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fix: resolve #22 feat(core): add deterministic env.uuid() and rng.u... #31

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Merged
sx4im merged 1 commit into from
Sep 29, 2026
Merged

fix: resolve #22 feat(core): add deterministic env.uuid() and rng.u... #31

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23 changes: 22 additions & 1 deletion packages/core/src/random.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -68,6 +68,27 @@ export class Rng {
return arr[this.nextInt(0, arr.length)]!;
}

/** Deterministic RFC 4122 v4 UUID. */
uuid(): string {
const u1 = this.nextU64();
const u2 = this.nextU64();
const bytes = new Uint8Array(16);
for (let i = 0; i < 8; i++) {
bytes[i] = Number((u1 >> BigInt(56 - i * 8)) & 0xFFn);
bytes[i + 8] = Number((u2 >> BigInt(56 - i * 8)) & 0xFFn);
}
bytes[6] = (bytes[6]! & 0x0f) | 0x40; // RFC 4122 v4
bytes[8] = (bytes[8]! & 0x3f) | 0x80; // RFC 4122 variant
let hex = "";
for (let i = 0; i < 16; i++) {
if (i === 4 || i === 6 || i === 8 || i === 10) {
hex += "-";
}
hex += bytes[i]!.toString(16).padStart(2, "0");
}
return hex;
}

/** Snapshot/restore for replay & node-restart determinism. */
getState(): [bigint, bigint, bigint, bigint] {
return [this.s0, this.s1, this.s2, this.s3];
Expand All @@ -76,4 +97,4 @@ export class Rng {
setState(s: [bigint, bigint, bigint, bigint]): void {
[this.s0, this.s1, this.s2, this.s3] = s;
}
}
}
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