Add bufferSize option

README.md

@@ -151,7 +151,7 @@ console.log(deserializedTodos)
 
 This library exports the following functions:
 
-- `createSer()`: creates a new serializer.
+- `createSer()`/`createSer({ bufferSize: number })`: creates a new serializer.
 - `createDes(buffer)`: creates a new deserializer.
 - `ser.serializeBoolean(b)`: serializes a boolean value.
 - `des.deserializeBoolean()`: deserializes a boolean value.

src/index.ts

@@ -26,8 +26,16 @@ export interface Des {
   deserializeIterable: <T>(deserialize: (des: Des) => T) => Iterable<T>
 }
 
-export function createSer (): Ser {
-  const buffer = new ArrayBuffer(2 ** 24)
+interface CreateSerOption {
+  bufferSize?: number
+}
+export function createSer ({ bufferSize }: CreateSerOption = {}): Ser {
+  const size = bufferSize || 2 ** 24
+  if (size >= 2 ** 32) {
+    throw new Error('bufferSize option must be strictly less than 2 ** 32')
+  }
+
+  const buffer = new ArrayBuffer(size)
   return {
     index: 0,
     buffer,

tests/index.test.ts

@@ -261,6 +261,28 @@ await t.test('iterable', async t => {
   })
 })
 
+await t.test('with option', async t => {
+  await t.test('bufferSize', async t => {
+    {
+      const ser = createSer({ bufferSize: 4 })
+      assert.equal(ser.buffer.byteLength, 4)
+    }
+    {
+      const ser = createSer({ bufferSize: 8 })
+      assert.equal(ser.buffer.byteLength, 8)
+    }
+    {
+      const ser = createSer({ bufferSize: 2 ** 32 - 4 })
+      assert.equal(ser.buffer.byteLength, 2 ** 32 - 4)
+    }
+    {
+      assert.throws(() => createSer({ bufferSize: 2 ** 32 }), err => {
+        return /bufferSize option must be strictly less than 2 \*\* 32/.test((err as Error).message)
+      })
+    }
+  })
+})
+
 await t.test('random items', async t => {
   const elements: any[] = [
     { item: 'foo', serializer: 'serializeString', deserializer: 'deserializeString' },