Add StoredFcl2DumpedFcl.java

This allows upgrading old graphs to be readable by the current versions, both Java and Rust

java/src/main/java/org/softwareheritage/graph/utils/StoredFcl2DumpedFcl.java

+/*
+ * Copyright (c) 2024 The Software Heritage developers
+ * See the AUTHORS file at the top-level directory of this distribution
+ * License: GNU General Public License version 3, or any later version
+ * See top-level LICENSE file for more information
+ */
+
+package org.softwareheritage.graph.utils;
+
+import com.martiansoftware.jsap.*;
+import com.martiansoftware.jsap.stringparsers.*;
+import it.unimi.dsi.big.util.FrontCodedStringBigList;
+import it.unimi.dsi.fastutil.io.BinIO;
+import org.apache.commons.configuration2.ex.ConfigurationException;
+import java.io.IOException;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class StoredFcl2DumpedFcl {
+
+    public static void main(final String[] arg)
+            throws JSAPException, IOException, ConfigurationException, ClassNotFoundException {
+        final SimpleJSAP jsap = new SimpleJSAP(StoredFcl2DumpedFcl.class.getName(),
+                "Reads a .fcl file and produces .fcl.bytearray, .fcl.pointers, and .fcl.properties file which can be mmapped",
+                new Parameter[]{
+                        new FlaggedOption("ratio", IntSizeStringParser.getParser(), "4", JSAP.NOT_REQUIRED, 'r',
+                                "ratio", "The compression ratio."),
+                        new UnflaggedOption("basename", JSAP.STRING_PARSER, JSAP.NO_DEFAULT, JSAP.REQUIRED,
+                                JSAP.NOT_GREEDY,
+                                "The basename of the files associated with the memory-mapped front-coded string list.")});
+
+        final JSAPResult args = jsap.parse(arg);
+        if (jsap.messagePrinted())
+            return;
+
+        final String basename = args.getString("basename");
+
+        final Logger logger = LoggerFactory.getLogger(StoredFcl2DumpedFcl.class);
+
+        logger.info("Reading front-coded string big list...");
+        final FrontCodedStringBigList nonutf8Fcl = (FrontCodedStringBigList) BinIO.loadObject(System.in);
+        final FrontCodedStringBigList utf8Fcl = new FrontCodedStringBigList(nonutf8Fcl, args.getInt("ratio"), true);
+
+        logger.info("Dumping files...");
+        utf8Fcl.dump(basename);
+    }
+}