[linux-dvb] Problems with ca_zap

Johannes Stezenbach js at linuxtv.org
Fri Jun 24 15:40:10 CEST 2005


Manu Abraham wrote:
> Allan Stirling wrote:
> >       p_program_descriptor->program_number =
> >               ((p_program_descriptor->program_number | buf[pos + 0]) << 8) | buf[pos + 1];
> >
> >Doesn't look quite right. Why do we care what the program_number is 
> >before it's been parsed?
> 
> Hmm, that is required because buf is 8 bits. All what i do is, get buf 
> into program_number and shift program_number to the left by 8.
> 
> >If I change this to
> >
> >       p_program_descriptor->program_number =
> >               ( buf[pos + 0] << 8) | buf[pos + 1];
> >
> 
> This would be wrong however, since if you left shift an 8 bit buffer by 
> 8 all you will get is 0.
> 
> The problem would be solved, if program_number is initialized to 0 just 
> before reading in from the buffer.

It still would be hard to read. How about:

       p_program_descriptor->program_number =
               ((uint16_t) buf[pos] << 8) | buf[pos + 1];

Johannes




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