Low-Latency Exchange Message Flag Packing

Ultra-low-latency financial protocols (such as OUCH and ITCH) pack execution parameters into a compact 64-bit integer bitfield to minimize network packet serialization overhead and memory footprint.

The protocol defines the following layout for a 64-bit unsigned integer flags:

• Bit 0: Order Side (0 = Buy, 1 = Sell)
• Bits 1..3: Time-in-Force (1 = IOC, 2 = FOK, 3 = GTC, 4 = DAY)
• Bit 4: Post-Only flag (0 = False, 1 = True)
• Bit 5: Cancel-on-Disconnect (COD) flag (0 = False, 1 = True)
• Bit 6: Hidden Order flag (0 = False, 1 = True)
• Bits 7..14: Algorithmic Execution Tag (8-bit integer, values $0$ to $255$)
• Bits 15..20: Client Risk Tier (6-bit integer, values $0$ to $63$)

Business Validation Rules:

1. Post-Only Incompatibility: A Post-Only order cannot have Time-in-Force set to Immediate-or-Cancel (IOC, 1) or Fill-or-Kill (FOK, 2). If violated, raise a ValueError('Post-Only incompatible with IOC/FOK').
2. Hidden Order Risk Tier Constraint: A Hidden order is restricted to institutional clients and requires risk_tier >= 2. If violated, raise a ValueError('Hidden orders require risk_tier >= 2').

Your Task

Implement two functions:

1. pack_order_flags(side: int, tif: int, post_only: bool, cod: bool, hidden: bool, algo_tag: int, risk_tier: int) -> int
2. unpack_order_flags(packed: int) -> dict returning a dictionary with keys: ['side', 'tif', 'post_only', 'cod', 'hidden', 'algo_tag', 'risk_tier'].

Constraints

• $side \in \{0, 1\}$
• $tif \in \{1, 2, 3, 4\}$
• $0 \le algo\_tag \le 255$
• $0 \le risk\_tier \le 63$