dlite-entity

dlite-entity#

API for instances and entities.

There is only data and transformations. All data are instances of their metadata and metadata are instances of their meta-metadata, etc…

In DLite, instances are struct’s starting with DLiteInstance_HEAD, which is a macro defining a few key fields that all instances has:

uuid: Instances are uniquely identified by their UUID. If an instance has an URI, its UUID is generated from it (as a version 5 SHA1-based UUID using the DNS namespace). Otherwise the UUID is random (generated as a version 4 UUID).
uri: An optional unique name identifying the instance (related to its UUID as described above). For metadata the URI is mandantory and should be of the form “namespace/version/name”.
refcount: Reference count. Do not access this directly.
meta: Pointer to the metadata describing the instance. All instances may be cast to an DLiteInstance, which is a minimal struct representing all instances.

Metadata

In DLite, instances are described by specialised instances called metadata. Metadata are struct’s starting with the fields provided by the DLiteMeta_HEAD macro. Since metadata themselves are instances, you can always cast a DLiteMeta (a struct representing any metadata) to a DLiteInstance. This also means that metadata is described by their meta-metadata, and so forth. To break this (in principle infinite) chain of abstractions, dlite provides a root abstraction, called BasicMetadataSchema, that all instances in DLite are instances of. The BasicMetadataSchema, has itself as metadata and must therefore be able to describe itself.

Most of the fields provided by the DLiteMeta_HEAD macro are not intended to be accessed by the user, except maybe for ndimensions, nproperties, nrelations, dimensions, properties and relations, which may be handy.

Memory model

All instances, including metadata, uses the same memory model. They are allocated in one chunk of memory holding both header, dimensions and property values. The only exception are dimensional properties, whos values are allocated on the heap. Care is taken to use the system padding rules when the memory is layed out, such that it can be mapped to a (possible generated) struct. Allocating dimensional properties seperately has two benefits:

the size of the memory chunk for an instance is described by its metadata (it is independent on the length of the dimensions of the instance itself)
it allows to change the length of the dimensions of a data instance (but not for metadata, since they are immutable)

The following table summarises the memory layout of an instance:

segment	nmemb	size	offset
header	1	meta->headersize	0
dimensions	meta->ndimensions	sizeof(size_t)	meta->dimoffset
properties	meta->nproperties	[a]	meta->propoffsets
relations	meta->nrelations	sizeof(DLiteRelation)	meta->reloffset
propdims	meta->npropdims	sizeof(size_t)	meta->propdimsoffset
propdiminds [b]	nproperties	sizeof(size_t)	meta->propdimindsoffset
propoffsets [b]	nproperties	sizeof(size_t)	DLITE_PROPOFFSETSOFFSET(meta)

[a]: The size of properties depends on their size and whether they are dimensional or not.

[b]: Only metadata instances have the last two segments.

header

The header for all instances must start with DLiteInstance_HEAD. This is a bare minimal, but sufficient for most data instances. It contains the UUID and (optionally) URI identifying the instance as well as a reference count and a pointer th the metadata describing the instance. Metadata and special data instances like collections, extends this.

The header of all metadata must start with DLiteMeta_HEAD (which itself starts with DLiteInstance_HEAD.

dimensions

The length of each dimension of the current instance.

properties

The value of each property of the current instance. The metadata for this instance defines the type and size for all properties. The size that the ith property occupies in an instance is given by meta->properties[i].size, except if the property has dimensions, in which case it is a pointer (of size sizeof(void *)) to a continuous allocated array with the property values.

Some property types, like dliteStringPtr and dliteProperty may allocate additional memory.

relations

Array of relations for the current instance.

propdims

Array of evaluated property dimension sizes (calculated from dimensions). Use the DLITE_PROP_DIM() macro to access these values.

propdiminds

Array with indices into propdims for the first dimension of each property. Note that only metadata has this segment.

propoffsets

Memory offset of each property of its instances. Don’t access this array directly, use the DLITE_PROP() macro instead. Note that only metadata instances has this segment.

Note that the allocated size of data instances are fully defined by their metadata. However, this is not true for metadata since it depends on nproperties - the number of properties it defines. Use the DLITE_INSTANCE_SIZE() macro to get the allocated size of an instance.

Typedefs and structs

DLITE_HASH_SIZE#: The size in bytes of sha3 hash used by transactions. Should be 32, 48 or 64.

DLiteInstance_HEAD#: Initial segment of all DLite instances.

DLiteMeta_HEAD#

Initial segment of all DLite metadata. With instance we here refer to the dataset described by this metadata.

For convinience we include ndimensions, nproperties and nrelations in the header of all MetaData, so we don’t have to check the existence of these dimensions in the meta-metadata. A consequence is that all meta-metadata must include these as the first 3 dimensions, regardless of whether they actually are used (as in the case for Entity, which don’t have relations).

enum _DLiteFlag#

Flags for describing the state of an instance. This should be as minimalistic as possible, but a flag for immutability is needed.

