xref: /isa-l/igzip/proc_heap_base.c (revision 55fbfabfc60f1002bc8133b730a59f6abd22cfce)

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  modification, are permitted provided that the following conditions
  are met:
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      contributors may be used to endorse or promote products derived
      from this software without specific prior written permission.

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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;
}