Provided by: libpmemkv-dev_1.5.0-4build1_amd64 
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_size(pmemkv_config *config, uint64_t value);
int pmemkv_config_put_path(pmemkv_config *config, const char *value);
int **deprecated** pmemkv_config_put_force_create(pmemkv_config *config,
bool value);
int pmemkv_config_put_create_or_error_if_exists(pmemkv_config *config, bool value);
int pmemkv_config_put_create_if_missing(pmemkv_config *config, bool value)
int pmemkv_config_put_comparator(pmemkv_config *config, pmemkv_comparator *comparator);
int pmemkv_config_put_oid(pmemkv_config *config, PMEMoid *oid);
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_object_cb(pmemkv_config *config, const char *key, void *value,
void *(*getter)(void *), 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);
pmemkv_comparator *pmemkv_comparator_new(pmemkv_compare_function *fn, const char *name,
void *arg);
void pmemkv_comparator_delete(pmemkv_comparator *comparator);
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_size(pmemkv_config *config, uint64_t value);
Puts value to a config at key size, it’s required when creating new database pool. This function
provides type safety for size parameter.
int pmemkv_config_put_path(pmemkv_config *config, const char *value);
Puts value to a config at key path. It’s a path to a database file or to a poolset file (see
poolset(5) for details), to open or create. Note that when using poolset file, size should be 0.
This function provides type safety for path parameter.
int pmemkv_config_put_force_create(pmemkv_config *config, bool value);
It is deprecated and kept for compatibility. It’s an alias for
pmemkv_config_put_create_or_error_if_exists - use it instead.
int pmemkv_config_put_create_or_error_if_exists(pmemkv_config *config, bool value);
Puts value to a config at key create_or_error_if_exists. This flag is mutually exclusive with
create_if_missing. It works only with engines supporting this flag and it means: If true: pmemkv
creates the pool, unless it exists - then it fails. If false: pmemkv opens the pool, unless the
path does not exist - then it fails. False by default.
int pmemkv_config_put_create_if_missing(pmemkv_config *config, bool value)
Puts value to a config at key create_if_missing. This flag is mutually exclusive with
create_or_error_if_exists. It works only with engines supporting this flag and it means: If true:
pmemkv tries to open the pool and if that doesn’t succeed it means there’s (most likely) no pool
to use, so it tries to create it. If false: pmemkv opens the pool, unless the path does not exist
- then it fails. False by default.
int pmemkv_config_put_comparator(pmemkv_config *config, pmemkv_comparator *comparator);
Puts comparator object to a config. To create an instance of pmemkv_comparator object,
pmemkv_comparator_new() function should be used.
int pmemkv_config_put_oid(pmemkv_config *config, PMEMoid *oid);
Puts PMEMoid object to a config (for details see libpmemkv(7)).
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_put_object_cb(pmemkv_config *config, const char *key, void *value, void *(*getter)(void
*), void (*deleter)(void *));
Extended version of pmemkv_config_put_object. It accepts one additional argument - a getter
callback. This callback interprets the custom object (value) and returns a pointer which is
expected by pmemkv.
Calling pmemkv_config_put_object_cb with getter implemented as:
void *getter(void *arg) { return arg; }
is equivalent to calling pmemkv_config_put_object.
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.
pmemkv_comparator *pmemkv_comparator_new(pmemkv_compare_function *fn, const char *name, void *arg);
Creates instance of a comparator object. Accepts comparison function fn, name and arg. In case of
persistent engines,nameis stored within the engine. Attempt to open a database which was createad
with different comparator of different name will fail with PMEMKV_STATUS_COMPARATOR_MISMATCH.arg`
is saved in the comparator and passed to a comparison function on each invocation.
Neither fn nor name can be NULL.
fn should perform a three-way comparison. Return values: * negative value if the first key is
less than the second one * zero if both keys are the same * positive value if the first key is
greater than the second one
The comparison function should be thread safe - it can be called from multiple threads.
On failure, NULL is returned.
void pmemkv_comparator_delete(pmemkv_comparator *comparator);
Removes the comparator object. Should be called ONLY for comparators which were not put to config
(as config takes ownership of the comparator).
To set a comparator for the database use pmemkv_config_put_object:
pmemkv_comparator *cmp = pmemkv_comparator_new(&compare_fn, "my_comparator", NULL);
pmemkv_config_put_object(cfg, "comparator", cmp, (void (*)(void *)) & pmemkv_comparator_delete);
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 examples are taken from examples/pmemkv_config_c directory.
BASIC EXAMPLE
Usage of basic config functions to set parameters based on their functionalities,
e.g. pmemkv_config_put_path() or pmemkv_config_put_size().
#include <assert.h>
#include <libpmemkv.h>
#include <libpmemobj/pool_base.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define ASSERT(expr) \
do { \
if (!(expr)) \
puts(pmemkv_errormsg()); \
assert(expr); \
} while (0)
static const uint64_t SIZE = 1024UL * 1024UL * 1024UL;
int key_length_compare(const char *key1, size_t keybytes1, const char *key2,
size_t keybytes2, void *arg)
{
if (keybytes2 < keybytes1)
return -1;
else if (keybytes2 > keybytes1)
return 1;
else
return 0;
}
int main(int argc, char *argv[])
{
if (argc < 2) {
fprintf(stderr, "Usage: %s file\n", argv[0]);
exit(1);
}
/* Create config */
pmemkv_config *config = pmemkv_config_new();
ASSERT(config != NULL);
/* Add path parameter to config. Meaning of this is dependent on chosen engine.
* E.g. if config is used with cmap engine,
* it is a path to a database file or to a poolset file. However for
* vcmap it is a path to an existing directory */
int status = pmemkv_config_put_path(config, argv[1]);
ASSERT(status == PMEMKV_STATUS_OK);
/* Specifies size of the database */
status = pmemkv_config_put_size(config, SIZE);
ASSERT(status == PMEMKV_STATUS_OK);
/* Specifies value of create_if_missing flag.
* Alternatively, another flag - 'create_or_error_if_exists' can be set using:
* `pmemkv_config_put_create_or_error_if_exists`
* For differences between the two, see manpage libpmemkv(7). */
status = pmemkv_config_put_create_if_missing(config, true);
ASSERT(status == PMEMKV_STATUS_OK);
/* Specifies comparator used by the engine */
pmemkv_comparator *cmp =
pmemkv_comparator_new(&key_length_compare, "key_length_compare", NULL);
ASSERT(cmp != NULL);
status = pmemkv_config_put_comparator(config, cmp);
ASSERT(status == PMEMKV_STATUS_OK);
/* Adds pointer to oid (for details see libpmemkv(7)) to the config */
PMEMoid oid;
status = pmemkv_config_put_oid(config, &oid);
ASSERT(status == PMEMKV_STATUS_OK);
pmemkv_config_delete(config);
return 0;
}
TYPE BASED CONFIGURATION EXAMPLE
Usage of config functions to set and get data based on their data type, e.g. pmemkv_config_put_int64() or
pmemkv_config_put_object().
#include <assert.h>
#include <libpmemkv.h>
#include <libpmemkv_json_config.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define ASSERT(expr) \
do { \
if (!(expr)) \
puts(pmemkv_errormsg()); \
assert(expr); \
} while (0)
/* 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>