rawRead using a struct with variable leght

[H. S. Teoh via Digitalmars-d-learn]

On Wed, Jun 07, 2017 at 06:24:22PM +0000, ade90036 via Digitalmars-d-learn wrote:
> On Monday, 5 June 2017 at 16:30:53 UTC, Era Scarecrow wrote:
> > On Monday, 5 June 2017 at 16:04:28 UTC, ade90036 wrote:
> > 
> > > Unfortunately the struct doesn't know at compile time what the
> > > size of the constant_pool array, or at-least was not able to
> > > specify it dynamically.
> > 
> >  It also won't know ahead of time how many fields, methods or
> >  attributes you have either.
> > 
> >  First I'd say all the arrays will have to be redefined to use [],
> >  rather than a fixed size.
> > 
> >  Glancing at the chapter information, you're probably not going to
> >  have an easy time, and will have to simply have to fill in the
> >  fields individually in order followed by allocating the arrays and
> >  probably filling/loading those immediately (although it's possible
> >  the array contents are done at the end, though it seems doubtful).
> 
> Thanks for the reply.
> 
> I guess i didnt pick such an easy task afterall.
> 
> I shall parse each fields individually.
[...]

"Structs" with variable size fields have no direct equivalent in D's
type system, so you'll probably have a hard time mapping this directly.

What you *could* do, though, is to load the data into a ubyte[] buffer,
then create a proxy struct containing arrays where you have
variable-sized fields, with the arrays slicing the ubyte[] buffer
appropriately.  Unfortunately, yes, this means you have to parse the
fields individually in order to construct these slices.


T

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