CEDB Database Support
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8/28/2008
Windows Embedded CE supports databases stored anywhere on a device, including on PC cards and other installed file systems. The object store is considered a single, special database volume that is always mounted.
Each CEDB database contains a maximum of CEDB_MAXSORTORDER sort indexes and one or more records.
The maximum size of a record is defined in the CEDB_MAXRECORDSIZE constant in Windbase.h and in Rapi.h for Remote API (RAPI) calls.
A record can have a variable number of properties, but it cannot contain another record. The maximum size of a property is defined in the CEDB_MAXPROPDATASIZE constant, and Windows Embedded CE allocates space for a record or property only when necessary.
The following table shows the types of record properties.
| Record property type | Contains |
|---|---|
CEVT_BOOL |
Boolean value |
CEVT_CEBLOB |
Binary object |
CEVT_R8 |
8-byte floating-point value |
CEVT_FILETIME |
Time and date data |
CEVT_I2 |
2-byte signed integer |
CEVT_I4 |
4-byte signed integer |
CEVT_LPWSTR |
Long pointer to a Unicode string |
CEVT_UI2 |
2-byte unsigned integer |
CEVT_UI4 |
4-byte unsigned integer |
Note
The BOOL and floating-point properties are available only in Windows CE 2.10 and later.
Creating a record requires 20 bytes. A property requires 4 bytes.
In addition to records, a database contains a name and type identifier. The database name is a null-terminated string of up to 32 characters. The type identifier is application-specific and commonly used to identify similar databases.
Because Windows Embedded CE is designed to operate in a relatively volatile environment, the Windows Embedded CE database does not only automatically update when the database opens or closes. It updates after each individual transaction, such as a call to the CeWriteRecordProps (CEDB) function. A database volume is a file that contains all data for the databases in it. Individual database volumes can be up to 16 MB.
See Also
Concepts
Databases
Creating a Database
Deleting a Database Volume
Deleting Database Information
Enumerating Databases and Database Volumes
Modifying the Sort Order
Mounted Database Example
Mounting and Unmounting a Database Volume
Opening a Database
Reading a Record
Writing and Creating a Record
Adding a Database Volume on an External Device