Add method for creating volume label

.gitignore

@@ -1,3 +1,5 @@
 .DS_Store
 .vscode/
 node_modules/
+package-lock.json
+tests/label.img

index.js

@@ -557,6 +557,20 @@ exports.createFileSystem = function (volume, opts, cb) {
         else _.delayedCall(cb, S.err.NOSYS());
     }, (_n_ === '_nested_')); };
 
+    fs.createLabel = function (name, cb) {
+        fs.open(name, "a", (e, _fd) => {
+            if (e) {
+                cb(e);
+            } else {
+                let fd = fileDescriptors[_fd]
+                fd.entry.Attr.volume_id = true
+                fd.entry.FstClusLO = 0
+                fd.entry.FstClusHI = 0
+
+                fs._updateEntry(fd.entry, {}, cb);
+            }
+        })
+    };
 
     return fs;
 }

package.json

@@ -4,7 +4,8 @@
   "description": "fs implementation on top of raw FAT16/FAT32 block source",
   "main": "index.js",
   "scripts": {
-    "test": "echo \"Error: no test specified\" && exit 1"
+    "test": "echo \"Error: no test specified\" && exit 1",
+    "label-testcase": "nodejs tests/label.js"
   },
   "repository": {
     "type": "git",

run_tests.sh

@@ -0,0 +1,37 @@
+#!/bin/bash
+
+if ! [ -x "$(command -v blkid)" ]; then
+  echo 'Error: util-linux is not installed.' >&2
+  exit 1
+fi
+
+if ! [ -x "$(command -v dosfslabel)" ]; then
+  echo 'Error: dosfstools is not installed.' >&2
+  exit 1
+fi
+
+rm tests/label.img || true
+
+set -e
+
+dd if=/dev/zero of=tests/label.img bs=1M count=10
+mkfs.vfat tests/label.img
+
+npm run label-testcase
+
+BLKID=$(blkid tests/label.img)
+DOSFSLABEL=$(dosfslabel tests/label.img)
+
+if ! [[ $BLKID == *'LABEL="CIDATA"'* ]]; then
+  echo "blkid: LABEL is invalid"
+  exit 1
+fi
+
+echo "blkid: LABEL is valid"
+
+if ! [[ $DOSFSLABEL == *"CIDATA"* ]]; then
+  echo "dosfslabel: label is invalid"
+  exit 1
+fi
+
+echo "dosfslabel: label is valid"

tests/label.js

@@ -0,0 +1,8 @@
+var fatfs = require("../");
+var createDriverSync = require("../img_volume").createDriverSync
+
+const buffer = createDriverSync("tests/label.img")
+
+const fs = fatfs.createFileSystem(buffer, {allowLowercaseNames: true})
+
+fs.createLabel("cidata", () => {})