[Freeciv-Dev] very simple specvecs

[Jason Dorje Short <jdorje@xxxxxxxxxxxx>]

It would be possible to make the specvec a simple array.

  struct {
    int a, b;
  } foo;

  #define SPECVEC_TAG foo
  #include "specvec.h"

  {
    foo_vector foo;

    foo_vector_init(&foo);
    foo_vector_reserve(&foo, 2);

    foo[0].a = 1;
    foo[0].b = 2;
    foo[1].a = 2;
    foo[1].b = 4;

    for (i = 0; i < foo_vector_size(&foo); i++) {
      printf("%d, %d\n", foo[i].a, foo[i].b);
    }

    foo_vector_free(&foo);
  }

However it would be _somewhat_ slower.  Lookups would obviously be a 
fast O(1) operation.  All other operations would still be O(1) but would 
be slightly slower.
Disregarding the potential ugliness of the implementation (no crazy 
memory tricks would be needed, don't worry Vasco), how useful would this be?
---

One implementation:

Obviously we now have a

  typedef struct foo *foo_vector;

As well we have a global hash of existing vector arrays (all vectors, 
not just foo_vectors).  When the _init is done this vector is added to 
the hash, and the size and size_alloc are put into the value stored in 
the hash (a second malloc is needed here).  Then these values are looked 
up in the hash (a slow O(1) operation) every time the vector's functions 
are accessed.
Perhaps this is too much of a reimplementation of malloc?

jason