Initial Commit

packages/foundation/bitpacker/bitpacker-strategies/src/strategies/bitset/bitset.ts

@@ -0,0 +1,65 @@
+import type {
+    BitPackerSchema,
+    PackingContext,
+    PackingStrategy,
+} from "@suaveplan/bitpacker";
+import { BITPACKER_CODES, BitpackerError } from "@suaveplan/bitpacker";
+
+function bitsRequired(maxValue: number): number {
+    if (maxValue <= 0) return 0;
+    return Math.floor(Math.log2(maxValue)) + 1;
+}
+
+/**
+ * Bitset schema: `{ _bitset: { maxSize: number } }`.
+ */
+export class BitsetPackingStrategy implements PackingStrategy {
+    canHandle(schema: BitPackerSchema): boolean {
+        return (
+            typeof schema === "object" && schema !== null && "_bitset" in schema
+        );
+    }
+
+    pack(
+        data: unknown,
+        schema: BitPackerSchema,
+        context: PackingContext
+    ): void {
+        const cfg = (schema as { _bitset: { maxSize: number } })._bitset;
+        const set = data as Set<number>;
+
+        if (!(set instanceof Set)) {
+            throw new BitpackerError(
+                BITPACKER_CODES.INVALID_SCHEMA,
+                `Expected Set<number> for bitset schema, got ${typeof data}`,
+                { context: { data } }
+            );
+        }
+
+        if (set.size > cfg.maxSize) {
+            throw new BitpackerError(
+                BITPACKER_CODES.VALUE_OUT_OF_RANGE,
+                `Bitset size ${set.size} exceeds max ${cfg.maxSize}`,
+                { context: { size: set.size, maxSize: cfg.maxSize } }
+            );
+        }
+
+        context.writer.writeUint(set.size, bitsRequired(cfg.maxSize));
+
+        for (const index of set) {
+            context.writer.writeUint(index, bitsRequired(cfg.maxSize));
+        }
+    }
+
+    unpack(schema: BitPackerSchema, context: PackingContext): unknown {
+        const cfg = (schema as { _bitset: { maxSize: number } })._bitset;
+        const size = context.reader.readUint(bitsRequired(cfg.maxSize));
+        const result = new Set<number>();
+
+        for (let i = 0; i < size; i++) {
+            result.add(context.reader.readUint(bitsRequired(cfg.maxSize)));
+        }
+
+        return result;
+    }
+}