From 1ffe9168c9a753c1a9201998af83d9b12bda67c9 Mon Sep 17 00:00:00 2001
From: Peter Wu <peter@lekensteyn.nl>
Date: Fri, 2 May 2014 19:42:32 +0200
Subject: CompressableDataWriter: Implement conversion from uncompressed

---
 src/io/CompressableDataWriter.java | 65 +++++++++++++++++++++++++++++++++++++-
 1 file changed, 64 insertions(+), 1 deletion(-)

diff --git a/src/io/CompressableDataWriter.java b/src/io/CompressableDataWriter.java
index 68bb789..7523b78 100644
--- a/src/io/CompressableDataWriter.java
+++ b/src/io/CompressableDataWriter.java
@@ -1,11 +1,15 @@
 package io;
 
 import java.io.BufferedInputStream;
+import java.io.File;
 import java.io.FileInputStream;
 import java.io.FileNotFoundException;
 import java.io.FileOutputStream;
 import java.io.IOException;
 import java.io.InputStream;
+import java.io.OutputStream;
+import java.util.logging.Level;
+import java.util.logging.Logger;
 import java.util.zip.GZIPInputStream;
 import java.util.zip.GZIPOutputStream;
 import org.apache.commons.io.IOUtils;
@@ -46,7 +50,10 @@ public class CompressableDataWriter extends DataWriter {
                 bis = new BufferedInputStream(new FileInputStream(getFileName()));
                 // file found containing magic? OK, gzip writable!
                 compressable = isCompressed(bis);
-                // TODO: convert uncompressed
+                if (CompressableDataWriter.this.convertUncompressed
+                        && !compressable) {
+                    tryConvertToGzip();
+                }
             } catch (FileNotFoundException ex) {
                 // file not found? Then we are free to write.
                 compressable = true;
@@ -75,6 +82,62 @@ public class CompressableDataWriter extends DataWriter {
             return false;
         }
 
+        private void tryConvertToGzip() {
+            // How to convert:
+            // 1. Rename old file
+            // 2. Create new compressed file in same dir
+            // 3. rename new file to old
+            // 4. if (3) fails, delete old file and rename again
+            File newTmpFile = null;
+            FileInputStream fis = null;
+            OutputStream os = null;
+            boolean deleteTmp = true;
+            try {
+                File origFile = new File(getFileName());
+                fis = new FileInputStream(origFile);
+                newTmpFile = File.createTempFile(getFileName(), "origFile",
+                        origFile.getParentFile());
+                os = new GZIPOutputStream(new FileOutputStream(newTmpFile));
+
+                // now compress data, hopefully we have enough time and disk
+                IOUtils.copy(fis, os);
+                os.close();
+                fis.close();
+
+                // compression ready! Don't delete the result!
+                deleteTmp = false;
+                // first try overwriting the file if possible on this platform.
+                if (!newTmpFile.renameTo(origFile)) {
+                    // that didn't work (Windows?), try deleting and rename
+                    if (!origFile.delete()) {
+                        deleteTmp = true;
+                        getLogger().warning("Cannot rename compressed nor "
+                                + "delete uncompressed " + getFileName());
+                    } else if (!newTmpFile.renameTo(origFile)) {
+                        getLogger().warning("Uncompressed file is deleted, but "
+                                + " compressed file cannot be renamed, sorry.");
+                    } else {
+                        compressable = true;
+                    }
+                } else {
+                    compressable = true;
+                }
+            } catch (IOException ex) {
+                // failed to convert (disk space too low? Not compressed?)
+                getLogger().log(Level.INFO, "Cannot compress/decompress", ex);
+            } finally {
+                IOUtils.closeQuietly(fis);
+                IOUtils.closeQuietly(os);
+                if (newTmpFile != null && deleteTmp) {
+                    newTmpFile.delete();
+                }
+            }
+        }
+
+        private Logger getLogger() {
+            return Logger.getLogger(this.getClass().getName());
+        }
+
         @Override
         public InputStream getInputStream() throws IOException {
             FileInputStream fis = new FileInputStream(getFileName());
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