/* Copyright (c) 2014, Google Inc.
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
 * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
 * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
 * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */

#ifndef OPENSSL_HEADER_ENGINE_H
#define OPENSSL_HEADER_ENGINE_H

#include <openssl/base.h>

#if defined(__cplusplus)
extern "C" {
#endif


/* Engines are collections of methods. Methods are tables of function pointers,
 * defined for certain algorithms, that allow operations on those algorithms to
 * be overridden via a callback. This can be used, for example, to implement an
 * RSA* that forwards operations to a hardware module.
 *
 * Methods are reference counted but |ENGINE|s are not. When creating a method,
 * you should zero the whole structure and fill in the function pointers that
 * you wish before setting it on an |ENGINE|. Any functions pointers that
 * are NULL indicate that the default behaviour should be used. */


/* Allocation and destruction. */

/* ENGINE_new returns an empty ENGINE that uses the default method for all
 * algorithms. */
OPENSSL_EXPORT ENGINE *ENGINE_new(void);

/* ENGINE_free decrements the reference counts for all methods linked from
 * |engine| and frees |engine| itself. */
OPENSSL_EXPORT void ENGINE_free(ENGINE *engine);


/* Method accessors.
 *
 * Method accessors take a method pointer and the size of the structure. The
 * size allows for ABI compatibility in the case that the method structure is
 * extended with extra elements at the end. Methods are always copied by the
 * set functions.
 *
 * Set functions return one on success and zero on allocation failure. */

OPENSSL_EXPORT int ENGINE_set_DH_method(ENGINE *engine, const DH_METHOD *method,
                                        size_t method_size);
OPENSSL_EXPORT DH_METHOD *ENGINE_get_DH_method(const ENGINE *engine);

OPENSSL_EXPORT int ENGINE_set_DSA_method(ENGINE *engine,
                                         const DSA_METHOD *method,
                                         size_t method_size);
OPENSSL_EXPORT DSA_METHOD *ENGINE_get_DSA_method(const ENGINE *engine);

OPENSSL_EXPORT int ENGINE_set_RSA_method(ENGINE *engine,
                                         const RSA_METHOD *method,
                                         size_t method_size);
OPENSSL_EXPORT RSA_METHOD *ENGINE_get_RSA_method(const ENGINE *engine);

OPENSSL_EXPORT int ENGINE_set_ECDSA_method(ENGINE *engine,
                                           const ECDSA_METHOD *method,
                                           size_t method_size);
OPENSSL_EXPORT ECDSA_METHOD *ENGINE_get_ECDSA_method(const ENGINE *engine);


/* Generic method functions.
 *
 * These functions take a void* type but actually operate on all method
 * structures. */

/* METHOD_ref increments the reference count of |method|. */
OPENSSL_EXPORT void METHOD_ref(void *method);

/* METHOD_unref decrements the reference count of |method| and frees it if the
 * reference count drops to zero. */
OPENSSL_EXPORT void METHOD_unref(void *method);


/* Private functions. */

/* openssl_method_common_st contains the common part of all method structures.
 * This must be the first member of all method structures. */
struct openssl_method_common_st {
  int references;
  char is_static;
};


#if defined(__cplusplus)
}  /* extern C */
#endif

#endif  /* OPENSSL_HEADER_ENGINE_H */