PA_LockResource

version 2003

PA_LockResource (resfile; kind; resID) → char

Parameter	Type		Description
resfile	short	→	File reference number of the file to access
kind	unsigned long	→	Kind (4 Bytes type) of resource to access
resID	short	→	Unique resource ID
Function result	char	←	1 = The resource has been locked. 0 = Already in use

Description

The routine PA_LockResource tries to lock the resource of type kind and the ID resID of the file resFile over the network; it returns 1 if successfully locked, and 0 if the resource is already in use by an other client.

You should always lock the resource before modifying it so that no one can modify it while you read or modify it. Once a resource is locked, it can not be modified by another process and it can neither be disposed or nor purged from memory.

If the resource does not exist or if resFile is an invalid file reference number, the routine does nothing and PA_GetLastError returns -5 ("Resource not found").

It is not necessary to lock the resource if the plug-in only wants to read it.

WARNING

In 4D single-user, the routine always returns 1. It is the plug-in's responsibility to manage multiprocess access in this case.

Example

Lock the resource 'pipf' ID 128.

   typedef struct {
      short   f1;
      short   f2;
      long   f3;
      /* ... */
   }PLUG_PREFS;
 
   // Lock the resource
   if( PA_LockResource(resFile, 'pipf', 128))
   {
   // Ok, no one can modify it on an other machine
   // Initialize one structure
      PLUG_PREFS   h = {1, 2, 3};
   // Change the resource content
      PA_SetResource(resFile, 'pipf', 128, (char *) &prefs, sizeof(PLUG_PREFS));
   //write the resource
      PA_Write(resFile)
   // Unlock it
      PA_Unlockresource(resFile, 'pipf', 128);
   }

Error Handling

Use PA_GetLastError to see if an error occurred