Values:

enumerator dliteImmutable#: Whether instance is immutable.

typedef int (*DLiteInit)(struct _DLiteInstance *inst)#: Function for additional initialisation of an instance. If defined, this function is called at end of dlite_instance_create(). Returns non-zero on error.

typedef int (*DLiteDeInit)(struct _DLiteInstance *inst)#: Function for additional de-initialisation of a metadata instance. If defined, this function is called at beginning of dlite_instance_free(). Returns non-zero on error.

typedef int (*DLiteGetHash)(const DLiteInstance *inst, unsigned char *hash, int hashsize)#: Function used by extended metadata to replace the standard hash calculation in dlite_instance_get_hash(). The calculated hash is stored in hash, where hashsize is the size of hash in bytes. It should be 32, 48 or 64. Returns non-zero on error.

typedef int (*DLiteGetDimension)(const DLiteInstance *inst, size_t i)#: Function for accessing internal dimension sizes of extended metadata. If provided it will be called by dlite_instance_save(), dlite_instance_get_dimension_size() and related functions. Returns size of dimension i or -1 on error.

typedef int (*DLiteSetDimension)(DLiteInstance *inst, size_t i, size_t value)#: Function for setting internal dimension sizes of extended metadata. If provided, it will be called by dlite_instance_set_dimension_size() and related functions. Returns zero on success. If the extended metadata does not support setting size of dimension i, 1 is returned. On other errors, a negative value is returned.

typedef int (*DLiteLoadProperty)(const DLiteInstance *inst, size_t i)#: Function used by extended metadata to load internal state from property number i. If provided, this function will be called by dlite_instance_set_property() and related functions. Returns non-zero on error.

typedef int (*DLiteSaveProperty)(DLiteInstance *inst, size_t i)#: Function used by extended metadata to save internal state to property number i. If provided, this function will be called by dlite_instance_save(), dlite_instance_get_property() and related functions. Returns non-zero on error.

typedef enum _DLiteFlag DLiteFlag#: Flags for describing the state of an instance. This should be as minimalistic as possible, but a flag for immutability is needed.

typedef struct _DLiteParent DLiteParent#: Reference to parent instance. Used by transactions.

typedef struct _DLiteMeta DLiteMeta#

Base definition of a DLite metadata, that all metadata objects can be cast to.

It may be instansiated, e.g. by the basic metadata schema.

typedef struct _DLiteMetaModel DLiteMetaModel#: Opaque datatype used for metadata models.

Macros

DLITE_NDIM(inst)#: Expands to number of dimensions –> (size_t)

DLITE_DIMS(inst)#: Expands to pointer to array of dimension values –> (size_t *)

DLITE_DIM(inst, n)#: Expands to length of dimension n –> (size_t)

DLITE_DIMS_DESCR(inst)#: Expands to array of dimension descriptions –> (DLiteDimension *)

DLITE_DIM_DESCR(inst, n)#: Expands to description of dimensions n –> (DLiteDimension *)

DLITE_NPROP(inst)#: Expands to number of properties –> (size_t).

DLITE_PROP(inst, n)#

Expands to pointer to the value of property n –> (void *)

Note: for arrays this pointer must be dereferred (since all arrays are allocated on the heap).

DLITE_PROP_NDIM(inst, n)#: Expands to number of dimensions of property n –> (int)

DLITE_PROP_DIMS(inst, n)#: Expands to array of dimension sizes for property n –> (size_t *)

DLITE_PROP_DIM(inst, n, m)#: Expands to size of the mth dimension of property n –> (size_t)

DLITE_PROPS_DESCR(inst)#: Expands to array of property descriptions –> (DLiteProperty *)

DLITE_PROP_DESCR(inst, n)#: Expands to pointer to description of property n –> (DLiteProperty *)

DLITE_NRELS(inst)#: Expands to number of relations –> (size_t)

DLITE_RELS(inst)#: Expands to pointer to array of relations –> (DLiteRelation *)

DLITE_REL(inst, n)#: Expands to pointer to relation n –> (DLiteRelation *)

DLITE_PROPOFFSETSOFFSET(inst)#: Expands to the offset of propoffsets memory section –> (size_t)

DLITE_INSTANCE_SIZE(inst)#: Expands to the allocated size of a data or metadata instance –> (size_t)

DLITE_UPDATE_EXTENEDE_META(meta, type, firstdim)#: Updates metadata for extended entities. meta: DLiteMeta type: the struct to extend firstdim: name of the first dimension

Framework internals and debugging

void dlite_instance_debug(const DLiteInstance *inst)#: Prints instance to stdout. Intended for debugging.

size_t dlite_instance_size(const DLiteMeta *meta, const size_t *shape)#

Returns the allocated size of an instance with metadata meta and dimensions dims. The length of dims is given by meta->_ndimensions. Mostly intended for internal use.

Returns -1 on error.

char **dlite_istore_get_uuids(int *nuuids)#

Returns a newly allocated NULL-terminated array of string pointers with uuids available in the internal storage (istore).

Mostly intended for internal/debugging use.

