VLC中涉及到的复杂宏和变量的小结。
1．消息映射宏
vlc_module_begin();
…………………..
vlc_module_end();
2．结构中包含函数
struct input_thread_t
{
VLC_COMMON_MEMBERS
/* Thread properties */
vlc_bool_t b_eof;
vlc_bool_t b_out_pace_control;
/* Access module */
module_t * p_access;
ssize_t (* pf_read ) ( input_thread_t *, byte_t *, size_t );
int (* pf_set_program )( input_thread_t *, pgrm_descriptor_t * );
int (* pf_set_area )( input_thread_t *, input_area_t * );
void (* pf_seek ) ( input_thread_t *, off_t );
}
3．宏与换行符妙用
#define VLC_COMMON_MEMBERS \
/** \name VLC_COMMON_MEMBERS \
* these members are common for all vlc objects \
*/ \
/**@{*/ \
int i_object_id; \
int i_object_type; \
char *psz_object_type; \
char *psz_object_name; \
\
/** Just a reminder so that people don't cast garbage */ \
int be_sure_to_add_VLC_COMMON_MEMBERS_to_struct; \
/**@}*/
#define VLC_OBJECT( x ) \
((vlc_object_t *)(x))+
0*(x)->be_sure_to_add_VLC_COMMON_MEMBERS_to_struct
struct vlc_object_t
{
VLC_COMMON_MEMBERS
};//定义一个结构来使用宏定义的公共成员
4．定义导出函数
#ifndef __PLUGIN__
# define VLC_EXPORT( type, name, args ) type name args
#else
# define VLC_EXPORT( type, name, args ) struct _u_n_u_s_e_d_
extern module_symbols_t* p_symbols;
#endif
5．定义回调函数
typedef int ( * vlc_callback_t ) ( vlc_object_t *, /* variable's object */
char const *, /* variable name */
vlc_value_t, /* old value */
vlc_value_t, /* new value */
void * ); /* callback data */
6．函数作为参数的定义方式
Int Fun(int n,int (*pf)(int ,int),char *pstr)
{ int j =10;
pf(n,j);
}
7．回调函数的声明
必须声明为global，或者static
Int vlc_callback_t (int ,int)
{。。。。。。。。。。。}
8．回调函数的使用
Fun(0, vlc_callback_t,"test");
9．函数表达式
#define input_BuffersInit(a) __input_BuffersInit(VLC_OBJECT(a))
void * __input_BuffersInit( vlc_object_t * );
#define module_Need(a,b,c,d) __module_Need(VLC_OBJECT(a),b,c,d)
VLC_EXPORT( module_t *, __module_Need, ( vlc_object_t *, const char *, const char *, vlc_bool_t ) );
10．定义函数
/* Dynamic array handling: realloc array, move data, increment position */
#define INSERT_ELEM( p_ar, i_oldsize, i_pos, elem ) \
do \
{ \
if( i_oldsize ) \
{ \
(p_ar) = realloc( p_ar, ((i_oldsize) + 1) * sizeof( *(p_ar) ) ); \
} \
else \
{ \
(p_ar) = malloc( ((i_oldsize) + 1) * sizeof( *(p_ar) ) ); \
} \
if( (i_oldsize) - (i_pos) ) \
{ \
memmove( (p_ar) + (i_pos) + 1, \
(p_ar) + (i_pos), \
((i_oldsize) - (i_pos)) * sizeof( *(p_ar) ) ); \
} \
(p_ar)[i_pos] = elem; \
(i_oldsize)++; \
} \
while( 0 )
应用为：
INSERT_ELEM( p_new->p_libvlc->pp_objects,
p_new->p_libvlc->i_objects,
p_new->p_libvlc->i_objects,
p_new );
11．改变地址的方式传递其值
stream_t *input_StreamNew( input_thread_t *p_input )
{ stream_t *s = vlc_object_create( p_input, sizeof( stream_t ) );
input_stream_sys_t *p_sys;
if( s )
{
s->p_sys = malloc( sizeof( input_stream_sys_t ) );
p_sys = (input_stream_sys_t*)s->p_sys;
p_sys->p_input = p_input;
}
return s;//注解：s->p_sys改变了
}
vlc_module_begin();
…………………..
