idgenerationpool.h

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#pragma once
//------------------------------------------------------------------------------
#include "util/array.h"
#include "id.h"
#include "util/queue.h"
 
const uint32_t ID_BITS = 24;
const uint32_t GENERATION_BITS = 8;
const uint32_t ID_MASK = (1<<ID_BITS) - 1;
const uint32_t GENERATION_MASK = (1<<GENERATION_BITS) - 1;
 
#if GENERATION_BITS <= 8
typedef uint8_t generation_t;
#elif GENERATION_BITS <= 16
typedef uint16_t generation_t;
#else 
typedef uint32_t generation_t;
#endif
#if ID_BITS + GENERATION_BITS > 32
#error bits in game id generation exceeds 32
#endif
 
//------------------------------------------------------------------------------
namespace Ids
{
class IdGenerationPool
{
public:
    IdGenerationPool();
    ~IdGenerationPool();
 
    bool Allocate(Id32& id);
    void Deallocate(Id32 id);
    bool IsValid(Id32 id) const;
    
private:
    Util::Array<generation_t> generations;
 
    Util::Queue<Id32> freeIds;
    SizeT freeIdsSize;
};
 
//------------------------------------------------------------------------------
constexpr static Id24 
Index(const Id32 id)
{
    return id & ID_MASK;
}
 
//------------------------------------------------------------------------------
constexpr static generation_t
Generation(const Id32 id)
{
    return (id >> ID_BITS) & GENERATION_MASK;
}
 
//------------------------------------------------------------------------------
static Id32
CreateId(const Id24 index, generation_t generation)
{
    Id32 id;
    id = (generation << ID_BITS) | index;
    n_assert2(index < (1 << ID_BITS), "index overflow");
    return id;
}
 
} // namespace Ids
//------------------------------------------------------------------------------