Arguments

 

context

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

item_code

   OpenVMS usage:longword_unsigned
   type:         longword (unsigned)
   access:       read only
   mechanism:    by reference
   Item code specifying information that you want DCX$ANALYZE_INIT
   to use in its analysis of data records and in its computation
   of the mapping function. DCX$ANALYZE_INIT reads this item_code
   argument, which is the address of the longword contained in the
   item code.

   For each item_code argument specified in the call, you must
   also specify a corresponding item_value argument. The item_value
   argument contains the interpretation of the item_code argument.

   The following symbolic names are the five legal values of the
   item_code argument:

      DCX$C_BOUNDED
      DCX$C_EST_BYTES
      DCX$C_EST_RECORDS
      DCX$C_LIST
      DCX$C_ONE_PASS
 

item_value

   OpenVMS usage:longword_unsigned
   type:         longword (unsigned)
   access:       read only
   mechanism:    by reference
   Value of the corresponding item_code argument. DCX$ANALYZE_INIT
   reads the item_value argument, which is the address of a longword
   containing the item value.

   The item_code and item_value arguments always occur as a pair,
   and together they specify one piece of "advice" for the DCX
   routines to use in computing the map function. Note that, unless
   stated otherwise in the list of item codes and item values, no
   piece of "advice" is binding on DCX; that is, DCX is free to
   follow or not to follow the "advice."

   The following table shows, for each item_code argument, the
   possible values for the corresponding item_value argument:

   Item Code        Corresponding Item Value

   DCX$C_BOUNDED    A Boolean variable. If bit <0> is true (equals
                    1), you are stating your intention to submit
                    for analysis all data records that will be
                    compressed; doing so often enables DCX to
                    compute a better compression algorithm. If
                    bit <0> is false (equals 0) or if the DCX$C_
                    BOUNDED item code is not specified, DCX computes
                    a compression algorithm without regard for
                    whether all records to be compressed will also
                    be submitted for analysis.
   DCX$C_EST_BYTES  A longword value containing your estimate of
                    the total number of data bytes that will be
                    submitted for compression. This estimate is
                    useful in those cases where fewer than the total
                    number of bytes are presented for analysis. If
                    you do not specify the DCX$C_EST_BYTES item
                    code, DCX submits for compression the same
                    number of bytes that was presented for analysis.
                    Note that you may specify DCX$C_EST_RECORDS or
                    DCX$C_EST_BYTES, or both.
   DCX$C_EST_       A longword value containing your estimate of
   RECORDS          the total number of data records that will be
                    submitted for compression. This estimate is
                    useful in those cases where fewer than the total
                    number of records are presented for analysis.
                    If you do not specify the DCX$C_EST_RECORDS
                    item code, DCX submits for compression the same
                    number of bytes that was presented for analysis.
   DCX$C_LIST       Address of an array of 2*n+1 longwords. The
                    first longword in the array contains the value
                    2*n+1. The remaining longwords are paired; there
                    are n pairs. The first member of the pair is
                    an item code, and the second member of the pair
                    is the address of its corresponding item value.
                    The DCX$C_LIST item code allows you to construct
                    an array of item-code and item-value pairs and
                    then to pass the entire array to DCX$ANALYZE_
                    INIT. This is useful when your language has
                    difficulty interpreting variable-length argument
                    lists. Note that the DCX$C_LIST item code may be
                    specified, in a single call, alone or together
                    with any of the other item-code and item-value
                    pairs.
   DCX$C_ONE_PASS   A Boolean variable. If bit <0> is true (equals
                    1), you make a binding request that DCX make
                    only one pass over the data to be analyzed. If
                    bit <0> is false (equals 0) or if the DCX$C_
                    ONE_PASS item code is not specified, DCX may
                    make multiple passes over the data, as required.
                    Typically, DCX makes one pass.