fix(read): various issues

lib/api/read.js

@@ -4,39 +4,39 @@ var BigInt = require('../tools/bigint');
 var request = require('../tools/smb2-forge').request;
 var MAX_READ_LENGTH = require('../structures/constants').MAX_READ_LENGTH;
 
-module.exports = function read(file, buffer, offset, length, position, cb) {
-  assert(position !== null, 'null position is not supported');
+module.exports = function read(file, buffer, offset, length, start, cb) {
+  assert(pos !== null, 'null pos is not supported');
 
-  var fileSize = BigInt.fromBuffer(file.EndofFile);
-  var bytesRead = 0;
   var connection = this;
-
-  position = new BigInt(8, position);
+  var end = Math.min(
+    start + length,
+    BigInt.fromBuffer(file.EndofFile).toNumber()
+  );
+  var pos = start;
 
   function onRead(err, chunk) {
     if (err != null) {
-      return cb(err, bytesRead, buffer);
+      return cb(err, pos - start, buffer);
     }
 
     chunk.copy(buffer, offset);
 
     var n = chunk.length;
-    bytesRead += n;
     offset += n;
-    position = position.add(n);
+    pos += n;
 
     readChunk();
   }
   function readChunk() {
-    if (bytesRead >= length || position.ge(fileSize)) {
-      return cb(null, bytesRead, buffer);
+    if (pos >= end) {
+      return cb(null, pos - start, buffer);
     }
     request(
       'read',
       {
         FileId: file.FileId,
-        Length: Math.min(MAX_READ_LENGTH, length - bytesRead),
-        Offset: position.toBuffer(),
+        Length: Math.min(MAX_READ_LENGTH, end - pos),
+        Offset: new BigInt(8, pos).toBuffer(),
       },
       connection,
       onRead