jnode-svn-commits

[Jnode-svn-commits] SF.net SVN: jnode:[5872] trunk/fs/src/fs/org/jnode/fs/ntfs/ CompressedDataRun.java

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Revision: 5872
          http://jnode.svn.sourceforge.net/jnode/?rev=5872&view=rev
Author:   galatnm
Date:     2011-12-09 15:48:02 +0000 (Fri, 09 Dec 2011)
Log Message:
-----------
Fix doc and method name.

Modified Paths:
--------------
    trunk/fs/src/fs/org/jnode/fs/ntfs/CompressedDataRun.java

Modified: trunk/fs/src/fs/org/jnode/fs/ntfs/CompressedDataRun.java
===================================================================
--- trunk/fs/src/fs/org/jnode/fs/ntfs/CompressedDataRun.java	2011-12-09 15:38:49 UTC (rev 5871)
+++ trunk/fs/src/fs/org/jnode/fs/ntfs/CompressedDataRun.java	2011-12-09 15:48:02 UTC (rev 5872)
@@ -127,7 +127,7 @@
         final byte[] tempUncompressed = new byte[compressionUnitSize * clusterSize];
         // XXX: We could potentially reduce the overhead by modifying the compression
         //      routine such that it's capable of skipping chunks that aren't needed.
-        uncompressUnit(tempCompressed, tempUncompressed);
+        unCompressUnit(tempCompressed, tempUncompressed);
 
         System.arraycopy(tempUncompressed, vcnOffsetWithinUnit * clusterSize,
                          dst, dstOffset + (int) (actFirstVcn - vcn) * clusterSize,
@@ -141,10 +141,9 @@
      *
      * @param compressed the compressed data (in.)
      * @param uncompressed the uncompressed data (out.)
-     * @param requiredBytes the number of bytes needed before the read can stop.
      * @throws IOException if the decompression fails.
      */
-    private static void uncompressUnit(final byte[] compressed,
+    private static void unCompressUnit(final byte[] compressed,
                                        final byte[] uncompressed) throws IOException {
 
         // This is just a convenient way to simulate the original code's pointer arithmetic.

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[Jnode-svn-commits] SF.net SVN: jnode:[5968] trunk/fs/src/fs/org/jnode/fs/ntfs/ CompressedDataRun.java

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Revision: 5968
          http://jnode.svn.sourceforge.net/jnode/?rev=5968&view=rev
Author:   galatnm
Date:     2013-02-20 12:01:01 +0000 (Wed, 20 Feb 2013)
Log Message:
-----------
Better implementation of mapVcnToLcn() for compressed data runs. (Luke Quinane)

Modified Paths:
--------------
    trunk/fs/src/fs/org/jnode/fs/ntfs/CompressedDataRun.java

Modified: trunk/fs/src/fs/org/jnode/fs/ntfs/CompressedDataRun.java
===================================================================
--- trunk/fs/src/fs/org/jnode/fs/ntfs/CompressedDataRun.java	2013-02-20 11:56:05 UTC (rev 5967)
+++ trunk/fs/src/fs/org/jnode/fs/ntfs/CompressedDataRun.java	2013-02-20 12:01:01 UTC (rev 5968)
@@ -224,7 +224,19 @@
 
 	@Override
 	public long mapVcnToLcn(long vcn) {
-		return compressedRun.mapVcnToLcn(vcn);
+        // This is the actual number of stored clusters after compression.
+        // If the number of stored clusters is the same as the compression unit size,
+        // then the data can be read directly without decompressing it.
+        final int compClusters = compressedRun.getLength();
+        if (compClusters == compressionUnitSize) {
+            return compressedRun.mapVcnToLcn(vcn);
+        }
+
+        // Now we know the data is compressed. Map the VCN to the corresponding compressed block...
+        final long actFirstVcn = Math.max(compressedRun.getFirstVcn(), vcn);
+        final int vcnOffsetWithinUnit = (int) (actFirstVcn % compressionUnitSize);
+        final long compFirstVcn = actFirstVcn - vcnOffsetWithinUnit;
+        return compressedRun.mapVcnToLcn(compFirstVcn);
 	}
 
 	/**

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