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      1 // Copyright 2014 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #include "extensions/browser/api/system_cpu/cpu_info_provider.h"
      6 
      7 #include <cstdio>
      8 #include <sstream>
      9 
     10 #include "base/files/file_util.h"
     11 #include "base/format_macros.h"
     12 
     13 namespace extensions {
     14 
     15 namespace {
     16 
     17 const char kProcStat[] = "/proc/stat";
     18 
     19 }  // namespace
     20 
     21 bool CpuInfoProvider::QueryCpuTimePerProcessor(
     22     std::vector<linked_ptr<core_api::system_cpu::ProcessorInfo> >* infos) {
     23   DCHECK(infos);
     24 
     25   // WARNING: this method may return incomplete data because some processors may
     26   // be brought offline at runtime. /proc/stat does not report statistics of
     27   // offline processors. CPU usages of offline processors will be filled with
     28   // zeros.
     29   //
     30   // An example of output of /proc/stat when processor 0 and 3 are online, but
     31   // processor 1 and 2 are offline:
     32   //
     33   //   cpu  145292 20018 83444 1485410 995 44 3578 0 0 0
     34   //   cpu0 138060 19947 78350 1479514 570 44 3576 0 0 0
     35   //   cpu3 2033 32 1075 1400 52 0 1 0 0 0
     36   std::string contents;
     37   if (!base::ReadFileToString(base::FilePath(kProcStat), &contents))
     38     return false;
     39 
     40   std::istringstream iss(contents);
     41   std::string line;
     42 
     43   // Skip the first line because it is just an aggregated number of
     44   // all cpuN lines.
     45   std::getline(iss, line);
     46   while (std::getline(iss, line)) {
     47     if (line.compare(0, 3, "cpu") != 0)
     48       continue;
     49 
     50     uint64 user = 0, nice = 0, sys = 0, idle = 0;
     51     uint32 pindex = 0;
     52     int vals =
     53         sscanf(line.c_str(),
     54                "cpu%" PRIu32 " %" PRIu64 " %" PRIu64 " %" PRIu64 " %" PRIu64,
     55                &pindex,
     56                &user,
     57                &nice,
     58                &sys,
     59                &idle);
     60     if (vals != 5 || pindex >= infos->size()) {
     61       NOTREACHED();
     62       return false;
     63     }
     64 
     65     infos->at(pindex)->usage.kernel = static_cast<double>(sys);
     66     infos->at(pindex)->usage.user = static_cast<double>(user + nice);
     67     infos->at(pindex)->usage.idle = static_cast<double>(idle);
     68     infos->at(pindex)->usage.total =
     69         static_cast<double>(sys + user + nice + idle);
     70   }
     71 
     72   return true;
     73 }
     74 
     75 }  // namespace extensions
     76