Slide 10.17: Line-by-line anatomy of DB.c (cont.)

Line-by-line Anatomy of DB.c (Cont.)


  FrmReturnToForm( 0 );

This function void FrmReturnToForm( UInt16 formId )

formID

It is assumed that the form being returned to is already loaded into memory and initialized. Passing a form ID of 0 returns to the first form in the window list, which is the last form to be loaded.


  recP = MemHandleLock( recH );

This function MemPtr MemHandleLock( MemHandle h ) locks a chunk and obtains a pointer to the chunk's data. MemHandleLock and MemHandleUnlock( ) should be used in pairs.

h


  DmWrite( recP, 0, &dbRecord, sizeof( DBRecordType ) );

This function Err DmWrite( void *recordP, UInt32 offset, const void *srcP, UInt32 bytes ) copies a specified number of bytes to a record within a database that is open for writing.

recordP: Pointer to locked data record (chunk pointer)
offset: Offset within record to start writing
srcP: Pointer to data to copy into record
bytes: Number of bytes to write


  MemPtrUnlock( recP );

This function Err MemPtrUnlock( MemPtr p ) unlocks a chunk, given a pointer to the chunk. It returns 0 if no error, or memErrInvalidParam if an error occurs. A chunk must not be unlocked more times than it was locked.

p