Add Linux LibC with sysinfo

CHANGES.md

@@ -28,6 +28,7 @@ Features
 * [#988](https://github.com/java-native-access/jna/issues/988): Added `PdhLookupPerfIndexByEnglishName` to `c.s.j.platform.win32.PdhUtil` - [@dbwiddis](https://github.com/dbwiddis).
 * [#992](https://github.com/java-native-access/jna/pull/992): Improve stability of windows tests and add appveyor configuration for windows CI builds - [@matthiasblaesing](https://github.com/matthiasblaesing).
 * [#995](https://github.com/java-native-access/jna/pull/995): Added structures and methods to `c.s.j.platform.mac.SystemB` for Process, Network interface, Swapfile, Time, and Filesystem info - [@dbwiddis](https://github.com/dbwiddis).
+* [#997](https://github.com/java-native-access/jna/issues/997): Added `Sysinfo` structure and function to `c.s.j.platform.linux.LibC` - [@dbwiddis](https://github.com/dbwiddis).
 
 Bug Fixes
 ---------

contrib/platform/src/com/sun/jna/platform/linux/LibC.java

@@ -0,0 +1,109 @@
+/* Copyright (c) 2017 Daniel Widdis, All Rights Reserved
+ * 
+ * The contents of this file is dual-licensed under 2 
+ * alternative Open Source/Free licenses: LGPL 2.1 or later and 
+ * Apache License 2.0. (starting with JNA version 4.0.0).
+ * 
+ * You can freely decide which license you want to apply to 
+ * the project.
+ * 
+ * You may obtain a copy of the LGPL License at:
+ * 
+ * http://www.gnu.org/licenses/licenses.html
+ * 
+ * A copy is also included in the downloadable source code package
+ * containing JNA, in file "LGPL2.1".
+ * 
+ * You may obtain a copy of the Apache License at:
+ * 
+ * http://www.apache.org/licenses/
+ * 
+ * A copy is also included in the downloadable source code package
+ * containing JNA, in file "AL2.0".
+ */
+package com.sun.jna.platform.linux;
+
+import java.lang.reflect.Field;
+import java.util.ArrayList;
+import java.util.Iterator;
+import java.util.List;
+
+import com.sun.jna.Library;
+import com.sun.jna.Native;
+import com.sun.jna.NativeLong;
+import com.sun.jna.Structure;
+import com.sun.jna.Structure.FieldOrder;
+import com.sun.jna.platform.unix.LibCAPI;
+
+/**
+ * LibC structures and functions unique to Linux
+ */
+public interface LibC extends LibCAPI, Library {
+    String NAME = "c";
+    LibC INSTANCE = Native.load(NAME, LibC.class);
+
+    @FieldOrder({ "uptime", "loads", "totalram", "freeram", "sharedram", "bufferram", "totalswap", "freeswap", "procs",
+            "totalhigh", "freehigh", "mem_unit", "_f" })
+    class Sysinfo extends Structure {
+        private static final int PADDING_SIZE = 20 - 2 * NativeLong.SIZE - 4;
+
+        public NativeLong uptime; // Seconds since boot
+        // 1, 5, and 15 minute load averages, divide by 2^16
+        public NativeLong[] loads = new NativeLong[3];
+        public NativeLong totalram; // Total usable main memory size
+        public NativeLong freeram; // Available memory size
+        public NativeLong sharedram; // Amount of shared memory
+        public NativeLong bufferram; // Memory used by buffers
+        public NativeLong totalswap; // Total swap space size
+        public NativeLong freeswap; // swap space still available
+        public short procs; // Number of current processes
+        public NativeLong totalhigh; // Total high memory size
+        public NativeLong freehigh; // Available high memory size
+        public int mem_unit; // Memory unit size in bytes
+        // Padding to 64 bytes
+        public byte[] _f = new byte[PADDING_SIZE];
+
+        /*
+         * getFieldList and getFieldOrder are overridden because PADDING_SIZE
+         * might be 0 - that is a GCC only extension and not supported by JNA
+         * 
+         * The dummy field at the end of the structure is just padding and so if
+         * the field is the zero length array, it is stripped from the fields
+         * and field order.
+         */
+        @Override
+        protected List<Field> getFieldList() {
+            List<Field> fields = new ArrayList<Field>(super.getFieldList());
+            if (PADDING_SIZE == 0) {
+                Iterator<Field> fieldIterator = fields.iterator();
+                while (fieldIterator.hasNext()) {
+                    Field field = fieldIterator.next();
+                    if ("_f".equals(field.getName())) {
+                        fieldIterator.remove();
+                    }
+                }
+            }
+            return fields;
+        }
+
+        @Override
+        protected List<String> getFieldOrder() {
+            List<String> fieldOrder = new ArrayList<String>(super.getFieldOrder());
+            if (PADDING_SIZE > 0) {
+                fieldOrder.add("_f");
+            }
+            return fieldOrder;
+        }
+    }
+
+    /**
+     * sysinfo() provides a simple way of getting overall system statistics.
+     * This is more portable than reading /dev/kmem.
+     * 
+     * @param info
+     *            A Sysinfo structure which will be populated
+     * @return On success, zero is returned. On error, -1 is returned, and errno
+     *         is set appropriately.
+     */
+    int sysinfo(Sysinfo info);
+}

