PMEMKV_CONFIG(3)

NAME

pmemkv_config - Configuration API for libpmemkv

SYNOPSIS

    #include <libpmemkv.h>

    pmemkv_config *pmemkv_config_new(void);
    void pmemkv_config_delete(pmemkv_config *config);
    int pmemkv_config_put_data(pmemkv_config *config, const char *key, const void *value,
                size_t value_size);
    int pmemkv_config_put_object(pmemkv_config *config, const char *key, void *value,
                void (*deleter)(void *));
    int pmemkv_config_put_uint64(pmemkv_config *config, const char *key, uint64_t value);
    int pmemkv_config_put_int64(pmemkv_config *config, const char *key, int64_t value);
    int pmemkv_config_put_string(pmemkv_config *config, const char *key, const char *value);
    int pmemkv_config_get_data(pmemkv_config *config, const char *key, const void **value,
                size_t *value_size);
    int pmemkv_config_get_object(pmemkv_config *config, const char *key, void **value);
    int pmemkv_config_get_uint64(pmemkv_config *config, const char *key, uint64_t *value);
    int pmemkv_config_get_int64(pmemkv_config *config, const char *key, int64_t *value);
    int pmemkv_config_get_string(pmemkv_config *config, const char *key, const char **value);

For general description of pmemkv and available engines see libpmemkv(7). For description of pmemkv core API see libpmemkv(3).

DESCRIPTION

pmemkv database is configured using pmemkv_config structure. It stores mappings of keys (null-terminated strings) to values. A value can be:

•   uint64_t

•   int64_t

•   c-style string

•   binary data

•   pointer to an object (with accompanying deleter function)

It also delivers methods to store and read configuration items provided by a user. Once the configuration object is set (with all required parameters), it can be passed to pmemkv_open() method.

List of options which are required by pmemkv database is specific to an engine. Every engine has documented all supported config parameters (please see libpmemkv(7) for details).

pmemkv_config *pmemkv_config_new(void);
    Creates an instance of configuration for pmemkv database.

    On failure, NULL is returned.

void pmemkv_config_delete(pmemkv_config *config);
    Deletes pmemkv_config. Should be called ONLY for configs which were not passed to pmemkv_open (as this function moves ownership of the config to the database).

int pmemkv_config_put_uint64(pmemkv_config *config, const char *key, uint64_t value);
    Puts uint64_t value value to pmemkv_config at key key.

int pmemkv_config_put_int64(pmemkv_config *config, const char *key, int64_t value);
    Puts int64_t value value to pmemkv_config at key key.

int pmemkv_config_put_string(pmemkv_config *config, const char *key, const char *value);
    Puts null-terminated string to pmemkv_config. The string is copied to the config.

int pmemkv_config_put_data(pmemkv_config *config, const char *key, const void *value, size_t value_size);
    Puts copy of binary data pointed by value to pmemkv_config. value_size specifies size of the data.

int pmemkv_config_put_object(pmemkv_config *config, const char *key, void *value, void (*deleter)(void *));
    Puts value to pmemkv_config. value can point to arbitrary object. deleter parameter specifies function which will be called for value when the config is destroyed (using pmemkv_config_delete).

int pmemkv_config_get_uint64(pmemkv_config *config, const char *key, uint64_t *value);
    Gets value of a config item with key key. Value is copied to variable pointed by value.

int pmemkv_config_get_int64(pmemkv_config *config, const char *key, int64_t *value);
    Gets value of a config item with key key. Value is copied to variable pointed by value.

int pmemkv_config_get_string(pmemkv_config *config, const char *key, const char **value);
    Gets pointer to a null-terminated string. The string is not copied. After successful call value points to string stored in pmemkv_config.

int pmemkv_config_get_data(pmemkv_config *config, const char *key, const void **value, size_t *value_size);
    Gets pointer to binary data. Data is not copied. After successful call *value points to data stored in pmemkv_config and value_size holds size of the data.

int pmemkv_config_get_object(pmemkv_config *config, const char *key, const void **value);
    Gets pointer to an object. After successful call, *value points to the object.

