/* zzekllti.f -- translated by f2c (version 19980913).
   You must link the resulting object file with the libraries:
	-lf2c -lm   (in that order)
*/

#include "f2c.h"

/* Table of constant values */

static integer c__2 = 2;
static integer c__1 = 1;
static integer c__3 = 3;
static doublereal c_b17 = 0.;
static logical c_false = FALSE_;
static integer c__5 = 5;

/* $Procedure ZZEKLLTI ( EK, last less than, integer ) */
/* Subroutine */ int zzekllti_(integer *handle, integer *segdsc, integer *
	coldsc, integer *ikey, integer *prvloc, integer *prvptr)
{
    extern /* Subroutine */ int zzekcnam_(integer *, integer *, char *, 
	    ftnlen);
    extern logical zzekscmp_(integer *, integer *, integer *, integer *, 
	    integer *, integer *, integer *, char *, doublereal *, integer *, 
	    logical *, ftnlen);
    extern /* Subroutine */ int zzekixlk_(integer *, integer *, integer *, 
	    integer *);
    integer begin;
    extern /* Subroutine */ int chkin_(char *, ftnlen), errch_(char *, char *,
	     ftnlen, ftnlen);
    integer dtype, nrows, middle;
    logical indexd;
    char column[32];
    integer begptr, endptr, midptr;
    extern /* Subroutine */ int setmsg_(char *, ftnlen), sigerr_(char *, 
	    ftnlen), chkout_(char *, ftnlen), errint_(char *, integer *, 
	    ftnlen);
    integer end;

/* $ Abstract */

/*     Find the last column value less than a specified key, */
/*     for a specified, indexed integer EK column. */

/* $ Disclaimer */

/*     THIS SOFTWARE AND ANY RELATED MATERIALS WERE CREATED BY THE */
/*     CALIFORNIA INSTITUTE OF TECHNOLOGY (CALTECH) UNDER A U.S. */
/*     GOVERNMENT CONTRACT WITH THE NATIONAL AERONAUTICS AND SPACE */
/*     ADMINISTRATION (NASA). THE SOFTWARE IS TECHNOLOGY AND SOFTWARE */
/*     PUBLICLY AVAILABLE UNDER U.S. EXPORT LAWS AND IS PROVIDED "AS-IS" */
/*     TO THE RECIPIENT WITHOUT WARRANTY OF ANY KIND, INCLUDING ANY */
/*     WARRANTIES OF PERFORMANCE OR MERCHANTABILITY OR FITNESS FOR A */
/*     PARTICULAR USE OR PURPOSE (AS SET FORTH IN UNITED STATES UCC */
/*     SECTIONS 2312-2313) OR FOR ANY PURPOSE WHATSOEVER, FOR THE */
/*     SOFTWARE AND RELATED MATERIALS, HOWEVER USED. */

/*     IN NO EVENT SHALL CALTECH, ITS JET PROPULSION LABORATORY, OR NASA */
/*     BE LIABLE FOR ANY DAMAGES AND/OR COSTS, INCLUDING, BUT NOT */
/*     LIMITED TO, INCIDENTAL OR CONSEQUENTIAL DAMAGES OF ANY KIND, */
/*     INCLUDING ECONOMIC DAMAGE OR INJURY TO PROPERTY AND LOST PROFITS, */
/*     REGARDLESS OF WHETHER CALTECH, JPL, OR NASA BE ADVISED, HAVE */
/*     REASON TO KNOW, OR, IN FACT, SHALL KNOW OF THE POSSIBILITY. */

/*     RECIPIENT BEARS ALL RISK RELATING TO QUALITY AND PERFORMANCE OF */
/*     THE SOFTWARE AND ANY RELATED MATERIALS, AND AGREES TO INDEMNIFY */
/*     CALTECH AND NASA FOR ALL THIRD-PARTY CLAIMS RESULTING FROM THE */
/*     ACTIONS OF RECIPIENT IN THE USE OF THE SOFTWARE. */

/* $ Required_Reading */

/*     EK */

/* $ Keywords */

/*     EK */
/*     PRIVATE */

/* $ Declarations */
/* $ Disclaimer */

/*     THIS SOFTWARE AND ANY RELATED MATERIALS WERE CREATED BY THE */
/*     CALIFORNIA INSTITUTE OF TECHNOLOGY (CALTECH) UNDER A U.S. */
/*     GOVERNMENT CONTRACT WITH THE NATIONAL AERONAUTICS AND SPACE */
/*     ADMINISTRATION (NASA). THE SOFTWARE IS TECHNOLOGY AND SOFTWARE */
/*     PUBLICLY AVAILABLE UNDER U.S. EXPORT LAWS AND IS PROVIDED "AS-IS" */
/*     TO THE RECIPIENT WITHOUT WARRANTY OF ANY KIND, INCLUDING ANY */
/*     WARRANTIES OF PERFORMANCE OR MERCHANTABILITY OR FITNESS FOR A */
/*     PARTICULAR USE OR PURPOSE (AS SET FORTH IN UNITED STATES UCC */
/*     SECTIONS 2312-2313) OR FOR ANY PURPOSE WHATSOEVER, FOR THE */
/*     SOFTWARE AND RELATED MATERIALS, HOWEVER USED. */

