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notify_capi.h
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notify_capi.h
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#ifndef NOTIFY_CAPI_H
#define NOTIFY_CAPI_H
#define NOTIFY_CAPI_ID_STRING "_capi_notify"
#define NOTIFY_CAPI_VERSION_MAJOR 0
#define NOTIFY_CAPI_VERSION_MINOR 0
#define NOTIFY_CAPI_VERSION_PATCH 2
#ifndef NOTIFY_CAPI_IMPLEMENT_SET_CAPI
# define NOTIFY_CAPI_IMPLEMENT_SET_CAPI 0
#endif
#ifndef NOTIFY_CAPI_IMPLEMENT_GET_CAPI
# define NOTIFY_CAPI_IMPLEMENT_GET_CAPI 0
#endif
#ifdef __cplusplus
extern "C" {
struct notify_notifier;
struct notify_capi;
#else /* __cplusplus */
typedef struct notify_notifier notify_notifier;
typedef struct notify_capi notify_capi;
#endif /* ! __cplusplus */
/**
* Type for pointer to function that may be called if an error occurs.
* ehdata: void pointer that is given in notify method (see below)
* msg: detailed error message
* msglen: length of error message
*/
typedef void (*notifier_error_handler)(void* ehdata, const char* msg, size_t msglen);
/**
* Notify C API.
*/
struct notify_capi
{
int version_major;
int version_minor;
int version_patch;
/**
* May point to another (incompatible) version of this API implementation.
* NULL if no such implementation exists.
*
* The usage of next_capi makes it possible to implement two or more
* incompatible versions of the C API.
*
* An API is compatible to another API if both have the same major
* version number and if the minor version number of the first API is
* greater or equal than the second one's.
*/
void* next_capi;
/**
* Must return a valid pointer if the Lua object at the given stack
* index is a valid notifier, otherwise must return NULL.
*
* The returned notifier object must be valid as long as the Lua
* object at the given stack index remains valid.
* To keep the notifier object beyond this call, the function
* retainNotifier() should be called (see below).
*/
notify_notifier* (*toNotifier)(lua_State* L, int index);
/**
* Increase the reference counter of the notifier object.
* Must be thread safe.
*
* This function must be called after the function toNotifier()
* as long as the Lua object on the given stack index is
* valid (see above).
*/
void (*retainNotifier)(notify_notifier* n);
/**
* Decrease the reference counter of the notifier object and
* destructs the notifier object if no reference is left.
* Must be thread safe.
*/
void (*releaseNotifier)(notify_notifier* n);
/**
* Calls the notify method of the given notifier object.
* Must be thread safe.
*
* eh: error handling function, may be NULL
* ehdata: additional data that is given to error handling function.
* Returns 0 - on success otherwise an error code != 0.
* 1 - if notifier is closed. The caller is expected to release the notifier.
* Subsequent calls will always result this return code again.
* All other error codes are implementation specific.
*/
int (*notify)(notify_notifier* n, notifier_error_handler eh, void* ehdata);
};
#if NOTIFY_CAPI_IMPLEMENT_SET_CAPI
/**
* Sets the Notify C API into the metatable at the given index.
*
* index: index of the table that is be used as metatable for objects
* that are associated to the given capi.
*/
static int notify_set_capi(lua_State* L, int index, const notify_capi* capi)
{
lua_pushlstring(L, NOTIFY_CAPI_ID_STRING, strlen(NOTIFY_CAPI_ID_STRING)); /* -> key */
void** udata = (void**) lua_newuserdata(L, sizeof(void*) + strlen(NOTIFY_CAPI_ID_STRING) + 1); /* -> key, value */
*udata = (void*)capi;
strcpy((char*)(udata + 1), NOTIFY_CAPI_ID_STRING); /* -> key, value */
lua_rawset(L, (index < 0) ? (index - 2) : index); /* -> */
return 0;
}
#endif /* NOTIFY_CAPI_IMPLEMENT_SET_CAPI */
#if NOTIFY_CAPI_IMPLEMENT_GET_CAPI
/**
* Gives the associated Notify C API for the object at the given stack index.
* Returns NULL, if the object at the given stack index does not have an
* associated Notify C API or only has a Notify C API with incompatible version
* number. If errorReason is not NULL it receives the error reason in this case:
* 1 for incompatible version nummber and 2 for no associated C API at all.
*/
static const notify_capi* notify_get_capi(lua_State* L, int index, int* errorReason)
{
if (luaL_getmetafield(L, index, NOTIFY_CAPI_ID_STRING) != LUA_TNIL) /* -> _capi */
{
const void** udata = (const void**) lua_touserdata(L, -1); /* -> _capi */
if ( udata
&& (lua_rawlen(L, -1) >= sizeof(void*) + strlen(NOTIFY_CAPI_ID_STRING) + 1)
&& (memcmp((char*)(udata + 1), NOTIFY_CAPI_ID_STRING,
strlen(NOTIFY_CAPI_ID_STRING) + 1) == 0))
{
const notify_capi* capi = (const notify_capi*) *udata; /* -> _capi */
while (capi) {
if ( capi->version_major == NOTIFY_CAPI_VERSION_MAJOR
&& capi->version_minor >= NOTIFY_CAPI_VERSION_MINOR)
{ /* -> _capi */
lua_pop(L, 1); /* -> */
return capi;
}
capi = (const notify_capi*) capi->next_capi;
}
if (errorReason) {
*errorReason = 1;
}
} else { /* -> _capi */
if (errorReason) {
*errorReason = 2;
}
}
lua_pop(L, 1); /* -> */
} else { /* -> */
if (errorReason) {
*errorReason = 2;
}
}
return NULL;
}
#endif /* NOTIFY_CAPI_IMPLEMENT_GET_CAPI */
#ifdef __cplusplus
} /* extern "C" */
#endif
#endif /* NOTIFY_CAPI_H */