Instance API

DLiteInstance *dlite_instance_create(const DLiteMeta *meta, const size_t *dims, const char *id)#

Returns a new dlite instance from Entiry meta and dimensions dims. The lengths of dims is found in meta->_ndimensions.

The id argment may be NULL, a valid UUID or an unique identifier to this instance (e.g. an uri). In the first case, a random UUID will be generated. In the second case, the instance will get the provided UUID. In the third case, an UUID will be generated from id. In addition, the instanc’s uri member will be assigned to id.

All properties are initialised to zero and arrays for all dimensional properties are allocated and initialised to zero.

On error, NULL is returned.

DLiteInstance *dlite_instance_create_from_id(const char *metaid, const size_t *dims, const char *id)#

Like dlite_instance_create() but takes the uri or uuid of the metadata as the first argument.

Returns NULL on error.

int dlite_instance_incref(DLiteInstance *inst)#

Increases reference count on inst.

Returns the new reference count.

int dlite_instance_decref(DLiteInstance *inst)#

Decrease reference count to inst. If the reference count reaches zero, the instance is free’ed.

Returns the new reference count.

DLiteInstance *dlite_instance_has(const char *id, bool check_storages)#

Checks whether an instance with the given id exists.

If check_storages is true, the storage plugin path is searched if the instance is not found in the in-memory store. This is equivalent to dlite_instance_get(), except that a borrowed reference is returned and no error is reported if the instance cannot be found.

Returns a pointer to the instance (borrowed reference) if it exists or NULL otherwise.

DLiteInstance *dlite_instance_get(const char *id)#

Returns a new reference to instance with given id or NULL if no such instance can be found.

If the instance exists in the in-memory store it is returned (with its refcount increased by one). Otherwise it is searched for in the storage plugin path (initiated from the DLITE_STORAGES environment variable).

It is an error if the instance cannot be found.

DLiteInstance *dlite_instance_get_casted(const char *id, const char *metaid)#: Like dlite_instance_get(), but maps the instance with the given id to an instance of metaid. If metaid is NULL, it falls back to dlite_instance_get(). Returns NULL on error.

DLiteInstance *dlite_instance_load(const DLiteStorage *s, const char *id)#

Loads instance identified by id from storage s and returns a new and fully initialised dlite instance.

In case the storage only contains one instance, it is possible to set id to NULL. However, it is an error to set id to NULL if the storage contains more than one instance.

On error, NULL is returned.

DLiteInstance *dlite_instance_load_loc(const char *driver, const char *location, const char *options, const char *id)#

A convenient function for loading an instance with given id from a storage specified with the driver, location and options arguments (see dlite_storage_open()).

The id argument may be NULL if the storage contains only one instance.

Returns the instance or NULL on error.

DLiteInstance *dlite_instance_load_url(const char *url)#

A convinient function that loads an instance given an URL of the form

driver://loc?options#id

where loc corresponds to the uri argument of dlite_storage_open(). If loc is not given, the instance is loaded from the metastore using id.

Returns the instance or NULL on error.

DLiteInstance *dlite_instance_load_casted(const DLiteStorage *s, const char *id, const char *metaid)#

Like dlite_instance_load(), but allows casting the loaded instance into an instance of metadata identified by metaid. If metaid is NULL, no casting is performed.

Some storages accept that id is NULL if the storage only contain one instance. In that case that instance is returned.

For the cast to be successful requires that the correct mappings have been registered.

Returns NULL on error or if no mapping can be found.

int dlite_instance_save(DLiteStorage *s, const DLiteInstance *inst)#: Saves instance inst to storage s. Returns non-zero on error.

int dlite_instance_save_loc(const char *driver, const char *location, const char *options, const DLiteInstance *inst)#

A convinient function that saves instance inst to the storage specified by driver, location and options.

Returns non-zero on error.

int dlite_instance_save_url(const char *url, const DLiteInstance *inst)#

A convinient function that saves instance inst to the storage specified by url, which should be of the form

driver://loc?options

Returns non-zero on error.

DLiteInstance *dlite_instance_memload(const char *driver, const unsigned char *buf, size_t size, const char *id, const char *options, const char *metaid)#: Loads instance id from memory buffer buf of size size and return it. Returns NULL on error.

int dlite_instance_memsave(const char *driver, unsigned char *buf, size_t size, const DLiteInstance *inst, const char *options)#

Stores instance inst to memory buffer buf of size size.

Returns number of bytes written to buf (or would have been written to buf if buf is not large enough). Returns a negative error code on error.

unsigned char *dlite_instance_to_memory(const char *driver, const DLiteInstance *inst, const char *options)#: Saves instance to a newly allocated memory buffer. Returns NULL on error.

const char *dlite_instance_get_uuid(const DLiteInstance *inst)#: Returns a pointer to instance UUID.

const char *dlite_instance_get_uri(const DLiteInstance *inst)#: Returns a pointer to instance URI.

const char *dlite_instance_get_meta_uuid(const DLiteInstance *inst)#: Returns a pointer to the UUID of the instance metadata.

const char *dlite_instance_get_meta_uri(const DLiteInstance *inst)#: Returns a pointer to the URI of the instance metadata.

bool dlite_instance_has_dimension(DLiteInstance *inst, const char *name)#: Returns true if instance has a dimension with the given name.

size_t dlite_instance_get_ndimensions(const DLiteInstance *inst)#: Returns number of dimensions or -1 on error.

size_t dlite_instance_get_nproperties(const DLiteInstance *inst)#: Returns number of properties or -1 on error.

size_t dlite_instance_get_dimension_size_by_index(const DLiteInstance *inst, size_t i)#: Returns size of dimension i or -1 on error.

void *dlite_instance_get_property_by_index(const DLiteInstance *inst, size_t i)#

Returns a pointer to data corresponding to property with index i or NULL on error.

