Added a getData() method to ByteBuffer.

Author: codedread

CHANGELOG.md

@@ -7,6 +7,7 @@ All notable changes to this project will be documented in this file.
 ### Added
 
 - archive: Support semantic methods for subscribing to unarchive events (onExtract), [Issue #47](https://github.com/codedread/bitjs/issues/47).
+- io: Added a getData() method to ByteBuffer to retrieve a copy of the bytes that have been written.
 
 ### Changed
 

io/bitstream.js

@@ -20,7 +20,7 @@ const BITMASK = [0, 0x01, 0x03, 0x07, 0x0F, 0x1F, 0x3F, 0x7F, 0xFF];
  *
  * Bit reading always proceeds from the first byte in the buffer, to the
  * second byte, and so on. The MTL flag controls which bit is considered
- * first *inside* the byte.
+ * first *inside* the byte. The default is least-to-most direction.
  *
  * An Example for how Most-To-Least vs Least-to-Most mode works:
  *

io/bytebuffer.js

@@ -30,17 +30,31 @@ export class ByteBuffer {
     this.data = new Uint8Array(numBytes);
 
     /**
+     * Points to the byte that will next be written.
      * @type {number}
      * @public
      */
     this.ptr = 0;
   }
 
+  /**
+   * Returns an exact copy of all the data that has been written to the ByteBuffer.
+   * @returns {Uint8Array}
+   */
+  getData() {
+    const dataCopy = new Uint8Array(this.ptr);
+    dataCopy.set(this.data.subarray(0, this.ptr));
+    return dataCopy;
+  }
 
   /**
    * @param {number} b The byte to insert.
    */
   insertByte(b) {
+    if (this.ptr + 1 > this.data.byteLength) {
+      throw `Cannot insert a byte, the buffer is full.`;
+    }
+
     // TODO: throw if byte is invalid?
     this.data[this.ptr++] = b;
   }
@@ -49,6 +63,10 @@ export class ByteBuffer {
    * @param {Array.<number>|Uint8Array|Int8Array} bytes The bytes to insert.
    */
   insertBytes(bytes) {
+    if (this.ptr + bytes.length > this.data.byteLength) {
+      throw `Cannot insert ${bytes.length} bytes, the buffer is full.`;
+    }
+
     // TODO: throw if bytes is invalid?
     this.data.set(bytes, this.ptr);
     this.ptr += bytes.length;

io/bytestream.js

@@ -66,21 +66,21 @@ export class ByteStream {
     this.littleEndian_ = true;
   }
 
-  /** @returns {boolean} Whether the stream is little-endian. */
+  /** @returns {boolean} Whether the stream is little-endian (least significant byte is first). */
   isLittleEndian() {
     return this.littleEndian_;
   }
 
   /**
-   * Big-Endian is sometimes called Motorola-style.
+   * Big-Endian means the most significant byte is first. it is sometimes called Motorola-style.
    * @param {boolean=} val The value to set. If not present, the stream is set to big-endian.
    */
   setBigEndian(val = true) {
     this.littleEndian_ = !val;
   }
 
   /**
-   * Little-Endian is sometimes called Intel-style.
+   * Little-Endian means the least significant byte is ifrst. is sometimes called Intel-style.
    * @param {boolean=} val The value to set. If not present, the stream is set to little-endian.
    */
   setLittleEndian(val = true) {

tests/io-bytebuffer.spec.js

@@ -18,10 +18,35 @@ describe('bitjs.io.ByteBuffer', () => {
     buffer = new ByteBuffer(4);
   });
 
+  describe('getData()', () => {
+    it('returns an empty array when nothing has been written', () => {
+      expect(buffer.getData().byteLength).equals(0);
+    });
+
+    it('is sized correctly', () => {
+      buffer.insertByte(42);
+      buffer.insertByte(81);
+      const data = buffer.getData();
+      expect(data.byteLength).equals(2);
+      expect(data[0]).equals(42);
+      expect(data[1]).equals(81);  
+    });
+  });
+
   it('throws when initialized incorrectly', () => {
     expect(() => new ByteBuffer()).throws();
   });
 
+  describe('Buffer overflow', () => {
+    it('insertByte() throws when buffer exceeded', () => {
+      buffer.insertBytes([0, 2, 4, 6]);
+      expect(() => buffer.insertByte(1)).throws();
+    });  
+    it('insertBytes() throws when buffer exceeded', () => {
+      expect(() => buffer.insertBytes([0, 2, 4, 6, 8])).throws();
+    });  
+  });
+
   it('insertByte()', () => {
     buffer.insertByte(192);
     expect(buffer.ptr).equals(1);