Compact<u64>

Compact 12 v393

About This Type

Variable-length encoded wrapper around u64.

Compact encoding uses fewer bytes for small values. Values 0–63 use 1 byte, 64–16,383 use 2 bytes, and larger values use 4 bytes.

Encoding: Two least-significant bits encode the mode: 00=single-byte, 01=two-byte, 10=four-byte, 11=big-integer.

Compact Wrapper

Wraps: u64
SCALE Encoding: Variable-length integer (1, 2, or 4 bytes depending on value)

SCALE Encoding

Rule: Variable-length integer encoding of u64. Uses fewer bytes for smaller values.
Size: variable (1–5 bytes)

Examples

Small value: 6 = 6

0x18

18 Single-byte mode: 6 << 2 = 24 = 0x18

Medium value: 100 = 100

0x9101

91 01 Two-byte mode: (100 << 2) | 0x01 = 401 = 0x0191, stored LE

Larger value: 1,000,000 = 1,000,000

0x02000f4002

02 00 0f 40 02 Four-byte mode: (1,000,000 << 2) | 0x02

Code Examples

import { TypeRegistry, compactToU8a } from "@polkadot/types";

const registry = new TypeRegistry();

// Encode as Compact<u64>
const value = registry.createType("Compact<u64>", 100);
console.log("Hex:", value.toHex());

// Or use the low-level utility
const bytes = compactToU8a(100);
console.log("Bytes:", bytes);

Referenced By (115)

#11 Weight via ref_time #11 Weight via proof_size #124 Timestamp::Call via set.now #137 Balances::Call via transfer_allow_death.value #137 Balances::Call via force_transfer.value #137 Balances::Call via transfer_keep_alive.value #137 Balances::Call via force_set_balance.new_free #137 Balances::Call via force_adjust_total_issuance.delta #137 Balances::Call via burn.value #149 Vec<Compact<u64>> #363 Crowdloan::Call via create.deposit #363 Crowdloan::Call via create.min_contribution #363 Crowdloan::Call via create.cap #363 Crowdloan::Call via contribute.amount #363 Crowdloan::Call via update_min_contribution.new_min_contribution #363 Crowdloan::Call via update_cap.new_cap #366 Contracts::Call via call_old_weight.value #366 Contracts::Call via call_old_weight.gas_limit #366 Contracts::Call via instantiate_with_code_old_weight.value #366 Contracts::Call via instantiate_with_code_old_weight.gas_limit

and 95 more...

Type Information

Type ID: 12
Kind: Compact
Runtime: v393