The returned pointer points to the actual data and should not be dereferred for arrays.

int dlite_instance_set_property_by_index(DLiteInstance *inst, size_t i, const void *ptr)#: Sets property i to the value pointed to by ptr. Returns non-zero on error.

int dlite_instance_get_property_ndims_by_index(const DLiteInstance *inst, size_t i)#: Returns number of dimensions of property with index i or -1 on error.

int dlite_instance_get_property_shape_by_index(const DLiteInstance *inst, size_t i, size_t j)#: Returns size of shape j in property i or -1 on error.

size_t *dlite_instance_get_property_dims_by_index(const DLiteInstance *inst, size_t i)#: Returns a malloc’ed array of dimensions of property i or NULL on error.

int dlite_instance_get_dimension_size(const DLiteInstance *inst, const char *name)#: Returns size of dimension i or -1 on error.

void *dlite_instance_get_property(const DLiteInstance *inst, const char *name)#: Returns a pointer to data corresponding to name or NULL on error.

int dlite_instance_set_property(DLiteInstance *inst, const char *name, const void *ptr)#: Copies memory pointed to by ptr to property name. Returns non-zero on error.

bool dlite_instance_has_property(const DLiteInstance *inst, const char *name)#: Returns true if instance has a property with the given name.

int dlite_instance_get_property_ndims(const DLiteInstance *inst, const char *name)#: Returns number of dimensions of property name or -1 on error.

size_t dlite_instance_get_property_dimssize(const DLiteInstance *inst, const char *name, size_t j)#: Returns size of dimension j of property name or NULL on error.

int dlite_instance_is_data(const DLiteInstance *inst)#: Returns non-zero if inst is a data instance.

int dlite_instance_is_meta(const DLiteInstance *inst)#

Returns non-zero if inst is metadata.

This is simply the inverse of dlite_instance_is_data().

int dlite_instance_is_metameta(const DLiteInstance *inst)#

Returns non-zero if inst is meta-metadata.

Meta-metadata contains either a “properties” property (of type DLiteProperty) or a “relations” property (of type DLiteRelation) in addition to a “dimensions” property (of type DLiteDimension).

int dlite_instance_print_property(char *dest, size_t n, const DLiteInstance *inst, const char *name, int width, int prec, DLiteTypeFlag flags)#

Write a string representation of property name to dest.

Arrays will be written with a JSON-like syntax.

No more than n bytes are written to dest (incl. the terminating NUL).

The width and prec arguments corresponds to the printf() minimum field width and precision/length modifier. If you set them to -1, a suitable value will selected according to type. To ignore their effect, set width to zero or prec to -2.

The flags provides some format options. If zero (default) bools and strings are expected to be quoted.

Returns number of bytes written to dest. If the output is truncated because it exceeds n, the number of bytes that would have been written if n was large enough is returned. On error, a negative value is returned.

int dlite_instance_print_property_by_index(char *dest, size_t n, const DLiteInstance *inst, size_t i, int width, int prec, DLiteTypeFlag flags)#: Lite dlite_print_property() but takes property index i as argument instead of property name.

int dlite_instance_aprint_property(char **dest, size_t *n, size_t pos, const DLiteInstance *inst, const char *name, int width, int prec, DLiteTypeFlag flags)#

Lite dlite_print_property() but prints to allocated buffer.

Prints to position pos in *dest, which should point to a buffer of size *n. *dest is reallocated if needed.

Returns number or bytes written or a negative number on error.

int dlite_instance_aprint_property_by_index(char **dest, size_t *n, size_t pos, const DLiteInstance *inst, size_t i, int width, int prec, DLiteTypeFlag flags)#: Lite dlite_aprint_property() but takes property index i as argument instead of property name.

int dlite_instance_scan_property(const char *src, const DLiteInstance *inst, const char *name, DLiteTypeFlag flags)#

Scans property name from src.

The flags provides some format options. If zero (default) bools and strings are expected to be quoted.

Returns number of characters consumed from src or a negative number on error.

int dlite_instance_scan_property_by_index(const char *src, const DLiteInstance *inst, size_t i, DLiteTypeFlag flags)#: Lite dlite_scan_property() but takes property index i as argument instead of property name.

int dlite_instance_sync_to_dimension_sizes(DLiteInstance *inst)#

Updates dimension sizes from internal state by calling the getdim() method of extended metadata. Does nothing, if the metadata has no getdim() method.

