int meta_data_get_string(meta_data_t *md, const char *key, char **value);
int meta_data_get_signed_int(meta_data_t *md, const char *key, int64_t *value);
int meta_data_get_unsigned_int(meta_data_t *md, const char *key,
uint64_t *value);
int meta_data_get_double(meta_data_t *md, const char *key, double *value);
int meta_data_get_string(meta_data_t *md, const char *key, char **value);
int meta_data_get_signed_int(meta_data_t *md, const char *key, int64_t *value);
int meta_data_get_unsigned_int(meta_data_t *md, const char *key,
uint64_t *value);
int meta_data_get_double(meta_data_t *md, const char *key, double *value);