feat: add IOBuffer.back() (#52)

Author: santi-mir

src/IOBuffer.ts

@@ -141,6 +141,15 @@ export class IOBuffer {
     return this;
   }
 
+  /**
+   * Move the pointer n bytes backward.
+   * @param n - Number of bytes to move back.
+   */
+  public back(n = 1): this {
+    this.offset -= n;
+    return this;
+  }
+
   /**
    * Move the pointer to the given offset.
    * @param offset

src/__tests__/core.ts

@@ -45,6 +45,17 @@ describe('core methods', () => {
     expect(buffer.offset).toBe(8);
   });
 
+  it('back', () => {
+    buffer.offset = 8;
+    buffer.back(5);
+    expect(buffer.offset).toBe(3);
+    buffer.back(1);
+    buffer.back();
+    expect(buffer.offset).toBe(1);
+    buffer.back();
+    expect(buffer.offset).toBe(0);
+  });
+
   it('seek', () => {
     buffer.seek(0);
     expect(buffer.offset).toBe(0);