Fields and data types mapping between HB++ and desktop databases

In order to synchronize the data from the HB++ tables and the desktop databases, it is necessary to specify, for each field of the HB++ database, whether this field has to be synchronized or not; and if the case arises the name of the corresponding field on the desktop database and some other type-specific options. This is done in the Structure Tab of the Table editor.

Field mapping

When an HB++ table is created, you must set the Sync Field attribute for each field so that the conduit will be able to associate each field of the HB++ table to its counterpart in the synchronized database. The names cannot exceed 32 characters. A star ('*') means that the name of the field in the desktop database is the same as the HB++ field on the handheld device. Leaving the Sync Field empty means that the field should not be synchronized.

The fields UniqueID, Category, Dirty and Secret must be synchronized.

Type mapping for numeric types

The following table lists which data types must be used on the desktop database to store numerical data of the corresponding HB++ data types.

HB++ type	SQL type	ADO type

Boolean	BIT, TINYINT, SMALLINT, INT	adBoolean, adTinyInt, adInteger, adSmallInt, adUnsignedTinyInt, adUnsignedInt, adUnsignedSmallInt
Byte	INT, SMALLINT	adUnsignedTinyInt, adInteger, adUnsignedInt,adSmallInt, adUnsignedSmallInt, adUnsignedInt
Integer	INT	adSmallInt, adInteger
Long	INT	adInteger
Long (for data serials)	BIGINT	adUnsignedInteger
Single	FLOAT, DOUBLE	adSingle, adDouble
Double	DOUBLE, FLOAT	adDouble, adSingle

The types mentioned in bold are those used when the database on the desktop doesn't exist and is automatically created by the conduit.

Several mapping options are available for fields of type Date, String, Bitmap and StreamMemory. You can access these options by clicking the "..." button at the right of the cells in the Sync Options column of the editor table.

Type mapping for date types

Three formats are available to store dates on the desktop PC :

The standard date format of the database manager (SQL type: DATETIME; ADO type: adDate) is used. The programmer must ensure that the date stays in the range of validity of the PalmOS^® dates.
An integer value equal to the number of seconds elapsed since January, the 1st, 1904, 00:00 (in this case refer to the section related to numeric types) is used. This is the native representation of dates for PalmOS^® handhelds and HB++.
A string containing the date and time in the "YYYY/MM/DD hh:mm:ss" format is used. In this case, the date must be stored in an adVarChar or adVarWChar field (SQL equivalent: VARCHAR).

Type mapping for StreamMemory and Bitmap types

Three formats are available to store these objects on the desktop PC :

The data is stored in an external file; and the name of this file is stored in a text field (SQL type: VARCHAR(255), ADO type: adVarChar or adVarWChar) of the database.
A blob field (SQL type: BLOB, ADO type: adLongVarBinary) is used. Note that in this case it might be difficult with some database managers to access the content of this field.
The data is stored as a Base64 encoded string in a memo field (SQL type: TEXT, ADO type: adLongVarChar or adLongVarWChar). This feature is present to ensure the maximum compatibility with older database manager which don't support Binary/Blob types.

In the case of a Bitmap Object, an extra option allows to chose between the native HB++ format and the.BMP format. The.BMP format will easily allow to read and modify the content of the bitmaps, especially when they are stored as external files; however, information such as transparency color or density won't be stored and will be replaced by default values (no transparency; 72 bpp). On the other hand,.HBB format (Handheld Basic Bitmap) stores properly the transparency color and density, but is not accepted by any application except HB++.

Type mapping for String types

Two options are available to store HB++ Strings on the desktop PC :

Using a memo field (SQL type: TEXT, ADO type: adLongVarChar or adLongVarWChar).
Using a short variable-length string (SQL type: VARCHAR, ADO type: adVarChar or adVarWChar). In this case, the maximum length of the string, less or equal than 255, has to be specified.