Added a utility class to hold util functions for implementing Launchers.

git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@270279 13f79535-47bb-0310-9956-ffa450edef68

proposal/myrmidon/src/java/org/apache/myrmidon/framework/exec/launchers/ExecUtil.java

@@ -0,0 +1,102 @@
+/*
+ * Copyright (C) The Apache Software Foundation. All rights reserved.
+ *
+ * This software is published under the terms of the Apache Software License
+ * version 1.1, a copy of which has been included  with this distribution in
+ * the LICENSE.txt file.
+ */
+package org.apache.myrmidon.framework.exec.launchers;
+
+import java.io.File;
+import java.io.IOException;
+import org.apache.myrmidon.framework.exec.ExecMetaData;
+
+/**
+ * A set of utility functions useful when writing CommandLaunchers.
+ *
+ * @author <a href="mailto:peter@apache.org">Peter Donald</a>
+ * @version $Revision$ $Date$
+ */
+class ExecUtil
+{
+    /**
+     * The file representing the current working directory.
+     */
+    private static final File c_cwd;
+
+    static
+    {
+        try
+        {
+            c_cwd = ( new File( "." ) ).getCanonicalFile();
+        }
+        catch( final IOException ioe )
+        {
+            //Should never happen
+            throw new IllegalStateException();
+        }
+    }
+
+    /**
+     * Private constructor to block instantiation.
+     */
+    private ExecUtil()
+    {
+    }
+
+    /**
+     * Create a new ExecMetaData representing the same command with the specified
+     * prefix. This is useful when you are launching the native executable via a
+     * script of some sort.
+     */
+    protected static ExecMetaData prepend( final ExecMetaData metaData,
+                                           final String[] prefix )
+    {
+        final String[] original = metaData.getCommand();
+        final String[] command = new String[ original.length + prefix.length ];
+
+        System.arraycopy( prefix, 0, command, 0, prefix.length );
+        System.arraycopy( original, 0, command, prefix.length, original.length );
+
+        return new ExecMetaData( command,
+                                 metaData.getEnvironment(),
+                                 metaData.getWorkingDirectory(),
+                                 metaData.isEnvironmentAdditive() );
+    }
+
+    /**
+     * Utility method to check if specified file is equal
+     * to the current working directory.
+     */
+    protected static boolean isCwd( final File file )
+        throws IOException
+    {
+        return file.getCanonicalFile().equals( getCwd() );
+    }
+
+    /**
+     * Return the current working directory of the JVM.
+     * This value is initialized when this class is first loaded.
+     */
+    protected static File getCwd()
+    {
+        return c_cwd;
+    }
+
+    /**
+     * Retrieve the directory in which Myrmidon is installed.
+     * This is used to determine the locaiton of scripts in various launchers.
+     */
+    protected static File getAntHomeDirectory()
+    {
+        final String antHome = System.getProperty( "ant.home" );
+        if( null == antHome )
+        {
+            final String message =
+                "Cannot locate antRun script: Property 'ant.home' not specified";
+            throw new IllegalStateException( message );
+        }
+
+        return new File( antHome );
+    }
+}