Re: typecasting...

"Jim Langston" <>
Sun, 29 Apr 2007 20:31:12 -0700
"aki" <> wrote in message

i am receiving a buffer from network as char pointer.
char * buffer;
this is an argument of my function.
well i want to decode this buffer.
buffer contain a packet with different fields

code of size 1 byte contain inter value
identifier of size 1 byte contain integer value
length of size 2 byte. contain integer value.

as struct lcpHeader
   uint8_t code;
   uint8_t identifier;
   uint16_t length;

i want to access it all fields.
1) code field

struct lcpHeader *hdr;
hdr=(struct lcpHeader*)buffer;

when i do switch(hdr->code)
will it give integer value contained in the code....?

how to access other fielsd?
i hope i have made clear what i wann do?

Do a sizeof kpHeader and make sure it's 32. It may be different although it
seems like it may be okay in this instance. I'm talking about padding
spaces. Lets say, for example, you had a structure:

struct kpHeader
   uint8_t Code;
   uint32_t Length;

You might think the sizeof that woudl be 40, but might be suprised that the
size (on my platform) would be 64. That's why it's generally not a good
idea to try to cast socket data into a structure as padding may throw it
off. I do not know if your system is 32 bit aligned, 16 bit, etc...For the
most part, two bytes followed by a short (16 bit) should fit in 32 bits, but
there is no guarantee.

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