Fixes used RAM value when reading from /proc/meminfo (and fixes units)

Details :
* Used RAM value : <KittyKatt/screenFetch#386 (comment)>
* RAM unit : We were also computing Mebibytes, not Megabytes (see upcoming `feature/btrfs` changes for `Disk` entry).

archey/entries/ram.py

@@ -40,19 +40,22 @@ def __init__(self):
                 }
 
             total = ram['MemTotal']
-            # Here, let's imitate the `free` command behavior
-            # (https://gitlab.com/procps-ng/procps/blob/master/proc/sysinfo.c#L787)
-            used = total - (ram['MemFree'] + ram['Cached'] + ram['Buffers'])
+            # Here, let's imitate Neofetch's behavior.
+            # See <https://github.com/dylanaraps/neofetch/wiki/Frequently-Asked-Questions>.
+            used = total + ram['Shmem'] - (
+                ram['MemFree'] + ram['Cached'] + ram['SReclaimable'] + ram['Buffers'])
+            # Imitates what `free` does when the obtained value happens to be incorrect.
+            # See <https://gitlab.com/procps-ng/procps/blob/master/proc/sysinfo.c#L790>.
             if used < 0:
-                used += ram['Cached'] + ram['Buffers']
+                used = total - ram['MemFree']
 
         # Based on the RAM percentage usage, select the corresponding threshold color.
         color_selector = bisect(
             [ram_limits['warning'], ram_limits['danger']],
             (used / total) * 100
         )
 
-        self.value = '{0}{1} MB{2} / {3} MB'.format(
+        self.value = '{0}{1} MiB{2} / {3} MiB'.format(
             COLOR_DICT['sensors'][color_selector],
             int(used),
             COLOR_DICT['clear'],

archey/test/test_archey_ram.py

@@ -91,30 +91,37 @@ def test_free_dash_m_danger(self, _, __):
         'archey.entries.ram.open',
         mock_open(
             read_data="""\
-MemTotal:        7590580 kB
-MemFree:         1502940 kB
-MemAvailable:    3173804 kB
-Buffers:          156976 kB
-Cached:          2289164 kB
-SwapCached:          220 kB
-Active:          3426704 kB
-Inactive:        2254292 kB
-Active(anon):    2221228 kB
-Inactive(anon):  1725868 kB
-Active(file):    1205476 kB
-Inactive(file):   528424 kB
-Unevictable:          32 kB
-Mlocked:              32 kB
-SwapTotal:       7790588 kB
-SwapFree:        7785396 kB
-Dirty:               200 kB
-"""),  # Some content have been truncated (because the following is useless)
+MemTotal:        7581000 kB
+MemFree:          716668 kB
+MemAvailable:    3632244 kB
+Buffers:          478524 kB
+Cached:          2807032 kB
+SwapCached:        67092 kB
+Active:          3947284 kB
+Inactive:        2447708 kB
+Active(anon):    2268724 kB
+Inactive(anon):  1106220 kB
+Active(file):    1678560 kB
+Inactive(file):  1341488 kB
+Unevictable:         128 kB
+Mlocked:             128 kB
+SwapTotal:       7811068 kB
+SwapFree:        7277708 kB
+Dirty:               144 kB
+Writeback:             0 kB
+AnonPages:       3067204 kB
+Mapped:           852272 kB
+Shmem:            451056 kB
+Slab:             314100 kB
+SReclaimable:     200792 kB
+SUnreclaim:       113308 kB
+"""),  # Some lines have been ignored as they are useless for computations.
         create=True
     )
     def test_proc_meminfo(self, _, __):
         """Test `/proc/meminfo` parsing (when `free` is not available)"""
         ram = RAM().value
-        self.assertTrue(all(i in ram for i in ['\x1b[0;33m', '3556', '7412']))
+        self.assertTrue(all(i in ram for i in ['\x1b[0;33m', '3739', '7403']))
 
 
 if __name__ == '__main__':