DDS Class Reference

#include <DDS.h>

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List of all members.

Public Types

typedef std::vector< BaseType
* >::const_iterator 
Vars_citer
typedef std::vector< BaseType
* >::iterator 
Vars_iter
typedef std::vector< BaseType
* >::reverse_iterator 
Vars_riter

Public Member Functions

void add_var (BaseType *bt)
 Adds a copy of the variable to the DDS. Using the ptr_duplicate() method, perform a deep copy on the variable bt and adds the result to this DDS.
bool check_semantics (bool all=false)
 Check the semantics of each of the variables represented in the DDS.
 DDS (const DDS &dds)
 DDS (BaseTypeFactory *factory, const string &n="")
void del_var (Vars_iter i1, Vars_iter i2)
 Removes a range of variables from the DDS.
void del_var (Vars_iter i)
 Removes a variable from the DDS.
void del_var (const string &n)
 Removes a variable from the DDS.
virtual void dump (ostream &strm) const
 dumps information about this object
virtual AttrTableget_attr_table ()
BaseTypeFactoryget_factory () const
int get_timeout ()
BaseTypeget_var_index (int i)
 Get a variable.
Vars_iter get_vars_iter (int i)
 Get an iterator.
bool mark (const string &name, bool state)
 Mark the send_p flag of the named variable to state.
void mark_all (bool state)
int num_var ()
 Returns the number of variables in the DDS.
DDSoperator= (const DDS &rhs)
void parse (FILE *in=stdin)
 Parse a DDS from a file indicated by the input file descriptor. Read the persistent representation of a DDS from the FILE *in, parse it and create a matching binary object.
void parse (int fd)
 Parse a DDS from a file indicated by the input file descriptor.
void parse (string fname)
 Parse a DDS from a file with the given name.
void print (FILE *out)
 Print the entire DDS to the specified file.
void print_constrained (FILE *out)
 Print a constrained DDS to the specified file.
void print_xml (FILE *out, bool constrained, const string &blob)
BaseTypeFactoryset_factory (BaseTypeFactory *factory)
void set_timeout (int t)
void tag_nested_sequences ()
 Traverse DDS, set Sequence leaf nodes.
void timeout_off ()
void timeout_on ()
virtual void transfer_attributes (DAS *das)
BaseTypevar (const string &n, btp_stack *s=0)
 Find the variable with the given name.
BaseTypevar (const string &n, btp_stack &s)
Vars_iter var_begin ()
 Return an iterator.
Vars_iter var_end ()
 Return an iterator.
Vars_riter var_rbegin ()
 Return a reverse iterator.
Vars_riter var_rend ()
 Return a reverse iterator.
virtual ~DDS ()

Protected Member Functions

void duplicate (const DDS &dds)
BaseTypeexact_match (const string &name, btp_stack *s=0)
virtual AttrTablefind_matching_container (AttrTable::entry *source, BaseType **dest_variable)
BaseTypeleaf_match (const string &name, btp_stack *s=0)

Friends

class DDSTest

Detailed Description

The DAP2 Data Descriptor Object (DDS) is a data structure used by the DAP2 software to describe datasets and subsets of those datasets. The DDS may be thought of as the declarations for the data structures that will hold data requested by some DAP2 client. Part of the job of a DAP2 server is to build a suitable DDS for a specific dataset and to send it to the client. Depending on the data access API in use, this may involve reading part of the dataset and inferring the DDS. Other APIs may require the server simply to read some ancillary data file with the DDS in it.

On the server side, in addition to the data declarations, the DDS holds the clauses of any constraint expression that may have accompanied the data request from the DAP2 client. The DDS object includes methods for modifying the DDS according to the given constraint expression. It also has methods for directly modifying a DDS, and for transmitting it from a server to a client.

For the client, the DDS object includes methods for reading the persistent form of the object sent from a server. This includes parsing the ASCII representation of the object and, possibly, reading data received from a server into a data object.

Note that the class DDS is used to instantiate both DDS and DataDDS objects. A DDS that is empty (contains no actual data) is used by servers to send structural information to the client. The same DDS can becomes a DataDDS when data values are bound to the variables it defines.

For a complete description of the DDS layout and protocol, please refer to The OPeNDAP User Guide.

