Fix length in units calculation for Access 97 text fields. Fixes #151

git-svn-id: https://svn.code.sf.net/p/jackcess/code/jackcess/trunk@1258 f203690c-595d-4dc9-a70b-905162fa7fd2

6 files changed, 181 insertions, 131 deletions

diff --git a/src/changes/changes.xml b/src/changes/changes.xml
index 904992d..efa4a64 100644
--- a/src/changes/changes.xml
+++ b/src/changes/changes.xml
@@ -27,6 +27,9 @@
         irrelevant failures when reading databases which have invalid column
         properties.
       </action>
+      <action dev="jahlborn" type="fix" system="SourceForge2" issue="151">
+        Fix length in units calculation for Access 97 text fields.
+      </action>
     </release>
     <release version="2.2.0" date="2018-09-08"
              description="Add support for expression evaluation">
diff --git a/src/main/java/com/healthmarketscience/jackcess/DataType.java b/src/main/java/com/healthmarketscience/jackcess/DataType.java
index 33496cf..380f7f1 100644
--- a/src/main/java/com/healthmarketscience/jackcess/DataType.java
+++ b/src/main/java/com/healthmarketscience/jackcess/DataType.java
@@ -389,12 +389,27 @@ public enum DataType {
     return _unitSize;
   }
 
+  public int getUnitSize(JetFormat format) {
+    if((format != null) && isTextual()) {
+      return format.SIZE_TEXT_FIELD_UNIT;
+    }
+    return _unitSize;
+  }
+
   public int toUnitSize(int size) {
-    return(size / getUnitSize());
+    return toUnitSize(size, null);
+  }
+
+  public int toUnitSize(int size, JetFormat format) {
+    return(size / getUnitSize(format));
   }
 
   public int fromUnitSize(int unitSize) {
-    return(unitSize * getUnitSize());
+    return fromUnitSize(unitSize, null);
+  }
+
+  public int fromUnitSize(int unitSize, JetFormat format) {
+    return(unitSize * getUnitSize(format));
   }
 
   public boolean isValidSize(int size) {
@@ -474,13 +489,15 @@ public enum DataType {
     if(rtnArr == null) {
       throw new SQLException("Unsupported SQL type: " + sqlType);
     }
+    JetFormat format =
+      ((fileFormat != null) ?
+       DatabaseImpl.getFileFormatDetails(fileFormat).getFormat() :
+       null);
     DataType rtn = rtnArr[0];
-    if((rtnArr.length > 1) && (fileFormat != null)) {
+    if((rtnArr.length > 1) && (format != null)) {
       // there are multiple possibilities, ordered from lowest version to
       // highest version supported.  go in opposite order to find the best
       // type for this format
-      JetFormat format = DatabaseImpl.getFileFormatDetails(fileFormat)
-        .getFormat();
       for(int i = rtnArr.length - 1; i >= 0; --i) {
         DataType tmp = rtnArr[i];
         if(format.isSupportedDataType(tmp)) {
@@ -491,7 +508,7 @@ public enum DataType {
     }
 
     // make sure size is reasonable
-    int size = rtn.fromUnitSize(lengthInUnits);
+    int size = rtn.fromUnitSize(lengthInUnits, format);
     if(rtn.isVariableLength() && !rtn.isValidSize(size)) {
       // try alternate type.  we always accept alternate "long value" types
       // regardless of the given lengthInUnits
diff --git a/src/main/java/com/healthmarketscience/jackcess/impl/CalculatedColumnUtil.java b/src/main/java/com/healthmarketscience/jackcess/impl/CalculatedColumnUtil.java
index fb76ad7..9aa7d17 100644
--- a/src/main/java/com/healthmarketscience/jackcess/impl/CalculatedColumnUtil.java
+++ b/src/main/java/com/healthmarketscience/jackcess/impl/CalculatedColumnUtil.java
@@ -242,10 +242,11 @@ class CalculatedColumnUtil
     }
 
     @Override
-    public short getLengthInUnits() {
+    protected int calcLengthInUnits() {
       // the byte "length" includes the calculated field overhead.  remove
       // that to get the _actual_ data length (in units)
-      return (short)getType().toUnitSize(getLength() - CALC_EXTRA_DATA_LEN);
+      return getType().toUnitSize(getLength() - CALC_EXTRA_DATA_LEN,
+                                  getFormat());
     }
 
