Initial Commit

packages/api-stack/api/api-sandbox-wasm-host-bridge/tests/fixtures/leb128.ts

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+/**
+ * Minimal LEB128 encoder utilities used by the hand-encoded WASM fixture
+ * builder. WebAssembly's binary format uses LEB128 for unsigned 32-bit
+ * indices / lengths and signed LEB128 for `i32.const` / `i64.const`
+ * literals. Both encoders are bounded by their bit-width and emit the
+ * minimal number of bytes.
+ */
+
+/** Encode `value` as unsigned LEB128. */
+export function encodeU32(value: number): Uint8Array {
+    if (value < 0 || !Number.isFinite(value)) {
+        throw new RangeError(`encodeU32: invalid value ${value}`);
+    }
+    const out: number[] = [];
+    let v = value >>> 0;
+    do {
+        let byte = v & 0x7f;
+        v >>>= 7;
+        if (v !== 0) byte |= 0x80;
+        out.push(byte);
+    } while (v !== 0);
+    return new Uint8Array(out);
+}
+
+/** Encode `value` as signed LEB128 (32-bit). */
+export function encodeI32(value: number): Uint8Array {
+    const out: number[] = [];
+    let v = value | 0;
+    while (true) {
+        const byte = v & 0x7f;
+        v >>= 7;
+        const signBit = (byte & 0x40) !== 0;
+        if ((v === 0 && !signBit) || (v === -1 && signBit)) {
+            out.push(byte);
+            break;
+        }
+        out.push(byte | 0x80);
+    }
+    return new Uint8Array(out);
+}
+
+/** Encode a name as length-prefixed UTF-8 bytes. */
+export function encodeName(name: string): Uint8Array {
+    const bytes = new TextEncoder().encode(name);
+    return concat(encodeU32(bytes.length), bytes);
+}
+
+/** Concatenate any number of byte arrays. */
+export function concat(...parts: Uint8Array[]): Uint8Array {
+    let total = 0;
+    for (const p of parts) total += p.length;
+    const out = new Uint8Array(total);
+    let offset = 0;
+    for (const p of parts) {
+        out.set(p, offset);
+        offset += p.length;
+    }
+    return out;
+}
+
+/** Wrap raw payload bytes in a WASM section frame: id + length + payload. */
+export function section(id: number, payload: Uint8Array): Uint8Array {
+    return concat(new Uint8Array([id]), encodeU32(payload.length), payload);
+}
+
+/** Encode a count-prefixed vector of pre-encoded items. */
+export function vec(items: readonly Uint8Array[]): Uint8Array {
+    return concat(encodeU32(items.length), concat(...items));
+}