The DDS has an ASCII representation, which is what is transmitted from a DAP2 server to a client. Here is the DDS representation of an entire dataset containing a time series of worldwide grids of sea surface temperatures:

    Dataset {
        Float64 lat[lat = 180];
        Float64 lon[lon = 360];
        Float64 time[time = 404];
        Grid {
         ARRAY:
            Int32 sst[time = 404][lat = 180][lon = 360];
         MAPS:
            Float64 time[time = 404];
            Float64 lat[lat = 180];
            Float64 lon[lon = 360];
        } sst;
    } weekly;
    

If the data request to this dataset includes a constraint expression, the corresponding DDS might be different. For example, if the request was only for northern hemisphere data at a specific time, the above DDS might be modified to appear like this:

    Dataset {
        Grid {
         ARRAY:
            Int32 sst[time = 1][lat = 90][lon = 360];
         MAPS:
            Float64 time[time = 1];
            Float64 lat[lat = 90];
            Float64 lon[lon = 360];
        } sst;
    } weekly;
    

Since the constraint has narrowed the area of interest, the range of latitude values has been halved, and there is only one time value in the returned array. Note that the simple arrays (lat, lon, and time) described in the dataset are also part of the sst Grid object. They can be requested by themselves or as part of that larger object.

See the The OPeNDAP User Guide, or the documentation of the BaseType class for descriptions of the DAP2 data types.

Note:
Make sure to pass a valid pointer to the DDS constructor or use the set_factory() method before actually using the DDS. Also make sure that the Factory's lifetime thereafter is the same as the DDS's. Never delete the factory until you're done using the DDS.

Update: I removed the DEFAULT_BASETYPE_FACTORY switch because it caused more confusion than it avoided. See Trac #130. jhrg

The compile-time symbol DEFAULT_BASETYPE_FACTORY controls whether the old (3.4 and earlier) DDS and DataDDS constructors are supported. These constructors now use a default factory class (BaseTypeFactory, implemented by this library) to instantiate Byte, ..., Grid variables. To use the default ctor in your code you must also define this symbol. If you do choose to define this and fail to provide a specialization of BaseTypeFactory when your software needs one, you code may not link or may fail at run time. In addition to the older ctors for DDS and DataDDS, defining the symbol also makes some of the older methods in Connect available (because those methods require the older DDS and DataDDS ctors.

See also:
BaseType

DAS

Definition at line 172 of file DDS.h.


Member Typedef Documentation

typedef std::vector<BaseType *>::const_iterator DDS::Vars_citer

Definition at line 214 of file DDS.h.

typedef std::vector<BaseType *>::iterator DDS::Vars_iter

Definition at line 215 of file DDS.h.

typedef std::vector<BaseType *>::reverse_iterator DDS::Vars_riter

Definition at line 216 of file DDS.h.


Constructor & Destructor Documentation

DDS::DDS ( BaseTypeFactory factory,
const string &  n = "" 
)

Make a DDS which uses the given BaseTypeFactory to create variables.

Parameters:
n The name of the dataset. Can also be set using the set_dataset_name() method.
factory BaseTypeFactory which instantiates Byte, ..., Grid. The caller is responsible for freeing the object after deleting this DDS. Can also be set using set_factory(). Never delete until just before deleting the DDS itself unless you intend to replace the factory with a new instance.
n The name of the data set. Can also be set using set_dataset_name().

Definition at line 107 of file DDS.cc.

DDS::DDS ( const DDS rhs  ) 

The DDS copy constructor.

Definition at line 112 of file DDS.cc.

References duplicate().

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DDS::~DDS (  )  [virtual]

Definition at line 117 of file DDS.cc.


Member Function Documentation

void DDS::add_var ( BaseType bt  ) 

Note:
The copy will not copy data values.
Parameters:
bt Source variable.

Definition at line 349 of file DDS.cc.

References DBG2, and BaseType::ptr_duplicate().

Referenced by duplicate().

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bool DDS::check_semantics ( bool  all = false  ) 

Check the semantics of the DDS describing a complete dataset. If ALL is true, check not only the semantics of THIS->TABLE, but also recurrsively all ctor types in the THIS->TABLE. By default, ALL is false since parsing a DDS input file runns semantic checks on all variables (but not the dataset itself.

