DBLock()

void *	DBLock(
        VMFileHandle		file,
        DBGroup		group,
        DBItem		item);

This routine locks the specified item and returns a pointer to it. It is passed the file, group, and item handles specifying a DB item. If it fails, it returns a null pointer.

Include: dbase.h

See Also: DBLockGetRef(),DBLockUngrouped().

DBLockGetRef()

void *	DBLockGetRef(
        VMFileHandle		file,			
        DBGroup		group,
        DBItem		item,
        optr *		ref);

This routine is just like DBLock(), except that it writes the item's optr to the passed address.

Include: dbase.h

Warnings: The optr is only valid until the DB item is unlocked.

DBLockGetRefUngrouped()

void *	DBLockGetRefUngrouped(
        VMFileHandle		file,			
        DBGroupAndItem		id,
        optr *		ref);

This routine is the same as DBLockGetRef(), except that it is passed a DBGroupAndItem value.

Include: dbase.h

DBLockMap()

void *	DBLockMap(
        VMFileHandle		file);

This routine locks the specified file's map item and returns its address. To unlock the map item, call DBUnlock() normally.

Include: dbase.h

See Also: DBLockMap().

DBLockUngrouped()

void *	DBLockUngrouped(
        VMFileHandle		file,			
        DBGroupAndItem		id);

This routine is the same as DBLock(), except that it is passed a DBGroupAndItem value.

Include: dbase.h

DBReAlloc()

void	DBReAlloc(
        VMFileHandle		file,			
        DBGroup		group,
        DBItem		item,
        word		size);

This routine changes the size of a DB item. It is passed the file, group, and item handles specifying the DB item, and a new size for the item (in bytes). If the new size is larger than the old, space will be added to the end of the item; if the new size is smaller than the old, the item will be truncated to fit.

Warnings: If the new size is larger than the old, all pointers to items in the group are invalidated. Space added is not zero-initialized.

Include: dbase.h

DBReAllocUngrouped()

void	DBReAllocUngrouped(
        VMFileHandle		file,			
        DBGroupAndItem		id,
        word		size);

This routine is just like DBReAlloc(), except it is passed a DBGroupAndItem value instead of separate group and item handles.

Warnings: If the new size is larger than the old, all pointers to ungrouped items are invalidated. Space added is not zero-initialized.

Include: dbase.h

DBSetMap()

void	DBSetMap(
        VMFileHandle		file,			
        DBGroup		group,
        DBItem		item);

This routine sets the DB map item. You can later retrieve a DBGroupAndItem structure identifying this item by calling DBGetMap(). The routine is passed the file, group, and item handles specifying the new map item; it does not return anything.

Include: dbase.h

DBSetMapUngrouped()

void	DBSetMapUngrouped(
        VMFileHandle		file,			
        DBGroupAndItem		id);

This routine is just like DBSetMap(), except it is passed a DBGroupAndItem value instead of separate group and item handles.

Include: dbase.h

DBUnlock()

void	DBUnlock(
        void *	ptr); /* address of item to unlock */

This routine unlocks the DB item whose address is passed.

Tips and Tricks: Only the segment address of the pointer is significant. Thus, you can pass a pointer to somewhere within an item (or immediately after it) to unlock it.

Be Sure To: If the item has been changed, make sure you call DBDirty() before you unlock it.

Include: dbase.h