Config items stored in pmemkv_config, which were put using a specific function can be obtained only using corresponding pmemkv_config_get_ function (for example, config items put using pmemkv_config_put_object can only be obtained using pmemkv_config_get_object). Exception from this rule are functions for uint64 and int64. If value put by pmemkv_config_put_int64 is in uint64_t range it can be obtained using pmemkv_config_get_uint64 and vice versa.

  ERRORS

Each function, except for pmemkv_config_new() and pmemkv_config_delete(), returns status. Possible return values are:

•   PMEMKV_STATUS_OK – no error

•   PMEMKV_STATUS_UNKNOWN_ERROR – unknown error

•   PMEMKV_STATUS_NOT_FOUND – record (or config item) not found

•   PMEMKV_STATUS_CONFIG_PARSING_ERROR – parsing data to config failed

•   PMEMKV_STATUS_CONFIG_TYPE_ERROR – config item has different type than expected

EXAMPLE

The following example is taken from examples/pmemkv_config_c/pmemkv_config.c.

    #include <assert.h>
    #include <libpmemkv.h>
    #include <libpmemkv_json_config.h>
    #include <stdlib.h>
    #include <string.h>

    /* deleter for int pointer */
    void free_int_ptr(void *ptr)
    {
        free(ptr);
    }

    int main()
    {
        pmemkv_config *config = pmemkv_config_new();
        assert(config != NULL);

        /* Put int64_t value */
        int status = pmemkv_config_put_int64(config, "size", 1073741824);
        assert(status == PMEMKV_STATUS_OK);

        char buffer[] = "ABC";

        /* Put binary data stored in buffer */
        status = pmemkv_config_put_data(config, "binary", buffer, 3);
        assert(status == PMEMKV_STATUS_OK);

        const void *data;
        size_t data_size;

        /* Get pointer to binary data stored in config */
        status = pmemkv_config_get_data(config, "binary", &data, &data_size);
        assert(status == PMEMKV_STATUS_OK);
        assert(data_size == 3);
        assert(((const char *)data)[0] == 'A');

        int *int_ptr = malloc(sizeof(int));
        assert(int_ptr != NULL);
        *int_ptr = 10;

        /* Put pointer to dynamically allocated object, free_int_ptr is called on
         * pmemkv_config_delete */
        status = pmemkv_config_put_object(config, "int_ptr", int_ptr, &free_int_ptr);
        assert(status == PMEMKV_STATUS_OK);

        int *get_int_ptr;

        /* Get pointer to object stored in config */
        status = pmemkv_config_get_object(config, "int_ptr", (void **)&get_int_ptr);
        assert(status == PMEMKV_STATUS_OK);
        assert(*get_int_ptr == 10);

        pmemkv_config_delete(config);

        pmemkv_config *config_from_json = pmemkv_config_new();
        assert(config_from_json != NULL);

        /* Parse JSON and put all items found into config_from_json */
        status = pmemkv_config_from_json(config_from_json, "{\"path\":\"/dev/shm\",\
             \"size\":1073741824,\
             \"subconfig\":{\
                \"size\":1073741824\
                }\
            }");
        assert(status == PMEMKV_STATUS_OK);

        const char *path;
        status = pmemkv_config_get_string(config_from_json, "path", &path);
        assert(status == PMEMKV_STATUS_OK);
        assert(strcmp(path, "/dev/shm") == 0);

        pmemkv_config *subconfig;

        /* Get pointer to nested configuration "subconfig" */
        status = pmemkv_config_get_object(config_from_json, "subconfig",
                          (void **)&subconfig);
        assert(status == PMEMKV_STATUS_OK);

        size_t sub_size;
        status = pmemkv_config_get_uint64(subconfig, "size", &sub_size);
        assert(status == PMEMKV_STATUS_OK);
        assert(sub_size == 1073741824);

        pmemkv_config_delete(config_from_json);

        return 0;
    }

SEE ALSO

libpmemkv(7), libpmemkv(3) , libpmemkv_json_config(3) and <https://pmem.io>