Graeme Geldenhuys wrote:
_pContentsData = a generic Pointer type that points to a block of data
(containing multiples of various structures). XXX bytes of
information.
pEntry = this is a pointer to a specific starting structure type and
will increment in blocks of data to point to the various structures
stored in _pContentsData. Each pEntry has a Length property that says
how many bytes of data is used for all it's information.
if pentry is
TEntry = record .. end;
pentry = ^ TEntry
pEnd = the ending point of all the data held by _pContentsData. This
variable is just a safety net, so pEntry doesn't move past the end of
data block by accident.
I have the following code...
------------------------
pEntry := _pContentsData;
// below toclen is in bytes
pEnd := _pContentsData + _pHeader^.toclen;
is toclen, in bytes, or in units (eg number of records)
the above assumes bytes, if
_pContentsData = pointer; //not typed
// START LOOP
[(a)...do various things with data pointed to by pEntry..]
....
// now increment pEntry to point to next data structure
// below, .Length is in bytes
inc( pEntry, pEntry^.Length);
inc(PEntry, 1)
since it increments by the size of the type
// now repeat from (a) above until all data is processed
// END LOOP
------------------------
Question:
Am I incrementing the pEnd and pEntry in the correct way? They are
pointers to structures, so I believe I don't need to dereference them,
because I am working with the pointer at that stage and not the actual
data.
Example:
inc(pEntry, pEntry^.Length);
vs
inc(pEntry, pEntry^.Length * sizeof(byte));
Luckily the above method is not the only way to read the data I am
interrested in. There is also a redundant array of file offsets
pointing to each pEntry I am interrested in. Using the array works
fine, but using the incrementing method shown below, I am having
problems. :-(
Purely for the purpose of learning I would like to be able to get both
methods working - how else am I supposed to learn these things. :)
[I think I need to dig up my old college handbooks and relearn the
basics of pointers and record structures with binary file data]
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