Returns non-zero on error.

int dlite_instance_sync_from_dimension_sizes(DLiteInstance *inst)#

Updates internal state of extended metadata from instance dimensions using setdim(). Does nothing, if the metadata has no setdim().

Returns non-zero on error.

int dlite_instance_sync_to_properties(DLiteInstance *inst)#

Help function that update properties from the saveprop() method of extended metadata. Does nothing, if the metadata has no saveprop() method.

Returns non-zero on error.

int dlite_instance_sync_from_properties(DLiteInstance *inst)#

Updates internal state of extended metadata from instance properties using loadprop(). Does nothing, if the metadata has no loadprop().

Returns non-zero on error.

int dlite_instance_set_dimension_sizes(DLiteInstance *inst, const int *dims)#

Updates the size of all dimensions in inst. The new dimension sizes are provided in shape, which must be of length inst->ndimensions. Dimensions corresponding to negative elements in shape will remain unchanged.

All properties whos dimension are changed will be reallocated and new memory will be zeroed. The values of properties with two or more dimensions, where any but the first dimension is updated, should be considered invalidated.

Returns non-zero on error.

int dlite_instance_set_dimension_size_by_index(DLiteInstance *inst, size_t i, size_t size)#: Like dlite_instance_set_dimension_sizes(), but only updates the size of dimension i to size size. Returns non-zero on error.

int dlite_instance_set_dimension_size(DLiteInstance *inst, const char *name, size_t size)#: Like dlite_instance_set_dimension_sizes(), but only updates the size of dimension name to size size. Returns non-zero on error.

DLiteInstance *dlite_instance_copy(const DLiteInstance *inst, const char *newid)#

Copies instance inst to a newly created instance.

If newid is NULL, the new instance will have no URI and a random UUID. If newid is a valid UUID, the new instance will have the given UUID and no URI. Otherwise, the URI of the new instance will be newid and the UUID assigned accordingly.

Returns NULL on error.

DLiteArray *dlite_instance_get_property_array_by_index(const DLiteInstance *inst, size_t i, int order)#

Returns a new DLiteArray object for property number i in instance inst.

order can be ‘C’ for row-major (C-style) order and ‘F’ for column-manor (Fortran-style) order.

The returned array object only describes, but does not own the underlying array data, which remains owned by the instance.

Scalars are treated as a one-dimensional array or length one.

Returns NULL on error.

DLiteArray *dlite_instance_get_property_array(const DLiteInstance *inst, const char *name, int order)#

Returns a new DLiteArray object for property name in instance inst.

order can be ‘C’ for row-major (C-style) order and ‘F’ for column-manor (Fortran-style) order.

The returned array object only describes, but does not own the underlying array data, which remains owned by the instance.

Scalars are treated as a one-dimensional array or length one.

Returns NULL on error.

int dlite_instance_copy_property(const DLiteInstance *inst, const char *name, int order, void *dest)#

Copy value of property name to memory pointed to by dest. It must be large enough to hole all the data. The meaning or order is: ‘C’: row-major (C-style) order, no reordering. ‘F’: coloumn-major (Fortran-style) order, transposed order.

Return non-zero on error.

int dlite_instance_copy_property_by_index(const DLiteInstance *inst, int i, int order, void *dest)#: Like dlite_instance_copy_property(), but the property is specified by its index i instead of name.

int dlite_instance_cast_property_by_index(const DLiteInstance *inst, int i, DLiteType type, size_t size, const size_t *shape, const int *strides, void *dest, DLiteTypeCast castfun)#

Copies and possible type-cast value of property number i to memory pointed to by dest using castfun. The destination memory is described by arguments type, size shape and strides. It must be large enough to hole all the data.

If castfun is NULL, it defaults to dlite_type_copy_cast().

Return non-zero on error.

int dlite_instance_assign_property(const DLiteInstance *inst, const char *name, int order, const void *src)#

Assigns property name to memory pointed to by src. The meaning of order is: ‘C’: row-major (C-style) order, no reordering. ‘F’: coloumn-major (Fortran-style) order, transposed order.

Return non-zero on error.

int dlite_instance_assign_casted_property_by_index(const DLiteInstance *inst, int i, DLiteType type, size_t size, const size_t *shape, const int *strides, const void *src, DLiteTypeCast castfun)#

Assigns property i by copying and possible type-cast memory pointed to by src using castfun. The memory pointed to by src is described by arguments type, size shape and strides.

If castfun is NULL, it defaults to dlite_type_copy_cast().

Return non-zero on error.

char *dlite_instance_default_uri(const DLiteInstance *inst)#

Return a newly allocated default instance URI constructed from the metadata URI and the UUID of the instance, as <meta_uri>/<uuid>.

Returns NULL on error.

int dlite_instance_get_hash(const DLiteInstance *inst, unsigned char *hash, int hashsize)#

Calculates a hash of instance inst. The calculated hash is stored in hash, where hashsize is the size of hash in bytes. It should be 32, 48 or 64.

Return non-zero on error.

Transactions

void dlite_instance_freeze(DLiteInstance *inst)#

Make instance immutable. This can never be reverted.

