[Octave-bug-tracker] [bug #54788] Implementation of memmapfile

[Guillaume]

Follow-up Comment #1, bug #54788 (project octave):

As a follow-up, I attach a version of the toy example I mentioned previously,
__mmap__.cc, rewritten as a DEFUN_DLD. It works like this:


octave> fid = fopen ("data.dat", "w");
octave> fwrite (fid, 1:128, "uint8");
octave> fclose (fid);
octave>
octave> h = __mmap__ ("data.dat", 128, 0); % mmap
octave> __mmap__ (h, "uint8", 0:7)
ans =
  1  2  3  4  5  6  7  8
octave> typecast (ans, "double")
ans =   5.4476e-270
octave> __mmap__ (h, "double", 0)
ans =   5.4476e-270
octave> __mmap__ (h, 128); % munmap


One question I have pertains to subsref/subsasgn: instead of having my own
inefficient implementation (speed- and memory-wise), is there a way to reuse
Octave's versions? I.e., given:


void *ptr; /* from mmap */
dim_vector dim; /* array dimensions */
std::string precision; /* eg, "uint32" */
octave_value_list idx; /* eg, {":", [3 4 5], 2, ":", [2 3]} */


would return a uint32NDArray containing the values from *prt corresponding to
idx.

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