libpmemkv_config - Man Page

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:

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>

Referenced By

libpmemkv(3), libpmemkv(7), libpmemkv_json_config(3).

2020-10-05 PMEMKV - pmemkv version 1.1 PMEMKV Programmer's Manual