HELPLIB.HLB  —  DCX Routines
    The Data Compression/Expansion (DCX) facility routines decrease
    the size of text, binary data, images, and any other type of
    data. There is no DCL-level interface to this facility, nor is
    there a DCX utility.

1  –  DCX$ANALYZE_DATA

    The DCX$ANALYZE_DATA routine performs statistical analysis
    on a data record. The results of the analysis are accumulated
    internally in the context area and are used by the DCX$MAKE_MAP
    routine to compute the mapping function.

    Format

      DCX$ANALYZE_DATA  context ,record

1.1  –  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.

1.2  –  Arguments

 context

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

 record

    OpenVMS usage:char_string
    type:         character string
    access:       read only
    mechanism:    by descriptor
    Record to be analyzed. DCX$ANALYZE_DATA reads the record
    argument, which is the address of a descriptor for the record
    string. The maximum length of the record string is 65,535
    characters.

1.3  –  Description

    The DCX$ANALYZE_DATA routine performs statistical analysis on
    a single data record. This routine is called once for each data
    record to be analyzed.

    During analysis, the DCX facility gathers information that
    DCX$MAKE_MAP uses to create the compression/expansion function
    for the file. After the data records have been analyzed, call
    the DCX$MAKE_MAP routine. Upon receiving the DCX$_AGAIN status
    code from DCX$MAKE_MAP, you must again analyze the same data
    records (in the same order) using DCX$ANALYZE_DATA and then call
    DCX$MAKE_MAP again. On the second iteration, DCX$MAKE_MAP returns
    the DCX$_NORMAL status code, and the data analysis is complete.

1.4  –  Condition Values Returned

    DCX$_INVCTX        Error. The context variable is invalid, or the
                       context area is invalid or corrupted. This may
                       be caused by a failure to call the appropriate
                       routine to initialize the context variable or
                       by an application program error.
    DCX$_NORMAL        Normal successful completion.

    This routine also returns any condition values returned by
    LIB$ANALYZE_SDESC_R2.

2  –  DCX$ANALYZE_DONE

    The DCX$ANALYZE_DONE routine deletes the context area and
    sets the context variable to zero, undoing the work of the
    DCX$ANALYZE_INIT routine.

    Call DCX$ANALYZE_DONE after data records have been analyzed and
    the DCX$MAKE_MAP routine has created the map.

    Format

      DCX$ANALYZE_DONE  context

2.1  –  Returns

    OpenVMS usage:cond_value
    type:         longword
    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.

2.2  –  Argument

 context

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

2.3  –  Condition Values Returned

    DCX$_INVCTX        Error. The context variable is invalid, or the
                       context area is invalid or corrupted. This may
                       be caused by a failure to call the appropriate
                       routine to initialize the context variable or
                       by an application program error.
    DCX$_NORMAL        Normal successful completion.

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

3  –  DCX$ANALYZE_INIT

    The DCX$ANALYZE_INIT routine initializes the context area for a
    statistical analysis of the data records to be compressed.

    Format

      DCX$ANALYZE_INIT  context [,item_code ,item_value]

3.1  –  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.

3.2  –  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.

3.3  –  Description

    The DCX$ANALYZE_INIT routine initializes the context area for a
    statistical analysis of the data records to be compressed. The
    first (and typically the only) argument passed to DCX$ANALYZE_
    INIT is an integer variable to contain the context value. The DCX
    facility assigns a value to the context variable and associates
    the value with the created work area. Each time you want a
    record analyzed in that area, specify the associated context
    variable. You can analyze two or more files at once by creating a
    different work area for each file, giving each area a different
    context variable, and analyzing the records of each file in the
    appropriate work area.

3.4  –  Condition Values Returned

    DCX$_INVITEM       Error; invalid item code. The number of
                       arguments specified in the call was incorrect
                       (this number should be odd), or an unknown
                       item code was specified.
    DCX$_NORMAL        Normal successful completion.

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

4  –  DCX$COMPRESS_DATA

    The DCX$COMPRESS_DATA routine compresses a data record. Call this
    routine for each data record to be compressed.

    Format

      DCX$COMPRESS_DATA  context ,in_rec ,out_rec [,out_length]

4.1  –  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.

4.2  –  Arguments

 context

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

 in_rec

    OpenVMS usage:char_string
    type:         character string
    access:       read only
    mechanism:    by descriptor
    Data record to be compressed. The in_rec argument is the address
    of the descriptor of the data record string.

 out_rec

    OpenVMS usage:char_string
    type:         character string
    access:       write only
    mechanism:    by descriptor
    Data record that has been compressed. The out_rec argument is
    the address of the descriptor of the compressed record that
    DCX$COMPRESS_DATA returns.

 out_length

    OpenVMS usage:word_signed
    type:         word integer (signed)
    access:       write only
    mechanism:    by reference
    Length (in bytes) of the compressed data record. The out_length
    argument is the address of a word into which DCX$COMPRESS_DATA
    returns the length of the compressed data record.

