(FILECREATED "30-Oct-87 16:07:03" {ERIS}<DANIELS>LISP>KOTO>LFEQFIX.;1
 3981   

      changes to:  (VARS LFEQFIXCOMS)
		   (FNS \LFReadPages))


(* Copyright (c) 1987 by Xerox Corporation. All rights reserved.)

(PRETTYCOMPRINT LFEQFIXCOMS)

(RPAQQ LFEQFIXCOMS
 ((FNS \LFReadPages \VFMCorrectBufferP \VFMMarkBufferDirty)))
(DEFINEQ

(\LFReadPages

  [LAMBDA (stream streamFirstPage buffers)                   (* edited: "30-Oct-87 16:04")


          (* * Reads a bunch of pages from stream, starting at firstPage. Returns number of bytes read.)




          (* * Modified " 4-Jul-85 04:47:22" by HTS to extend the backing file whenever it tries to read past the end of the 

	  backing file. This generally ensures that data subsequently written on these buffer pages will not be lost if you 

	  run out of disk space)




          (* * If asked to read a page which is off the end of the stream, it will zero the page. Odd though it may seem, 

	  reading off the end of the file is reasonable behavior for copybytes: buffer pages must come from somewhere, and 

	  copybytes may not have to write the whole page, and in general copybytes does not know whether a page is actually 

	  in a file or off the end of it. Seems inefficient, but since reading past eof does not actually require disk 

	  access, its not that bad.)




          (* * Extend backing file if necessary to accomodate buffers.)



    (
\LFExtendFileIfNecessary
 stream streamFirstPage buffers)

          (* * Write out the buffers to the backing file.)



    (for
 buffer inside
 buffers as
 streamPageNumber from
 streamFirstPage as
 
									    backingFilePageNumber
       from
 (
ADD1
 streamFirstPage) bind
 (file ←(fetch
 (DLIONSTREAM FILEDESC) of
 stream))
					      lastStreamPage offset
       first
 (
\UPDATEOF
 stream)
	       (
SETQ
 lastStreamPage (
PLUS
 (fetch
 (DLIONSTREAM EPAGE) of
 stream)
					      (if
 (
EQ
 0 (fetch
 (DLIONSTREAM EOFFSET)
							       of
 stream))
						  then
 -1
						else
 0)))
       sum
 (if
 (
LEQ
 streamPageNumber lastStreamPage)
		 then
 

          (* * If page inside stream, then it has presumably already been written; read it in.)



			(
\PFGetPage
 file backingFilePageNumber (
\PFFindPageAddr
 file 
									    backingFilePageNumber)
				      buffer)

          (* * If this was the last page in the file, then fill in the trailing bytes with nulls.)



			(if
 (
EQP
 streamPageNumber lastStreamPage)
			    then
 (
SETQ
 offset (fetch
 (DLIONSTREAM EOFFSET) of
 stream))
				   (if
 (
EQ
 offset 0)
				       then
 (
SETQ
 offset BYTESPERPAGE)
				     else
 (
\CLEARBYTES
 buffer offset (
DIFFERENCE
 BYTESPERPAGE 
										       offset)))
				   offset
			  else
 BYTESPERPAGE)
	       else
 

          (* * If this was outside the stream, clear the buffer.)



		      (
\CLEARWORDS
 buffer WORDSPERPAGE)
		      0])

(\VFMCorrectBufferP

  [LAMBDA (BUFFER VOLPAGENUM)                                (* edited: "30-Oct-87 16:05")


          (* * True iff BUFFER is the right buffer for VOLPAGENUM)



    (
AND
 (
EQ
 (fetch
 (\BTREEBUF VOLUME) of
 BUFFER)
		 \VFMvolumeHandle)
	   (
EQP
 (fetch
 (\BTREEBUF VOLPAGENUM) of
 BUFFER)
		  VOLPAGENUM])

(\VFMMarkBufferDirty

  [DLAMBDA ((BUFFERPAGE Buffer)
            (RETURNS NIL))
                                                             (* edited: "30-Oct-87 16:05")


          (* * Note that the specified buffer has been written into and will have to be flushed out to disk.)



    (replace
 (\BTREEBUF DIRTY) of
 (for
 BUF in
 \VFMbufferPool
					 thereis
 (
EQP
 BUFFERPAGE (fetch
 (\BTREEBUF PAGE)
									of
 BUF)))
       with
 T)
    NIL])
)
(PUTPROPS LFEQFIX COPYRIGHT ("Xerox Corporation" 1987))
(DECLARE: DONTCOPY
  (FILEMAP (NIL (331 3903 (\LFReadPages 341 . 3049) (\VFMCorrectBufferP 3051 . 3409) (
\VFMMarkBufferDirty 3411 . 3901)))))
STOP