better error handling and mount callback

example.js

@@ -47,6 +47,9 @@ fuse.mount('./mnt', {
     buf.write(str)
     return cb(str.length)
   }
+}, function (err) {
+  if (err) throw err
+  console.log('filesystem mounted on ./mnt')
 })
 
 process.on('SIGINT', function () {

fuse-bindings.cc

@@ -18,6 +18,7 @@ using namespace v8;
 
 enum bindings_ops_t {
   OP_INIT = 0,
+  OP_ERROR,
   OP_ACCESS,
   OP_STATFS,
   OP_FGETATTR,
@@ -54,6 +55,7 @@ static Persistent<Function> buffer_constructor;
 static struct stat empty_stat;
 
 // TODO support more than a single mount
+static int bindings_in_use = 0;
 static struct {
   // fuse data
   char mnt[1024];
@@ -68,6 +70,7 @@ static struct {
 
   // methods
   NanCallback *ops_init;
+  NanCallback *ops_error;
   NanCallback *ops_access;
   NanCallback *ops_statfs;
   NanCallback *ops_getattr;
@@ -471,11 +474,9 @@ static void *bindings_thread (void *) {
     (char *) bindings.mntopts
   };
 
-  // bindings_unmount(bindings.mnt); // should probably throw instead if mounted
-
   if (fuse_main(!strcmp(bindings.mntopts, "-o") ? 4 : 5, argv, &ops, NULL)) {
-    // TODO: error handle somehow
+    bindings.op = OP_ERROR;
-    printf("fuse-binding: mount failed\n");
+    bindings_call();
   }
 
   return NULL;
@@ -623,6 +624,12 @@ static void bindings_dispatch (uv_async_t* handle, int status) {
     }
     return;
 
+    case OP_ERROR: {
+      Local<Value> tmp[] = {callback};
+      bindings_call_op(bindings.ops_error, 1, tmp);
+    }
+    return;
+
     case OP_STATFS: {
       Local<Value> tmp[] = {NanNew<String>(bindings.path), callback};
       bindings_call_op(bindings.ops_statfs, 2, tmp);
@@ -849,12 +856,17 @@ static void bindings_append_opt (char *name) {
 NAN_METHOD(Mount) {
   NanScope();
 
+  if (!args[0]->IsString()) return NanThrowError("mnt must be a string");
+  if (bindings_in_use) return NanThrowError("Currently only a single filesystem can be mounted at the time");
+  bindings_in_use = 1;
+
   memset(&empty_stat, 0, sizeof(empty_stat)); // zero empty stat
 
   NanUtf8String path(args[0]);
   Local<Object> ops = args[1].As<Object>();
 
   bindings.ops_init = ops->Has(NanNew<String>("init")) ? new NanCallback(ops->Get(NanNew<String>("init")).As<Function>()) : NULL;
+  bindings.ops_error = ops->Has(NanNew<String>("error")) ? new NanCallback(ops->Get(NanNew<String>("error")).As<Function>()) : NULL;
   bindings.ops_access = ops->Has(NanNew<String>("access")) ? new NanCallback(ops->Get(NanNew<String>("access")).As<Function>()) : NULL;
   bindings.ops_statfs = ops->Has(NanNew<String>("statfs")) ? new NanCallback(ops->Get(NanNew<String>("statfs")).As<Function>()) : NULL;
   bindings.ops_getattr = ops->Has(NanNew<String>("getattr")) ? new NanCallback(ops->Get(NanNew<String>("getattr")).As<Function>()) : NULL;
@@ -944,6 +956,8 @@ NAN_METHOD(SetBuffer) {
 
 NAN_METHOD(Unmount) {
   NanScope();
+
+  if (!args[0]->IsString()) return NanThrowError("mnt must be a string");
   NanUtf8String path(args[0]);
   Local<Function> callback = args[1].As<Function>();
 

index.js

@@ -1,8 +1,10 @@
 var bindings = require('bindings')
 var fuse = bindings('fuse_bindings')
+var fs = require('fs')
 var path = require('path')
 
 var noop = function () {}
+var call = function (cb) { cb() }
 
 var FuseBuffer = function () {
   this.length = 0
@@ -13,10 +15,33 @@ FuseBuffer.prototype = Buffer.prototype
 
 fuse.setBuffer(FuseBuffer)
 
-exports.mount = function (mnt, ops) {
+exports.mount = function (mnt, ops, cb) {
+  if (!cb) cb = noop
   if (!ops) ops = {}
+
   if (/\*|(^,)fuse-bindings(,$)/.test(process.env.DEBUG)) ops.options = ['debug'].concat(ops.options || [])
-  return fuse.mount(path.resolve(mnt), ops)
+  mnt = path.resolve(mnt)
+
+  var init = ops.init || call
+  ops.init = function (next) {
+    cb()
+    init(next)
+  }
+
+  var error = ops.error || call
+  ops.error = function (next) {
+    cb(new Error('Mount failed'))
+    error(next)
+  }
+
+  fs.stat(mnt, function (err, stat) {
+    if (err) return cb(new Error('Mountpoint does not exist'))
+    if (!stat.isDirectory()) return cb(new Error('Mountpoint is not a directory'))
+    fs.stat(path.join(mnt, '..'), function(_, parent) {
+      if (parent && parent.dev !== stat.dev) return cb(new Error('Mountpoint in use'))
+      fuse.mount(mnt, ops)
+    })
+  })
 }
 
 exports.unmount = function (mnt, cb) {