* to zero and/or cmd_name set to NULL. */
typedef struct ENGINE_CMD_DEFN_st
	{
	unsigned int cmd_num; /* The command number */
	const char *cmd_name; /* The command name itself */
	const char *cmd_desc; /* A short description of the command */
	unsigned int cmd_flags; /* The input the command expects */
	} ENGINE_CMD_DEFN;

/* Generic function pointer */
typedef int (*ENGINE_GEN_FUNC_PTR)(void);
/* Generic function pointer taking no arguments */
typedef int (*ENGINE_GEN_INT_FUNC_PTR)(ENGINE *);
/* Specific control function pointer */
typedef int (*ENGINE_CTRL_FUNC_PTR)(ENGINE *, int, long, void *, void (*f)(void));
/* Generic load_key function pointer */
typedef EVP_PKEY * (*ENGINE_LOAD_KEY_PTR)(ENGINE *, const char *,
	UI_METHOD *ui_method, void *callback_data);
/* These callback types are for an ENGINE's handler for cipher and digest logic.
 * These handlers have these prototypes;
 *   int foo(ENGINE *e, const EVP_CIPHER **cipher, const int **nids, int nid);
 *   int foo(ENGINE *e, const EVP_MD **digest, const int **nids, int nid);
 * Looking at how to implement these handlers in the case of cipher support, if
 * the framework wants the EVP_CIPHER for 'nid', it will call;
 *   foo(e, &p_evp_cipher, NULL, nid);    (return zero for failure)
 * If the framework wants a list of supported 'nid's, it will call;
 *   foo(e, NULL, &p_nids, 0); (returns number of 'nids' or -1 for error)
 */
/* Returns to a pointer to the array of supported cipher 'nid's. If the second
 * parameter is non-NULL it is set to the size of the returned array. */
typedef int (*ENGINE_CIPHERS_PTR)(ENGINE *, const EVP_CIPHER **, const int **, int);
typedef int (*ENGINE_DIGESTS_PTR)(ENGINE *, const EVP_MD **, const int **, int);

/* STRUCTURE functions ... all of these functions deal with pointers to ENGINE
 * structures where the pointers have a "structural reference". This means that
 * their reference is to allowed access to the structure but it does not imply
 * that the structure is functional. To simply increment or decrement the
 * structural reference count, use ENGINE_by_id and ENGINE_free. NB: This is not
 * required when iterating using ENGINE_get_next as it will automatically
 * decrement the structural reference count of the "current" ENGINE and
 * increment the structural reference count of the ENGINE it returns (unless it
 * is NULL). */

/* Get the first/last "ENGINE" type available. */
ENGINE *ENGINE_get_first(void);
ENGINE *ENGINE_get_last(void);
/* Iterate to the next/previous "ENGINE" type (NULL = end of the list). */
ENGINE *ENGINE_get_next(ENGINE *e);
ENGINE *ENGINE_get_prev(ENGINE *e);
/* Add another "ENGINE" type into the array. */
int ENGINE_add(ENGINE *e);
/* Remove an existing "ENGINE" type from the array. */
int ENGINE_remove(ENGINE *e);
/* Retrieve an engine from the list by its unique "id" value. */
ENGINE *ENGINE_by_id(const char *id);
/* Add all the built-in engines. */
void ENGINE_load_openssl(void);
void ENGINE_load_dynamic(void);
#ifndef OPENSSL_NO_STATIC_ENGINE
void ENGINE_load_4758cca(void);
void ENGINE_load_aep(void);
void ENGINE_load_atalla(void);
void ENGINE_load_chil(void);
void ENGINE_load_cswift(void);
#ifndef OPENSSL_NO_GMP
void ENGINE_load_gmp(void);
#endif
void ENGINE_load_nuron(void);
void ENGINE_load_sureware(void);
void ENGINE_load_ubsec(void);
#endif
void ENGINE_load_cryptodev(void);
void ENGINE_load_padlock(void);
void ENGINE_load_builtin_engines(void);

/* Get and set global flags (ENGINE_TABLE_FLAG_***) for the implementation
 * "registry" handling. */
unsigned int ENGINE_get_table_flags(void);
void ENGINE_set_table_flags(unsigned int flags);

/* Manage registration of ENGINEs per "table". For each type, there are 3
 * functions;
 *   ENGINE_register_***(e) - registers the implementation from 'e' (if it has one)
 *   ENGINE_unregister_***(e) - unregister the implementation from 'e'
 *   ENGINE_register_all_***() - call ENGINE_register_***() for each 'e' in the list
 * Cleanup is automatically registered from each table when required, so
 * ENGINE_cleanup() will reverse any "register" operations. */

int ENGINE_register_RSA(ENGINE *e);
void ENGINE_unregister_RSA(ENGINE *e);
void ENGINE_register_all_RSA(void);

int ENGINE_register_DSA(ENGINE *e);
void ENGINE_unregister_DSA(ENGINE *e);
void ENGINE_register_all_DSA(void);

int ENGINE_register_ECDH(ENGINE *e);
void ENGINE_unregister_ECDH(ENGINE *e);
void ENGINE_register_all_ECDH(void);