     @Override
@@ -285,10 +286,11 @@ class CalculatedColumnUtil
     }
 
     @Override
-    protected int getMaxLengthInUnits() {
+    protected int calcMaxLengthInUnits() {
       // the byte "length" includes the calculated field overhead.  remove
       // that to get the _actual_ data length (in units)
-      return getType().toUnitSize(getType().getMaxSize() - CALC_EXTRA_DATA_LEN);
+      return getType().toUnitSize(getType().getMaxSize() - CALC_EXTRA_DATA_LEN,
+                                  getFormat());
     }
 
     @Override
diff --git a/src/main/java/com/healthmarketscience/jackcess/impl/ColumnImpl.java b/src/main/java/com/healthmarketscience/jackcess/impl/ColumnImpl.java
index 0016687..3445ba3 100644
--- a/src/main/java/com/healthmarketscience/jackcess/impl/ColumnImpl.java
+++ b/src/main/java/com/healthmarketscience/jackcess/impl/ColumnImpl.java
@@ -159,6 +159,8 @@ public class ColumnImpl implements Column, Comparable<ColumnImpl> {
   /** auto numbers must be > 0 */
   static final int INVALID_AUTO_NUMBER = 0;
 
+  static final int INVALID_LENGTH = -1;
+
 
   /** owning table */
   private final TableImpl _table;
@@ -192,6 +194,8 @@ public class ColumnImpl implements Column, Comparable<ColumnImpl> {
   private ColumnValidator _validator = SimpleColumnValidator.INSTANCE;
   /** default value generator */
   private ColDefaultValueEvalContext _defValue;
+  /** length of the column in units, lazily computed */
+  private int _lengthInUnits = INVALID_LENGTH;
 
   /**
    * @usage _advanced_method_
@@ -429,8 +433,15 @@ public class ColumnImpl implements Column, Comparable<ColumnImpl> {
     return _columnLength;
   }
 
-  public short getLengthInUnits() {
-    return (short)getType().toUnitSize(getLength());
+  public final short getLengthInUnits() {
+    if(_lengthInUnits == INVALID_LENGTH) {
+      _lengthInUnits = calcLengthInUnits();
+    }
+    return (short)_lengthInUnits;
+  }
+
+  protected int calcLengthInUnits() {
+    return getType().toUnitSize(getLength(), getFormat());
   }
 
   public boolean isCalculated() {
diff --git a/src/main/java/com/healthmarketscience/jackcess/impl/JetFormat.java b/src/main/java/com/healthmarketscience/jackcess/impl/JetFormat.java
index a230edf..6ca0dd1 100644
--- a/src/main/java/com/healthmarketscience/jackcess/impl/JetFormat.java
+++ b/src/main/java/com/healthmarketscience/jackcess/impl/JetFormat.java
@@ -34,7 +34,7 @@ import com.healthmarketscience.jackcess.Database;
  * @author Tim McCune
  */
 public abstract class JetFormat {
-  
+
   /** Maximum size of a record minus OLE objects and Memo fields */
   public static final int MAX_RECORD_SIZE = 1900;  //2kb minus some overhead
 
