Standard Library types

[Alex J. Dam]

Hi,

I'm reposting this since I posted it as an answer and the topic changed a
little (guess no one bothered looking at it).

If I need to store the location of some data within a binary file, in that
same binary file, should I store the pos_type value returned by
ostream::teelp()? (That would be strange. I would be storing extra
information, since I need only the position).

I'm confused as to what types should be used when calling Standard Library
functions, especially when mixing variables of different types, e.g., if I
divide an off_type by a size_t, what do I get?

Thanks.

 

[Victor Bazarov]

If I need to store the location of some data within a binary file, in that
same binary file, should I store the pos_type value returned by
ostream::teelp()? (That would be strange. I would be storing extra
information, since I need only the position).

I'm confused as to what types should be used when calling Standard Library
functions, especially when mixing variables of different types, e.g., if I
divide an off_type by a size_t, what do I get?

I would say, you get off_type. If it's an arithmetic type, a value of
that type retains its type no matter how you slice it or dice it.

My solution was always simpler: since binary files are platform-specific
(in most cases, anyway), then store the position as a long or unsigned
long (or any other type that can accommodate the maximum size of the
file). Once you retrieve it, convert it to the necessary off_type or
pos_type or whatever.

V

 

[Jonathan Turkanis]

Hi,

I'm reposting this since I posted it as an answer and the topic changed a
little (guess no one bothered looking at it).

If I need to store the location of some data within a binary file, in that
same binary file, should I store the pos_type value returned by
ostream::teelp()? (That would be strange. I would be storing extra
information, since I need only the position).

I'm confused as to what types should be used when calling Standard Library
functions, especially when mixing variables of different types, e.g., if I
divide an off_type by a size_t, what do I get?

Be aware that a stream's pos_type is not an intergral type, although
it can be converted to one. In general, this conversion could loose
information, although this may be unlikely with a stream in binary
mode.

Jonathan