int ENGINE_register_ECDSA(ENGINE *e);
void ENGINE_unregister_ECDSA(ENGINE *e);
void ENGINE_register_all_ECDSA(void);

int ENGINE_register_DH(ENGINE *e);
void ENGINE_unregister_DH(ENGINE *e);
void ENGINE_register_all_DH(void);

int ENGINE_register_RAND(ENGINE *e);
void ENGINE_unregister_RAND(ENGINE *e);
void ENGINE_register_all_RAND(void);

int ENGINE_register_STORE(ENGINE *e);
void ENGINE_unregister_STORE(ENGINE *e);
void ENGINE_register_all_STORE(void);

int ENGINE_register_ciphers(ENGINE *e);
void ENGINE_unregister_ciphers(ENGINE *e);
void ENGINE_register_all_ciphers(void);

int ENGINE_register_digests(ENGINE *e);
void ENGINE_unregister_digests(ENGINE *e);
void ENGINE_register_all_digests(void);

/* These functions register all support from the above categories. Note, use of
 * these functions can result in static linkage of code your application may not
 * need. If you only need a subset of functionality, consider using more
 * selective initialisation. */
int ENGINE_register_complete(ENGINE *e);
int ENGINE_register_all_complete(void);

/* Send parametrised control commands to the engine. The possibilities to send
 * down an integer, a pointer to data or a function pointer are provided. Any of
 * the parameters may or may not be NULL, depending on the command number. In
 * actuality, this function only requires a structural (rather than functional)
 * reference to an engine, but many control commands may require the engine be
 * functional. The caller should be aware of trying commands that require an
 * operational ENGINE, and only use functional references in such situations. */
int ENGINE_ctrl(ENGINE *e, int cmd, long i, void *p, void (*f)(void));

/* This function tests if an ENGINE-specific command is usable as a "setting".
 * Eg. in an application's config file that gets processed through
 * ENGINE_ctrl_cmd_string(). If this returns zero, it is not available to
 * ENGINE_ctrl_cmd_string(), only ENGINE_ctrl(). */
int ENGINE_cmd_is_executable(ENGINE *e, int cmd);

/* This function works like ENGINE_ctrl() with the exception of taking a
 * command name instead of a command number, and can handle optional commands.
 * See the comment on ENGINE_ctrl_cmd_string() for an explanation on how to
 * use the cmd_name and cmd_optional. */
int ENGINE_ctrl_cmd(ENGINE *e, const char *cmd_name,
        long i, void *p, void (*f)(void), int cmd_optional);

/* This function passes a command-name and argument to an ENGINE. The cmd_name
 * is converted to a command number and the control command is called using
 * 'arg' as an argument (unless the ENGINE doesn't support such a command, in
 * which case no control command is called). The command is checked for input
 * flags, and if necessary the argument will be converted to a numeric value. If
 * cmd_optional is non-zero, then if the ENGINE doesn't support the given
 * cmd_name the return value will be success anyway. This function is intended
 * for applications to use so that users (or config files) can supply
 * engine-specific config data to the ENGINE at run-time to control behaviour of
 * specific engines. As such, it shouldn't be used for calling ENGINE_ctrl()
 * functions that return data, deal with binary data, or that are otherwise
 * supposed to be used directly through ENGINE_ctrl() in application code. Any
 * "return" data from an ENGINE_ctrl() operation in this function will be lost -
 * the return value is interpreted as failure if the return value is zero,
 * success otherwise, and this function returns a boolean value as a result. In
 * other words, vendors of 'ENGINE'-enabled devices should write ENGINE
 * implementations with parameterisations that work in this scheme, so that
 * compliant ENGINE-based applications can work consistently with the same
 * configuration for the same ENGINE-enabled devices, across applications. */
int ENGINE_ctrl_cmd_string(ENGINE *e, const char *cmd_name, const char *arg,
				int cmd_optional);