Returns:
TRUE if the conventions for the DDS are not violated, FALSE otherwise.
Parameters:
all If true, recursively check the individual members of compound variables.
See also:
BaseType::check_semantics

Definition at line 780 of file DDS.cc.

References unique_names().

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void DDS::del_var ( Vars_iter  i1,
Vars_iter  i2 
)

Remove the variables referenced by the range of iterators and free their storage.

Note:
Invalidates any iterators that reference the contents of the DDS.
Parameters:
i1 The start of the range.
i2 The end of the range.

Definition at line 402 of file DDS.cc.

void DDS::del_var ( Vars_iter  i  ) 

Remove the variable referenced by the iterator and free its storage.

Note:
Invalidates any iterators that reference the contents of the DDS.
Parameters:
i The Vars_iter which refers to the variable.

Definition at line 386 of file DDS.cc.

void DDS::del_var ( const string &  n  ) 

Remove the named variable from the DDS. This method is not smart about looking up names. The variable must exist at the top level of the DDS and must match exactly the name given.

Note:
Invalidates any iterators that reference the contents of the DDS.
Parameters:
n The name of the variable to remove.

Definition at line 369 of file DDS.cc.

void DDS::dump ( ostream &  strm  )  const [virtual]

Displays the pointer value of this instance and then calls parent dump

Parameters:
strm C++ i/o stream to dump the information to
Returns:
void

Implements DapObj.

Reimplemented in DataDDS.

Definition at line 873 of file DDS.cc.

References AttrTable::dump(), DapIndent::Indent(), DapIndent::LMarg(), and DapIndent::UnIndent().

Referenced by DataDDS::dump().

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void DDS::duplicate ( const DDS dds  )  [protected]

Definition at line 84 of file DDS.cc.

References add_var(), d_factory, name, var_begin(), and var_end().

Referenced by DDS(), and operator=().

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BaseType * DDS::exact_match ( const string &  name,
btp_stack s = 0 
) [protected]

Definition at line 473 of file DDS.cc.

References DBG2, BaseType::name(), BaseType::var(), and var().

Referenced by var().

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void DDS::filename ( const string &  fn  ) 

Set the dataset's filename.

Definition at line 337 of file DDS.cc.

string DDS::filename (  ) 

Gets the dataset file name.

Definition at line 330 of file DDS.cc.

AttrTable * DDS::find_matching_container ( AttrTable::entry source,
BaseType **  dest_variable 
) [protected, virtual]

Given an attribute container from a DAS, find or make a destination for its contents in the DDS.

Parameters:
source Attribute table
dest_variable result param that holds the BaseType
Returns:
Destination Attribute Table

Definition at line 180 of file DDS.cc.

References AttrTable::append_container(), Attr_container, DBG, dods_grid_c, AttrTable::find_container(), BaseType::get_attr_table(), BaseType::get_parent(), AttrTable::entry::name, BaseType::type(), AttrTable::entry::type, and var().

Referenced by transfer_attributes().

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AttrTable & DDS::get_attr_table (  )  [virtual]

Get the attribute table for the global attributes.

Definition at line 315 of file DDS.cc.

Referenced by DDXParser::ddx_start_document().

string DDS::get_dataset_name (  )  const

Returns the dataset's name.

Definition at line 299 of file DDS.cc.

BaseTypeFactory* DDS::get_factory (  )  const [inline]

Return the factory which makes instances of the Byte, ..., Grid type classes. Specialize BaseTypeFactory so that a DDS will be populated with your client or server's specialized types.

Returns:
An instance of BaseTypeFactory.

Definition at line 234 of file DDS.h.

Referenced by Connect::request_ddx().

int DDS::get_timeout (  ) 

Definition at line 578 of file DDS.cc.

BaseType * DDS::get_var_index ( int  i  ) 

Return the ith variable.

Parameters:
i the index
Returns:
The corresponding variable

Definition at line 542 of file DDS.cc.

DDS::Vars_iter DDS::get_vars_iter ( int  i  ) 

Return the iterator for the ith variable.

Parameters:
i the index
Returns:
The corresponding Vars_iter

Definition at line 533 of file DDS.cc.

