/*

Copyright 2020 Google LLC

Use of this source code is governed by a BSD-style

license that can be found in the LICENSE file or at

https://developers.google.com/open-source/licenses/bsd

*/

#include "pq.h"

#include "reftable-record.h"

#include "system.h"

#include "basics.h"

int pq_less(struct pq_entry *a, struct pq_entry *b)

{

  int cmp = reftable_record_cmp(a->rec, b->rec);

  if (cmp == 0)

    return a->index > b->index;

  return cmp < 0;

}

struct pq_entry merged_iter_pqueue_remove(struct merged_iter_pqueue *pq)

{

  size_t i = 0;

  struct pq_entry e = pq->heap[0];

  pq->heap[0] = pq->heap[pq->len - 1];

  pq->len--;

  while (i < pq->len) {

    size_t min = i;

    size_t j = 2 * i + 1;

    size_t k = 2 * i + 2;

    if (j < pq->len && pq_less(&pq->heap[j], &pq->heap[i]))

      min = j;

    if (k < pq->len && pq_less(&pq->heap[k], &pq->heap[min]))

      min = k;

    if (min == i)

      break;

    SWAP(pq->heap[i], pq->heap[min]);

    i = min;

  }

  return e;

}

void merged_iter_pqueue_add(struct merged_iter_pqueue *pq, const struct pq_entry *e)

{

  size_t i = 0;

  REFTABLE_ALLOC_GROW(pq->heap, pq->len + 1, pq->cap);

  pq->heap[pq->len++] = *e;

  i = pq->len - 1;

  while (i > 0) {

    size_t j = (i - 1) / 2;

    if (pq_less(&pq->heap[j], &pq->heap[i]))

      break;

    SWAP(pq->heap[j], pq->heap[i]);

    i = j;

  }

}

void merged_iter_pqueue_release(struct merged_iter_pqueue *pq)

{

  FREE_AND_NULL(pq->heap);

  memset(pq, 0, sizeof(*pq));

}