Clean up HID backend and API.

device/hid/hid_utils_mac.cc

 // Copyright (c) 2014 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 "device/hid/hid_utils_mac.h"
 
 #include "base/basictypes.h"
 #include "base/logging.h"

[Mark Mentovai, 2014/02/13 22:37:51]

Unused, remove.

[Ken Rockot(use gerrit already), 2014/02/18 19:43:09]

Done.

 #include "base/mac/foundation_util.h"
 #include "base/strings/sys_string_conversions.h"
 
 #if defined(OS_MACOSX)

[Mark Mentovai, 2014/02/13 22:37:51]

This is kinda silly, this file is only compiled on Mac.

 #include <CoreFoundation/CoreFoundation.h>

[Mark Mentovai, 2014/02/13 22:37:51]

Without the #ifdef, you can move these up after hid_utils_mac.h.

[Ken Rockot(use gerrit already), 2014/02/18 19:43:09]

Done.

 #include <IOKit/hid/IOHIDManager.h>
 #endif
 
 namespace device {
 
-bool GetHidIntProperty(IOHIDDeviceRef device,
-                       CFStringRef key,
-                       int32_t* result) {
+int32_t GetHidIntProperty(IOHIDDeviceRef device, CFStringRef key) {
+  int32_t value;
+  if (TryGetHidIntProperty(device, key, &value))
+    return value;
+  return 0;
+}
+
+std::string GetHidStringProperty(IOHIDDeviceRef device, CFStringRef key) {
+  std::string value;
+  TryGetHidStringProperty(device, key, &value);
+  return value;
+}
+
+bool TryGetHidIntProperty(IOHIDDeviceRef device,
+                          CFStringRef key,
+                          int32_t* result) {
   CFNumberRef ref = base::mac::CFCast<CFNumberRef>(

[Mark Mentovai, 2014/02/13 22:37:51]

You might think this is crazy-paranoid (and we can talk about it if you do), but
you might want to add something that makes sure that the number actually fits
into an int32_t. There’s CFNumberGetType, but it’s clunky to use. Unfortunately,
there’s no really good way to ask a CFNumber (or an NSNumber) “hey, will your
value fit into this data type without truncation or sign-flipping?”

[Ken Rockot(use gerrit already), 2014/02/18 19:43:09]

I would be happy to add this, but it does look like it would be cumbersome. I'm
imagining that the result of CFNumberGetType would have to be tested against the
set kCFNumber{SInt8, SInt16, SIn32, Float32, Char, [additional compiler
dependent types]}Type.

       IOHIDDeviceGetProperty(device, key));
   return ref && CFNumberGetValue(ref, kCFNumberSInt32Type, result);
 }
 
-bool GetHidStringProperty(IOHIDDeviceRef device,
-                          CFStringRef key,
-                          std::string* result) {
+bool TryGetHidStringProperty(IOHIDDeviceRef device,
+                             CFStringRef key,
+                             std::string* result) {
   CFStringRef ref = base::mac::CFCast<CFStringRef>(
       IOHIDDeviceGetProperty(device, key));
   if (!ref) {
     return false;
   }
   *result = base::SysCFStringRefToUTF8(ref);
   return true;
 }
 
 }  // namespace device