fix: Respect view length when writing slice with BufferWriter (#36)

iwoplaza · Oct 5, 2024 · 82bde4d · 82bde4d
1 parent e809845
commit 82bde4d
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Showing 3 changed files with 32 additions and 3 deletions.
diff --git a/packages/typed-binary/src/io/bufferReaderWriter.test.ts b/packages/typed-binary/src/io/bufferReaderWriter.test.ts
@@ -76,6 +76,21 @@ describe('BufferWriter', () => {
     expect(reader.readUint32()).to.eq(8);
     expect(reader.readUint32()).to.eq(4_294_967_295);
   });
+
+  it('respects view length when writing slice (#35)', () => {
+    // Create a 512 byte ArrayBuffer.
+    const srcBuffer = new ArrayBuffer(512);
+
+    // Create a 100 byte Uint8Array view into the ArrayBuffer at offset 10.
+    const srcView = new Uint8Array(srcBuffer, 10, 100);
+
+    // Write the Uint8Array into a BufferWriter.
+    const dstBuffer = new ArrayBuffer(512);
+    const output = new BufferWriter(dstBuffer);
+    expect(output.currentByteOffset).toEqual(0);
+    output.writeSlice(srcView);
+    expect(output.currentByteOffset).toEqual(100);
+  });
 });
 
 describe('BufferReader', () => {

diff --git a/packages/typed-binary/src/io/bufferWriter.ts b/packages/typed-binary/src/io/bufferWriter.ts
@@ -57,7 +57,13 @@ export class BufferWriter extends BufferIOBase implements ISerialOutput {
 
   writeSlice(bufferView: ArrayLike<number> & ArrayBufferView): void {
     const unwrapped = unwrapBuffer(bufferView);
-    const srcU8 = new Uint8Array(unwrapped.buffer, unwrapped.byteOffset);
+
+    const srcU8 = new Uint8Array(
+      unwrapped.buffer,
+      unwrapped.byteOffset,
+      unwrapped.byteLength,
+    );
+
     for (const srcByte of srcU8) {
       this.uint8View[this.byteOffset++] = srcByte;
     }

diff --git a/packages/typed-binary/src/io/unwrapBuffer.ts b/packages/typed-binary/src/io/unwrapBuffer.ts
@@ -1,7 +1,15 @@
+interface UnwrapBufferResult {
+  buffer: ArrayBufferLike;
+  byteOffset: number;
+  byteLength: number;
+}
+
 /**
  * Removes up to one layer of view over a buffer.
  */
-export function unwrapBuffer(buffer: ArrayBufferLike | ArrayBufferView) {
+export function unwrapBuffer(
+  buffer: ArrayBufferLike | ArrayBufferView,
+): UnwrapBufferResult {
   let byteOffset = 0;
   let innerBuffer = buffer;
 
@@ -11,5 +19,5 @@ export function unwrapBuffer(buffer: ArrayBufferLike | ArrayBufferView) {
     innerBuffer = innerBuffer.buffer;
   }
 
-  return { buffer: innerBuffer, byteOffset };
+  return { buffer: innerBuffer, byteOffset, byteLength: buffer.byteLength };
 }