/* These functions are useful for manufacturing new ENGINE structures. They
 * don't address reference counting at all - one uses them to populate an ENGINE
 * structure with personalised implementations of things prior to using it
 * directly or adding it to the builtin ENGINE list in OpenSSL. These are also
 * here so that the ENGINE structure doesn't have to be exposed and break binary
 * compatibility! */
ENGINE *ENGINE_new(void);
int ENGINE_free(ENGINE *e);
int ENGINE_up_ref(ENGINE *e);
int ENGINE_set_id(ENGINE *e, const char *id);
int ENGINE_set_name(ENGINE *e, const char *name);
int ENGINE_set_RSA(ENGINE *e, const RSA_METHOD *rsa_meth);
int ENGINE_set_DSA(ENGINE *e, const DSA_METHOD *dsa_meth);
int ENGINE_set_ECDH(ENGINE *e, const ECDH_METHOD *ecdh_meth);
int ENGINE_set_ECDSA(ENGINE *e, const ECDSA_METHOD *ecdsa_meth);
int ENGINE_set_DH(ENGINE *e, const DH_METHOD *dh_meth);
int ENGINE_set_RAND(ENGINE *e, const RAND_METHOD *rand_meth);
int ENGINE_set_STORE(ENGINE *e, const STORE_METHOD *store_meth);
int ENGINE_set_destroy_function(ENGINE *e, ENGINE_GEN_INT_FUNC_PTR destroy_f);
int ENGINE_set_init_function(ENGINE *e, ENGINE_GEN_INT_FUNC_PTR init_f);
int ENGINE_set_finish_function(ENGINE *e, ENGINE_GEN_INT_FUNC_PTR finish_f);
int ENGINE_set_ctrl_function(ENGINE *e, ENGINE_CTRL_FUNC_PTR ctrl_f);
int ENGINE_set_load_privkey_function(ENGINE *e, ENGINE_LOAD_KEY_PTR loadpriv_f);
int ENGINE_set_load_pubkey_function(ENGINE *e, ENGINE_LOAD_KEY_PTR loadpub_f);
int ENGINE_set_ciphers(ENGINE *e, ENGINE_CIPHERS_PTR f);
int ENGINE_set_digests(ENGINE *e, ENGINE_DIGESTS_PTR f);
int ENGINE_set_flags(ENGINE *e, int flags);
int ENGINE_set_cmd_defns(ENGINE *e, const ENGINE_CMD_DEFN *defns);
/* These functions allow control over any per-structure ENGINE data. */
int ENGINE_get_ex_new_index(long argl, void *argp, CRYPTO_EX_new *new_func,
		CRYPTO_EX_dup *dup_func, CRYPTO_EX_free *free_func);
int ENGINE_set_ex_data(ENGINE *e, int idx, void *arg);
void *ENGINE_get_ex_data(const ENGINE *e, int idx);

/* This function cleans up anything that needs it. Eg. the ENGINE_add() function
 * automatically ensures the list cleanup function is registered to be called
 * from ENGINE_cleanup(). Similarly, all ENGINE_register_*** functions ensure
 * ENGINE_cleanup() will clean up after them. */
void ENGINE_cleanup(void);

/* These return values from within the ENGINE structure. These can be useful
 * with functional references as well as structural references - it depends
 * which you obtained. Using the result for functional purposes if you only
 * obtained a structural reference may be problematic! */
const char *ENGINE_get_id(const ENGINE *e);
const char *ENGINE_get_name(const ENGINE *e);
const RSA_METHOD *ENGINE_get_RSA(const ENGINE *e);
const DSA_METHOD *ENGINE_get_DSA(const ENGINE *e);
const ECDH_METHOD *ENGINE_get_ECDH(const ENGINE *e);
const ECDSA_METHOD *ENGINE_get_ECDSA(const ENGINE *e);
const DH_METHOD *ENGINE_get_DH(const ENGINE *e);
const RAND_METHOD *ENGINE_get_RAND(const ENGINE *e);
const STORE_METHOD *ENGINE_get_STORE(const ENGINE *e);
ENGINE_GEN_INT_FUNC_PTR ENGINE_get_destroy_function(const ENGINE *e);
ENGINE_GEN_INT_FUNC_PTR ENGINE_get_init_function(const ENGINE *e);
ENGINE_GEN_INT_FUNC_PTR ENGINE_get_finish_function(const ENGINE *e);
ENGINE_CTRL_FUNC_PTR ENGINE_get_ctrl_function(const ENGINE *e);
ENGINE_LOAD_KEY_PTR ENGINE_get_load_privkey_function(const ENGINE *e);
ENGINE_LOAD_KEY_PTR ENGINE_get_load_pubkey_function(const ENGINE *e);
ENGINE_CIPHERS_PTR ENGINE_get_ciphers(const ENGINE *e);
ENGINE_DIGESTS_PTR ENGINE_get_digests(const ENGINE *e);
const EVP_CIPHER *ENGINE_get_cipher(ENGINE *e, int nid);
const EVP_MD *ENGINE_get_digest(ENGINE *e, int nid);
const ENGINE_CMD_DEFN *ENGINE_get_cmd_defns(const ENGINE *e);
int ENGINE_get_flags(const ENGINE *e);

/* FUNCTIONAL functions. These functions deal with ENGINE structures
 * that have (or will) be initialised for use. Broadly speaking, the
 * structural functions are useful for iterating the list of available
 * engine types, creating new engine types, and other "list" operations.
 * These functions actually deal with ENGINEs that are to be used. As
 * such these functions can fail (if applicable) when particular
 * engines are unavailable - eg. if a hardware accelerator is not
 * attached or not functioning correctly. Each ENGINE has 2 reference
 * counts; structural and functional. Every time a functional reference
 * is obtained or released, a corresponding structural reference is
 * automatically obtained or released too. */

/* Initialise a engine type for use (or up its reference count if it's
 * already in use). This will fail if the engine is not currently
 * operational and cannot initialise. */
int ENGINE_init(ENGINE *e);
/* Free a functional reference to a engine type. This does not require
 * a corresponding call to ENGINE_free as it also releases a structural
 * reference. */
int ENGINE_finish(ENGINE *e);