@@ -46,7 +46,7 @@ public abstract class JetFormat {
   public enum CodecType {
     NONE, JET, MSISAM, OFFICE;
   }
-  
+
   /** Offset in the file that holds the byte describing the Jet format
       version */
   private static final int OFFSET_VERSION = 20;
@@ -67,7 +67,7 @@ public abstract class JetFormat {
   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;
-  
+
   private final static byte[] MSISAM_ENGINE = new byte[] {
     'M', 'S', 'I', 'S', 'A', 'M', ' ', 'D', 'a', 't', 'a', 'b', 'a', 's', 'e'
   };
@@ -78,11 +78,11 @@ public abstract class JetFormat {
     (byte)0xC2, (byte)0x55, (byte)0xEB, (byte)0xA9, (byte)0x67, (byte)0x72,
     (byte)0x43, (byte)0x3F, (byte)0x00, (byte)0x9C, (byte)0x7A, (byte)0x9F,
     (byte)0x90, (byte)0xFF, (byte)0x80, (byte)0x9A, (byte)0x31, (byte)0xC5,
-    (byte)0x79, (byte)0xBA, (byte)0xED, (byte)0x30, (byte)0xBC, (byte)0xDF, 
+    (byte)0x79, (byte)0xBA, (byte)0xED, (byte)0x30, (byte)0xBC, (byte)0xDF,
     (byte)0xCC, (byte)0x9D, (byte)0x63, (byte)0xD9, (byte)0xE4, (byte)0xC3,
     (byte)0x7B, (byte)0x42, (byte)0xFB, (byte)0x8A, (byte)0xBC, (byte)0x4E,
     (byte)0x86, (byte)0xFB, (byte)0xEC, (byte)0x37, (byte)0x5D, (byte)0x44,
-    (byte)0x9C, (byte)0xFA, (byte)0xC6, (byte)0x5E, (byte)0x28, (byte)0xE6, 
+    (byte)0x9C, (byte)0xFA, (byte)0xC6, (byte)0x5E, (byte)0x28, (byte)0xE6,
     (byte)0x13, (byte)0xB6, (byte)0x8A, (byte)0x60, (byte)0x54, (byte)0x94,
     (byte)0x7B, (byte)0x36, (byte)0xF5, (byte)0x72, (byte)0xDF, (byte)0xB1,
     (byte)0x77, (byte)0xF4, (byte)0x13, (byte)0x43, (byte)0xCF, (byte)0xAF,
@@ -95,7 +95,7 @@ public abstract class JetFormat {
     (byte)0x27, (byte)0x44, (byte)0xD2, (byte)0xEE, (byte)0xCF, (byte)0x65,
     (byte)0xED, (byte)0xFF, (byte)0x07, (byte)0xC7, (byte)0x46, (byte)0xA1,
     (byte)0x78, (byte)0x16, (byte)0x0C, (byte)0xED, (byte)0xE9, (byte)0x2D,
-    (byte)0x62, (byte)0xD4};    
+    (byte)0x62, (byte)0xD4};
 
   /** value of the "AccessVersion" property for access 2000 dbs:
       {@code "08.50"} */
@@ -111,22 +111,22 @@ public abstract class JetFormat {
 
   // use nested inner class to avoid problematic static init loops
   private static final class PossibleFileFormats {
-    private static final Map<String,Database.FileFormat> POSSIBLE_VERSION_3 = 
+    private static final Map<String,Database.FileFormat> POSSIBLE_VERSION_3 =
       Collections.singletonMap((String)null, Database.FileFormat.V1997);
 
-    private static final Map<String,Database.FileFormat> POSSIBLE_VERSION_4 = 
+    private static final Map<String,Database.FileFormat> POSSIBLE_VERSION_4 =
       new HashMap<String,Database.FileFormat>();
 
-    private static final Map<String,Database.FileFormat> POSSIBLE_VERSION_12 = 
+    private static final Map<String,Database.FileFormat> POSSIBLE_VERSION_12 =
       Collections.singletonMap((String)null, Database.FileFormat.V2007);
 
-    private static final Map<String,Database.FileFormat> POSSIBLE_VERSION_14 = 
+    private static final Map<String,Database.FileFormat> POSSIBLE_VERSION_14 =
       Collections.singletonMap((String)null, Database.FileFormat.V2010);
 
-    private static final Map<String,Database.FileFormat> POSSIBLE_VERSION_16 = 
+    private static final Map<String,Database.FileFormat> POSSIBLE_VERSION_16 =
       Collections.singletonMap((String)null, Database.FileFormat.V2016);
 
-    private static final Map<String,Database.FileFormat> POSSIBLE_VERSION_MSISAM = 
+    private static final Map<String,Database.FileFormat> POSSIBLE_VERSION_MSISAM =
       Collections.singletonMap((String)null, Database.FileFormat.MSISAM);
 
     static {
@@ -137,10 +137,10 @@ public abstract class JetFormat {
   }
 
   /** calculated types supported in version 14 */
-  private static final Set<DataType> V14_CALC_TYPES = 
+  private static final Set<DataType> V14_CALC_TYPES =
     EnumSet.of(DataType.BOOLEAN, DataType.BYTE, DataType.INT, DataType.LONG,
-               DataType.FLOAT, DataType.DOUBLE, DataType.GUID, 
-               DataType.SHORT_DATE_TIME, DataType.MONEY, DataType.NUMERIC, 
+               DataType.FLOAT, DataType.DOUBLE, DataType.GUID,
+               DataType.SHORT_DATE_TIME, DataType.MONEY, DataType.NUMERIC,
                DataType.TEXT, DataType.MEMO);
 
   /** calculated types supported in version 16 */
@@ -168,20 +168,20 @@ public abstract class JetFormat {
 
