minor refactors

git-svn-id: https://svn.code.sf.net/p/jackcess/code/jackcess/trunk@500 f203690c-595d-4dc9-a70b-905162fa7fd2

src/java/com/healthmarketscience/jackcess/Database.java

@@ -1129,8 +1129,15 @@ public class Database
     _buffer.position(_format.OFFSET_PASSWORD);
     _buffer.get(pwdBytes);
 
-    // de-mask password
-    applyPasswordMask(pwdBytes);
+    // de-mask password using extra password mask if necessary (the extra
+    // password mask is generated from the database creation date stored in
+    // the header)
+    byte[] pwdMask = getPasswordMask(_buffer, _format);
+    if(pwdMask != null) {
+      for(int i = 0; i < pwdBytes.length; ++i) {
+        pwdBytes[i] ^= pwdMask[i % pwdMask.length];
+      }
+    }
     
     boolean hasPassword = false;
     for(int i = 0; i < pwdBytes.length; ++i) {
@@ -1155,30 +1162,6 @@ public class Database
     return pwd;
   }
 
-  /**
-   * Applies an extra mask to the password if required for the current
-   * JetFormat.
-   */
-  private void applyPasswordMask(byte[] pwdBytes)
-  {
-    // apply extra password mask if necessary (the extra password mask is
-    // generated from the database creation date stored in the header)
-    int pwdMaskPos = _format.OFFSET_HEADER_DATE;
-    if(pwdMaskPos >= 0) {
-
-      _buffer.position(pwdMaskPos);
-      double dateVal = Double.longBitsToDouble(_buffer.getLong());
-
-      byte[] pwdMask = new byte[4];
-      ByteBuffer.wrap(pwdMask).order(PageChannel.DEFAULT_BYTE_ORDER)
-        .putInt((int)dateVal);
-
-      for(int i = 0; i < pwdBytes.length; ++i) {
-        pwdBytes[i] ^= pwdMask[i % pwdMask.length];
-      }
-    }
-  }
-
   /**
    * Finds the relationships matching the given from and to tables from the
    * given cursor and adds them to the given list.
@@ -1635,6 +1618,30 @@ public class Database
     }
   }
 
+  /**
+   * Returns the password mask retrieved from the given header page and
+   * format, or {@code null} if this format does not use a password mask.
+   */
+  static byte[] getPasswordMask(ByteBuffer buffer, JetFormat format)
+  {
+    // get extra password mask if necessary (the extra password mask is
+    // generated from the database creation date stored in the header)
+    int pwdMaskPos = format.OFFSET_HEADER_DATE;
+    if(pwdMaskPos < 0) {
+      return null;
+    }
+
+    buffer.position(pwdMaskPos);
+    double dateVal = Double.longBitsToDouble(buffer.getLong());
+
+    byte[] pwdMask = new byte[4];
+    ByteBuffer.wrap(pwdMask).order(PageChannel.DEFAULT_BYTE_ORDER)
+      .putInt((int)dateVal);
+
+    return pwdMask;
+  }
+
+
   /**
    * Utility class for storing table page number and actual name.
    */

src/java/com/healthmarketscience/jackcess/JetFormat.java

@@ -64,7 +64,9 @@ public abstract class JetFormat {
   private static final byte CODE_VERSION_5 = 0x2;
 
   /** location of the engine name in the header */
-  private static final int OFFSET_ENGINE_NAME = 0x4;
+  static final int OFFSET_ENGINE_NAME = 0x4;
+  /** length of the engine name in the header */
+  static final int LENGTH_ENGINE_NAME = 0xF;
   /** amount of initial data to be read to determine database type */
   private static final int HEADER_LENGTH = 21;