我们研究了Mediastreamer2 VoIP引擎。第11部分

文章资料取自我的禅宗频道。

数据移动机制

• dblk_t数据块
• 讯息mblk_t
• Mblk_t消息传递功能
• Queue_t队列
• Queue_t排队功能
• 过滤器连接
• 数据处理图的信号点
• 后台股票行情活动
• 缓冲MSBufferizer
• MSBufferizer功能

. . .

queue_t. mblk_t, , , . , , , . , , . , mblk_t, mblk_t. . .

, , . " ", ( — ) , .

, , .

dblk_t

. ,

typedef struct datab
{
unsigned char *db_base; //     .
unsigned char *db_lim;  //     .
void (*db_freefn)(void*); //      .
int db_ref; //  .
} dblk_t;

, , . db_ref — , , . datab_alloc() , . - . , .

:

dblk_t *datab_alloc(int size);

, . , — datab. , . , db_base , db_lim . db_ref . .

mblk_t

, mblk_t, :

typedef struct msgb
{
  struct msgb *b_prev;   //     .
  struct msgb *b_next;   //     .
  struct msgb *b_cont;   //       ,    .
  struct datab *b_datap; //     .
  unsigned char *b_rptr; //          b_datap.
  unsigned char *b_wptr; //          b_datap.
  uint32_t reserved1;    //  1,     . 
  uint32_t reserved2;    //  2,     .
  #if defined(ORTP_TIMESTAMP)
  struct timeval timestamp;
  #endif
  ortp_recv_addr_t recv_addr;
} mblk_t;

mblk_t b_prev, b_next, ( queue_t).

b_cont, , . .

b_datap, . , . b_rptr , . b_wptr , .

.

m1 d1.

m1, m1_1, m1_2.

mblk_t

mblk_t :

mblk_t *allocb(int size, int pri); 

mblk_t size, — pri . BPRI_MED, ( ). mblk_init(), , datab_alloc(), . :

mp->b_datap=datab;
mp->b_rptr=mp->b_wptr=datab->db_base;
mp->b_next=mp->b_prev=mp->b_cont=NULL;

. , :

memcpy(msg->b_rptr, data, size);

data — , size — .
, :

msg->b_wptr = msg->b_wptr + size

, , :

mblk_t *esballoc(uint8_t *buf, int size, int pri, void (*freefn)(void*)); 

, buf. .. , datab_alloc(). , , .

mblk_t . :

mblk_t * appendb(mblk_t *mp, const char *data, int size, bool_t pad); 

mp — ;
data — , ;
size — ;
pad — , 4 ( ).

, . size, , . , b_cont. .

, :

void msgappend(mblk_t *mp, const char *data, int size, bool_t pad);

( b_cont ) appendb().

:

int msgdsize(const mblk_t *mp);

. :

 mp->b_wptr - mp->b_rptr

:

mblk_t *concatb(mblk_t *mp, mblk_t *newm);

newm mp .

, , :

void msgpullup(mblk_t *mp,int len);

len -1, . len , . , . . , .

mblk_t , freeb() , mblk_t, .

:

void mblk_init(mblk_t *mp);

:

mblk_t * appendb(mblk_t *mp, const char *data, size_t size, bool_t pad);

, ( ) .

:

void msgappend(mblk_t *mp, const char *data, size_t size, bool_t pad); 

appendb() .

:

mblk_t *concatb(mblk_t *mp, mblk_t *newm);

newm mp.

:

mblk_t *copyb(const mblk_t *mp);

:

mblk_t *copymsg(const mblk_t *mp);

copyb().

mblk_t. , db_ref:

mblk_t *dupb(mblk_t *mp);

. , db_ref:

mblk_t *dupmsg(mblk_t* m);

:

void msgpullup(mblk_t *mp,size_t len);

len -1, .

, :

void freemsg(mblk_t *mp);

. , .