4.3  –  Description

    The DCX$COMPRESS_DATA routine compresses a data record. Call this
    routine for each data record to be compressed. As you compress
    each record, write the compressed record to the file containing
    the compression/expansion map. For each record, write the length
    of the record and substring string containing the record to the
    same file.

4.4  –  Condition Values Returned

    DCX$_INVCTX        Error. The context variable is invalid, or the
                       context area is invalid or corrupted. This may
                       be caused by a failure to call the appropriate
                       routine to initialize the context variable or
                       by an application program error.
    DCX$_INVDATA       Error. You specified the item value DCX$C_
                       BOUNDED in the DCX$ANALYZE_INIT routine and
                       attempted to compress a data record (using
                       DCX$COMPRESS_DATA) that was not presented for
                       analysis (using DCX$ANALYZE_DATA). Specifying
                       the DCX$C_BOUNDED item value means that you
                       must analyze all data records that are to be
                       compressed.
    DCX$_INVMAP        Error; invalid map. The map argument was not
                       specified correctly in the DCX$ANALYZE_INIT
                       routine or the context area is invalid.
    DCX$_NORMAL        Normal successful completion.
    DCX$_TRUNC         Error. The compressed data record has been
                       truncated because the out_rec descriptor did
                       not specify enough memory to accommodate the
                       record.

    This routine also returns any condition values returned by
    LIB$ANALYZE_SDESC_R2 and LIB$SCOPY_R_DX.

5  –  DCX$COMPRESS_DONE

    The DCX$COMPRESS_DONE routine deletes the context area and sets
    the context variable to zero.

    Format

      DCX$COMPRESS_DONE  context

5.1  –  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.

5.2  –  Argument

 context

    OpenVMS usage:context
    type:         longword (unsigned)
    access:       write only
    mechanism:    by reference
    Value identifying the data stream that DCX$COMPRESS_DONE deletes.
    The context argument is the address of a longword containing
    this value. DCX$COMPRESS_INIT writes the value 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.

5.3  –  Description

    The DCX$COMPRESS_DONE routine deletes the context area and
    sets the context variable to zero, undoing the work of the
    DCX$COMPRESS_INIT routine. Call DCX$COMPRESS_DONE when all data
    records have been compressed (using DCX$COMPRESS_DATA). After
    calling DCX$COMPRESS_DONE, call LIB$FREE_VM to free the virtual
    memory that DCX$MAKE_MAP used for the compression/expansion
    function.

5.4  –  Condition Values Returned

    DCX$_INVCTX        Error. The context variable is invalid or the
                       context area is invalid or corrupted. This may
                       be caused by a failure to call the appropriate
                       routine to initialize the context variable or
                       by an application program error.
    DCX$_NORMAL        Normal successful completion.

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

6  –  DCX$COMPRESS_INIT

    The DCX$COMPRESS_INIT routine initializes the context area for
    the compression of data records.

    Format

      DCX$COMPRESS_INIT  context ,map

6.1  –  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.

6.2  –  Arguments

 context

    OpenVMS usage:context
    type:         longword (unsigned)
    access:       write only
    mechanism:    by reference
    Value identifying the data stream that DCX$COMPRESS_INIT
    initializes. The context argument is the address of a longword
    containing this value. You should not modify the context value
    after DCX$COMPRESS_INIT initializes 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
    The 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
    compression is completed and the context is deleted by means
    of a call to DCX$COMPRESS_DONE.

6.3  –  Description

    The DCX$COMPRESS_INIT routine initializes the context area for
    the compression of data records.

    Call the DCX$COMPRESS_INIT routine after calling the DCX$ANALYZE_
    DONE routine.

6.4  –  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$GET_VM and LIB$FREE_VM.

7  –  DCX$EXPAND_DATA

    The DCX$EXPAND_DATA routine expands (or restores) a compressed
    data record to its original state.

    Format

      DCX$EXPAND_DATA  context ,in_rec ,out_rec [,out_length]

7.1  –  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.

7.2  –  Arguments

 context

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

 in_rec

    OpenVMS usage:char_string
    type:         character string
    access:       read only
    mechanism:    by descriptor
    Data record to be expanded. The in_rec argument is the address of
    the descriptor of the data record string.

 out_rec

    OpenVMS usage:char_string
    type:         character string
    access:       write only
    mechanism:    by descriptor
    Data record that has been expanded. The out_rec argument is the
    address of the descriptor of the expanded record returned by
    DCX$EXPAND_DATA.

 out_length

    OpenVMS usage:word_signed
    type:         word integer (signed)
    access:       write only
    mechanism:    by reference
    Length (in bytes) of the expanded data record. The out_length
    argument is the address of a word into which DCX$EXPAND_DATA
    returns the length of the expanded data record.

