1;

        unsigned stack[CONT_STACKSIZE / 4];

        unsigned stack_guard2;
        unsigned* struct_start;
} cont_t;

// Initialize the cont_t structure before calling cont_run
void cont_init(cont_t*);

// Run function pfn in a separate stack, or continue execution
// at the point where cont_yield was called
void cont_run(cont_t*, void (*pfn)(void));

// Return to the point where cont_run was called, saving the
// execution state (registers and stack)
void cont_yield(cont_t*);

// Check guard bytes around the stack. Return 0 in case everything is ok,
// return 1 if guard bytes were overwritten.
int cont_check(cont_t* cont);

// Go through stack and check how many bytes are most probably still unchanged
// and thus weren't used by the user code. i.e. that stack space is free. (high water mark)
int cont_get_free_stack(cont_t* cont);

// Check if yield() may be called. Returns true if we are running inside
// continuation stack
bool cont_can_yield(cont_t* cont);

#endif /* CONT_H_ */