proof of concept delta-rd5

brouter-mapaccess/src/main/java/btools/mapaccess/Rd5DiffTool.java

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+/**
+ * Proof of concept for delta rd5's
+ *
+ * @author ab
+ */
+package btools.mapaccess;
+
+import java.io.File;
+
+import btools.codec.DataBuffers;
+import btools.codec.MicroCache;
+import btools.codec.MicroCache2;
+import btools.codec.StatCoderContext;
+
+final public class Rd5DiffTool
+{
+  public static void main( String[] args ) throws Exception
+  {
+    diff2files( new File( args[0] ),new File( args[1] ) );
+  }
+
+  /**
+   * Compute the delta between 2 RD5 files and
+   * show statistics on the expected size of the delta file
+   */
+  public static void diff2files( File f1, File f2 ) throws Exception
+  {
+    byte[] abBuf1 = new byte[10 * 1024 * 1024];
+    byte[] abBuf2 = new byte[10 * 1024 * 1024];
+    
+    int nodesTotal = 0;
+    int nodesDiff = 0;
+    
+    long bytesDiff = 0L;
+
+    PhysicalFile pf1 = null;
+    PhysicalFile pf2 = null;
+    try
+    {
+      DataBuffers dataBuffers = new DataBuffers();
+      pf1 = new PhysicalFile( f1, dataBuffers, -1, -1 );
+      pf2 = new PhysicalFile( f2, dataBuffers, -1, -1 );
+      int div = pf1.divisor;
+      for ( int lonDegree = 0; lonDegree < 5; lonDegree++ ) // does'nt really matter..
+      {
+        for ( int latDegree = 0; latDegree < 5; latDegree++ ) // ..where on earth we are
+        {
+          OsmFile osmf1 = new OsmFile( pf1, lonDegree, latDegree, dataBuffers );
+          OsmFile osmf2 = new OsmFile( pf2, lonDegree, latDegree, dataBuffers );
+          for ( int lonIdx = 0; lonIdx < div; lonIdx++ )
+          {
+            for ( int latIdx = 0; latIdx < div; latIdx++ )
+            {
+              int lonIdxDiv = lonDegree * div + lonIdx;
+              int latIdxDiv = latDegree * div + latIdx;
+              
+            
+              MicroCache mc1 = osmf1.hasData() ? 
+                osmf1.createMicroCache( lonIdxDiv, latIdxDiv, dataBuffers, null, null, true, null )
+              : MicroCache.emptyCache();
+              MicroCache mc2 = osmf2.hasData() ? 
+                osmf2.createMicroCache( lonIdxDiv, latIdxDiv, dataBuffers, null, null, true, null )
+              : MicroCache.emptyCache();
+              
+              MicroCache mc = new MicroCache2( mc1.getSize() + mc2.getSize(), abBuf2, lonIdxDiv, latIdxDiv, div );
+              mc.calcDelta( mc1, mc2 );
+              
+              nodesTotal += mc2.getSize();
+              
+              if ( latIdx == 15 )
+              {
+                // System.out.println( "hier!" );
+              }
+              
+              if ( mc.getSize() > 0 )
+              {
+                 int len = mc.encodeMicroCache( abBuf1 );
+                 byte[] bytes = new byte[len];
+                 System.arraycopy( abBuf1, 0, bytes, 0, len );
+
+                 bytesDiff += len;
+                 nodesDiff += mc.getSize();
+                 
+                 // cross-check the encoding: re-instantiate the cache
+                 MicroCache mcCheck = new MicroCache2( new StatCoderContext( bytes ), new DataBuffers( null ), lonIdxDiv, latIdxDiv, div, null, null );
+
+                 // ..and check if still the same
+                 if ( mc.size() != mcCheck.size() )
+                 {
+                   // mc.compareWith finds link-ordering differences,
+                   // so we compare only if there's also a size missmatch...
+                 
+                   String diffMessage = mc.compareWith( mcCheck );
+                   if ( diffMessage != null )
+                   {
+                     throw new RuntimeException( "files differ: " + diffMessage );
+                   }
+                 }
+              }
+            }
+          }
+        }
+      }
+      System.out.println( "nodesTotal=" + nodesTotal + " nodesDiff=" + nodesDiff + " bytesDiff=" + bytesDiff );
+    }
+    finally
+    {
+      if ( pf1 != null )
+      {
+        try
+        {
+          pf1.ra.close();
+        }
+        catch (Exception ee)
+        {
+        }
+      }
+      if ( pf2 != null )
+      {
+        try
+        {
+          pf2.ra.close();
+        }
+        catch (Exception ee)
+        {
+        }
+      }
+    }
+  }
+}