itch::book::OrderIndex Class Reference

A flat, open-addressed hash map from order reference number to pool index, used for O(1) order lookup without per-order heap allocation. More...

#include <order_index.hpp>

Public Member Functions
	OrderIndex ()
	Constructs an empty map with the initial table capacity pre-allocated.
auto	size () const noexcept -> std::size_t
	The number of stored keys.
auto	empty () const noexcept -> bool
	Whether the map holds no keys.
auto	find (std::uint64_t key) const noexcept -> std::uint32_t
	Returns the value for key, or NPOS if absent.
auto	contains (std::uint64_t key) const noexcept -> bool
	Whether key is present.
auto	insert (std::uint64_t key, std::uint32_t value) -> void
	Inserts or overwrites the value for key.
auto	erase (std::uint64_t key) -> void
	Removes key if present, repairing the probe chain in place.
auto	clear () -> void
	Drops all keys (retaining capacity).

Static Public Attributes
static constexpr std::uint32_t	NPOS = 0xFFFFFFFFU
	Sentinel returned by find when a key is absent.

Detailed Description

A flat, open-addressed hash map from order reference number to pool index, used for O(1) order lookup without per-order heap allocation.

std::unordered_map allocates a node on every insert and frees one on every erase, which on a feed of hundreds of millions of add/delete messages dominates the book's cost and defeats the allocation-free goal. This map stores its slots in a single contiguous vector, probes linearly (cache friendly), and uses backward-shift deletion so heavy add/cancel churn does not accumulate tombstones. It only allocates when it grows.

Definition at line 29 of file order_index.hpp.

Constructor & Destructor Documentation

OrderIndex()

itch::book::OrderIndex::OrderIndex ( )

inline

Constructs an empty map with the initial table capacity pre-allocated.

Definition at line 36 of file order_index.hpp.

Member Function Documentation

size()

auto itch::book::OrderIndex::size ( ) const -> std::size_t

inlinenoexcept

The number of stored keys.

Returns

The count of stored keys.

Definition at line 40 of file order_index.hpp.

empty()

auto itch::book::OrderIndex::empty ( ) const -> bool

inlinenoexcept

Whether the map holds no keys.

Returns

True if the map holds no keys, false otherwise.

Definition at line 44 of file order_index.hpp.

Referenced by itch::book::L3Book::empty().

find()

auto itch::book::OrderIndex::find ( std::uint64_t  key ) const -> std::uint32_t

inlinenoexcept

Returns the value for key, or NPOS if absent.

Parameters

key	The order reference number to look up.

Returns

The stored pool index for key, or NPOS if absent.

Definition at line 49 of file order_index.hpp.

References NPOS.

Referenced by contains().

contains()

auto itch::book::OrderIndex::contains ( std::uint64_t  key ) const -> bool

inlinenoexcept

Whether key is present.

Parameters

key	The order reference number to check.

Returns

True if key is present, false otherwise.

Definition at line 63 of file order_index.hpp.

References find(), and NPOS.

insert()

auto itch::book::OrderIndex::insert ( std::uint64_t  key, std::uint32_t  value  ) -> void

inline

Inserts or overwrites the value for key.

Parameters

key	The order reference number to insert or update.
value	The pool index to associate with key.

Definition at line 70 of file order_index.hpp.

erase()

auto itch::book::OrderIndex::erase ( std::uint64_t  key ) -> void

inline

Removes key if present, repairing the probe chain in place.

Parameters

key	The order reference number to remove.

Definition at line 88 of file order_index.hpp.

clear()

auto itch::book::OrderIndex::clear ( ) -> void

inline

Drops all keys (retaining capacity).

Definition at line 100 of file order_index.hpp.

Member Data Documentation

NPOS

constexpr std::uint32_t itch::book::OrderIndex::NPOS = 0xFFFFFFFFU

staticconstexpr

Sentinel returned by find when a key is absent.

Definition at line 32 of file order_index.hpp.

Referenced by itch::book::L3Book::add_order(), contains(), itch::book::L3Book::delete_order(), itch::book::L3Book::execute_order(), find(), itch::book::L3Book::order_price(), itch::book::L3Book::order_side(), and itch::book::L3Book::replace_order().

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The documentation for this class was generated from the following file:

• order_index.hpp