contrib/platform/src/com/sun/jna/platform/linux/package.html

@@ -0,0 +1,13 @@
+<html>
+<head>
+<!-- 
+  Copyright (c) 2017 Daniel Widdis
+-->
+</head>
+<body bgcolor="white">
+
+<!-- One sentence summary -->
+Provides common library mappings for Linux.
+
+</body>
+</html>

contrib/platform/test/com/sun/jna/platform/linux/LibCTest.java

@@ -0,0 +1,54 @@
+/* Copyright (c) 2017 Daniel Widdis, All Rights Reserved
+ * 
+ * The contents of this file is dual-licensed under 2 
+ * alternative Open Source/Free licenses: LGPL 2.1 or later and 
+ * Apache License 2.0. (starting with JNA version 4.0.0).
+ * 
+ * You can freely decide which license you want to apply to 
+ * the project.
+ * 
+ * You may obtain a copy of the LGPL License at:
+ * 
+ * http://www.gnu.org/licenses/licenses.html
+ * 
+ * A copy is also included in the downloadable source code package
+ * containing JNA, in file "LGPL2.1".
+ * 
+ * You may obtain a copy of the Apache License at:
+ * 
+ * http://www.apache.org/licenses/
+ * 
+ * A copy is also included in the downloadable source code package
+ * containing JNA, in file "AL2.0".
+ */
+package com.sun.jna.platform.linux;
+
+import org.junit.Test;
+
+import com.sun.jna.platform.linux.LibC.Sysinfo;
+
+import junit.framework.TestCase;
+
+/**
+ * Exercise the {@link LibC} class.
+ */
+public class LibCTest extends TestCase {
+
+    @Test
+    public void testSysinfo() {
+        Sysinfo info = new Sysinfo();
+        assertEquals(0, LibC.INSTANCE.sysinfo(info));
+
+        // Get loadavg for comparison (rounds to nearest hundredth)
+        double[] loadavg = new double[3];
+        LibC.INSTANCE.getloadavg(loadavg, 3);
+        // Sysinfo loadavg longs must be divided by 2^16
+        for (int i = 0; i < 3; i++) {
+            assertEquals(loadavg[i], info.loads[i].longValue() / (double) (1 << 16), 0.02);
+        }
+        assertTrue(info.uptime.longValue() > 0);
+        assertTrue(info.totalram.longValue() > 0);
+        assertTrue(info.freeram.longValue() <= info.totalram.longValue());
+        assertTrue(info.freeswap.longValue() <= info.totalswap.longValue());
+    }
+}