Implement querying CPU time on Windows for systemInfo.cpu API

chrome/browser/extensions/api/system_info_cpu/cpu_info_provider_win.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/system_info_cpu/cpu_info_provider.h"
 
+#include <windows.h>
+#include <winternl.h>
+
+#include "base/sys_info.h"
+
 namespace extensions {
 
+namespace {
+
+const wchar_t kNtdll[] = L"ntdll.dll";
+const char kNtQuerySystemInformationName[] = "NtQuerySystemInformation";
+
+// See MSDN about NtQuerySystemInformation definition.
+typedef DWORD (WINAPI *NtQuerySystemInformationPF)(DWORD system_info_class,
+                                                   PVOID system_info,
+                                                   ULONG system_info_length,
+                                                   PULONG return_length);
+
+}  // namespace
+
 bool CpuInfoProvider::QueryCpuTimePerProcessor(std::vector<CpuTime>* times) {
-  // TODO(hongbo): use NtQuerySystemInformation to query the cpu time.
-  return false;
+  if (!times)
+    return false;
+
+  std::vector<CpuTime> results;
+
+  HMODULE ntdll = GetModuleHandle(kNtdll);
+  CHECK(ntdll != NULL);
+  NtQuerySystemInformationPF NtQuerySystemInformation =
+      reinterpret_cast<NtQuerySystemInformationPF>(
+          ::GetProcAddress(ntdll, kNtQuerySystemInformationName));
+
+  CHECK(NtQuerySystemInformation != NULL);
+  if (!NtQuerySystemInformation)

[alexeypa (please no reviews), 2012/09/13 16:45:48]

nit: remove the if statement. CHECK will crash the process if the pointer is
NULL (in both debug and release build), so the condition in the if statement
will never be true.

[Hongbo Min, 2012/09/14 02:56:40]

Done.

+    return false;
+
+  int num_of_processors = base::SysInfo::NumberOfProcessors();
+  scoped_array<SYSTEM_PROCESSOR_PERFORMANCE_INFORMATION> processor_info(
+      new SYSTEM_PROCESSOR_PERFORMANCE_INFORMATION[num_of_processors]);
+  DCHECK_GT(num_of_processors, 0);
+
+  ULONG bytes = 0, returned_bytes = 0;

[alexeypa (please no reviews), 2012/09/13 16:45:48]

nit: Sorry, what I mean is:

ULONG bytes = sizeof(SYSTEM_PROCESSOR_PERFORMANCE_INFORMATION) *
num_of_processors;
ULONG returned_bytes = 0;

+  bytes = sizeof(SYSTEM_PROCESSOR_PERFORMANCE_INFORMATION) * num_of_processors;
+  if (!NT_SUCCESS(NtQuerySystemInformation(
+          SystemProcessorPerformanceInformation,
+          processor_info.get(), bytes, &returned_bytes)))
+    return false;
+
+  int returned_num_of_processors =

[alexeypa (please no reviews), 2012/09/13 16:45:48]

nit: The type should be ULONG since |returned_bytes| and sizeof() are unsigned.

[Hongbo Min, 2012/09/14 02:56:40]

Yes, but because the num_of_processors is int type, so use int to avoid
static_cast when comparison.

+      returned_bytes / sizeof(SYSTEM_PROCESSOR_PERFORMANCE_INFORMATION);
+
+  if (returned_num_of_processors != num_of_processors)
+    return false;
+
+  results.reserve(returned_num_of_processors);
+  for (int i = 0; i < returned_num_of_processors; ++i) {
+    CpuTime time;
+    time.kernel = processor_info[i].KernelTime.QuadPart;
+    time.user = processor_info[i].UserTime.QuadPart;
+    time.idle = processor_info[i].IdleTime.QuadPart;
+    results.push_back(time);
+  }
+
+  results.swap(*times);

[alexeypa (please no reviews), 2012/09/13 16:45:48]

nit: This probably is more readable if it says times->swap(results).

[Hongbo Min, 2012/09/14 02:56:40]

Done.

+  return true;
 }
 
 }  // namespace extensions