<< Previous | Next >>

registry_prep_write

int registry_prep_write( RegistryContext * r, char * basename, ServerContext * context);

Description

Prepare for updating a registry. This function helps organize registry resources in order to create a robust registry.

Most applications will use the sequence of functions

   

registry_prep_write()
registry_write()
registry_finish_write()

or, more simply, just

   

registry_update()

See the function description for registry_prep_read() for details concerning the organization of registry files.

Like registry_prep_read(), this function opens an existing presumed non-corrupt registry for reading, and also a new empty registry (the "next" registry) for writing the updated esults, as required by registry_write().

Parameters

r

RegistryContext struct. This is used to pass information in a consistent manner between the major registry API functions. It may be passed uninitialized to this function.

basename

Base name (including path) of the registry. This should NOT include any extension (e.g. ".foo") since the extension is manipulated by this function. In practice, this will need to be a resource name on non-volatile storage, which supports names with extensions. In practice, this limits the appropriate filesystem to FAT filesystem only. For example

registry_prep_write("/A/myreg", &oldspec, &newspec);

will select from a set of registry files called

/A/myreg.1, /A/myreg.2, /A/myreg.3\ of which, normally, only two will exist at any time; one will be opened for reading, and the other will be empty and ready for writing.

context

ServerContext structure. E.g. from http_getContext().

Return Value

<0: general failure, code will be negative of one of the codes in ERRNO.LIB.

 0: there is currently no resource of the given name. *oldp will be set to -1 in this case. This is not necessarily an error, since it will be returned if the registry has not yet been created. You can pass *oldp to registry_write() in this case, and it will correctly create the new registry without attempting to read the (non-existent) "old" registry.

1,2,3: An existing presumed non-corrupt resource has been opened, and the open resource handle returned in *oldp. The numeric return code indicates which of the extensions was located. Note that the "new" registry file will be this number plus 1 (except that 4 becomes 1).

Library

register.lib

See Also

registry_read, registry_finish_read, registry_prep_read, registry_write, registry_finish_write, registry_enumerate, registry_update, registry_get