Add type formatting helpers

Created the <maxbase/format.hh> header that contains various helper
functions for formatting values into human readable forms. Currently only
binary to human readable size conversion is implemented.

maxutils/maxbase/include/maxbase/format.hh

@@ -0,0 +1,32 @@
+/*
+ * Copyright (c) 2018 MariaDB Corporation Ab
+ *
+ * Use of this software is governed by the Business Source License included
+ * in the LICENSE.TXT file and at www.mariadb.com/bsl11.
+ *
+ * Change Date: 2022-01-01
+ *
+ * On the date above, in accordance with the Business Source License, use
+ * of this software will be governed by version 2 or later of the General
+ * Public License.
+ */
+
+#pragma once
+
+#include <maxbase/ccdefs.hh>
+
+#include <cstdint>
+#include <string>
+
+namespace maxbase
+{
+
+/**
+ * Convert a number into the IEC human readable representation
+ *
+ * @param size Value to convert
+ *
+ * @return Value as a human readable size e.g. 5.01MiB
+ */
+std::string to_binary_size(int64_t size);
+}

maxutils/maxbase/src/CMakeLists.txt

@@ -1,6 +1,7 @@
 add_library(maxbase STATIC
   atomic.cc
   eventcount.cc
+  format.cc
   log.cc
   logger.cc
   maxbase.cc

maxutils/maxbase/src/format.cc

@@ -0,0 +1,68 @@
+/*
+ * Copyright (c) 2018 MariaDB Corporation Ab
+ *
+ * Use of this software is governed by the Business Source License included
+ * in the LICENSE.TXT file and at www.mariadb.com/bsl11.
+ *
+ * Change Date: 2022-01-01
+ *
+ * On the date above, in accordance with the Business Source License, use
+ * of this software will be governed by version 2 or later of the General
+ * Public License.
+ */
+
+#include <maxbase/format.hh>
+
+#include <cmath>
+#include <cstdio>
+
+namespace
+{
+
+const char* get_binary_size_suffix(int i)
+{
+    switch (i)
+    {
+    case 0:
+        return "B";
+
+    case 1:
+        return "KiB";
+
+    case 2:
+        return "MiB";
+
+    case 3:
+        return "GiB";
+
+    case 4:
+        return "TiB";
+
+    case 5:
+        return "PiB";
+
+    case 6:
+        return "EiB";
+
+    case 7:
+        return "ZiB";
+
+    default:
+        return "YiB";
+    }
+}
+}
+
+namespace maxbase
+{
+
+std::string to_binary_size(int64_t size)
+{
+    // Calculate log1024(size) and round it up
+    int idx = ceil(log(size) / log(1024));
+    double num = size / pow(1024, idx);
+    char buf[200];      // Enough for all possible values
+    snprintf(buf, sizeof(buf), "%.2lf%s", num, get_binary_size_suffix(idx));
+    return buf;
+}
+}

server/core/config.cc

@@ -40,6 +40,7 @@
 #include <vector>
 #include <unordered_set>
 
+#include <maxbase/format.hh>
 #include <maxscale/adminusers.h>
 #include <maxscale/alloc.h>
 #include <maxscale/clock.h>
@@ -1226,26 +1227,8 @@ bool config_load_global(const char* filename)
             }
             else
             {
-                std::vector<const char*> suffixes
-                {
-                    "B",
-                    "KiB",
-                    "MiB",
-                    "GiB",
-                    "TiB",
-                    "PiB",
-                    "EiB",
-                    "ZiB",
-                    "YiB"
-                };
-                // Get the total used cache memory
-                int64_t total_mem = mem_per_thr * gateway.n_threads;
-                // Calculate log1024(total_mem) and round it up
-                double c = ceil(log(total_mem) / log(1024));
-                // In case someone still uses MaxScale in the year 3054
-                int idx = std::min(c, (double)(suffixes.size())) - 1;
-                double num = total_mem / pow(1024, idx);
-                MXS_NOTICE("Using up to %.2lf%s of memory for query classifier cache", num, suffixes[idx]);
+                MXS_NOTICE("Using up to %s of memory for query classifier cache",
+                           mxb::to_binary_size(mem_per_thr * gateway.n_threads).c_str());
             }
         }
     }