// Copyright (c) Vitaliy Filippov, 2023+
// License: VNPL-1.1 or GNU GPL-2.0+ (see README.md for details)

#include <assert.h>
#include "freelist.h"

uint64_t freelist_allocator_t::alloc(uint64_t data_size)
{
    for (int i = 0; i < freelist.size(); i++)
    {
        if (freelist[i].size >= data_size)
        {
            uint64_t r = freelist[i].start;
            freelist[i].start += data_size;
            freelist[i].size -= data_size;
            return r;
        }
    }
    return UINT64_MAX;
}

void freelist_allocator_t::free(uint64_t start, uint64_t size)
{
    int min = 0, max = freelist.size();
    if (max && freelist[freelist.size()-1].start < start)
    {
        min = max;
    }
    if (max && freelist[0].start >= start)
    {
        max = 0;
    }
    while (max-min > 1)
    {
        int mid = (min+max)/2;
        if (freelist[mid].start >= start)
            max = mid;
        else
            min = mid;
    }
    // max = the first item where freelist[max].start >= start
    if (max > 0 && freelist[max-1].start+freelist[max-1].size >= start)
    {
        assert(freelist[max-1].start+freelist[max-1].size == start);
        freelist[max-1].size += size;
    }
    else if (max < freelist.size() && freelist[max].start <= size+start)
    {
        assert(freelist[max].start == size+start);
        freelist[max].start -= size;
        freelist[max].size += size;
    }
    else
    {
        freelist.insert(freelist.begin()+min, (freelist_item_t){ .start = start, .size = size });
        max = min; // to skip the if below
    }
    if (min != max && max < freelist.size() && freelist[max].start == freelist[min].start+freelist[min].size)
    {
        freelist[min].size += freelist[max].size;
        freelist.erase(freelist.begin()+max, freelist.begin()+max+1);
    }
}