BaseType * DDS::leaf_match ( const string &  name,
btp_stack s = 0 
) [protected]

Definition at line 454 of file DDS.cc.

References DBG2.

Referenced by var().

bool DDS::mark ( const string &  n,
bool  state 
)

Mark the named variable by setting its SEND_P flag to STATE (true indicates that it is to be sent). Names must be fully qualified.

Note:
For aggregate types this sets each part to STATE when STATE is True. Thus, if State is True and N is `exp1.test', then both `exp1' and `test' have their SEND_P flag set to True. If STATE is False, then the SEND_P flag of the `test' is set to False, but `exp1' is left unchanged. This means that a single variable can be removed from the current projection without removing all the other children of its parent. See the mfunc set_send_p().
Returns:
True if the named variable was found, false otherwise.
Todo:
This should throw an exception on error!!!
Todo:
These methods that use the btp_stack to keep track of the path from the top of a dataset to a particular variable can be rewritten to use the parent field instead.
Todo:
All the methods that use names to identify variables should have counterparts that take BaseType pointers.

Definition at line 826 of file DDS.cc.

References DBG2, BaseType::name(), BaseType::set_send_p(), and var().

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void DDS::mark_all ( bool  state  ) 

Mark the member variable send_p flags to state.

Returns:
Void

Definition at line 859 of file DDS.cc.

int DDS::num_var (  ) 

Definition at line 549 of file DDS.cc.

DDS & DDS::operator= ( const DDS rhs  ) 

Definition at line 127 of file DDS.cc.

References duplicate().

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void DDS::parse ( FILE *  in = stdin  ) 

Parameters:
in Read the persistent DDS from this FILE*.
Exceptions:
InternalErr Thrown if in is null
Error Thrown if the parse fails.

Definition at line 648 of file DDS.cc.

References DBG2, dds_buffer(), dds_delete_buffer(), dds_switch_to_buffer(), and ddsparse().

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void DDS::parse ( int  fd  ) 

Definition at line 619 of file DDS.cc.

References parse().

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void DDS::parse ( string  fname  ) 

Definition at line 598 of file DDS.cc.

References can_not_read_file.

Referenced by parse(), DODSFilter::read_ancillary_dds(), Connect::request_dds(), Connect::request_dds_url(), Connect::request_ddx(), and Connect::request_ddx_url().

void DDS::print ( FILE *  out  ) 

Definition at line 675 of file DDS.cc.

References id2www().

Referenced by main(), and DODSFilter::send_dds().

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void DDS::print_constrained ( FILE *  out  ) 

Print those parts (variables) of the DDS structure to OS that are marked to be sent after evaluating the constraint expression.

Note:
This function only works for scalars at the top level.
Returns:
true.

Definition at line 699 of file DDS.cc.

References id2www().

Referenced by DODSFilter::dataset_constraint(), and DODSFilter::send_dds().

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void DDS::print_xml ( FILE *  out,
bool  constrained,
const string &  blob 
)

Print an XML represnetation of this DDS. This method is used to generate the part of the DDX response. The Dataset tag is not written by this code. The caller of this method must handle writing that and including the dataBLOB tag.

Parameters:
out Destination.
constrained True if the output should be limited to just those variables that are in the projection of the current constraint expression.
blob The dataBLOB href.

Definition at line 740 of file DDS.cc.

References default_schema_location, dods_namespace, id2xml(), AttrTable::print_xml(), var_begin(), and var_end().

Referenced by main(), and DODSFilter::send_ddx().

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void DDS::set_dataset_name ( const string &  n  ) 

Sets the dataset name.

Definition at line 306 of file DDS.cc.

Referenced by DDXParser::ddx_start_element().

BaseTypeFactory* DDS::set_factory ( BaseTypeFactory factory  )  [inline]

Set the factory class used to instantiate variables during the parse of a DDS.

Parameters:
factory The factory this DDS should use. Caller must free factory when done with this DDS.
See also:
BaseTypeFactory

Definition at line 244 of file DDS.h.

void DDS::set_timeout ( int  t  ) 

Definition at line 571 of file DDS.cc.

Referenced by DODSFilter::send_data().

void DDS::tag_nested_sequences (  ) 

Definition at line 586 of file DDS.cc.