   /** the name of this format */
   private final String _name;
-  
+
   /** the read/write mode of this format */
   public final boolean READ_ONLY;
-  
+
   /** whether or not we can use indexes in this format */
   public final boolean INDEXES_SUPPORTED;
 
   /** type of page encoding supported */
   public final CodecType CODEC_TYPE;
-  
+
   /** Database page size in bytes */
   public final int PAGE_SIZE;
   public final long MAX_DATABASE_SIZE;
-  
+
   public final int MAX_ROW_SIZE;
   public final int DATA_PAGE_INITIAL_FREE_SPACE;
 
@@ -207,10 +207,10 @@ public abstract class JetFormat {
   public final int OFFSET_OWNED_PAGES;
   public final int OFFSET_FREE_SPACE_PAGES;
   public final int OFFSET_INDEX_DEF_BLOCK;
-  
+
   public final int SIZE_INDEX_COLUMN_BLOCK;
   public final int SIZE_INDEX_INFO_BLOCK;
-  
+
   public final int OFFSET_COLUMN_TYPE;
   public final int OFFSET_COLUMN_NUMBER;
   public final int OFFSET_COLUMN_PRECISION;
@@ -224,26 +224,26 @@ public abstract class JetFormat {
   public final int OFFSET_COLUMN_VARIABLE_TABLE_INDEX;
   public final int OFFSET_COLUMN_FIXED_DATA_OFFSET;
   public final int OFFSET_COLUMN_FIXED_DATA_ROW_OFFSET;
-  
+
   public final int OFFSET_TABLE_DEF_LOCATION;
-  
+
   public final int OFFSET_ROW_START;
   public final int OFFSET_USAGE_MAP_START;
-  
+
   public final int OFFSET_USAGE_MAP_PAGE_DATA;
-  
+
   public final int OFFSET_REFERENCE_MAP_PAGE_NUMBERS;
-  
+
   public final int OFFSET_FREE_SPACE;
   public final int OFFSET_NUM_ROWS_ON_DATA_PAGE;
   public final int MAX_NUM_ROWS_ON_DATA_PAGE;
-  
+
   public final int OFFSET_INDEX_COMPRESSED_BYTE_COUNT;
   public final int OFFSET_INDEX_ENTRY_MASK;
   public final int OFFSET_PREV_INDEX_PAGE;
   public final int OFFSET_NEXT_INDEX_PAGE;
   public final int OFFSET_CHILD_TAIL_INDEX_PAGE;
-  
+
   public final int SIZE_INDEX_DEFINITION;
   public final int SIZE_COLUMN_HEADER;
   public final int SIZE_ROW_LOCATION;
@@ -263,7 +263,7 @@ public abstract class JetFormat {
   public final int SIZE_NAME_LENGTH;
   public final int SIZE_ROW_COLUMN_COUNT;
   public final int SIZE_ROW_VAR_COL_OFFSET;
-  
+
   public final int USAGE_MAP_TABLE_BYTE_LENGTH;
 
   public final int MAX_COLUMNS_PER_TABLE;
@@ -273,11 +273,12 @@ public abstract class JetFormat {
   public final int MAX_INDEX_NAME_LENGTH;
 