vlc_module_end();
2．结构中包含函数
struct input_thread_t
{
VLC_COMMON_MEMBERS
/* Thread properties */
vlc_bool_t b_eof;
vlc_bool_t b_out_pace_control;
/* Access module */
module_t * p_access;
ssize_t (* pf_read ) ( input_thread_t *, byte_t *, size_t );
int (* pf_set_program )( input_thread_t *, pgrm_descriptor_t * );
int (* pf_set_area )( input_thread_t *, input_area_t * );
void (* pf_seek ) ( input_thread_t *, off_t );
}
3．宏与换行符妙用
#define VLC_COMMON_MEMBERS \
/** \name VLC_COMMON_MEMBERS \
* these members are common for all vlc objects \
*/ \
/**@{*/ \
int i_object_id; \
int i_object_type; \
char *psz_object_type; \
char *psz_object_name; \
\
/** Just a reminder so that people don't cast garbage */ \
int be_sure_to_add_VLC_COMMON_MEMBERS_to_struct; \
/**@}*/
#define VLC_OBJECT( x ) \
((vlc_object_t *)(x))+
0*(x)->be_sure_to_add_VLC_COMMON_MEMBERS_to_struct
struct vlc_object_t
{
VLC_COMMON_MEMBERS
};//定义一个结构来使用宏定义的公共成员
4．定义导出函数
#ifndef __PLUGIN__
# define VLC_EXPORT( type, name, args ) type name args
#else
# define VLC_EXPORT( type, name, args ) struct _u_n_u_s_e_d_
extern module_symbols_t* p_symbols;
#endif
5．定义回调函数
typedef int ( * vlc_callback_t ) ( vlc_object_t *, /* variable's object */
char const *, /* variable name */
vlc_value_t, /* old value */
vlc_value_t, /* new value */
void * ); /* callback data */
6．函数作为参数的定义方式
Int Fun(int n,int (*pf)(int ,int),char *pstr)
{ int j =10;
pf(n,j);
}
7．回调函数的声明
必须声明为global，或者static
Int vlc_callback_t (int ,int)
{。。。。。。。。。。。}
8．回调函数的使用
Fun(0, vlc_callback_t,"test");
9．函数表达式
#define input_BuffersInit(a) __input_BuffersInit(VLC_OBJECT(a))
void * __input_BuffersInit( vlc_object_t * );
#define module_Need(a,b,c,d) __module_Need(VLC_OBJECT(a),b,c,d)
VLC_EXPORT( module_t *, __module_Need, ( vlc_object_t *, const char *, const char *, vlc_bool_t ) );
10．定义函数
/* Dynamic array handling: realloc array, move data, increment position */
#define INSERT_ELEM( p_ar, i_oldsize, i_pos, elem ) \
do \
{ \
if( i_oldsize ) \
{ \
(p_ar) = realloc( p_ar, ((i_oldsize) + 1) * sizeof( *(p_ar) ) ); \
} \
else \
{ \
(p_ar) = malloc( ((i_oldsize) + 1) * sizeof( *(p_ar) ) ); \
} \
if( (i_oldsize) - (i_pos) ) \
{ \
memmove( (p_ar) + (i_pos) + 1, \
(p_ar) + (i_pos), \
((i_oldsize) - (i_pos)) * sizeof( *(p_ar) ) ); \
} \
(p_ar)[i_pos] = elem; \
(i_oldsize)++; \
} \
while( 0 )
应用为：
INSERT_ELEM( p_new->p_libvlc->pp_objects,
p_new->p_libvlc->i_objects,
p_new->p_libvlc->i_objects,
p_new );
11．改变地址的方式传递其值
stream_t *input_StreamNew( input_thread_t *p_input )
{ stream_t *s = vlc_object_create( p_input, sizeof( stream_t ) );
input_stream_sys_t *p_sys;
if( s )
{
s->p_sys = malloc( sizeof( input_stream_sys_t ) );
p_sys = (input_stream_sys_t*)s->p_sys;
p_sys->p_input = p_input;
}
return s;//注解：s->p_sys改变了
}