Arguments

 

func

   OpenVMS usage:function_code
   type:         longword
   access:       read only
   mechanism:    by value
   I/O function code. Must be one of the following:

   o  IO$_READVBLK

   o  IO$_WRITEVBLK

   o  IO$_READLBLK

   o  IO$_WRITELBLK

   Various function modifiers are supported, depending on the
   device and driver. Disk drivers support IO$M_NOVCACHE and
   IO$M_DATACHECK. Some tape devices support IO$M_REVERSE. Illegal
   modifiers are detected by the $IO_PERFORM(W) service.
 

bufobj

   OpenVMS usage:buffer object
   type:         quadword (unsigned)
   access:       read only
   mechanism:    by 32- or 64-bit reference
   Handle describing the buffer object that contains the user's
   buffer. This identifier cannot be 0.
 

iosobj

   OpenVMS usage:object handle
   type:         vector longword (unsigned)
   access:       read only
   mechanism:    by 32- or 64-bit reference
   Buffer object handle describing the buffer object that contains
   the I/O Status Area (IOSA). This might or might not be the same
   identifier as the bufobj argument. This identifier cannot be 0.
 

astadr

   OpenVMS usage:ast_procedure
   type:         procedure value
   access:       read only
   mechanism:    by 32- or 64-bit reference
   Completion AST routine address (0, if none). There is no
   AST parameter argument. When the AST routine is called, the AST
   parameter will be the address of the IOSA for the operation.
   Applications can store data in the IOSA at offset IOSA$IH_
   CONTEXT.
 

flags

   OpenVMS usage:mask_longword
   type:         64-bit integer (unsigned)
   access:       read only
   mechanism:    by value
   Flag mask. The flags argument is a bit vector in which each bit
   corresponds to a flag. Flags are defined in the module IOSADEF.

   The following table describes the flags that are valid for the
   $IO_SETUP service:

   Flag            Description

   FIO$M_          This is a high priority I/O; that is, it is
   EXPEDITE        to be given preferential treatment by the I/O
                   subsystem. Use of this bit requires ALTPRI or
                   PHY_IO privilege.

   FIO$M_AST_      The AST procedure does not use, or call any
   NOFLOAT         procedure that uses, any floating-point
                   registers. This is a performance option. If
                   set, AST delivery will neither save nor restore
                   floating-point registers. Caution: Use of
                   floating-point registers when FIO$M_AST_NOFLOAT
                   has been specified can cause unpredictable,
                   difficult to detect, error conditions.

   All other bits in the flags argument are reserved for future use
   by VSI and should be specified as 0.
 

return_fandle

   OpenVMS usage:fandle
   type:         64-bit integer (unsigned)
   access:       write only
   mechanism:    by 32- or 64-bit reference
   Address of an aligned quadword to receive the fandle for this I/O
   operation.