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GNOME Data Access 3.0 manual | ![]() |
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Top | Description | Object Hierarchy |
Gda ValueGda Value — Single value stored in a GdaDataModel |
GdaGeometricPoint; GdaNumeric; GdaTime; GdaTimestamp; GdaBinary; GdaBlob; typedef GdaValueList; GValue * gda_value_new (GType type
); #define gda_value_new_null GValue * gda_value_new_binary (const guchar *val
,glong size
); GValue * gda_value_new_blob (const guchar *val
,glong size
); GValue * gda_value_new_timestamp_from_timet (time_t val
); GValue * gda_value_new_from_string (const gchar *as_string
,GType type
); GValue * gda_value_new_from_xml (const xmlNodePtr node
); void gda_value_free (GValue *value
); void gda_value_reset_with_type (GValue *value
,GType type
); gboolean gda_value_is_null (const GValue *value
); gboolean gda_value_is_number (const GValue *value
); #define gda_value_isa (value, type) GValue * gda_value_copy (const GValue *value
); gpointer gda_binary_copy (gpointer boxed
); void gda_binary_free (gpointer boxed
); gpointer gda_blob_copy (gpointer boxed
); void gda_blob_free (gpointer boxed
); gpointer gda_geometricpoint_copy (gpointer boxed
); void gda_geometricpoint_free (gpointer boxed
); gpointer gda_numeric_copy (gpointer boxed
); void gda_numeric_free (gpointer boxed
); gpointer gda_time_copy (gpointer boxed
); void gda_time_free (gpointer boxed
); gpointer gda_timestamp_copy (gpointer boxed
); void gda_timestamp_free (gpointer boxed
); const GdaBinary * gda_value_get_binary (const GValue *value
); void gda_value_set_binary (GValue *value
,const GdaBinary *binary
); void gda_value_take_binary (GValue *value
,const GdaBinary *binary
); const GdaBlob * gda_value_get_blob (const GValue *value
); void gda_value_set_blob (GValue *value
,const GdaBlob *blob
); void gda_value_take_blob (GValue *value
,const GdaBlob *blob
); const GdaGeometricPoint * gda_value_get_geometric_point (const GValue *value
); void gda_value_set_geometric_point (GValue *value
,const GdaGeometricPoint *val
); const GdaValueList * gda_value_get_list (const GValue *value
); void gda_value_set_list (GValue *value
,const GdaValueList *val
); void gda_value_set_null (GValue *value
); const GdaNumeric * gda_value_get_numeric (const GValue *value
); void gda_value_set_numeric (GValue *value
,const GdaNumeric *val
); gshort gda_value_get_short (const GValue *value
); void gda_value_set_short (GValue *value
,const gshort val
); gushort gda_value_get_ushort (const GValue *value
); void gda_value_set_ushort (GValue *value
,const gushort val
); const GdaTime * gda_value_get_time (const GValue *value
); void gda_value_set_time (GValue *value
,const GdaTime *val
); const GdaTimestamp * gda_value_get_timestamp (const GValue *value
); void gda_value_set_timestamp (GValue *value
,const GdaTimestamp *val
); gboolean gda_value_set_from_string (GValue *value
,const gchar *as_string
,GType type
); gboolean gda_value_set_from_value (GValue *value
,const GValue *from
); gchar * gda_value_stringify (const GValue *value
); gint gda_value_compare (const GValue *value1
,const GValue *value2
); gint gda_value_compare_ext (const GValue *value1
,const GValue *value2
); xmlNodePtr gda_value_to_xml (const GValue *value
); gchar * gda_binary_to_string (const GdaBinary *bin
,guint maxlen
); gboolean gda_string_to_binary (const gchar *str
,GdaBinary *bin
);
GBoxed +----GdaGeometricPoint
GBoxed +----GdaNumeric
GBoxed +----GdaTime
GBoxed +----GdaTimestamp
GBoxed +----GdaBinary
GBoxed +----GdaValueList
libgda manages each individual value within an opaque GValue structure. Any GValue type can be used, and libgda adds a few more data types usually found in DBMS such as NUMERIC, TIME, TIMESTAMP, GEOMETRIC POINT, BINARY and BLOB.
