从ts流中提取pid号

unsigned short Find_PAT(char * srcfile)//从PAT表中找出PMT表的PID
{
FILE *fpr;
int size=0;
int ret;
unsigned short PID;//TS包头PID
unsigned short PMT_PID;//PMT表的PID
unsigned short program_number;//节目号
unsigned char adaptation_field_control;//自适应字段标志
unsigned char *p;
unsigned char *pat;//指向PAT表的指针
unsigned char *p_program_num;//指向节目号的指针
unsigned short pat_section_length;
fpr=fopen(srcfile,"rb");
if(NULL==fpr)return 0;
while(!feof(fpr))
{
ret=fread(m_buf+size,1,sizeof(m_buf)-size,fpr);
size+=ret;
p=m_buf;
while(p+188<m_buf+size)
{
if((0x47==p[0])&&(0x47==p[188]))
{
PID=(p[1]&0x1f)<<8|p[2];
if(0==PID)
{
    adaptation_field_control=(p[3]>>4)&0x3;
    switch(adaptation_field_control)
{