Program Listing for File freelist.hpp

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/* SPDX-License-Identifier: BSD-2-Clause */
#pragma once
#include <cstdint>
#include <lib/error.hpp>
#include <lib/result.hpp>

namespace Gaia {

class Freelist {
public:
  struct Region {
    size_t size;
    Region *next;
  };

  explicit Freelist(size_t quantum) : quantum(quantum) {}
  Freelist() : quantum(1) {}

  void set_quantum(size_t new_quantum) { quantum = new_quantum; }

  void add_region(Region *region) {
    region->next = head;
    head = region;
  }

  Result<uintptr_t, Error> alloc() {
    if (!head) {
      return Err(Error::OUT_OF_MEMORY);
    }

    auto region = head;
    region->size -= quantum;

    if (!head->size) {
      head = head->next;
    }

    return Ok((uintptr_t)region + region->size);
  }

  void free(uintptr_t mem) {
    auto region = reinterpret_cast<Region *>(mem);
    region->size = quantum;
    add_region(region);
  }

private:
  Region *head = nullptr;
  size_t quantum = 0;
};

} // namespace Gaia