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H5PT: HDF5 Packet Table
C++ Wrappers


Classes: Functions (none are static; all must be called on an object):

Packet Table:
Name: Null Constructor
Signature:
PacketTable( )
Purpose:
Creates an invalid packet table object.
Description:
The object created with this call will return false if IsValid() is called on it. To create a valid packet table, use the FL_Packet_Table constructors. This function does not make any change to the underlying HDF5 file.
Name: "Open" Constructor
Signature:
PacketTable(hid_t fileID, char* name)
Purpose:
Opens an existing packet table.
Description:
Opens an existing packet table, which can contain either fixed-length or variable-length packets.
Parameters:
hid_t fileID
IN: file or group in which the packet table is located
char* name
IN: the packet table's name
Name: Destructor
Signature:
~PacketTable()
Description:
The destructor closes the packet table in the file, so a packet table created or opened with the C++ wrapper does not need to be closed manually.
Name: IsValid
Signature:
bool IsValid()
Purpose:
Determines if this is an valid packet table.
Description:
This function is used to ensure that a PacketTable object corresponds to an open packet table in the file. It should be called after the constructor to check that there were no errors creating or opening the packet table.
Returns:
Returns true if this is an open packet table, false otherwise.
Name: ResetIndex
Signature:
void ResetIndex()
Purpose:
Resets the packet table's index to point to the first packet.
Description:
A packet table keeps track of the user's current location in the table so that the user can iterate through packets. This function should be called before using GetNextPacket.
Name: SetIndex
Signature:
int SetIndex(hsize_t index);
Purpose:
Sets a packet table's current index.
Description:
This function allows the user to begin iterating through packets starting from any arbitrary index. Packet tables are zero-indexed, so packet 0 is the first packet.
Parameters:
hsize_t index
IN: The value to which the packet table's index should be set
Returns:
Returns non-negative on success, negative on error.
Name: GetIndex
Signature:
hsize_t GetIndex(int& error);
Purpose:
Returns the position of the current packet.
Description:
This function allows the user to determine the position of the current packet.

If GetIndex returns 0 (zero), you must then check the value of the parameter error. If error is negative, GetIndex has failed; if error is 0 (zero), the position of the current packet is 0 (zero).

Parameters:
int& error (optional)
OUT: Non-negative if index was successfully retrieved, negative on failure.
Returns:
Returns the position of the current packet on success, 0 (zero) on error.
Name: GetPacketCount
Signatures:
hsize_t GetPacketCount()
hsize_t GetPacketCount(int& error)
Purpose:
Retrieves the number of packets in the packet table.
Description:
This function is overloaded so that it can be called with or without returning an error value. If error is not supplied, any error value is ignored. Using this parameter allows the user to distinguish between an open packet table with 0 packets and an invalid packet table.
Parameters:
int& error (optional)
OUT: Non-negative if packet count was successfully retrieved, negative if packet table is invalid.
Returns:
Number of packets in packet table. Returns 0 if packet table contains zero packets or on error.
FL_Packet_Table:
Name: "Create" Constructor
Signature:
FL_PacketTable(hid_t fileID, char* name, hid_t dtypeID, int chunkSize, int compression)
Purpose:
Creates a new packet table for storing fixed-length packets.
Description:
This constructor creates and opens a packet table in the file specified by fileID named name. Packets will be of the datatype specified by dtypeID.
Parameters:
hid_t fileID
IN: Identifier of the file or group to create the table within.
const char * dset_name
IN: The name of the packet table to create.
hid_t dtype_id
IN: The datatype of a packet.
hsize_t chunkSize
IN: The packet table uses HDF5 chunked storage to allow it to grow. This value allows the user to set the size of a chunk. The chunk size affects performance.
int compression
IN: Desired compression level: 0 (zero) through 9, or -1 for no compression.
Name: "Open" Constructor
Signature:
FL_PacketTable(hid_t fileID, char* name)
Purpose:
Opens a fixed-length packet table.
Description:
This constructor opens an existing packet table named name in the location fileID. This packet table must be fixed-length.
Parameters:
hid_t fileID
IN: Identifier of the file or group containing the packet table.
const char * dset_name
IN: The name of the packet table to open.
Name: AppendPacket / AppendPackets
Signature:
int AppendPacket(void * data)
int AppendPackets(size_t numPackets, void *data)
Purpose:
Appends fixed-length packets to the packet table.
Description:
This function writes packets to the end of the packet table. If only one argument is given, it is assumed that only a single packet is being written.
Parameters:
size_t numPackets (optional)
IN: Number of packets to add. Default is one.
void * data:
IN: Data to write. Must be a buffer of packets of the packet table's datatype.
Returns:
Returns non-negative value on success, negative on error.
Name: GetPacket / GetPackets
Signatures:
int GetPacket(hsize_t index, void * data)
int GetPackets(hsize_t startIndex, hsize_t endIndex, void * data)
Purpose:
Reads packets from the packet table.
Description:
This function fills a buffer, data, with fixed-length packets from the packet table. The one-argument function can be called to retrieve a single packet at the given index, or the two-argument function used to read a range of packets (zero-indexed, inclusive).
Parameters:
hsize_t index (single packet)
IN: Index of the single packet to be read
hsize_t startIndex (multiple packets)
IN: Index at which to start reading packets
hsize_t endIndex (multiple packets)
IN: Index at which to stop reading packets
void * data
OUT: Buffer for packets being retrieved
Returns:
Returns non-negative on success, negative on error.
Name: GetNextPacket / Get Next Packets
Signatures:
int GetNextPacket(void * data)
int GetNextPackets(size_t numPackets, void * data)
Purpose:
Iterates through packets from the packet table.
Description:
This function reads packets starting from the current index in the packet table and updates the index. It can be used with the ResetIndex and SetIndex functions to iterate through the packet table. There are versions of this function that can be called with or without the numPackets argument; if this argument is not supplied, it defaults to one.
Parameters:
size_t numPackets (optional)
IN: How many packets to read. Defaults to one.
void * data
OUT: Buffer to hold packets being read.
Returns:
Returns non-negative on success, negative on error.
HDF5 documents and links 
Introduction to HDF5 
HDF5 User Guide 
Other High-level API documents 		And in this document, the HDF5 Reference Manual  
H5DS   H5IM   H5LT   H5PT   H5TB  
H5   H5A   H5D   H5E   H5F   H5G   H5I   H5L  
H5O   H5P   H5R   H5S   H5T   H5Z   Tools   Datatypes