Adding find duplicate files. Closes #79.

app/cli-acx/src/main/java/io/github/applecommander/acx/Main.java

@@ -32,6 +32,7 @@ import io.github.applecommander.acx.command.DeleteCommand;
 import io.github.applecommander.acx.command.DiskMapCommand;
 import io.github.applecommander.acx.command.DumpCommand;
 import io.github.applecommander.acx.command.ExportCommand;
+import io.github.applecommander.acx.command.FindDuplicateFilesCommand;
 import io.github.applecommander.acx.command.ImportCommand;
 import io.github.applecommander.acx.command.InfoCommand;
 import io.github.applecommander.acx.command.ListCommand;
@@ -65,6 +66,7 @@ import picocli.CommandLine.Option;
     		DiskMapCommand.class,
     		DumpCommand.class,
             ExportCommand.class,
+            FindDuplicateFilesCommand.class,
             HelpCommand.class,
             ImportCommand.class,
             InfoCommand.class,

app/cli-acx/src/main/java/io/github/applecommander/acx/command/FindDuplicateFilesCommand.java

@@ -0,0 +1,105 @@
+/*
+ * AppleCommander - An Apple ][ image utility.
+ * Copyright (C) 2019-2022 by Robert Greene and others
+ * robgreene at users.sourceforge.net
+ *
+ * This program is free software; you can redistribute it and/or modify it 
+ * under the terms of the GNU General Public License as published by the 
+ * Free Software Foundation; either version 2 of the License, or (at your 
+ * option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but 
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 
+ * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 
+ * for more details.
+ *
+ * You should have received a copy of the GNU General Public License along 
+ * with this program; if not, write to the Free Software Foundation, Inc., 
+ * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+package io.github.applecommander.acx.command;
+
+import java.math.BigInteger;
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.function.Supplier;
+import java.util.stream.Collectors;
+
+import com.webcodepro.applecommander.storage.FormattedDisk;
+import com.webcodepro.applecommander.util.filestreamer.FileStreamer;
+import com.webcodepro.applecommander.util.filestreamer.FileTuple;
+import com.webcodepro.applecommander.util.filestreamer.TypeOfFile;
+
+import io.github.applecommander.acx.base.ReadOnlyDiskImageCommandOptions;
+import picocli.CommandLine.Command;
+import picocli.CommandLine.Option;
+
+@Command(name = "dups", description = "Find duplicate files.")
+public class FindDuplicateFilesCommand extends ReadOnlyDiskImageCommandOptions {
+    @Option(names = { "-a", "--all" }, description = "Compare all files across all volumes; useful for formats like UniDOS.")
+    private boolean compareAcrossVolumes;
+    
+    @Override
+    public int handleCommand() throws Exception {
+        Map<String,List<FileTuple>> content = new HashMap<>();
+        Supplier<Map<String,List<FileTuple>>> supplier = () -> content;
+        int dupsFound = 0;
+        
+        for (FormattedDisk formattedDisk : disk.getFormattedDisks()) {
+            FileStreamer.forDisk(formattedDisk)
+                    .includeTypeOfFile(TypeOfFile.FILE)
+                    .recursive(true)
+                    .stream()
+                    .collect(Collectors.groupingBy(this::contentHash, supplier, Collectors.toList()));
+            if (compareAcrossVolumes && !content.isEmpty()) {
+                System.out.printf("Differences in: %s\n", formattedDisk.getDiskName());
+                dupsFound += report(content);
+                content.clear();
+            }
+        }
+        
+        if (!content.isEmpty()) {
+            System.out.println("Differences:");
+            dupsFound += report(content);
+        }
+        
+        if (dupsFound == 0) {
+            System.out.println("There are no duplicate files.");
+        }
+        
+        return 0;
+    }
+
+    private String contentHash(FileTuple tuple) {
+        try {
+            MessageDigest messageDigest = MessageDigest.getInstance("MD5");
+            byte[] digest = messageDigest.digest(tuple.fileEntry.getFileData());
+            return String.format("%032X", new BigInteger(1, digest));
+        } catch (NoSuchAlgorithmException ex) {
+            throw new RuntimeException(ex);
+        }
+    }
+    
+    private int report(Map<String,List<FileTuple>> content) {
+        int dups = 0;
+        for (Map.Entry<String,List<FileTuple>> entry : content.entrySet()) {
+            if (entry.getValue().size() > 1) {
+                dups++;
+                boolean first = true;
+                for (FileTuple tuple : entry.getValue()) {
+                    if (first) {
+                        System.out.printf("%s has the following duplicates:\n", tuple.fullPath());
+                        first= false;
+                    }
+                    else {
+                        System.out.printf("    - %s\n", tuple.fullPath());
+                    }
+                }
+            }
+        }
+        return dups;
+    }
+}