NAME: MRD_SKIP PURPOSE: Skip a number of bytes from the current location in a file or a pipe EXPLANATION: First tries using POINT_LUN and if this doesn't work, perhaps because the unit is a pipe or a socket, MRD_SKIP will just read in the requisite number of bytes. CALLING SEQUENCE: MRD_SKIP, Unit, Nskip INPUTS: Unit - File unit for the file or pipe in question, integer scalar Nskip - Number of bytes to be skipped, positive integer NOTES: This routine should be used in place of POINT_LUN wherever a pipe or socket may be the input unit (see the procedure FXPOSIT for an example). Note that it assumes that it can only work with nskip >= 0 so it doesn't even try for negative values. For reading a pipe, MRD_SKIP currently uses a maximum buffer size of 8 MB. This chunk value can be increased for improved efficiency (or decreased if you really have little memory.) REVISION HISTORY: Written, Thomas A. McGlynn July 1995 Don't even try to skip bytes on a pipe with POINT_LUN, since this might reset the current pointer W. Landsman April 1996 Increase buffer size, check fstat.compress W. Landsman Jan 2001 Only a warning if trying read past EOF W. Landsman Sep 2001 Use 64bit longword for skipping in very large files W. Landsman Sep 2003 Assume since V5.4, fstat.compress available W. Landsman April 2006 POINT_LUN for compressed files is as fast as any W. Landsman Oct 2006 Don't try to use POINT_LUN on compressed files W. Landsman Dec. 2006