VMS Help MACRO, /MIGRATION, Page-Related Calculations, $PREVIOUS PAGE  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    Computes the virtual address of the first byte in the previous
    page.

    Format

      $PREVIOUS_PAGE  source_va, dest_va, clearbwp=NO,

                      user_pagesize_addr, user_mask_addr,

                      quad=YES

1 - Parameters

 source_va

    Source virtual address.

 dest_va

    Destination of virtual address within previous page.

 clearbwp=NO

    If YES, masks the byte-within-page portion of the source virtual
    address. The clearbwp=NO option is a performance enhancement,
    avoiding unnecessary instructions if you know you are starting
    on a page boundary or you are intending to divide by page-size
    anyway.

 user_pagesize_addr

    Location of the page-size value (returned by a call to the
    $GETSYI system service specifying the SYI$_PAGESIZE item
    descriptor) in the application data area. If this argument is
    blank, the macro uses MMG$GL_PAGESIZE (bigpage) or MMG$C-VAX-
    PAGE-SIZE (vaxpage).

 user_mask_addr

    Location of the application-provided byte-within-page mask. If
    this argument is blank, the macro uses MMG$GL_BWP_MASK if user_
    pagesize_addr is also blank. Otherwise, it subtracts one from the
    contents of the user_pagesize_addr and uses that value.

 quad=YES

    If YES, the conversion supports 64-bit addressing. If NO, the
    conversion does not support 64-bit addressing.