sane-sysload: implement CPU measurement

pkgs/additional/sane-sysload/sane-sysload

@@ -16,15 +16,19 @@ formatstr is a Python format string.
 variables available for formatting:
 - {bat_icon}
 - {bat_time}
+- {cpu_icon}
+- {cpu_pct}
 - {mem_icon}
 - {mem_pct}
 and some presets, encapsulating the above:
 - {bat}
+- {cpu}
 - {mem}
 """
 
 import argparse
 import logging
+import time
 
 from dataclasses import dataclass
 from enum import Enum
@@ -34,6 +38,7 @@ logger = logging.getLogger(__name__)
 # these icons may only render in nerdfonts
 ICON_BAT_CHG = ["󰢟", "󱊤", "󱊥", "󰂅"]
 ICON_BAT_DIS = ["󰂎", "󱊡", "󱊢", "󱊣"]
+ICON_CPU=""
 ICON_MEM="☵"
 SUFFIX_ICON = " "  # thin space
 SUFFIX_PERCENT = "%"
@@ -82,6 +87,9 @@ class Formatter:
     def render_charge_icon(self, direction: ChargeDirection, percentage: float) -> str:
         return f"{self._choose_icon(direction, percentage)}{self.suffix_icon}"
 
+    def render_cpu_icon(self) -> str:
+        return f"{ICON_CPU}{self.suffix_icon}"
+
     def render_mem_icon(self) -> str:
         return f"{ICON_MEM}{self.suffix_icon}"
 
@@ -147,6 +155,83 @@ class MemInfo:
         logger.debug(f"/proc/meminfo: {entry}={v}")
         return v
 
+class ProcStat:
+    """
+    reads vaues from /proc/stat, mostly CPU-related.
+    """
+    # /proc/stat format is documented here: <https://www.linuxhowtos.org/System/procstat.htm>
+    # these are AGGREGATES SINCE SYSTEM BOOT
+    # to measure current CPU usage, need to take multiple samples
+    # cpu  <user> <system> <nice> <idle> <iowait> <irg> <softirq> 0 0 0
+    # (what are the last three fields?)
+    # where:
+    # measurements are in units of jiffies or USER_HZ
+    # user: normal processes executing in user mode
+    # nice: niced processes executing in user mode
+    # system: processes executing in kernel mode
+    # idle: twiddling thumbs
+    # iowait: waiting for I/O to complete
+    # irq: servicing interrupts
+    # softirq: servicing softirqs
+    def __init__(self, entries=None):
+        if entries is not None:
+            self.entries = entries
+            return
+
+        # else, read from procfs...
+        try:
+            lines = open("/proc/stat").readlines()
+        except Exception as e:
+            logger.info(f"failed to open /proc/stat: {e}")
+            lines = []
+
+        self.entries = {}
+        for l in lines:
+            pieces = l.strip().split(" ")
+            name, values = pieces[0], [p for p in pieces[1:] if p]
+            if name:
+                self.entries[name] = [int(v) for v in values]
+
+    @staticmethod
+    def sample(seconds: float = 1.0):
+        sample1 = ProcStat()
+        time.sleep(seconds)
+        sample2 = ProcStat()
+        return sample2 - sample1
+
+    def __sub__(self, other: 'ProcStat') -> 'ProcStat':
+        entries = {}
+        for k in self.entries:
+            entries[k] = [i - j for i, j in zip(self.entries[k], other.entries[k])]
+        return ProcStat(entries)
+
+    @property
+    def cpu_user(self) -> int:
+        return self.entries["cpu"][0]
+    @property
+    def cpu_system(self) -> int:
+        return self.entries["cpu"][1]
+    @property
+    def cpu_nice(self) -> int:
+        return self.entries["cpu"][2]
+    @property
+    def cpu_idle(self) -> int:
+        return self.entries["cpu"][3]
+    @property
+    def cpu_iowait(self) -> int:
+        return self.entries["cpu"][4]
+    @property
+    def cpu_irq(self) -> int:
+        return self.entries["cpu"][5]
+    @property
+    def cpu_softirq(self) -> int:
+        return self.entries["cpu"][6]
+
+    @property
+    def cpu_total(self) -> int:
+        # TODO: not sure if i'm supposed to include irq stuff here?
+        return self.cpu_user + self.cpu_system + self.cpu_nice + self.cpu_idle + self.cpu_iowait + self.cpu_irq + self.cpu_softirq
+
 class PowerSupply:
     """
     reads values from /sys/class/power_supply/$dev/ API
@@ -273,16 +358,39 @@ def try_all_batteries() -> BatteryInfo | None:
 @dataclass
 class AllInfo:
     _fmt: Formatter
-    _mem: MemInfo | None
-    _bat: BatteryInfo | None
+    __bat: BatteryInfo | None = None
+    __cpu: ProcStat | None = None
+    __mem: MemInfo | None = None
 
+    # lazy-loading
+    @property
+    def _bat(self):
+        if self.__bat is None:
+            self.__bat = try_all_batteries()
+        return self.__bat
+    @property
+    def _cpu(self):
+        if self.__cpu is None:
+            self.__cpu = ProcStat.sample()
+        return self.__cpu
+    @property
+    def _mem(self):
+        if self.__mem is None:
+            self.__mem = MemInfo()
+        return self.__mem
+
+    # user-facing format shorthands
     @property
     def bat(self) -> str:
         return f"{self.bat_icon}{self.bat_time}"
     @property
+    def cpu(self) -> str:
+        return f"{self.cpu_icon}{self.cpu_pct}"
+    @property
     def mem(self) -> str:
         return f"{self.mem_icon}{self.mem_pct}"
 
+    # manual/low-level fields
     @property
     def mem_icon(self) -> str:
         if self._mem is None: return ""
@@ -324,6 +432,23 @@ class AllInfo:
         else:
             return self._fmt.render_percent(self._bat.percent_charged)
 
+    @property
+    def cpu_icon(self) -> str:
+        if self._cpu is None: return ""
+        return self._fmt.render_cpu_icon()
+
+    @property
+    def cpu_pct(self) -> str:
+        if self._cpu is None:
+            return ""
+
+        idle = self._cpu.cpu_idle + self._cpu.cpu_iowait
+        total = self._cpu.cpu_total
+
+        cpu_use_pct = int((total - idle) / total * 100)
+        return self._fmt.render_percent(cpu_use_pct)
+
+
 class LazyFormatter:
     def __init__(self, obj: object, attr: str):
         self.obj = obj
@@ -357,15 +482,14 @@ def main() -> None:
     f.suffix_hr = args.hour_suffix
     f.suffix_min = args.minute_suffix
 
-    info = AllInfo(
-        f,
-        MemInfo(),
-        try_all_batteries(),
-    )
+    info = AllInfo(f)
     print(args.formatstr.format(
       bat=LazyFormatter(info, "bat"),
       bat_icon=LazyFormatter(info, "bat_icon"),
       bat_time=LazyFormatter(info, "bat_time"),
+      cpu=LazyFormatter(info, "cpu"),
+      cpu_icon=LazyFormatter(info, "cpu_icon"),
+      cpu_pct=LazyFormatter(info, "cpu_pct"),
       mem=LazyFormatter(info, "mem"),
       mem_icon=LazyFormatter(info, "mem_icon"),
       mem_pct=LazyFormatter(info, "mem_pct"),