[boost] array.hpp

From: Victor A. Wagner, Jr. (vawjr_at_[hidden])
Date: 2002-05-08 02:13:46

We're writing a library to handle some large collections of data and have 
been very heavily using std::vector in anticipation of perhaps needing to 
hand this data off to a C or FORTRAN 'system' for further 
processing.  Thusfar, there aren't any problems.  We just got the news that 
our "library" will need to be callable from C, FORTRAN, or even MATLAB 
programs.  The problem that crops up immediately is that there is no STL 
container which will handle an array _which already exists_.

boost/array would more than suit our needs if only there were some way 
(other than wholesale copying of the .hpp file and making a couple _very_ 
small changes) to convince the array<class T, std::size_t N> that rather 
than doing the:

T elem[N];

declaration in the class (and thereby allocating the array) we could 
somehow(????) do

T* elem;  //I tried to figure out how to write a "reference to an array of 
N elements of type T" and failed

and figure out how to get the address of this already extant array put into 
the pointer elem.  None of the rest of the class would need to change, 
since the syntax elem[x] works "identically" in both instances.

I know that the "normal" way of doing this would be to copy the array into 
a vector then do all the magic C++/STL stuff.  This is impractical for two 
reasons:
1) The array is often used as an in/out parameter, and this would entail 
copying it twice (a rather large performance hit)
2) some of the arrays exceed 1/2 of the virtual space available so there 
isn't any place to copy them to!

If anyone else is facing this problem we'd be glad to assist coming up with 
a boostified solution.  I just hate to "cheap out" and edit array.hpp into 
foreignarray.hpp just to solve this problem (especially after reading 
Andrei's book and seeing all the "policy" template type discussions here).
Victor A. Wagner Jr.      http://rudbek.com
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