From 9de0b7f8937b7f6ce990132609f0b26851b31f2b Mon Sep 17 00:00:00 2001
From: Roland Reichwein <mail@reichwein.it>
Date: Fri, 3 Jan 2025 15:36:22 +0100
Subject: Monitor CPU

---
 cpuload.cpp | 71 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 71 insertions(+)
 create mode 100644 cpuload.cpp

(limited to 'cpuload.cpp')

diff --git a/cpuload.cpp b/cpuload.cpp
new file mode 100644
index 0000000..77abc3e
--- /dev/null
+++ b/cpuload.cpp
@@ -0,0 +1,71 @@
+#include "cpuload.h"
+
+#include <chrono>
+#include <numeric>
+
+#include <libreichwein/file.h>
+#include <libreichwein/stringhelper.h>
+
+int get_number_of_cpus()
+{
+  int result{};
+  std::string stat = Reichwein::File::getFile("/proc/stat");
+  std::vector<std::string> lines = Reichwein::Stringhelper::split(stat, "\n");
+  for (const auto& line: lines) {
+    std::vector<std::string> words = Reichwein::Stringhelper::split(line, " ");
+    // /proc/stat line, e.g.: cpu0 1132 34 1441 11311718 3675 127 438
+    if (words.size() >= 8) {
+      if (words[0].size() > 3 && words[0].substr(0, 3) == "cpu") {
+        ++result;
+      }
+    }
+  }
+  return result;
+}
+
+// returns empty vector if no data is available yet
+// Note: to be called several times, because data is generated differentially from /proc/stat
+std::vector<int> get_cpu_loads()
+{
+  using clock_type = std::chrono::high_resolution_clock;
+  static int number_of_cpus = get_number_of_cpus();
+  static std::vector<int> stat_cpus_sum(number_of_cpus);
+  static std::vector<int> stat_cpus_idle(number_of_cpus);
+  static std::chrono::time_point<clock_type> timestamp{};
+
+  std::string stat = Reichwein::File::getFile("/proc/stat");
+
+  std::vector<std::string> lines = Reichwein::Stringhelper::split(stat, "\n");
+
+  std::vector<int> result;
+
+  int i = 0;
+  for (const auto& line: lines) {
+    std::vector<std::string> words = Reichwein::Stringhelper::split(line, " ");
+    // /proc/stat line, e.g.: cpu0 1132 34 1441 11311718 3675 127 438
+    // idle value is at index 4
+    if (words.size() >= 8) {
+      if (words[0].size() > 3 && words[0].substr(0, 3) == "cpu") {
+        uint64_t sum = std::accumulate(words.begin() + 1, words.end(), uint64_t{}, [](uint64_t sum, const std::string& s){return sum + std::stoull(s);});
+        uint64_t idle = std::stoull(words[4]);
+
+        // previous data available
+        if (timestamp == std::chrono::time_point<clock_type>{})
+        {
+          uint64_t sum_diff = sum - stat_cpus_sum[i];
+          uint64_t idle_diff = idle - stat_cpus_idle[i];
+          int percentage = (sum_diff == 0) ? 0 : ((sum_diff - idle_diff) * 100 / sum_diff);
+          result.push_back(percentage);
+        }
+
+        stat_cpus_sum[i] = sum;
+        stat_cpus_idle[i] = idle;
+
+        ++i;
+      }
+    }
+  }
+
+  return result;
+}
+
-- 
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