/*
   +----------------------------------------------------------------------+
   | Zend Engine                                                          |
   +----------------------------------------------------------------------+
   | Copyright © Zend Technologies Ltd., a subsidiary company of          |
   |     Perforce Software, Inc., and Contributors.                       |
   +----------------------------------------------------------------------+
   | This source file is subject to the Modified BSD License that is      |
   | bundled with this package in the file LICENSE, and is available      |
   | through the World Wide Web at <https://www.php.net/license/>.        |
   |                                                                      |
   | SPDX-License-Identifier: BSD-3-Clause                                |
   +----------------------------------------------------------------------+
   | Authors: Aaron Piotrowski <aaron@trowski.com>                        |
   |          Martin Schröder <m.schroeder2007@gmail.com>                 |
   +----------------------------------------------------------------------+
*/

#ifndef ZEND_FIBERS_H
#define ZEND_FIBERS_H

#include "zend_API.h"
#include "zend_types.h"

#define ZEND_FIBER_GUARD_PAGES 1

#define ZEND_FIBER_DEFAULT_C_STACK_SIZE (4096 * (((sizeof(void *)) < 8) ? 256 : 512))
#define ZEND_FIBER_VM_STACK_SIZE (1024 * sizeof(zval))

BEGIN_EXTERN_C()

typedef enum {
	ZEND_FIBER_STATUS_INIT,
	ZEND_FIBER_STATUS_RUNNING,
	ZEND_FIBER_STATUS_SUSPENDED,
	ZEND_FIBER_STATUS_DEAD,
} zend_fiber_status;

typedef enum {
	ZEND_FIBER_FLAG_THREW     = 1 << 0,
	ZEND_FIBER_FLAG_BAILOUT   = 1 << 1,
	ZEND_FIBER_FLAG_DESTROYED = 1 << 2,
} zend_fiber_flag;

typedef enum {
	ZEND_FIBER_TRANSFER_FLAG_ERROR = 1 << 0,
	ZEND_FIBER_TRANSFER_FLAG_BAILOUT = 1 << 1
} zend_fiber_transfer_flag;

void zend_register_fiber_ce(void);
void zend_fiber_init(void);
void zend_fiber_shutdown(void);

extern ZEND_API zend_class_entry *zend_ce_fiber;

typedef struct _zend_fiber_stack zend_fiber_stack;

/* Encapsulates data needed for a context switch. */
typedef struct _zend_fiber_transfer {
	/* Fiber that will be switched to / has resumed us. */
	zend_fiber_context *context;

	/* Value to that should be send to (or was received from) a fiber. */
	zval value;

	/* Bitmask of flags defined in enum zend_fiber_transfer_flag. */
	uint8_t flags;
} zend_fiber_transfer;

/* Coroutine functions must populate the given transfer with a new context
 * and (optional) data before they return. */
typedef void (*zend_fiber_coroutine)(zend_fiber_transfer *transfer);
typedef void (*zend_fiber_clean)(zend_fiber_context *context);

struct _zend_fiber_context {
	/* Pointer to boost.context or ucontext_t data. */
	void *handle;

	/* Pointer that identifies the fiber type. */
	void *kind;

	/* Entrypoint function of the fiber. */
	zend_fiber_coroutine function;

	/* Cleanup function for fiber. */
	zend_fiber_clean cleanup;

	/* Assigned C stack. */
	zend_fiber_stack *stack;

	/* Fiber status. */
	zend_fiber_status status;

	/* Observer state */
	zend_execute_data *top_observed_frame;

	/* Reserved for extensions */
	void *reserved[ZEND_MAX_RESERVED_RESOURCES];
};

struct _zend_fiber {
	/* PHP object handle. */
	zend_object std;

	/* Flags are defined in enum zend_fiber_flag. */
	uint8_t flags;

	/* Native C fiber context. */
	zend_fiber_context context;

	/* Fiber that resumed us. */
	zend_fiber_context *caller;

	/* Fiber that suspended us. */
	zend_fiber_context *previous;

	/* Callback and info / cache to be used when fiber is started. */
	zend_fcall_info fci;
	zend_fcall_info_cache fci_cache;

	/* Current Zend VM execute data being run by the fiber. */
	zend_execute_data *execute_data;

	/* Frame on the bottom of the fiber vm stack. */
	zend_execute_data *stack_bottom;

	/* Active fiber vm stack. */
	zend_vm_stack vm_stack;

	/* Storage for fiber return value. */
	zval result;
};

ZEND_API zend_result zend_fiber_start(zend_fiber *fiber, zval *return_value);
ZEND_API void zend_fiber_resume(zend_fiber *fiber, zval *value, zval *return_value);
ZEND_API void zend_fiber_suspend(zend_fiber *fiber, zval *value, zval *return_value);

/* These functions may be used to create custom fiber objects using the bundled fiber switching context. */
ZEND_API zend_result zend_fiber_init_context(zend_fiber_context *context, void *kind, zend_fiber_coroutine coroutine, size_t stack_size);
ZEND_API void zend_fiber_destroy_context(zend_fiber_context *context);
ZEND_API void zend_fiber_switch_context(zend_fiber_transfer *transfer);
#ifdef ZEND_CHECK_STACK_LIMIT
ZEND_API void* zend_fiber_stack_limit(zend_fiber_stack *stack);
ZEND_API void* zend_fiber_stack_base(zend_fiber_stack *stack);
#endif /* ZEND_CHECK_STACK_LIMIT */

ZEND_API void zend_fiber_switch_block(void);
ZEND_API void zend_fiber_switch_unblock(void);
ZEND_API bool zend_fiber_switch_blocked(void);

END_EXTERN_C()

static zend_always_inline zend_fiber *zend_fiber_from_context(zend_fiber_context *context)
{
	ZEND_ASSERT(context->kind == zend_ce_fiber && "Fiber context does not belong to a Zend fiber");

	return ZEND_CONTAINER_OF(context, zend_fiber, context);
}

static zend_always_inline zend_fiber_context *zend_fiber_get_context(zend_fiber *fiber)
{
	return &fiber->context;
}

#endif