Libgda makes a distinction between binary and blob types
binary data can be inserted into an SQL statement using a (DBMS dependant) syntax, such as "X'ABCD'" syntax for SQLite or the binary strings syntax for PostgreSQL. Binary data is manipulated using a GdaBinary structure (which is basically a bytes buffer and a length attribute).
blob data are a special feature that some DBMS have which requires some non SQL code to manipulate them. Usually only a reference is stored in each table containing a blob, and the actual blob data resides somewhere on the disk (while still being managed transparently by the database). For example PotsgreSQL stores blobs as files on the disk and references them using object identifiers (Oid). Blob data is manipulated using a GdaBlob structure which encapsulates a GdaBinary structure and adds a reference to a GdaBlobOp object used to read and write data from and to the blob.
Please note that is distinction between binary data and blobs is Libgda only and does not reflect the DBMS's documentations; for instance MySQL has several BLOB types but Libgda interprets them as binary types.
Each provider or connection can be queried about its blob support using the gda_server_provider_supports_feature()
or
gda_connection_supports_feature()
methods.
The NULL value is a special case value: it is represented by to a zero-filled (uninitialized) GValue and has a type equal to GDA_TYPE_NULL.
typedef struct { gushort hour; gushort minute; gushort second; gulong fraction; glong timezone; /* # of seconds to the east UTC */ } GdaTime;
typedef struct { gshort year; gushort month; gushort day; gushort hour; gushort minute; gushort second; gulong fraction; glong timezone; /* # of seconds to the east UTC */ } GdaTimestamp;
typedef struct { GdaBinary data; GdaBlobOp *op; /* set up by providers if the GdaBlob is linked to something actually existing in the database, useable by anyone */ } GdaBlob;
GValue * gda_value_new (GType type
);
Makes a new GValue of type type
.
|
the new value type. |
Returns : |
the newly created GValue with the specified type .
You need to set the value in the returned GValue. |
GValue * gda_value_new_binary (const guchar *val
,glong size
);
Makes a new GValue of type GDA_TYPE_BINARY with value val
.
|
value to set for the new GValue. |
|
the size of the memory pool pointer to by val . |
Returns : |
the newly created GValue. |
GValue * gda_value_new_blob (const guchar *val
,glong size
);
Makes a new GValue of type GDA_TYPE_BLOB with value val
.
|
value to set for the new GValue. |
|
the size of the memory pool pointer to by val . |
Returns : |
the newly created GValue. |
GValue * gda_value_new_timestamp_from_timet (time_t val
);
Makes a new GValue of type GDA_TYPE_TIMESTAMP with value val
(of type time_t).
|
value to set for the new GValue. |
Returns : |
the newly created GValue. |
GValue * gda_value_new_from_string (const gchar *as_string
,GType type
);
Makes a new GValue of type type
from its string representation.
|
stringified representation of the value. |
|
the new value type. |
Returns : |
the newly created GValue or NULL if the string representation
cannot be converted to the specified type . |
GValue * gda_value_new_from_xml (const xmlNodePtr node
);
Creates a GValue from a XML representation of it. That XML node corresponds to the following string representation: <value type="gdatype">value</value>
|
a XML node representing the value. |
Returns : |
the newly created GValue. |
void gda_value_free (GValue *value
);
Deallocates all memory associated to a GValue.
|
the resource to free. |
gboolean gda_value_is_null (const GValue *value
);
Tests if a given value
is of type GDA_TYPE_NULL.
|
value to test. |
Returns : |
a boolean that says whether or not value is of type
GDA_TYPE_NULL. |
gboolean gda_value_is_number (const GValue *value
);
Gets whether the value stored in the given GValue is of numeric type or not.