Note** Immutability of the underlying data cannot be enforced in C as long as the someone has a pointer to the instance. However, functions like dlite_instance_set_property() and dlite_instance_set_dimension_size() will refuse to change the instance if it is immutable. Furthermore, if the instance is used as a parent in a transaction, any changes to the underlying data will be detected by calling dlite_instance_verify_transaction().

int dlite_instance_is_frozen(const DLiteInstance *inst)#: Returns non-zero if instance is immutable (frozen).

int dlite_instance_snapshot(DLiteInstance *inst)#

Make a snapshop of mutable instance inst.

The inst will be a transaction whos parent is the snapshot. If inst already has a parent, that will now be the parent of the snapshot.

The reason that inst must be mutable, is that its hash will change due to change in its parent.

The snapshot will be assigned an URI of the form “snapshot-XXXXXXXXXXXX” (or inst->uri::snapshot-XXXXXXXXXXXX if inst->uri is not NULL) where each X is replaces with a random character.

On error non-zero is returned and inst is unchanged.

const DLiteInstance *dlite_instance_get_snapshot(const DLiteInstance *inst, int n)#

Returns a borrowed reference to shapshot number n of inst, where n counts backward from inst. Hence, n=0 returns inst, n=1 returns the parent of inst, etc…

Snapshots may be pulled back into memory using dlite_instance_get(). Use dlite_instance_pull() if you know the storage that the snapshots are stored in.

Returns NULL on error.

const DLiteInstance *dlite_instance_pull_snapshot(const DLiteInstance *inst, DLiteStorage *s, int n)#

Like dlite_instance_get_snapshot(), except that stored snapshots are pulled from s to memory.

Returns a borrowed reference to snapshot n or NULL on error.

int dlite_instance_push_snapshot(const DLiteInstance *inst, DLiteStorage *s, int n)#

Push all ancestors of snapshot n from memory to storage s, where n=0 corresponds to inst, n=1 to the parent of inst, etc…

No snapshot is pulled back from storage, so if the snapshots are already in storage, this function has no effect.

This function starts pushing closest to the root to ensure that the transaction is in a consistent state at all times.

Returns zero on success or the (positive) index of the snapshot that fails to push.

int dlite_instance_print_transaction(const DLiteInstance *inst)#: Prints transaction to stdout. Returns non-zero on error.

int dlite_instance_set_parent(DLiteInstance *inst, const DLiteInstance *parent)#

Turn instance inst into a transaction node with parent parent.

This require that inst is mutable, and parent is immutable.

If inst already has a parent, it will be replaced.

Use dlite_instance_freeze() and dlite_instance_is_frozen() to make and check that an instance is immutable, respectively.

Returns non-zero on error.

int dlite_instance_has_parent(const DLiteInstance *inst)#

Returns non-zero if inst has a parent.

int dlite_instance_verify_hash(const DLiteInstance *inst, uint8_t *hash, int recursive)#

Verify that the hash of instance inst.

If hash is not NULL, this function verifies that the hash of inst corresponds to the memory pointed to by hash. The size of the memory should be DLITE_HASH_SIZE bytes.

If hash is NULL and inst has a parent, this function will instead verify that the parent hash stored in inst corresponds to the value of the parent.

If recursive is non-zero, all ancestors of inst are also included in the verification.

Returns zero if the hash is valid. Otherwise non-zero is returned and an error message is issued.

Todo:: If recursive is non-zero and inst is a collection or has properties of type dliteRef, we should also verify the instances that are referred to. This is currently not implemented, because we have to detect cyclic references to avoid infinite recursion.

int dlite_instance_verify_transaction(const DLiteInstance *inst)#

Verifies a transaction.

Equivalent to calling dlite_instance_very_hash(inst, NULL, 1).

Returns zero if the hash is valid. Otherwise non-zero is returned and an error message is issued.

Metadata API

DLiteMeta *dlite_meta_create(const char *uri, const char *description, size_t ndimensions, const DLiteDimension *dimensions, size_t nproperties, const DLiteProperty *properties)#: Specialised function that returns a new metadata created from the given arguments. It is an instance of DLITE_ENTITY_SCHEMA.

int dlite_meta_init(DLiteMeta *meta)#

Initialises internal data of metadata meta.

Note, even though this function is called internally in dlite_instance_create(), it has to be called again after properties has been assigned to the metadata. This because _npropdims and __propdiminds depends on the property dimensions.

Returns non-zero on error.

int dlite_meta_incref(DLiteMeta *meta)#

Increase reference count to meta-metadata.

Returns the new reference count.

int dlite_meta_decref(DLiteMeta *meta)#

Decrease reference count to meta-metadata. If the reference count reaches zero, the meta-metadata is free’ed.

Returns the new reference count.

DLiteMeta *dlite_meta_get(const char *id)#: Returns a new reference to metadata with given id or NULL if no such instance can be found.

DLiteMeta *dlite_meta_load(const DLiteStorage *s, const char *id)#: Loads metadata identified by id from storage s and returns a new fully initialised meta instance.

