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  modification, are permitted provided that the following conditions
  are met:
    * Redistributions of source code must retain the above copyright
      notice, this list of conditions and the following disclaimer.
    * Redistributions in binary form must reproduce the above copyright
      notice, this list of conditions and the following disclaimer in
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      distribution.
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      contributors may be used to endorse or promote products derived
      from this software without specific prior written permission.

  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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#include "igzip_lib.h"
#include "huff_codes.h"
#include "unaligned.h"

static inline void
heapify(uint64_t *heap, uint64_t heap_size, uint64_t index)
{
        uint64_t child = 2 * index, tmp;
        while (child <= heap_size) {
                child = (heap[child] <= heap[child + 1]) ? child : child + 1;

                if (heap[index] > heap[child]) {
                        tmp = heap[index];
                        heap[index] = heap[child];
                        heap[child] = tmp;
                        index = child;
                        child = 2 * index;
                } else
                        break;
        }
}

void
build_heap(uint64_t *heap, uint64_t heap_size)
{
        uint64_t i;
        heap[heap_size + 1] = -1;
        for (i = heap_size / 2; i > 0; i--)
                heapify(heap, heap_size, i);
}

uint32_t
build_huff_tree(struct heap_tree *heap_space, uint64_t heap_size, uint64_t node_ptr)
{
        uint64_t *heap = (uint64_t *) heap_space;
        uint64_t h1, h2;

        while (heap_size > 1) {
                h1 = heap[1];
                heap[1] = heap[heap_size];
                heap[heap_size--] = -1;

                heapify(heap, heap_size, 1);

                h2 = heap[1];
                heap[1] = ((h1 + h2) & ~0xFFFFull) | node_ptr;

                heapify(heap, heap_size, 1);

                store_native_u16_to_u64(&heap[node_ptr], h1);
                store_native_u16_to_u64(&heap[node_ptr - 1], h2);
                node_ptr -= 2;
        }
        h1 = heap[1];
        store_native_u16_to_u64(&heap[node_ptr], h1);
        return node_ptr;
}