WT_CONFIG_PARSER Struct Reference

A handle that can be used to search and traverse configuration strings compatible with the WiredTiger API. More...

Public Member Functions
int	close (WT_CONFIG_PARSER *config_parser)
	Close the configuration scanner releasing any resources. More...
int	next (WT_CONFIG_PARSER *config_parser, WT_CONFIG_ITEM *key, WT_CONFIG_ITEM *value)
	Return the next key/value pair. More...
int	get (WT_CONFIG_PARSER *config_parser, const char *key, WT_CONFIG_ITEM *value)
	Return the value of an item in the configuration string. More...

Detailed Description

A handle that can be used to search and traverse configuration strings compatible with the WiredTiger API.

To parse the contents of a list or nested configuration string use a new configuration parser handle based on the content of the WT_CONFIG_ITEM retrieved from the parent configuration string.

Configuration String Parsing examples

This could be used in C to create a configuration parser as follows:

        WT_CONFIG_ITEM k, v;
        WT_CONFIG_PARSER *parser;
        const char *config_string = "path=/dev/loop,page_size=1024,log=(file_max=20MB,remove=true)";
 
        error_check(
          wiredtiger_config_parser_open(NULL, config_string, strlen(config_string), &parser));
        error_check(parser->close(parser));

Once the parser has been created the content can be queried directly:

            int64_t my_page_size;
            /*
             * Retrieve the value of the integer configuration string "page_size".
             */
            error_check(parser->get(parser, "page_size", &v));
            my_page_size = v.val;

Or the content can be traversed linearly:

            /*
             * Retrieve and print the values of the configuration strings.
             */
            while ((ret = parser->next(parser, &k, &v)) == 0) {
                printf("%.*s:", (int)k.len, k.str);
                if (v.type == WT_CONFIG_ITEM_NUM)
                    printf("%" PRId64 "\n", v.val);
                else
                    printf("%.*s\n", (int)v.len, v.str);
            }
            scan_end_check(ret == WT_NOTFOUND);

Nested configuration values can be queried using a shorthand notation:

        /*
         * Retrieve the value of the nested log file_max configuration string using dot shorthand.
         * Utilize the configuration parsing automatic conversion of value strings into an integer.
         */
        v.type = WT_CONFIG_ITEM_NUM;
        error_check(parser->get(parser, "log.file_max", &v));
        printf("log file max: %" PRId64 "\n", v.val);

Nested configuration values can be traversed using multiple WT_CONFIG_PARSER handles:

        {
            WT_CONFIG_PARSER *sub_parser;
            while ((ret = parser->next(parser, &k, &v)) == 0) {
                if (v.type == WT_CONFIG_ITEM_STRUCT) {
                    printf("Found nested configuration: %.*s\n", (int)k.len, k.str);
                    error_check(wiredtiger_config_parser_open(NULL, v.str, v.len, &sub_parser));
                    while ((ret = sub_parser->next(sub_parser, &k, &v)) == 0)
                        printf("\t%.*s\n", (int)k.len, k.str);
                    scan_end_check(ret == WT_NOTFOUND);
                    error_check(sub_parser->close(sub_parser));
                }
            }
            scan_end_check(ret == WT_NOTFOUND);

Examples

ex_file_system.c.

Member Function Documentation

close()

int WT_CONFIG_PARSER::close

(

WT_CONFIG_PARSER *

config_parser

)

Close the configuration scanner releasing any resources.

Parameters

config_parser

the configuration parser handle

Returns

zero on success and a non-zero error code on failure. See Error handling for details.

Examples

ex_file_system.c.

get()

int WT_CONFIG_PARSER::get	(	WT_CONFIG_PARSER *	config_parser,
		const char *	key,
		WT_CONFIG_ITEM *	value
	)

Return the value of an item in the configuration string.

Parameters

config_parser	the configuration parser handle
key	configuration key string
value	the returned value

Returns

zero on success and a non-zero error code on failure. See Error handling for details.

next()

int WT_CONFIG_PARSER::next	(	WT_CONFIG_PARSER *	config_parser,
		WT_CONFIG_ITEM *	key,
		WT_CONFIG_ITEM *	value
	)

Return the next key/value pair.

If an item has no explicitly assigned value, the item will be returned in key and the value will be set to the boolean "true" value.

Parameters

config_parser	the configuration parser handle
key	the returned key
value	the returned value

Returns

zero on success and a non-zero error code on failure. See Error handling for details. When iteration would pass the end of the configuration string WT_NOTFOUND will be returned.

Examples

ex_file_system.c.