SUBROUTINE GETFRE (IREC)
C
C     NAME:  GETFRE
C
C    LANGUAGE:  FORTRAN
C
C    OPERATING SYSTEM:  UNIVERSAL
C
C    ORDER NUMBER:  5428-SE
C
C    PART NUMBER:  000-026366  NOVEMBER 1985
C
C    PRODUCT:  UNIVERSAL VERSAPLOT COLOR RANDOM 2.0
C
C    VERSATEC, INC., SANTA CLARA, CALIFORNIA 95051
C    A XEROX COMPANY
C
C    Copyright (C) 1985 by Xerox Corporation.  All rights reserved.
C
C    "NOTICE. THIS PROGRAM IS THE EXCLUSIVE PROPERTY OF VERSATEC,
C    INC. AND IS ISSUED IN STRICT CONFIDENCE UNDER A PREARRANGED
C    LICENSE AGREEMENT AND IS NOT TO BE DISCLOSED IN ANY MANNER TO
C    PERSONS OUTSIDE THE LICENSED ORGANIZATION AND SHALL NOT BE
C    REPRODUCED OR DISSEMINATED, IN WHOLE OR PART, TO ANYONE OUTSIDE
C    THE LICENSED ORGANIZATION WITHOUT THE PRIOR WRITTEN APPROVAL OF
C    VERSATEC, INC. UNLESS OTHERWISE PROVIDED FOR BY SUCH LICENSE
C    AGREEMENT.  THIS WORK IS PROTECTED AS AN UNPUBLISHED WORK UNDER
C    THE COPYRIGHT ACT OF 1976."
C
C     REVISION HISTORY
C     REV. C        8/30/85  VARIABLES VSTACK, MAXVS, AND
C                           VSUSED ARE USED TO DETERMINE AN
C                           OPTIMUM STACK SIZE.
C                           LOST RECORDS THAT COULD HAVE
C                           BEEN USED ARE COUNTED.
C     GETFRE - GET A FREE DISK RECORD
C
C     SUBROUTINE GETFRE IS USED BY THE BAND ROUTINE TO
C     HANDLE ALLOCATION OF DISK RECORDS FOR THE SORTED
C     OUTPUT DATA.
C
C     GETFRE AND SETFRE MAINTAIN A STACK OF FREE DISK-RECORD
C     NUMBERS FOR ALLOCATION PURPOSES. IF THE STACK IS EMPTY,
C     GETFRE EXTENDS THE SIZE OF THE FILE.
C
C     ENTRY:  CALL GETFRE (IREC)
C
C     EXIT:  IREC = INDEX OF A FREE DISK RECORD
C
C     CALLS:  NONE
C
C     CALLED BY: WCHUNK,BAND
C
C     COMMON USED:
C     /STKCOM/
C            I NEXTFR  - INDEX TO DISK RECORD IF FILE MUST BE
C                       EXTENDED
C            I NLOSTA  - NUMBER OF RECORDS LOST THAT WOULD NOT
C                       HAVE BEEN REUSED
C            I NLOSTB  - NUMBER OF RECORDS LOST THAT WOULD HAVE
C                       BEEN REUSED
C            I STKPTR  - STACK POINTER
C            I VSTACK  - VIRTUAL STACK SIZE IF WE WERE USING
C                       AN UNLIMITED STACK
C            I MAXVS   - MAX. SIZE OF VSTACK
C            I VSUSED  - MAX. NUMBER OF STACK ENTRIES THAT WOULD
C                       HAVE BEEN USED ASSUMING AN UNLIMITED STACK
C
C     LOCAL:
C            NONE
C
C
C...  COMMON /STKCOM/ - DISK RECORD ALLOCATION STACK VARIABLES
C
      INTEGER NEXTFR,STKPTR,STKMAX,STACK
      INTEGER VSTACK,MAXVS,VSUSED,NLOSTA,NLOSTB
C
      COMMON /STKCOM/
     *    NEXTFR,STKPTR,STKMAX,VSTACK,MAXVS,VSUSED,
     *    NLOSTA,NLOSTB,STACK(1000)
C
C
C
C...  UPDATE VIRTUAL STACK
      IF (VSTACK .GT. 0) VSTACK = VSTACK - 1
      IF ((MAXVS - VSTACK) .GT. VSUSED) VSUSED = MAXVS - VSTACK
C
C...  CHECK FOR STACK EMPTY
      IF (STKPTR.EQ.0) GO TO 100
      IREC = STACK(STKPTR)
      STKPTR = STKPTR - 1
      RETURN
C
C...  STACK EMPTY,MUST EXTEND THE FILE
  100 IREC = NEXTFR
      NEXTFR = NEXTFR + 1
C
C...  CHECK IF A LOST RECORD COULD HAVE BEEN USED
      IF (NLOSTA .EQ. 0)  GO TO 200
        NLOSTB = NLOSTB + 1
        NLOSTA = NLOSTA - 1
C
  200 RETURN
      END