fix: add du to README (#46)

Author: billiegoose

README.md

@@ -182,6 +182,10 @@ Options object:
 | ------ | ---------------- | ---------------------- |
 | `mode` | number = 0o666   | Posix mode permissions |
 
+### `fs.du(filepath, cb)`
+
+Returns the size of a file or directory in bytes.
+
 ### `fs.promises`
 
 All the same functions as above, but instead of passing a callback they return a promise.

src/__tests__/fs.spec.js

@@ -444,4 +444,34 @@ describe("fs module", () => {
     });
   });
 
+  describe("du", () => {
+    it("du returns the total file size of a path", done => {
+      fs.mkdir("/du", () => {
+        fs.writeFile("/du/a.txt", "hello", () => {
+          fs.writeFile("/du/b.txt", "hello", () => {
+            fs.mkdir("/du/sub", () => {
+              fs.writeFile("/du/sub/a.txt", "hello", () => {
+                fs.writeFile("/du/sub/b.txt", "hello", () => {
+                  fs.du("/du/sub/a.txt", (err, size) => {
+                    expect(err).toBe(null)
+                    expect(size).toBe(5)
+                    fs.du("/du/sub", (err, size) => {
+                      expect(err).toBe(null)
+                      expect(size).toBe(10)
+                      fs.du("/du", (err, size) => {
+                        expect(err).toBe(null)
+                        expect(size).toBe(20)
+                        done();
+                      });
+                    });
+                  });
+                });
+              });
+            });
+          });
+        });
+      });
+    });
+  });
+
 });

src/index.js

@@ -15,6 +15,7 @@ module.exports = class FS {
   constructor(...args) {
     this.promises = new PromisifiedFS(...args)
     // Needed so things don't break if you destructure fs and pass individual functions around
+    this.init = this.init.bind(this)
     this.readFile = this.readFile.bind(this)
     this.writeFile = this.writeFile.bind(this)
     this.unlink = this.unlink.bind(this)
@@ -27,6 +28,7 @@ module.exports = class FS {
     this.readlink = this.readlink.bind(this)
     this.symlink = this.symlink.bind(this)
     this.backFile = this.backFile.bind(this)
+    this.du = this.du.bind(this)
   }
   init(name, options) {
     this.promises.init(name, options)
@@ -79,4 +81,8 @@ module.exports = class FS {
     const [resolve, reject] = wrapCallback(opts, cb);
     this.promises.backFile(filepath, opts).then(resolve).catch(reject);
   }
+  du(filepath, cb) {
+    const [resolve, reject] = wrapCallback(cb);
+    this.promises.du(filepath).then(resolve).catch(reject);
+  }
 }