VMS Help DCX Routines, DCX$EXPAND_INIT  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    The DCX$EXPAND_INIT routine initializes the context area for the
    expansion of data records.

    Format

      DCX$EXPAND_INIT  context ,map

1 - Returns

    OpenVMS usage:cond_value
    type:         longword (unsigned)
    access:       write only
    mechanism:    by value

    Longword condition value. Most utility routines return a
    condition value in R0. Condition values that this routine can
    return are listed under Condition Values Returned.

2 - Arguments

 context

    OpenVMS usage:context
    type:         longword (unsigned)
    access:       write only
    mechanism:    by reference
    Value identifying the data stream that DCX$EXPAND_INIT
    initializes. The context argument is the address of a longword
    containing this value. After DCX$EXPAND_INIT initializes this
    context value, you should not modify it. You can define multiple
    context arguments to identify multiple data streams that are
    processed simultaneously.

 map

    OpenVMS usage:address
    type:         longword (unsigned)
    access:       read only
    mechanism:    by reference
    Compression/expansion function (created by DCX$MAKE_MAP). The map
    argument is the address of the compression/expansion function's
    virtual address.

    The map argument must remain at this address until data expansion
    is completed and context is deleted by means of a call to
    DCX$EXPAND_DONE.

3 - Description

    The DCX$EXPAND_INIT routine initializes the context area for the
    expansion of data records.

    Call the DCX$EXPAND_INIT routine as the first step in the
    expansion (or restoration) of compressed data records to their
    original state.

    Before you call DCX$EXPAND_INIT, read the length of the
    compressed file from the compression/expansion function (the
    map). Invoke LIB$GET_VM to get the necessary amount of storage
    for the function. LIB$GET_VM returns the address of the first
    byte of the storage area.

4 - Condition Values Returned

    DCX$_INVMAP        Error; invalid map. The map argument was not
                       specified correctly, or the context area is
                       invalid.
    DCX$_NORMAL        Normal successful completion.

    This routine also returns any condition values returned by
    LIB$GET_VM.