Method prepend_alloc

libCacheSim/dataStructure/sparsepp/spp_dlalloc.h:2439–2482

Allocate chunk and prepend remainder with chunk in successor base. */

/* Allocate chunk and prepend remainder with chunk in successor base. */
void* malloc_state::prepend_alloc(char* newbase, char* oldbase, size_t nb)
{
    mchunkptr p = align_as_chunk(newbase);
    mchunkptr oldfirst = align_as_chunk(oldbase);
    size_t psize = (char*)oldfirst - (char*)p;
    mchunkptr q = (mchunkptr)p->chunk_plus_offset(nb);
    size_t qsize = psize - nb;
    set_size_and_pinuse_of_inuse_chunk(p, nb);

    assert((char*)oldfirst > (char*)q);
    assert(oldfirst->pinuse());
    assert(qsize >= MIN_CHUNK_SIZE);

    // consolidate remainder with first chunk of old base
    if (oldfirst == _top)
    {
        size_t tsize = _topsize += qsize;
        _top = q;
        q->_head = tsize | PINUSE_BIT;
        check_top_chunk(q);
    }
    else if (oldfirst == _dv)
    {
        size_t dsize = _dvsize += qsize;
        _dv = q;
        q->set_size_and_pinuse_of_free_chunk(dsize);
    }
    else
    {
        if (!oldfirst->is_inuse())
        {
            size_t nsize = oldfirst->chunksize();
            unlink_chunk(oldfirst, nsize);
            oldfirst = (mchunkptr)oldfirst->chunk_plus_offset(nsize);
            qsize += nsize;
        }
        q->set_free_with_pinuse(qsize, oldfirst);
        insert_chunk(q, qsize);
        check_free_chunk(q);
    }

    check_malloced_chunk(chunk2mem(p), nb);
    return chunk2mem(p);
}

// Add a segment to hold a new noncontiguous region
void malloc_state::add_segment(char* tbase, size_t tsize, flag_t mmapped)