   public final boolean LEGACY_NUMERIC_INDEXES;
-  
+
   public final Charset CHARSET;
   public final ColumnImpl.SortOrder DEFAULT_SORT_ORDER;
   public final byte[] PROPERTY_MAP_TYPE;
-  
+  public final int SIZE_TEXT_FIELD_UNIT;
+
   /**
    * @param channel the database file.
    * @return The Jet Format represented in the passed-in file
@@ -309,20 +310,20 @@ public abstract class JetFormat {
                           ((version < CODE_VERSION_3) ? "older" : "newer") +
                           " version: " + version);
   }
-  
+
   private JetFormat(String name) {
     _name = name;
-    
+
     READ_ONLY = defineReadOnly();
     INDEXES_SUPPORTED = defineIndexesSupported();
     CODEC_TYPE = defineCodecType();
-    
+
     PAGE_SIZE = definePageSize();
     MAX_DATABASE_SIZE = defineMaxDatabaseSize();
-    
+
     MAX_ROW_SIZE = defineMaxRowSize();
     DATA_PAGE_INITIAL_FREE_SPACE = defineDataPageInitialFreeSpace();
-    
+
     OFFSET_MASKED_HEADER = defineOffsetMaskedHeader();
     HEADER_MASK = defineHeaderMask();
     OFFSET_HEADER_DATE = defineOffsetHeaderDate();
@@ -345,10 +346,10 @@ public abstract class JetFormat {
     OFFSET_OWNED_PAGES = defineOffsetOwnedPages();
     OFFSET_FREE_SPACE_PAGES = defineOffsetFreeSpacePages();
     OFFSET_INDEX_DEF_BLOCK = defineOffsetIndexDefBlock();
-    
+
     SIZE_INDEX_COLUMN_BLOCK = defineSizeIndexColumnBlock();
     SIZE_INDEX_INFO_BLOCK = defineSizeIndexInfoBlock();
-    
+
     OFFSET_COLUMN_TYPE = defineOffsetColumnType();
     OFFSET_COLUMN_NUMBER = defineOffsetColumnNumber();
     OFFSET_COLUMN_PRECISION = defineOffsetColumnPrecision();
@@ -362,26 +363,26 @@ public abstract class JetFormat {
     OFFSET_COLUMN_VARIABLE_TABLE_INDEX = defineOffsetColumnVariableTableIndex();
     OFFSET_COLUMN_FIXED_DATA_OFFSET = defineOffsetColumnFixedDataOffset();
     OFFSET_COLUMN_FIXED_DATA_ROW_OFFSET = defineOffsetColumnFixedDataRowOffset();
-    
+
     OFFSET_TABLE_DEF_LOCATION = defineOffsetTableDefLocation();
-    
+
     OFFSET_ROW_START = defineOffsetRowStart();
     OFFSET_USAGE_MAP_START = defineOffsetUsageMapStart();
-    
+
     OFFSET_USAGE_MAP_PAGE_DATA = defineOffsetUsageMapPageData();
-    
+
     OFFSET_REFERENCE_MAP_PAGE_NUMBERS = defineOffsetReferenceMapPageNumbers();
-    
+
     OFFSET_FREE_SPACE = defineOffsetFreeSpace();
     OFFSET_NUM_ROWS_ON_DATA_PAGE = defineOffsetNumRowsOnDataPage();
     MAX_NUM_ROWS_ON_DATA_PAGE = defineMaxNumRowsOnDataPage();
-    
+
     OFFSET_INDEX_COMPRESSED_BYTE_COUNT = defineOffsetIndexCompressedByteCount();
     OFFSET_INDEX_ENTRY_MASK = defineOffsetIndexEntryMask();
     OFFSET_PREV_INDEX_PAGE = defineOffsetPrevIndexPage();
     OFFSET_NEXT_INDEX_PAGE = defineOffsetNextIndexPage();
     OFFSET_CHILD_TAIL_INDEX_PAGE = defineOffsetChildTailIndexPage();
-    
+
     SIZE_INDEX_DEFINITION = defineSizeIndexDefinition();
     SIZE_COLUMN_HEADER = defineSizeColumnHeader();
     SIZE_ROW_LOCATION = defineSizeRowLocation();
@@ -409,24 +410,25 @@ public abstract class JetFormat {
     MAX_TABLE_NAME_LENGTH = defineMaxTableNameLength();
     MAX_COLUMN_NAME_LENGTH = defineMaxColumnNameLength();
     MAX_INDEX_NAME_LENGTH = defineMaxIndexNameLength();
-    
+
     LEGACY_NUMERIC_INDEXES = defineLegacyNumericIndexes();
-    
+
     CHARSET = defineCharset();
     DEFAULT_SORT_ORDER = defineDefaultSortOrder();
     PROPERTY_MAP_TYPE = definePropMapType();
+    SIZE_TEXT_FIELD_UNIT = defineSizeTextFieldUnit();
   }
-  
+
   protected abstract boolean defineReadOnly();
   protected abstract boolean defineIndexesSupported();
   protected abstract CodecType defineCodecType();
-  
+
   protected abstract int definePageSize();
   protected abstract long defineMaxDatabaseSize();
-  
+
   protected abstract int defineMaxRowSize();
   protected abstract int defineDataPageInitialFreeSpace();
-  
+
   protected abstract int defineOffsetMaskedHeader();
   protected abstract byte[] defineHeaderMask();
   protected abstract int defineOffsetHeaderDate();
@@ -449,10 +451,10 @@ public abstract class JetFormat {
   protected abstract int defineOffsetOwnedPages();
   protected abstract int defineOffsetFreeSpacePages();
   protected abstract int defineOffsetIndexDefBlock();
-  
+
   protected abstract int defineSizeIndexColumnBlock();
   protected abstract int defineSizeIndexInfoBlock();
-  
+
   protected abstract int defineOffsetColumnType();
   protected abstract int defineOffsetColumnNumber();
   protected abstract int defineOffsetColumnPrecision();
@@ -466,26 +468,26 @@ public abstract class JetFormat {
   protected abstract int defineOffsetColumnVariableTableIndex();
   protected abstract int defineOffsetColumnFixedDataOffset();
   protected abstract int defineOffsetColumnFixedDataRowOffset();
-  
+
   protected abstract int defineOffsetTableDefLocation();
-  
+
   protected abstract int defineOffsetRowStart();
   protected abstract int defineOffsetUsageMapStart();
-  
+
   protected abstract int defineOffsetUsageMapPageData();
-  
+
   protected abstract int defineOffsetReferenceMapPageNumbers();
-  
+
   protected abstract int defineOffsetFreeSpace();
   protected abstract int defineOffsetNumRowsOnDataPage();
   protected abstract int defineMaxNumRowsOnDataPage();
-  
+
   protected abstract int defineOffsetIndexCompressedByteCount();
   protected abstract int defineOffsetIndexEntryMask();
   protected abstract int defineOffsetPrevIndexPage();
   protected abstract int defineOffsetNextIndexPage();
   protected abstract int defineOffsetChildTailIndexPage();
-  
+
   protected abstract int defineSizeIndexDefinition();
   protected abstract int defineSizeColumnHeader();
   protected abstract int defineSizeRowLocation();
@@ -513,10 +515,11 @@ public abstract class JetFormat {
   protected abstract int defineMaxTableNameLength();
   protected abstract int defineMaxColumnNameLength();
   protected abstract int defineMaxIndexNameLength();
-  
+
   protected abstract Charset defineCharset();
   protected abstract ColumnImpl.SortOrder defineDefaultSortOrder();
   protected abstract byte[] definePropMapType();
+  protected abstract int defineSizeTextFieldUnit();
 