.

size_t msgdsize(const mblk_t *mp);

:

mblk_t *ms_queue_peek_last (q);

( , ):

mblk_meta_copy(const mblk_t *source, mblk *dest);

queue_t

. . , , . .. .
queue_t, :

typedef struct _queue
{
   mblk_t _q_stopper; /* ""  ,    ,     .    (qinit())    ,      . */
   int q_mcount;        //    .
} queue_t;

— _q_stopper *mblk_t, () . , .
c q1, 4 m1,m2, m3, m4.

c q1, 4 m1,m2, m3, m4. m2 , m2_1 m2_2.

queue_t

:

void qinit(queue_t *q);

_q_stopper ( "") mblk_init(), , . .

():

void putq(queue_t *q, mblk_t *m);

m , , , . .

:

mblk_t * getq(queue_t *q); 

, , . , , , 0.

:

void insq(queue_t *q, mblk_t *emp, mblk_t *mp); 

mp emp. emp=0, .

:

void remq(queue_t *q, mblk_t *mp); 

.

:

mblk_t * peekq(queue_t *q); 

:

void flushq(queue_t *q, int how);

how . .

:

mblk_t * qlast(queue_t *q);

, ms_queue_put(q, m) , . . ms_queue_next(q, m).

. . "". , " ". _MSCPoint, , .

typedef struct _MSCPoint{
struct _MSFilter *filter; //    .
int pin;                        //       , .. .
} MSCPoint;

.

_MSQueue, , :

typedef struct _MSQueue
{
queue_t q;
MSCPoint prev;
MSCPoint next;
}MSQueue;

. , (MSQueue). , MSFilterDesc, . , MSFilter:

struct _MSFilter{
    MSFilterDesc *desc;    /*    . */
    /*  ,           . */
    ms_mutex_t lock;      /* . */
    MSQueue **inputs;     /*   . */
    MSQueue **outputs;    /*   . */
    struct _MSFactory *factory; /*   ,     . */
    void *padding;              /*  ,      . */
    void *data;                 /*             . */
    struct _MSTicker *ticker;   /*    ,         process(). */
    /*private attributes, they can be moved and changed at any time*/
    MSList *notify_callbacks; /*   ,     . */
    uint32_t last_tick;       /*   ,    process(). */ 
    MSFilterStats *stats;     /*   .*/
    int postponed_task; /*  .       ( process())   .*/
    bool_t seen;  /* ,   ,            .*/
};
typedef struct _MSFilter MSFilter;

, - ( ), , , MSFilter, MSQueue.

— , . , process() () . - , , , . , , . "" , seen. , .

, , , . , .

"", , , preprocess(). ( 10 ), process() , . , process() , . , "" . . .

. , , , , . , , , . 512 . , 160 . , . , . . , process() .

512 , , .. 640 512 , . , , . — MSBufferizer (), .

MSBufferizer

, . , , . , process() , .
, .

, :

struct _MSBufferizer{
queue_t q; /*  . */
int size; /*         . */
};
typedef struct _MSBufferizer MSBufferizer;

MSBufferizer

:

MSBufferizer * ms_bufferizer_new(void);

, ms_bufferizer_init() .

:

void ms_bufferizer_init(MSBufferizer *obj); 

q, size .

:

void ms_bufferizer_put(MSBufferizer *obj, mblk_t *m); 

m . size.

q:

void ms_bufferizer_put_from_queue(MSBufferizer *obj, MSQueue *q);   

q ms_bufferizer_put().

:

int ms_bufferizer_read(MSBufferizer *obj, uint8_t *data, int datalen); 

(datalen), , data . . . , datalen . , , . .

, :

int ms_bufferizer_get_avail(MSBufferizer *obj); 

size .

, :

void ms_bufferizer_skip_bytes(MSBufferizer *obj, int bytes);

. .

:

void ms_bufferizer_flush(MSBufferizer *obj); 

.

:

void ms_bufferizer_uninit(MSBufferizer *obj); 

.

:

void ms_bufferizer_destroy(MSBufferizer *obj);  

. MS_L16_ENC, , : l16.c

, .