|
a GValue. |
Returns : |
TRUE if a number, FALSE otherwise. |
GValue * gda_value_copy (const GValue *value
);
Creates a new GValue from an existing one.
|
value to get a copy from. |
Returns : |
a newly allocated GValue with a copy of the data in value . |
gpointer gda_binary_copy (gpointer boxed
);
Creates a new GdaBinary structure from an existing one.
|
source to get a copy from. |
Returns : |
a newly allocated GdaBinary which contains a copy of
information in boxed . |
void gda_binary_free (gpointer boxed
);
Deallocates all memory associated to the given GdaBinary.
|
GdaBinary to free. |
gpointer gda_blob_copy (gpointer boxed
);
Creates a new GdaBlob structure from an existing one.
|
source to get a copy from. |
Returns : |
a newly allocated GdaBlob which contains a copy of
information in boxed . |
void gda_blob_free (gpointer boxed
);
Deallocates all memory associated to the given GdaBlob.
|
GdaBlob to free. |
gpointer gda_numeric_copy (gpointer boxed
);
Creates a new GdaNumeric structure from an existing one.
|
source to get a copy from. |
Returns : |
a newly allocated GdaNumeric which contains a copy of
information in boxed . |
void gda_numeric_free (gpointer boxed
);
Deallocates all memory associated to the given boxed
const GdaBinary * gda_value_get_binary (const GValue *value
);
|
a GValue whose value we want to get. |
Returns : |
the value stored in value . |
void gda_value_set_binary (GValue *value
,const GdaBinary *binary
);
Stores val
into value
.
|
a GValue that will store val . |
|
a GdaBinary structure with the data and its size to be stored in value . |
void gda_value_take_binary (GValue *value
,const GdaBinary *binary
);
Stores val
into value
, but on the contrary to gda_value_set_binary()
, the binary
argument is not copied, but used as-is and it should be considered owned by value
.
|
a GValue that will store val . |
|
a GdaBinary structure with the data and its size to be stored in value . |
const GdaBlob * gda_value_get_blob (const GValue *value
);
|
a GValue whose value we want to get. |
Returns : |
the value stored in value . |
void gda_value_set_blob (GValue *value
,const GdaBlob *blob
);
Stores val
into value
.
|
a GValue that will store val . |
|
a GdaBlob structure with the data and its size to be stored in value . |
void gda_value_take_blob (GValue *value
,const GdaBlob *blob
);
Stores val
into value
, but on the contrary to gda_value_set_blob()
, the blob
argument is not copied, but used as-is and it should be considered owned by value
.
|
a GValue that will store val . |
|
a GdaBlob structure with the data and its size to be stored in value . |
const GdaGeometricPoint * gda_value_get_geometric_point (const GValue *value
);
|
a GValue whose value we want to get. |
Returns : |
the value stored in value . |
void gda_value_set_geometric_point (GValue *value
,const GdaGeometricPoint *val
);
Stores val
into value
.
|
a GValue that will store val . |
|
value to be stored in value . |
const GdaValueList * gda_value_get_list (const GValue *value
);
|
a GValue whose value we want to get. |
Returns : |
the value stored in value . |
void gda_value_set_list (GValue *value
,const GdaValueList *val
);
Stores val
into value
.
|
a GValue that will store val . |
|
value to be stored in value . |
void gda_value_set_null (GValue *value
);
Sets the type of value
to GDA_TYPE_NULL.
|
a GValue that will store a value of type GDA_TYPE_NULL. |
const GdaNumeric * gda_value_get_numeric (const GValue *value
);
|
a GValue whose value we want to get. |
Returns : |
the value stored in value . |
void gda_value_set_numeric (GValue *value
,const GdaNumeric *val
);
Stores val
into value
.
|
a GValue that will store val . |
|
value to be stored in value . |
gshort gda_value_get_short (const GValue *value
);
|
a GValue whose value we want to get. |
Returns : |
the value stored in value . |
void gda_value_set_short (GValue *value
,const gshort val
);
Stores val
into value
.
