Allocate a one-byte IOBuffer for transfers that are zero-length.

chrome/browser/extensions/api/usb/usb_device_resource.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/extensions/api/usb/usb_device_resource.h"
 
 #include <string>
 #include <vector>
 
 #include "base/bind.h"
@@ skipping 93 matching lines @@
       *output = input.data->size();
       return true;
     }
   }
   return false;
 }
 
 template<class T>
 static scoped_refptr<net::IOBuffer> CreateBufferForTransfer(const T& input) {
   size_t size = 0;
-  if (!GetTransferSize(input, &size)) {
+  if (!GetTransferSize(input, &size))
     return NULL;
-  }
 
-  scoped_refptr<net::IOBuffer> buffer = new net::IOBuffer(size);
-  if (!input.data.get()) {
+  // Allocate a |size|-bytes buffer, or a one-byte buffer if |size| is 0. This
+  // is due to an impedance mismatch between IOBuffer and URBs. An IOBuffer
+  // cannot represent a zero-length buffer, while an URB can.
+  scoped_refptr<net::IOBuffer> buffer = new net::IOBuffer(std::max(
+      static_cast<size_t>(1), size));
+  if (!input.data.get())
     return buffer;
-  }
 
   memcpy(buffer->data(), input.data->data(), size);
-
   return buffer;
 }
 
 static const char* ConvertTransferStatusToErrorString(
     const UsbTransferStatus status) {
   switch (status) {
     case USB_TRANSFER_COMPLETED:
       return "";
     case USB_TRANSFER_ERROR:
       return kErrorGeneric;
@@ skipping 102 matching lines @@
                                          UsbTransferStatus status) {
   if (buffer) {
     base::BinaryValue* const response_buffer =
         base::BinaryValue::CreateWithCopiedBuffer(buffer->data(), length);
     event_notifier()->OnTransferComplete(status,
         ConvertTransferStatusToErrorString(status), response_buffer);
   }
 }
 
 }  // namespace extensions