References dods_sequence_c, and dods_structure_c.

Referenced by DODSFilter::send_data().

void DDS::timeout_off (  ) 

Definition at line 563 of file DDS.cc.

Referenced by Sequence::read_row(), Vector::serialize(), UInt32::serialize(), UInt16::serialize(), Structure::serialize(), Str::serialize(), Int32::serialize(), Int16::serialize(), Grid::serialize(), Float64::serialize(), Float32::serialize(), and Byte::serialize().

void DDS::timeout_on (  ) 

Definition at line 555 of file DDS.cc.

Referenced by Sequence::read_row(), Vector::serialize(), UInt32::serialize(), UInt16::serialize(), Structure::serialize(), Str::serialize(), Int32::serialize(), Int16::serialize(), Grid::serialize(), Float64::serialize(), Float32::serialize(), and Byte::serialize().

void DDS::transfer_attributes ( DAS das  )  [virtual]

Given a DAS object, scavenge attributes from it and load them into this object and the variables it contains.

If a DAS contans attributes from the current (8/2006) HDF4 server with names like var_dim_0, var_dim_1, then make those attribute tables sub tables of the var table.

Todo:
Generalize the code that treats the _dim_? attributes or make is obsolete by fixing the HDF4 server.
Note:
This method is technically unnecessary because a server (or client) can easily add attributes directly using the DDS::get_attr_table or BaseType::get_attr_table methods and then poke values in using any of the methods AttrTable provides. This method exists to ease the transition to DDS objects which contain attribute information for the existing servers (Since they all make DAS objects separately from the DDS). They could be modified to use the same AttrTable methods but operate on the AttrTable instances in a DDS/BaseType instead of those in a DAS.
Parameters:
das Get attribute information from this DAS.

Definition at line 244 of file DDS.cc.

References AttrTable::append_attr(), AttrTable::append_container(), AttrTable::attr_begin(), Attr_container, AttrTable::attr_end(), AttrTable::entry::attributes, DBG, find_matching_container(), AttrTable::get_attr_vector(), AttrTable::get_name(), AttrTable::get_type(), and BaseType::is_constructor_type().

Referenced by main().

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BaseType * DDS::var ( const string &  n,
btp_stack s = 0 
)

Returns a pointer to the named variable. If the name contains one or more field separators then the function looks for a variable whose name matches exactly. If the name contains no field separators then the funciton looks first in the top level and then in all subsequent levels and returns the first occurrence found. In general, this function searches constructor types in the order in which they appear in the DDS, but there is no requirement that it do so.

Note:
If a dataset contains two constructor types which have field names that are the same (say point.x and pair.x) you should use fully qualified names to get each of those variables.
Parameters:
n The name of the variable to find.
s If given, this value-result parameter holds the path to the returned BaseType. Thus, this method can return the FQN for the variable n.
Returns:
A BaseType pointer to the variable or null if not found.

Definition at line 443 of file DDS.cc.

References exact_match(), leaf_match(), and www2id().

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BaseType * DDS::var ( const string &  n,
btp_stack s 
)

Search for for variable n as above but record all compound type variables which ultimately contain n on s. This stack can then be used to mark the contained compound-type variables as part of the current projection.

Returns:
A BaseType pointer to the variable n or 0 if n could not be found.

Definition at line 419 of file DDS.cc.

Referenced by exact_match(), find_matching_container(), and mark().

DDS::Vars_iter DDS::var_begin (  ) 

Definition at line 506 of file DDS.cc.

Referenced by DODSFilter::dataset_constraint(), duplicate(), and print_xml().

DDS::Vars_iter DDS::var_end (  ) 

Definition at line 518 of file DDS.cc.

Referenced by DODSFilter::dataset_constraint(), duplicate(), and print_xml().

DDS::Vars_riter DDS::var_rbegin (  ) 

Definition at line 512 of file DDS.cc.

DDS::Vars_riter DDS::var_rend (  ) 

Definition at line 524 of file DDS.cc.


Friends And Related Function Documentation

friend class DDSTest [friend]

Definition at line 196 of file DDS.h.


The documentation for this class was generated from the following files:
Generated on Wed Jun 27 12:57:45 2007 for libdap++ by  doxygen 1.4.7