The mi_lo_expand() function

The mi_lo_expand() function copies multirepresentational data to a new smart large object.

Syntax

MI_LO_FD mi_lo_expand(conn, LOhdl_dptr, multirep_ptr, multirep_len,
   open_mode, LO_spec)
   MI_CONNECTION *conn;
   MI_LO_HANDLE **LOhdl_dptr;
   MI_MULTIREP_DATA *multirep_ptr;
   mi_integer multirep_len;
   mi_integer open_mode;
   MI_LO_SPEC *LO_spec;
conn
This value is one of the following connection values:

A pointer to a connection descriptor established by a previous call to mi_open(), mi_server_connect(), or mi_server_reconnect().

A NULL-valued pointer (database server only)

LOhdl_dptr
A doubly indirected pointer to an LO handle that identifies the new smart large object into which mi_lo_expand() copies the multirepresentational data.
multirep_ptr
A pointer to a buffer that contains the multirepresentational data to store in the new smart large object.
multirep_len
An integer that specifies the size of the multirep_ptr data, in bytes.
open_mode
An integer bitmask that specifies the open mode for the smart large object that LOhdl_dptr references.
LO_spec
A pointer to the LO-specification structure that contains the storage characteristics to use for the new smart large object.
Valid in client LIBMI application? Valid in user-defined routine?
Yes Yes

Usage

The mi_lo_expand() function performs the following steps to create a new smart large object that LOhdl_dptr references and to copy multirepresentational data into this new smart large object:
  1. It obtains an LO handle for the new smart large object and assigns a pointer to the handle to the argument that LOhdl_dptr references.

    If the LOhdl_dptr argument is NULL, mi_lo_expand() allocates a new LO handle for the new smart large object and assigns a pointer to this handle to LOhdl_dptr. If LOhdl_dptr is not NULL, mi_lo_expand() assumes that you have already allocated an LO handle and uses the LOhdl_ptr argument to locate the LO handle for the new smart large object.

  2. It assigns the storage characteristics from the LO-specification structure, LO_spec, to the new smart large object.

    If the LO-specification structure has not been updated with storage characteristics (the associated fields are null), the mi_lo_expand() function uses the system-specified storage characteristics.

    If the LO-specification structure was updated with storage characteristics, mi_lo_expand() uses the storage characteristics that the LO-specification structure defines for the new smart large object.

  3. It opens the new smart large object in the open mode that the open_mode argument specifies.

    The bitmask value for the open_mode argument indicates the open mode of the smart large object after mi_lo_expand() successfully completes. For more information about valid open-mode flags, see the HCL OneDB™ DataBlade® API Programmer's Guide.

  4. It copies the contents of the multirepresentational data in the multirep_ptr buffer into the new smart large object that LOhdl_dptr references.

    The mi_lo_expand() function copies multirep_len bytes of the multirepresentational data to the sbspace of the new smart large object.

  5. It returns an LO file descriptor that identifies the new smart large object and is positioned at the start of this smart large object.

    When the mi_lo_expand() function is successful, it returns a valid LO file descriptor. You can then use this file descriptor to identify which smart large object to access in subsequent function calls, such as mi_lo_read() and mi_lo_write().

The mi_lo_expand() function is a constructor function for both an LO file descriptor and an LO handle.

Server only: If the mi_lo_expand() function allocates an LO handle, it allocates this LO handle in the current memory duration. The mi_lo_expand() function does not allocate memory for the LO file descriptor. Your UDR can assign this LO file descriptor to user memory with a desired memory duration.

Each mi_lo_expand() call is implicitly associated with the current session. When this session ends, the database server deallocates any smart large objects that mi_lo_expand() has created if its LO handle has not been stored in a column (its reference count is zero) and no open LO file descriptors exist for the smart large object.

Server only: The mi_lo_expand() function does not need a connection descriptor to execute. If your UDR does not need a valid connection for other operations, you can specify a NULL-valued pointer for the conn parameter to establish a NULL connection. For information about the advantages of a NULL connection, see the HCL OneDB DataBlade API Programmer's Guide.
Important: The DataBlade API provides this function only for compatibility with earlier applications. For new DataBlade API modules, use the mi_lo_create() or mi_lo_from_file() function.

Return values

An MI_LO_FD value
The LO file descriptor for the open smart large object that LOhdl_dptr references. The function also initializes the LO handle that LOhdl_dptr references.
MI_ERROR
The function was not successful.