   protected abstract boolean defineLegacyNumericIndexes();
 
@@ -530,7 +533,7 @@ public abstract class JetFormat {
   public String toString() {
     return _name;
   }
-  
+
   private static class Jet3Format extends JetFormat {
 
     private Jet3Format() {
@@ -539,33 +542,33 @@ public abstract class JetFormat {
 
     @Override
     protected boolean defineReadOnly() { return true; }
-	    
+
     @Override
     protected boolean defineIndexesSupported() { return false; }
 
     @Override
-    protected CodecType defineCodecType() { 
-      return CodecType.JET; 
+    protected CodecType defineCodecType() {
+      return CodecType.JET;
     }
-	    
+
     @Override
     protected int definePageSize() { return 2048; }
-	    
+
     @Override
     protected long defineMaxDatabaseSize() {
       return (1L * 1024L * 1024L * 1024L);
     }
-	    
+
     @Override
     protected int defineMaxRowSize() { return 2012; }
     @Override
     protected int defineDataPageInitialFreeSpace() { return PAGE_SIZE - 14; }
-	    
+
     @Override
     protected int defineOffsetMaskedHeader() { return 24; }
     @Override
-    protected byte[] defineHeaderMask() { 
-      return ByteUtil.copyOf(BASE_HEADER_MASK, BASE_HEADER_MASK.length - 2); 
+    protected byte[] defineHeaderMask() {
+      return ByteUtil.copyOf(BASE_HEADER_MASK, BASE_HEADER_MASK.length - 2);
     }
     @Override
     protected int defineOffsetHeaderDate() { return -1; }
@@ -612,7 +615,7 @@ public abstract class JetFormat {
     protected int defineSizeIndexColumnBlock() { return 39; }
     @Override
     protected int defineSizeIndexInfoBlock() { return 20; }
-	    
+
     @Override
     protected int defineOffsetColumnType() { return 0; }
     @Override
@@ -639,28 +642,28 @@ public abstract class JetFormat {
     protected int defineOffsetColumnFixedDataOffset() { return 14; }
     @Override
     protected int defineOffsetColumnFixedDataRowOffset() { return 1; }
-	  
+
     @Override
     protected int defineOffsetTableDefLocation() { return 4; }
-	    
+
     @Override
     protected int defineOffsetRowStart() { return 10; }
     @Override
     protected int defineOffsetUsageMapStart() { return 5; }
-	    
+
     @Override
     protected int defineOffsetUsageMapPageData() { return 4; }
-	    
+
     @Override
     protected int defineOffsetReferenceMapPageNumbers() { return 1; }
-	    
+
     @Override
     protected int defineOffsetFreeSpace() { return 2; }
     @Override
     protected int defineOffsetNumRowsOnDataPage() { return 8; }
     @Override
     protected int defineMaxNumRowsOnDataPage() { return 255; }
-	    
+
     @Override
     protected int defineOffsetIndexCompressedByteCount() { return 20; }
     @Override
@@ -671,7 +674,7 @@ public abstract class JetFormat {
     protected int defineOffsetNextIndexPage() { return 12; }
     @Override
     protected int defineOffsetChildTailIndexPage() { return 16; }
-	    
+
     @Override
     protected int defineSizeIndexDefinition() { return 8; }
     @Override
@@ -710,25 +713,25 @@ public abstract class JetFormat {
     protected int defineSizeRowColumnCount() { return 1; }
     @Override
     protected int defineSizeRowVarColOffset() { return 1; }
-	    
+
     @Override
     protected int defineUsageMapTableByteLength() { return 128; }
-	      
+
     @Override
     protected int defineMaxColumnsPerTable() { return 255; }
-	      
+
     @Override
     protected int defineMaxIndexesPerTable() { return 32; }
-	      
+
     @Override
     protected int defineMaxTableNameLength() { return 64; }
-	      
+
     @Override
     protected int defineMaxColumnNameLength() { return 64; }
-	      
+
     @Override
     protected int defineMaxIndexNameLength() { return 64; }
-	      
+
     @Override
