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xo-alloc2: header reorg

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Roland Conybeare 2025-12-14 17:01:48 -05:00
commit 019913bb51
5 changed files with 4 additions and 4 deletions
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132
include/xo/alloc2/DArena.hpp
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/** @file DArena.hpp
*
* @author Roland Conybeare, Dec 2025
**/
#pragma once
#include "ArenaConfig.hpp"
namespace xo {
namespace mm {
/** @class DArena
*
* @brief represent arena allocator state
*
* Provides minimal RAII functionality around memory mapping.
* For allocation implementation see @ref IAllocator_DArena
**/
struct DArena {
/*
* <----------------------------size-------------------------->
* <------------committed-----------><-------uncommitted------>
* <--allocated-->
*
* XXXXXXXXXXXXXXX___________________..........................
*
* [X] allocated: in use
* [_] committed: physical memory obtained
* [.] uncommitted: mapped in virtual memory, not backed by memory
*/
/** @defgroup mm-arena-traits arena type traits **/
///@{
/** @brief an amount of memory **/
using size_type = std::size_t;
/** @brief a contiguous memory range **/
using range_type = std::pair<std::byte*,std::byte*>;
/** @brief type for allocation header (if enabled) **/
using header_type = std::uint64_t;
///@}
/** @defgroup mm-arena-ctors arena constructors and destructors **/
///@{
/** create arena per configuration @p cfg. **/
static DArena map(const ArenaConfig & cfg);
/** null ctor **/
DArena() = default;
/** ctor from already-mapped (but not committed) address range **/
DArena(const ArenaConfig & cfg, size_type page_z, std::byte * lo, std::byte * hi);
/** DArena is not copyable **/
DArena(const DArena & other) = delete;
/** move ctor **/
DArena(DArena && other);
/** dtor releases mapped memory **/
~DArena();
/** move-assignment **/
DArena & operator=(DArena && other);
///@}
/** obtain uncommitted contiguous memory range comprising
* a whole multiple of @p hugepage_z bytes, of at least size @p req_z,
* aligned on a @p hugepage_z boundary
**/
static range_type map_aligned_range(size_type req_z, size_type hugepage_z);
/** @defgroup mm-arena-methods **/
///@{
/** true if arena is mapped i.e. has a reserved address range **/
bool is_mapped() const { return (lo_ != nullptr) && (hi_ != nullptr); }
///@}
/** @defgroup mm-arena-instance-vars **/
///@{
/** arena configuration **/
ArenaConfig config_;
/** size of a VM page (obtained automatically via getpagesize()). Likely 4k **/
size_type page_z_ = 0;
/** arena owns memory in range [@ref lo_, @ref hi_)
**/
std::byte * lo_ = nullptr;
/** prefix of this size is committed.
* Remainder mapped but uncommitted.
**/
size_type committed_z_ = 0;
/** if config_.store_header_flag_:
* Pointer to header for last allocation.
**/
header_type * last_header_ = nullptr;
/** free pointer.
* Memory in range [@ref lo_, @ref free_) current in use
**/
std::byte * free_ = nullptr;
/** soft limit; end of committed virtual memory
* Memory in range [@ref lo_, @ref limit_) is committed
* (backed by physical memory)
**/
std::byte * limit_ = nullptr;
/** hard limit; end of reserved virtual memory
* Memory in range [@ref limit_, @ref hi_) is uncommitted
**/
std::byte * hi_ = nullptr;
/** count runtime errors. Each error updates @ref last_error_ **/
uint32_t error_count_ = 0;
/** capture some error details if/when error **/
AllocatorError last_error_;
///@}
};
} /*namespace mm*/
} /*namespace xo*/
/* end DArena.hpp */