procutils: introduce parse_meminfo()

apport/procutils.py

@@ -0,0 +1,51 @@
+# Copyright (C) 2026 Canonical Ltd.
+# Author: Benjamin Drung <bdrung@ubuntu.com>
+#
+# This program is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License as published by the
+# Free Software Foundation; either version 2 of the License, or (at your
+# option) any later version.  See http://www.gnu.org/copyleft/gpl.html for
+# the full text of the license.
+
+"""Functions to operate on files in /proc."""
+
+import dataclasses
+
+
+@dataclasses.dataclass
+class Meminfo:
+    """Data from /proc/meminfo. Values are in KiB.
+
+    Only the needed values from /proc/meminfo are provided.
+    This dataclass can be extended when needed.
+    """
+
+    mem_total: int
+    mem_free: int
+    mem_available: int
+    cached: int
+    writeback: int
+
+
+def parse_meminfo() -> Meminfo:
+    """Parse /proc/meminfo and return a dictionary for the requested keys."""
+    remaining_keys = {"MemTotal", "MemFree", "MemAvailable", "Cached", "Writeback"}
+    meminfo = {}
+    with open("/proc/meminfo", "r", encoding="utf-8") as meminfo_file:
+        for line in meminfo_file:
+            key, remaining = line.split(":", maxsplit=1)
+            if key not in remaining_keys:
+                continue
+            value, unit = remaining.strip().split(maxsplit=2)
+            assert unit == "kB" or value == "0"
+            meminfo[key] = int(value)
+            remaining_keys.remove(key)
+            if not remaining_keys:
+                return Meminfo(
+                    meminfo["MemTotal"],
+                    meminfo["MemFree"],
+                    meminfo["MemAvailable"],
+                    meminfo["Cached"],
+                    meminfo["Writeback"],
+                )
+    raise KeyError(f"{', '.join(sorted(remaining_keys))} not found in /proc/meminfo")

data/apport

@@ -43,6 +43,7 @@ from collections.abc import Callable
 
 import apport.fileutils
 import apport.report
+from apport.procutils import parse_meminfo
 from apport.user_group import UserGroupID
 from problem_report import CompressedFile
 
@@ -339,20 +340,11 @@ def write_user_coredump(
     os.close(core_file)
 
 
-def usable_ram():
+def usable_ram() -> int:
     """Return how many bytes of RAM is currently available that can be
     allocated without causing major thrashing."""
-
-    # abuse our excellent RFC822 parser to parse /proc/meminfo
-    r = apport.report.Report()
-    with open("/proc/meminfo", "rb") as f:
-        r.load(f)
-
-    memfree = int(r["MemFree"].split()[0])
-    cached = int(r["Cached"].split()[0])
-    writeback = int(r["Writeback"].split()[0])
-
-    return (memfree + cached - writeback) * 1024
+    meminfo = parse_meminfo()
+    return (meminfo.mem_free + meminfo.cached - meminfo.writeback) * 1024
 
 
 def _run_with_output_limit_and_timeout(

tests/system/test_apport_valgrind.py

@@ -17,14 +17,11 @@
 
 import pytest
 
+from apport.procutils import parse_meminfo
 from tests.helper import get_gnu_coreutils_cmd, skip_if_command_is_missing
 from tests.paths import local_test_environment
 
-with open("/proc/meminfo", encoding="utf-8") as f:
-    for line in f.readlines():
-        if line.startswith("MemTotal"):
-            MEM_TOTAL_MiB = int(line.split()[1]) // 1024
-            break
+MEM_TOTAL_MiB = parse_meminfo().mem_total // 1024
 
 
 @skip_if_command_is_missing("valgrind")

tests/system/test_signal_crashes.py

@@ -17,6 +17,7 @@
 
 import apport.fileutils
 import apport.report
+from apport.procutils import parse_meminfo
 from tests.helper import (
     get_gnu_coreutils_cmd,
     get_init_system,
@@ -159,12 +160,8 @@ def test_limit_size(self) -> None:
         assert self.apport_path is not None
         # determine how much data we have to pump into apport in order to make
         # sure that it will refuse the core dump
-        r = apport.report.Report()
-        with open("/proc/meminfo", "rb") as f:
-            r.load(f)
-        totalmb = int(r["MemFree"].split()[0]) + int(r["Cached"].split()[0])
-        totalmb = int(totalmb / 1024)
-        del r
+        meminfo = parse_meminfo()
+        totalmb = (meminfo.mem_free + meminfo.cached) // 1024
 
         test_proc = self.create_test_process()
         try:

tests/unit/test_procutils.py

@@ -0,0 +1,50 @@
+# Copyright (C) 2026 Canonical Ltd.
+# Author: Benjamin Drung <bdrung@ubuntu.com>
+#
+# This program is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License as published by the
+# Free Software Foundation; either version 2 of the License, or (at your
+# option) any later version.  See http://www.gnu.org/copyleft/gpl.html for
+# the full text of the license.
+
+"""Unit tests for the apport.procutils module."""
+
+from unittest.mock import mock_open, patch
+
+import pytest
+
+from apport.procutils import Meminfo, parse_meminfo
+
+
+def test_parse_meminfo() -> None:
+    """Test parse_meminfo() reading all values successfully."""
+    open_mock = mock_open(
+        read_data=(
+            "MemTotal:       64249228 kB\n"
+            "MemFree:        25066812 kB\n"
+            "MemAvailable:   40437820 kB\n"
+            "Buffers:          587236 kB\n"
+            "Cached:         19694816 kB\n"
+            "Writeback:             0 kB\n"
+        )
+    )
+    with patch("builtins.open", open_mock):
+        meminfo = parse_meminfo()
+    assert meminfo == Meminfo(64249228, 25066812, 40437820, 19694816, 0)
+
+
+def test_parse_meminfo_missing_key() -> None:
+    """Test parse_meminfo() failing to read the requested keys."""
+    open_mock = mock_open(
+        read_data=(
+            "MemTotal:       64249228 kB\n"
+            "MemFree:        23434628 kB\n"
+            "MemAvailable:   38809072 kB\n"
+            "Buffers:          589372 kB\n"
+            "Cached:         20099444 kB\n"
+        )
+    )
+    with patch("builtins.open", open_mock):
+        with pytest.raises(KeyError) as exc_info:
+            parse_meminfo()
+    exc_info.match("Writeback not found in /proc/meminfo")