7.3  –  Description

    The DCX$EXPAND_DATA routine expands (or restores) a compressed
    data record to its original state. Call this routine for each
    data record to be expanded.

7.4  –  Condition Values Returned

    DCX$_INVCTX        Error. The context variable is invalid, or the
                       context area is invalid or corrupted. This may
                       be caused by a failure to call the appropriate
                       routine to initialize the context variable or
                       by an application program error.
    DCX$_INVDATA       Error. A compressed data record is invalid
                       (probably truncated) and therefore cannot be
                       expanded.
    DCX$_INVMAP        Error; invalid map. The map argument was not
                       specified correctly, or the context area is
                       invalid.
    DCX$_NORMAL        Normal successful completion.
    DCX$_TRUNC         Warning. The expanded data record has been
                       truncated because the out_rec descriptor did
                       not specify enough memory to accommodate the
                       record.

    This routine also returns any condition values returned by
    LIB$ANALYZE_SDESC_R2 and LIB$SCOPY_R_DX.

8  –  DCX$EXPAND_DONE

    The DCX$EXPAND_DONE routine deletes the context area and sets the
    context variable to zero.

    Format

      DCX$EXPAND_DONE  context

8.1  –  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.

8.2  –  Argument

 context

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

8.3  –  Description

    The DCX$EXPAND_DONE routine deletes the context area and sets
    the context variable to zero, thus undoing the work of the
    DCX$EXPAND_INIT routine. Call DCX$EXPAND_DONE when all data
    records have been expanded (using DCX$EXPAND_DATA).

8.4  –  Condition Values Returned

    DCX$_INVCTX        Error. The context variable is invalid, or the
                       context area is invalid or corrupted. This may
                       be caused by a failure to call the appropriate
                       routine to initialize the context variable or
                       by an application program error.
    DCX$NORMAL         Normal successful completion.

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

9  –  DCX$EXPAND_INIT

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

    Format

      DCX$EXPAND_INIT  context ,map

9.1  –  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.

9.2  –  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.

9.3  –  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.

9.4  –  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.

10  –  DCX$MAKE_MAP

    The DCX$MAKE_MAP routine uses the statistical information
    gathered by DCX$ANALYZE_DATA to compute the compression/expansion
    function.

    Format

      DCX$MAKE_MAP  context ,map_addr [,map_size]

10.1  –  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.

10.2  –  Arguments

 context

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

 map_addr

    OpenVMS usage:address
    type:         longword (unsigned)
    access:       write only
    mechanism:    by reference
    Starting address of the compression/expansion function. The map_
    addr argument is the address of a longword into which DCX$MAKE_
    MAP stores the virtual address of the compression/expansion
    function.

 map_size

    OpenVMS usage:longword_signed
    type:         longword (unsigned)
    access:       write only
    mechanism:    by reference
    Length of the compression/expansion function. The map_size
    argument is the address of the longword into which DCX$MAKE_MAP
    writes the length of the compression/expansion function.

10.3  –  Description

    The DCX$MAKE_MAP routine uses the statistical information
    gathered by DCX$ANALYZE_DATA to compute the compression/expansion
    function. In essence, this map is the algorithm used to shorten
    (or compress) the original data records as well as to expand the
    compressed records to their original form.

    The map must be available in memory when any data compression
    or expansion takes place; the address of the map is passed as an
    argument to the DCX$COMPRESS_INIT and DCX$EXPAND_INIT routines,
    which initialize the data compression and expansion procedures,
    respectively.

    The map is stored with the compressed data records, because the
    compressed data records are indecipherable without the map. When
    compressed data records have been expanded to their original
    state and no further compression is desired, you should delete
    the map using the LIB$FREE_VM routine.

    DCX requires that you submit data records for analysis and then
    call the DCX$MAKE_MAP routine. Upon receiving the DCX$_AGAIN
    status code, you must again submit data records for analysis
    (in the same order) and call DCX$MAKE_MAP again; on the second
    iteration, DCX$MAKE_MAP returns the DCX$_NORMAL status code.

10.4  –  Condition Values Returned

    DCX$_AGAIN         Informational. The map has not been created
                       and the map_addr and map_size arguments have
                       not been written because further analysis is
                       required. The data records must be analyzed
                       (using DCX$ANALYZE_DATA) again, and DCX$MAKE_
                       MAP must be called again before DCX$MAKE_MAP
                       will create the map and return the DCX$_NORMAL
                       status code.
    DCX$_INVCTX        Error. The context variable is invalid, or the
                       context area is invalid or corrupted. This may
                       be caused by a failure to call the appropriate
                       routine to initialize the context variable or
                       by an application program error.
    DCX$_NORMAL        Normal successful completion.

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