Sectors

Market account data begins with a MarketHeader followed by a contiguous array of fixed-size sectors. Each sector holds one of three node types (Order, Seat, or StackNode), but a node does not necessarily occupy the entire sector.

Because the market account is at a fixed position in the input buffer, its data offsets are persisted across transactions. MarketHeader stores absolute SBPF pointers into the sector array (seats, asks, bids, top, next) that remain valid without recomputation.

+----------------+----------+----------+----------+-----+
| MarketHeader   | Sector 0 | Sector 1 | Sector 2 | ... |
+----------------+----------+----------+----------+-----+

A Sector is a byte buffer sized to the largest node type:

The first byte of every sector is a NodeTag discriminant that identifies its contents:

Order

A sector holding an Order is an active node in one of the market's order trees.

+-----+--------------------------------------------------+
| tag |                   (unused)                       |
+-----+--------------------------------------------------+

Seat

A sector holding a Seat is an active node in the market's seat tree.

+-----+--------+------+-------+------+-----+------+------+
| tag | parent | left | right | user | ... | asks | bids |
+-----+--------+------+-------+------+-----+------+------+

StackNode

A sector holding a StackNode is a freed sector on the free sector stack.

+-----+------+-------------------------------------------+
| tag | next |                (unused)                   |
+-----+------+-------------------------------------------+

Allocation

MarketHeader.next points to the next unallocated sector in the memory map. MarketHeader.top points to the top of the free sector stack. When a sector is freed, it becomes a StackNode pushed onto the stack. New allocations pop from the stack first; when the stack is empty, next advances.