/*
	cache.c
		caching of tensor coefficients in
		dynamically allocated memory
		this file is part of LoopTools
		last modified 27 Jun 04 th
*/


#include <stdlib.h>
#include <stdio.h>
#include <string.h>


#ifdef HAVE_UNDERSCORE
#define cachelookup cachelookup_
#define setcachelast setcachelast_
#define getcachelast getcachelast_
#endif


#ifndef REALSIZE
#define REALSIZE sizeof(double)
#endif

#define CPLXSIZE (2*REALSIZE)

#define ptrdiff(a, b) (long)((char *)a - (char *)b)


int cachelookup(char *para, char **base,
  void (*calc)(char *, char *), int *npara, int *nval)
{
  char *node, *last, **next = base;
  const int parasize = *npara*REALSIZE;
  const int valsize = *nval*CPLXSIZE;

  last = *(base + 1);
  if( last ) {
    do {
      node = *next;
      next = (char **)(node - sizeof(char *));
      if( memcmp(para, node + valsize, parasize) == 0 ) goto done;
    } while( node != last );
  }
  node = *next;
  if( node == NULL ) {
    node = malloc(sizeof(char *) + valsize + parasize + CPLXSIZE);
	/* MUST have extra CPLXSIZE for alignment so that node
	   can be reached with an integer offset into base */
    if( node == NULL ) {
      fputs("Out of cache memory.\n", stderr);
      exit(1);
    }
    node += sizeof(char *);
    node += ptrdiff(base, node) & (CPLXSIZE - 1);
    *next = node;
    *(char **)(node - sizeof(char *)) = NULL;
  }
  *(base + 1) = node;
  memcpy(node + valsize, para, parasize);
  calc(para, node);
done:
  return ptrdiff(node, base)/CPLXSIZE;
}


void setcachelast(char **base, int *offset)
{
  *(base + 1) = *offset ? (char *)base + *offset*CPLXSIZE : NULL;
}


int getcachelast(char **base)
{
  return *(base + 1) ? ptrdiff(*(base + 1), base)/CPLXSIZE : 0;
}