|
a GValue that will store val . |
|
value to be stored in value . |
gushort gda_value_get_ushort (const GValue *value
);
|
a GValue whose value we want to get. |
Returns : |
the value stored in value . |
void gda_value_set_ushort (GValue *value
,const gushort val
);
Stores val
into value
.
|
a GValue that will store val . |
|
value to be stored in value . |
const GdaTime * gda_value_get_time (const GValue *value
);
|
a GValue whose value we want to get. |
Returns : |
the value stored in value . |
void gda_value_set_time (GValue *value
,const GdaTime *val
);
Stores val
into value
.
|
a GValue that will store val . |
|
value to be stored in value . |
const GdaTimestamp * gda_value_get_timestamp (const GValue *value
);
|
a GValue whose value we want to get. |
Returns : |
the value stored in value . |
void gda_value_set_timestamp (GValue *value
,const GdaTimestamp *val
);
Stores val
into value
.
|
a GValue that will store val . |
|
value to be stored in value . |
gboolean gda_value_set_from_string (GValue *value
,const gchar *as_string
,GType type
);
Stores the value data from its string representation as type
.
|
a GValue that will store val . |
|
the stringified representation of the value. |
|
the type of the value |
Returns : |
TRUE if the value has been converted to type from
its string representation; it not means that the value is converted
successfully, just that the transformation is avairable. FALSE otherwise. |
gboolean gda_value_set_from_value (GValue *value
,const GValue *from
);
Sets the value of a GValue from another GValue. This
is different from gda_value_copy, which creates a new GValue.
gda_value_set_from_value, on the other hand, copies the contents
of copy
into value
, which must already be allocated.
|
a GValue. |
|
the value to copy from. |
Returns : |
TRUE if successful, FALSE otherwise. |
gchar * gda_value_stringify (const GValue *value
);
Converts a GValue to its string representation which is a human readable value. Note that the returned string does not take into account the current locale of the user (on the contrary to the GdaDataHandler objects). Using this function should be limited to debugging and values serialization purposes.
Dates are converted in a YYYY-MM-DD format.
|
a GValue. |
Returns : |
a new string, or NULL if the conversion cannot be done. Free the value with a g_free() when you've finished
using it. |
gint gda_value_compare (const GValue *value1
,const GValue *value2
);
Compares two values of the same type.
|
a GValue to compare. |
|
the other GValue to be compared to value1 . |
Returns : |
if both values have the same type, returns 0 if both contain
the same value, an integer less than 0 if value1 is less than value2 or
an integer greater than 0 if value1 is greater than value2 . |
gint gda_value_compare_ext (const GValue *value1
,const GValue *value2
);
Like gda_value_compare()
, compares two values of the same type, except that NULL values and values
of type GDA_TYPE_NULL are considered equals
|
a GValue to compare. |
|
the other GValue to be compared to value1 . |
Returns : |
0 if both contain the same value, an integer less than 0 if value1 is less than value2 or
an integer greater than 0 if value1 is greater than value2 . |
xmlNodePtr gda_value_to_xml (const GValue *value
);
Serializes the given GValue to a XML node string.
|
a GValue. |
Returns : |
the XML node. Once not needed anymore, you should free it. |
gchar * gda_binary_to_string (const GdaBinary *bin
,guint maxlen
);
Converts all the non printable characters of bin->data into the \xxx representation where xxx is the octal representation of the byte, and the '\' (backslash) character is converted to "\\".
|
a correctly filled GdaBinary structure |
|
a maximum len used to truncate, or 0 for no maximum length |
Returns : |
a new string from bin
|
gboolean gda_string_to_binary (const gchar *str
,GdaBinary *bin
);
Performs the reverse of gda_binary_to_string()
.
|
a string to convert |
|
a non filled GdaBinary structure |
Returns : |
TRUE if no error were found in str , or FALSE otherwise |