static void treehash_update()

in xmss_fast.c [249:291]

• 38 lines of code
• 4 McCabe index (conditional complexity)

static void treehash_update(treehash_inst *treehash, bds_state *state, const unsigned char *sk_seed, const xmss_params *params, const unsigned char *pub_seed, const uint32_t addr[8]) {
  int n = params->n;

  uint32_t ots_addr[8];
  uint32_t ltree_addr[8];
  uint32_t  node_addr[8];
  // only copy layer and tree address parts
  memcpy(ots_addr, addr, 12);
  // type = ots
  setType(ots_addr, 0);
  memcpy(ltree_addr, addr, 12);
  setType(ltree_addr, 1);
  memcpy(node_addr, addr, 12);
  setType(node_addr, 2);

  setLtreeADRS(ltree_addr, treehash->next_idx);
  setOTSADRS(ots_addr, treehash->next_idx);

  unsigned char nodebuffer[2 * n];
  unsigned int nodeheight = 0;
  gen_leaf_wots(nodebuffer, sk_seed, params, pub_seed, ltree_addr, ots_addr);
  while (treehash->stackusage > 0 && state->stacklevels[state->stackoffset-1] == nodeheight) {
    memcpy(nodebuffer + n, nodebuffer, n);
    memcpy(nodebuffer, state->stack + (state->stackoffset-1)*n, n);
    setTreeHeight(node_addr, nodeheight);
    setTreeIndex(node_addr, (treehash->next_idx >> (nodeheight+1)));
    hash_h(nodebuffer, nodebuffer, pub_seed, node_addr, n);
    nodeheight++;
    treehash->stackusage--;
    state->stackoffset--;
  }
  if (nodeheight == treehash->h) { // this also implies stackusage == 0
    memcpy(treehash->node, nodebuffer, n);
    treehash->completed = 1;
  }
  else {
    memcpy(state->stack + state->stackoffset*n, nodebuffer, n);
    treehash->stackusage++;
    state->stacklevels[state->stackoffset] = nodeheight;
    state->stackoffset++;
    treehash->next_idx++;
  }
}