     protected boolean defineLegacyNumericIndexes() { return true; }
 
@@ -744,7 +747,10 @@ public abstract class JetFormat {
     protected byte[] definePropMapType() {
       return PROPERTY_MAP_TYPES[1];
     }
-    
+
+    @Override
+    protected int defineSizeTextFieldUnit() { return 1; }
+
     @Override
     protected Map<String,Database.FileFormat> getPossibleFileFormats()
     {
@@ -762,7 +768,7 @@ public abstract class JetFormat {
       return false;
     }
   }
-  
+
   private static class Jet4Format extends JetFormat {
 
     private Jet4Format() {
@@ -775,28 +781,28 @@ public abstract class JetFormat {
 
     @Override
     protected boolean defineReadOnly() { return false; }
-    
+
     @Override
     protected boolean defineIndexesSupported() { return true; }
-	    
+
     @Override
-    protected CodecType defineCodecType() { 
-      return CodecType.JET; 
+    protected CodecType defineCodecType() {
+      return CodecType.JET;
     }
 
     @Override
     protected int definePageSize() { return 4096; }
-    
+
     @Override
     protected long defineMaxDatabaseSize() {
       return (2L * 1024L * 1024L * 1024L);
     }
-    
+
     @Override
     protected int defineMaxRowSize() { return 4060; }
     @Override
     protected int defineDataPageInitialFreeSpace() { return PAGE_SIZE - 14; }
-    
+
     @Override
     protected int defineOffsetMaskedHeader() { return 24; }
     @Override
@@ -846,7 +852,7 @@ public abstract class JetFormat {
     protected int defineSizeIndexColumnBlock() { return 52; }
     @Override
     protected int defineSizeIndexInfoBlock() { return 28; }
-    
+
     @Override
     protected int defineOffsetColumnType() { return 0; }
     @Override
@@ -873,28 +879,28 @@ public abstract class JetFormat {
     protected int defineOffsetColumnFixedDataOffset() { return 21; }
     @Override
     protected int defineOffsetColumnFixedDataRowOffset() { return 2; }
-  
+
     @Override
     protected int defineOffsetTableDefLocation() { return 4; }
-    
+
     @Override
     protected int defineOffsetRowStart() { return 14; }
     @Override
     protected int defineOffsetUsageMapStart() { return 5; }
-    
+
     @Override
     protected int defineOffsetUsageMapPageData() { return 4; }
-    
+
     @Override
     protected int defineOffsetReferenceMapPageNumbers() { return 1; }
-    
+
     @Override
     protected int defineOffsetFreeSpace() { return 2; }
     @Override
     protected int defineOffsetNumRowsOnDataPage() { return 12; }
     @Override
     protected int defineMaxNumRowsOnDataPage() { return 255; }
-    
+
     @Override
     protected int defineOffsetIndexCompressedByteCount() { return 24; }
     @Override
@@ -905,7 +911,7 @@ public abstract class JetFormat {
     protected int defineOffsetNextIndexPage() { return 16; }
     @Override
     protected int defineOffsetChildTailIndexPage() { return 20; }
-    
+
     @Override
     protected int defineSizeIndexDefinition() { return 12; }
     @Override
@@ -944,25 +950,25 @@ public abstract class JetFormat {
     protected int defineSizeRowColumnCount() { return 2; }
     @Override
     protected int defineSizeRowVarColOffset() { return 2; }
-    
+
     @Override
     protected int defineUsageMapTableByteLength() { return 64; }
-      
+
     @Override
     protected int defineMaxColumnsPerTable() { return 255; }
-	      
+
     @Override
     protected int defineMaxIndexesPerTable() { return 32; }
-      
+
     @Override
     protected int defineMaxTableNameLength() { return 64; }
-      
+
     @Override
     protected int defineMaxColumnNameLength() { return 64; }
-      
+
     @Override
     protected int defineMaxIndexNameLength() { return 64; }
-      
+
     @Override
     protected boolean defineLegacyNumericIndexes() { return true; }
 
