On 28.06.2011, at 21:37, Charles Srstka wrote:
> On Jun 28, 2011, at 12:00 PM, Jens Alfke wrote:
>
>> Another way (that I often use) is to define a C struct that matches the
>> fields and layout of the header, then cast the bytes to a pointer to that
>> struct and read the fields. It makes your code look a lot cleaner, but you
>> have to be careful to (a) make sure the compiler packs the struct fields
>> properly, and (b) you byte-swap all integer/float fields appropriately.
>
> It’s my understanding that reading/writing a struct directly to/from a file
> is considered poor practice, because of the two things you mentioned: endian
> issues, and the fact that you don’t know how the compiler will align the
> fields — and even if you test that, you don’t know that it’s not going to
> change in some future version of clang or gcc, or that Apple’s not going to
> switch to a new architecture or something in which the compilers will emit
> different output.
- the endian issue you'll have to deal with anyway
- regarding struct alignment:
the 80ies file format had tons of of serialized struct data which usually
better end up in a struct.
Well, streamed reading has bad performance, so you'd not want to use it in
image (or movie) manipulation code.
Streamed reading just to put it back into a struct is another anti-pattern.
The "don't" is to use binary structs for new defined protocols for transfer,
for the given reasons.
Regards,
Tom_E
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