DLiteMeta *dlite_meta_load_url(const char *url)#: Like dlite_instance_load_url(), but loads metadata instead. Returns the metadata or NULL on error.

int dlite_meta_save(DLiteStorage *s, const DLiteMeta *meta)#: Saves metadata meta to storage s. Returns non-zero on error.

int dlite_meta_save_url(const char *url, const DLiteMeta *meta)#: Saves metadata meta to url. Returns non-zero on error.

int dlite_meta_get_dimension_index(const DLiteMeta *meta, const char *name)#: Returns index of dimension named name or -1 on error.

int dlite_meta_get_property_index(const DLiteMeta *meta, const char *name)#: Returns index of property named name or -1 on error.

const DLiteDimension *dlite_meta_get_dimension_by_index(const DLiteMeta *meta, size_t i)#: Returns a pointer to dimension with index i or NULL on error.

const DLiteDimension *dlite_meta_get_dimension(const DLiteMeta *meta, const char *name)#: Returns a pointer to dimension named name or NULL on error.

const DLiteProperty *dlite_meta_get_property_by_index(const DLiteMeta *meta, size_t i)#: Returns a pointer to property with index i or NULL on error.

const DLiteProperty *dlite_meta_get_property(const DLiteMeta *meta, const char *name)#: Returns a pointer to property named name or NULL on error.

int dlite_meta_is_metameta(const DLiteMeta *meta)#: Returns non-zero if meta is meta-metadata (i.e. its instances are metadata).

Note

If meta contains either a “properties” property (of type DLiteProperty) or a “relations” property (of type DLiteRelation) in addition to a “dimensions” property (of type DLiteDimension), then it is able to describe metadata and is considered to be meta-metadata. Otherwise it is not.

bool dlite_meta_has_dimension(const DLiteMeta *meta, const char *name)#: Returns true if meta has a dimension with the given name.

bool dlite_meta_has_property(const DLiteMeta *meta, const char *name)#: Returns true if meta has a property with the given name.

DLiteMeta *dlite_meta_from_instance(DLiteInstance *inst)#: Safe type casting from instance to metadata.

DLiteInstance *dlite_meta_to_instance(DLiteMeta *meta)#: Type cast metadata to instance - always possible.

Dimensions

DLiteDimension *dlite_dimension_create(const char *name, const char *description)#

Returns a newly malloc’ed DLiteDimension or NULL on error.

The description arguments may be NULL.

void dlite_dimension_free(DLiteDimension *dim)#: Frees a DLiteDimension.

Properties

DLiteProperty *dlite_property_create(const char *name, DLiteType type, size_t size, const char *unit, const char *description)#

Returns a newly malloc’ed DLiteProperty or NULL on error.

It is created with no dimensions. Use dlite_property_add_dim() to add dimensions to the property.

The arguments unit, and description may be NULL.

void dlite_property_clear(DLiteProperty *prop)#

Clear DLiteProperty.

Free all memory referred to by the property and it, but free prop itself.

void dlite_property_free(DLiteProperty *prop)#: Frees a DLiteProperty.

int dlite_property_add_dim(DLiteProperty *prop, const char *expr)#: Add dimension expression expr to property. Returns non-zero on error.

int dlite_property_print(char *dest, size_t n, const void *ptr, const DLiteProperty *p, const size_t *shape, int width, int prec, DLiteTypeFlag flags)#

Writes a string representation of data for property p to dest.

The pointer ptr should point to the memory where the data is stored. The meaning and layout of the data is described by property p. The actual sizes of the property dimension is provided by shape. Use dlite_instance_get_property_dims_by_index() or the DLITE_PROP_DIMS macro for accessing shape.

No more than n bytes are written to dest (incl. the terminating NUL). Arrays will be written with a JSON-like syntax.

The width and prec arguments corresponds to the printf() minimum field width and precision/length modifier. If you set them to -1, a suitable value will selected according to type. To ignore their effect, set width to zero or prec to -2.

Returns number of bytes written to dest. If the output is truncated because it exceeds n, the number of bytes that would have been written if n was large enough is returned. On error, a negative value is returned.

int dlite_property_aprint(char **dest, size_t *n, size_t pos, const void *ptr, const DLiteProperty *p, const size_t *shape, int width, int prec, DLiteTypeFlag flags)#

Like dlite_type_print(), but prints to allocated buffer.

Prints to position pos in *dest, which should point to a buffer of size *n. *dest is reallocated if needed.

Returns number or bytes written or a negative number on error.

int dlite_property_scan(const char *src, void *ptr, const DLiteProperty *p, const size_t *shape, DLiteTypeFlag flags)#

Scans property from src and write it to memory pointed to by ptr.

The property is described by p.

For arrays, ptr should points to the first element and will not be not dereferenced. Evaluated dimension sizes are given by shape.

The flags provides some format options. If zero (default) bools and strings are expected to be quoted.

Returns number of characters consumed from src or a negative number on error.

int dlite_property_jscan(const char *src, const jsmntok_t *item, const char *key, void *ptr, const DLiteProperty *p, const size_t *shape, DLiteTypeFlag flags)#

Scan property from JSON data.