@@ -980,6 +986,9 @@ public abstract class JetFormat {
     }
 
     @Override
+    protected int defineSizeTextFieldUnit() { return TEXT_FIELD_UNIT_SIZE; }
+
+    @Override
     protected Map<String,Database.FileFormat> getPossibleFileFormats()
     {
       return PossibleFileFormats.POSSIBLE_VERSION_4;
@@ -996,15 +1005,15 @@ public abstract class JetFormat {
       return false;
     }
   }
-  
+
   private static final class MSISAMFormat extends Jet4Format {
     private MSISAMFormat() {
       super("MSISAM");
     }
 
     @Override
-    protected CodecType defineCodecType() { 
-      return CodecType.MSISAM; 
+    protected CodecType defineCodecType() {
+      return CodecType.MSISAM;
     }
 
     @Override
@@ -1024,8 +1033,8 @@ public abstract class JetFormat {
     }
 
     @Override
-    protected CodecType defineCodecType() { 
-      return CodecType.OFFICE; 
+    protected CodecType defineCodecType() {
+      return CodecType.OFFICE;
     }
 
     @Override
@@ -1041,7 +1050,7 @@ public abstract class JetFormat {
 
     @Override
     protected int defineOffsetColumnComplexId() { return 11; }
-    
+
     @Override
     public boolean isSupportedDataType(DataType type) {
       return (type != DataType.BIG_INT);
@@ -1088,7 +1097,7 @@ public abstract class JetFormat {
     private Jet16Format() {
       super("VERSION_16");
     }
-    
+
     @Override
     public boolean isSupportedDataType(DataType type) {
       return true;
diff --git a/src/main/java/com/healthmarketscience/jackcess/impl/LongValueColumnImpl.java b/src/main/java/com/healthmarketscience/jackcess/impl/LongValueColumnImpl.java
index f878562..d1b2a07 100644
--- a/src/main/java/com/healthmarketscience/jackcess/impl/LongValueColumnImpl.java
+++ b/src/main/java/com/healthmarketscience/jackcess/impl/LongValueColumnImpl.java
@@ -55,6 +55,7 @@ class LongValueColumnImpl extends ColumnImpl
 
   /** Holds additional info for writing long values */
   private LongValueBufferHolder _lvalBufferH;
+  private int _maxLenInUnits = INVALID_LENGTH;
 
   LongValueColumnImpl(InitArgs args) throws IOException
   {
@@ -84,8 +85,15 @@ class LongValueColumnImpl extends ColumnImpl
     super.postTableLoadInit();
   }
 
-  protected int getMaxLengthInUnits() {
-    return getType().toUnitSize(getType().getMaxSize());
+  protected final int getMaxLengthInUnits() {
+    if(_maxLenInUnits == INVALID_LENGTH) {
+      _maxLenInUnits = calcMaxLengthInUnits();
+    }
+    return _maxLenInUnits;
+  }
+
+  protected int calcMaxLengthInUnits() {
+    return getType().toUnitSize(getType().getMaxSize(), getFormat());
   }
 
   @Override