Section 25.4. Modifying the Database

   


25.4. Modifying the Database

There are two operations that modify qdbm databases: adding records and removing records. Updating records is done using the same function as adding records.

25.4.1. Adding Records

New and updated records are recorded in the database through the dpput() function.

 int dpput(DEPOT * depot, const char * key, int keySize,           const char * data, int dataSize, int dmode); 


The key is the index value that can later be used to retrieve the information referenced by data. Both keySize and dataSize may be -1, which tells dpput() to use strlen() to get the size of that field. It looks at the dmode parameter only if there is already a data item associated with key in the database. dmode can have one of the following values:

DP_DCAT

The new data is appended to the end of the data already in the database.

DP_DKEEP

The database is not modified; dpput() returns failure and dpecode is set to DP_EKEEP.

DP_DOVER

The data in the database is overwritten with the new value.


dpput() returns zero if an error occurred (or if the key already existed and DP_DKEEP was specified), and nonzero if the data for the key was updated successfully.

25.4.2. Removing Records

Remove records from the database by passing the key whose data should be removed to dpout().

 int dpout(DEPOT * depot, const char * key, int keySize); 


The specified key and the data associated with it are removed from the database, and a nonzero value is returned. If there is no data for that key, zero is returned. As for all of the other functions that take a key, if the keySize is -1, dpout uses strlen() to find the length of the key.


       
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    Linux Application Development
    Linux Application Development (paperback) (2nd Edition)
    ISBN: 0321563220
    EAN: 2147483647
    Year: 2003
    Pages: 168

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