Arguments:

src: JSON data to scan.
item: Pointer into array of JSMN tokens corresponding to the item to scan.
key: The key corresponding to the scanned value when scanning from a JSON object. May be NULL otherwise.
ptr: Pointer to memory that the scanned value will be written to. For arrays, ptr should points to the first element and will not be not dereferenced.
p: DLite property describing the data to scan.
shape: Evaluated shape of property to scan.
flags: Format options. If zero (default) strings are expected to be quoted.

Returns:

Number of characters consumed from src or a negative number on error.

MetaModel - a data model for metadata

An interface for easy creation of metadata programically. This is especially useful in bindings to other languages like Fortran where code generation is more difficult.

DLiteMetaModel *dlite_metamodel_create(const char *uri, const char *metaid)#

Create and return a new empty metadata model. may be NULL.

Returns NULL on error.

void dlite_metamodel_free(DLiteMetaModel *model)#: Frees metadata model.

int dlite_metamodel_set_dimension_value(DLiteMetaModel *model, const char *name, size_t value)#: Sets actual value of dimension name, where name must correspond to a named dimension in the metadata of this model.

int dlite_metamodel_add_value(DLiteMetaModel *model, const char *name, const void *value)#

Adds a data value to model corresponding to property name of the metadata for this model.

Note that model only stores a pointer to value. This means that value must not be reallocated or free’ed while model is in use.

This can e.g. be used to add description.

Returns non-zero on error.

int dlite_metamodel_set_value(DLiteMetaModel *model, const char *name, const void *value)#

Like dlite_metamodel_add_value(), but if a value exists, it is replaced instead of added.

Returns non-zero on error.

int dlite_metamodel_add_string(DLiteMetaModel *model, const char *name, const char *s)#

Adds a string to model corresponding to property name of the metadata for this model.

Returns non-zero on error.

int dlite_metamodel_set_string(DLiteMetaModel *model, const char *name, const char *s)#

Like dlite_metamodel_add_string(), but if the string already exists, it is replaced instead of added.

Returns non-zero on error.

int dlite_metamodel_add_dimension(DLiteMetaModel *model, const char *name, const char *description)#

Adds a dimension to the property named “dimensions” of the metadata for model.

The name and description of the new dimension is given by name and description, respectively. description may be NULL.

Returns non-zero on error.

int dlite_metamodel_add_property(DLiteMetaModel *model, const char *name, const char *typename, const char *unit, const char *description)#

Adds a new property to the property named “properties” of the metadata for model.

Arguments:

model: datamodel that the property is added to
name: name of new property
typename: type of new property, ex. “string80”, “int64”, “string”,…
unit: unit of new type. May be NULL
description: description of property. May be NULL

Use dlite_metamodel_add_property_dim() to add dimensions to the property.

Returns non-zero on error.

int dlite_metamodel_add_property_dim(DLiteMetaModel *model, const char *name, const char *expr)#

Add dimension expression expr to property name (which must have been added with dlite_metamodel_add_property()).

Returns non-zero on error.

const char *dlite_metamodel_missing_value(const DLiteMetaModel *model)#

If model is missing a value described by a property in its metadata, return a pointer to the name of the first missing value.

If all values are assigned, NULL is returned.

const void *dlite_metamodel_get_property(const DLiteMetaModel *model, const char *name)#

Returns a pointer to the value, dimension or property added with the given name.

Returns NULL on error.

DLiteMeta *dlite_meta_create_from_metamodel(DLiteMetaModel *model)#: Creates and return a new dlite metadata from model.

struct _DLiteParent#

#include <dlite-entity.h>

Reference to parent instance. Used by transactions.

Public Members

const struct _DLiteInstance *parent#: Pointer to parent instance. May be NULL, in which case the parent must be accessed via uuid.

char uuid[DLITE_UUID_LENGTH + 1]#: UUID of parent instance.

uint8_t hash[DLITE_HASH_SIZE]#: Hash of parent instance.

struct _DLiteInstance#: #include <dlite-entity.h>

Base definition of a DLite instance, that all instance (and metadata) objects can be cast to. Is never actually instansiated.

struct _DLiteDimension#

#include <dlite-entity.h>

DLite dimension

Public Members

char *name#: Name of this dimension.

char *description#: Description of this dimension.

struct _DLiteProperty#

#include <dlite-entity.h>

DLite property

Public Members

char *name#: Name of this property.

DLiteType type#: Type of the described data.

size_t size#: Size of one data element.

char *ref#: Reference to metadata URI for type=dliteRef.

int ndims#: Number of dimension of the described data. Zero if scalar.

char **shape#: Array of dimension strings. May be NULL.

char *unit#: Unit of the described data. May be NULL.

char *description#: Human described of the described data.

struct _DLiteMeta#

#include <dlite-entity.h>

Base definition of a DLite metadata, that all metadata objects can be cast to.

It may be instansiated, e.g. by the basic metadata schema.

dlite-entity

Contents

dlite-entity#