PROP_INGEST(3)

NAME
prop_ingest, prop_ingest_context_alloc, prop_ingest_context_free, prop_ingest_context_error, prop_ingest_context_type, prop_ingest_context_key, prop_ingest_context_private, prop_dictionary_ingest - Ingest a dictionary into an arbitrary binary format

SYNOPSIS
#include <prop/proplib.h>
prop_ingest_context_t
prop_ingest_context_alloc(void *private);
void
prop_ingest_context_free(prop_ingest_context_t ctx);
prop_ingest_error_t
prop_ingest_context_error(prop_ingest_context_t ctx);
prop_type_t
prop_ingest_context_type(prop_ingest_context_t ctx);
const char *
prop_ingest_context_key(prop_ingest_context_t ctx);
void *
prop_ingest_context_private(prop_ingest_context_t ctx);
bool
prop_dictionary_ingest(prop_dictionary_t dict, const prop_ingest_table_entry rules[], prop_ingest_context_t ctx);

typedef bool
(*prop_ingest_handler_t)(prop_ingest_context_t, prop_object_t);

DESCRIPTION
The prop_dictionary_ingest() function provides a convenient way to convert a property list into an arbitrary binary format or to extract values from dictionaries in a way that is convenient to an application (for configuration files, for example).

prop_dictionary_ingest() is driven by a table of rules provided by the application. Each rule consists of three items:

•   A C string containing a key to be looked up in the dictionary.

•   The expected property type of the object associated with the key (or PROP_TYPE_UNKNOWN to specify that any type is allowed).

•   A callback function of type prop_ingest_handler_t that will perform the translation for the application.

The table is constructed using a series of macros as follows:

    static const prop_ingest_table_entry ingest_rules[] = {
    	PROP_INGEST("file-name", PROP_TYPE_STRING, ingest_filename),
    	PROP_INGEST("count", PROP_TYPE_NUMBER, ingest_count),
    	PROP_INGEST_OPTIONAL("required", PROP_TYPE_BOOL, ingest_required),
    	PROP_INGEST_OPTIONAL("extra", PROP_TYPE_UNKNOWN, ingest_extra),
    	PROP_INGEST_END
    };

The PROP_INGEST macro specifies that the key is required to be present in the dictionary. The PROP_INGEST_OPTIONAL macro specifies that the presence of the key in the dictionary is optional. The PROP_INGEST_END macro marks the end of the rules table.

In each case, prop_dictionary_ingest() looks up the rule's key in the dictionary. If an object is present in the dictionary at that key, its type is checked against the type specified in the rule. A type specification of PROP_TYPE_UNKNOWN allows the object to be of any type. If the object does not exist and the rule is not marked as optional, then an error is returned. Otherwise, the handler specified in the rule is invoked with the ingest context and the object (or NULL if the key does not exist in the dictionary). The handler should return false if the value of the object is invalid to indicate failure and true otherwise.

The ingest context contains several pieces of information that are useful during the ingest process. The context also provides specific error information should the ingest fail.

prop_ingest_context_alloc(void *private)
    Allocate an ingest context. The argument private may be used to pass application-specific context to the ingest handlers. Note that an ingest context can be re-used to perform multiple ingests. Returns NULL on failure.

prop_ingest_context_free(prop_ingest_context_t ctx)
    Free an ingest context.

prop_ingest_context_error(prop_ingest_context_t ctx)
    Returns the code indicating the error encountered during ingest. The following error codes are defined:

    PROP_INGEST_ERROR_NO_ERROR
        No error was encountered during ingest.
    PROP_INGEST_ERROR_NO_KEY
        A non-optional key was not found in the dictionary.
    PROP_INGEST_ERROR_WRONG_TYPE
        An object in the dictionary was not the same type specified in the rules.
    PROP_INGEST_ERROR_HANDLER_FAILED
        An object's handler returned false.

prop_ingest_context_type(prop_ingest_context_t ctx)
    Returns the type of the last object visited during an ingest. When called by an ingest handler, it returns the type of the object currently being processed.

prop_ingest_context_key(prop_ingest_context_t ctx)
    Returns the last dictionary key looked up during an ingest. When called by an ingest handler, it returns the dictionary key corresponding to the object currently being processed.

prop_ingest_context_private(prop_ingest_context_t ctx)
    Returns the private data set when the context was allocated with prop_ingest_context_alloc().

SEE ALSO
prop_dictionary(3), proplib(3)

HISTORY
The proplib(3) property container object library first appeared in NetBSD 4.0.