core: reduce latency when loading shared sessions through event compaction

1 files changed, 48 insertions, 0 deletions

diff --git a/packages/util/src/identifier.ts b/packages/util/src/identifier.ts
new file mode 100644
index 000000000..ba28a351b
--- /dev/null
+++ b/packages/util/src/identifier.ts
@@ -0,0 +1,48 @@
+import { randomBytes } from "crypto"
+
+export namespace Identifier {
+  const LENGTH = 26
+
+  // State for monotonic ID generation
+  let lastTimestamp = 0
+  let counter = 0
+
+  export function ascending() {
+    return create(false)
+  }
+
+  export function descending() {
+    return create(true)
+  }
+
+  function randomBase62(length: number): string {
+    const chars = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
+    let result = ""
+    const bytes = randomBytes(length)
+    for (let i = 0; i < length; i++) {
+      result += chars[bytes[i] % 62]
+    }
+    return result
+  }
+
+  export function create(descending: boolean, timestamp?: number): string {
+    const currentTimestamp = timestamp ?? Date.now()
+
+    if (currentTimestamp !== lastTimestamp) {
+      lastTimestamp = currentTimestamp
+      counter = 0
+    }
+    counter++
+
+    let now = BigInt(currentTimestamp) * BigInt(0x1000) + BigInt(counter)
+
+    now = descending ? ~now : now
+
+    const timeBytes = Buffer.alloc(6)
+    for (let i = 0; i < 6; i++) {
+      timeBytes[i] = Number((now >> BigInt(40 - 8 * i)) & BigInt(0xff))
+    }
+
+    return timeBytes.toString("hex") + randomBase62(LENGTH - 12)
+  }
+}