/*     IN NO EVENT SHALL CALTECH, ITS JET PROPULSION LABORATORY, OR NASA */
/*     BE LIABLE FOR ANY DAMAGES AND/OR COSTS, INCLUDING, BUT NOT */
/*     LIMITED TO, INCIDENTAL OR CONSEQUENTIAL DAMAGES OF ANY KIND, */
/*     INCLUDING ECONOMIC DAMAGE OR INJURY TO PROPERTY AND LOST PROFITS, */
/*     REGARDLESS OF WHETHER CALTECH, JPL, OR NASA BE ADVISED, HAVE */
/*     REASON TO KNOW, OR, IN FACT, SHALL KNOW OF THE POSSIBILITY. */

/*     RECIPIENT BEARS ALL RISK RELATING TO QUALITY AND PERFORMANCE OF */
/*     THE SOFTWARE AND ANY RELATED MATERIALS, AND AGREES TO INDEMNIFY */
/*     CALTECH AND NASA FOR ALL THIRD-PARTY CLAIMS RESULTING FROM THE */
/*     ACTIONS OF RECIPIENT IN THE USE OF THE SOFTWARE. */


/*     Include Section:  EK Boolean Enumerated Type */


/*        ekbool.inc Version 1   21-DEC-1994 (NJB) */


/*     Within the EK system, boolean values sometimes must be */
/*     represented by integer or character codes.  The codes and their */
/*     meanings are listed below. */

/*     Integer code indicating `true': */


/*     Integer code indicating `false': */


/*     Character code indicating `true': */


/*     Character code indicating `false': */


/*     End Include Section:  EK Boolean Enumerated Type */

/* $ Disclaimer */

/*     THIS SOFTWARE AND ANY RELATED MATERIALS WERE CREATED BY THE */
/*     CALIFORNIA INSTITUTE OF TECHNOLOGY (CALTECH) UNDER A U.S. */
/*     GOVERNMENT CONTRACT WITH THE NATIONAL AERONAUTICS AND SPACE */
/*     ADMINISTRATION (NASA). THE SOFTWARE IS TECHNOLOGY AND SOFTWARE */
/*     PUBLICLY AVAILABLE UNDER U.S. EXPORT LAWS AND IS PROVIDED "AS-IS" */
/*     TO THE RECIPIENT WITHOUT WARRANTY OF ANY KIND, INCLUDING ANY */
/*     WARRANTIES OF PERFORMANCE OR MERCHANTABILITY OR FITNESS FOR A */
/*     PARTICULAR USE OR PURPOSE (AS SET FORTH IN UNITED STATES UCC */
/*     SECTIONS 2312-2313) OR FOR ANY PURPOSE WHATSOEVER, FOR THE */
/*     SOFTWARE AND RELATED MATERIALS, HOWEVER USED. */

/*     IN NO EVENT SHALL CALTECH, ITS JET PROPULSION LABORATORY, OR NASA */
/*     BE LIABLE FOR ANY DAMAGES AND/OR COSTS, INCLUDING, BUT NOT */
/*     LIMITED TO, INCIDENTAL OR CONSEQUENTIAL DAMAGES OF ANY KIND, */
/*     INCLUDING ECONOMIC DAMAGE OR INJURY TO PROPERTY AND LOST PROFITS, */
/*     REGARDLESS OF WHETHER CALTECH, JPL, OR NASA BE ADVISED, HAVE */
/*     REASON TO KNOW, OR, IN FACT, SHALL KNOW OF THE POSSIBILITY. */

/*     RECIPIENT BEARS ALL RISK RELATING TO QUALITY AND PERFORMANCE OF */
/*     THE SOFTWARE AND ANY RELATED MATERIALS, AND AGREES TO INDEMNIFY */
/*     CALTECH AND NASA FOR ALL THIRD-PARTY CLAIMS RESULTING FROM THE */
/*     ACTIONS OF RECIPIENT IN THE USE OF THE SOFTWARE. */


/*     Include Section:  EK Column Name Size */

/*        ekcnamsz.inc Version 1    17-JAN-1995 (NJB) */


/*     Size of column name, in characters. */


/*     End Include Section:  EK Column Name Size */

/* $ Disclaimer */

/*     THIS SOFTWARE AND ANY RELATED MATERIALS WERE CREATED BY THE */
/*     CALIFORNIA INSTITUTE OF TECHNOLOGY (CALTECH) UNDER A U.S. */
/*     GOVERNMENT CONTRACT WITH THE NATIONAL AERONAUTICS AND SPACE */
/*     ADMINISTRATION (NASA). THE SOFTWARE IS TECHNOLOGY AND SOFTWARE */
/*     PUBLICLY AVAILABLE UNDER U.S. EXPORT LAWS AND IS PROVIDED "AS-IS" */
/*     TO THE RECIPIENT WITHOUT WARRANTY OF ANY KIND, INCLUDING ANY */
/*     WARRANTIES OF PERFORMANCE OR MERCHANTABILITY OR FITNESS FOR A */
/*     PARTICULAR USE OR PURPOSE (AS SET FORTH IN UNITED STATES UCC */
/*     SECTIONS 2312-2313) OR FOR ANY PURPOSE WHATSOEVER, FOR THE */
/*     SOFTWARE AND RELATED MATERIALS, HOWEVER USED. */

/*     IN NO EVENT SHALL CALTECH, ITS JET PROPULSION LABORATORY, OR NASA */
/*     BE LIABLE FOR ANY DAMAGES AND/OR COSTS, INCLUDING, BUT NOT */
/*     LIMITED TO, INCIDENTAL OR CONSEQUENTIAL DAMAGES OF ANY KIND, */
/*     INCLUDING ECONOMIC DAMAGE OR INJURY TO PROPERTY AND LOST PROFITS, */
/*     REGARDLESS OF WHETHER CALTECH, JPL, OR NASA BE ADVISED, HAVE */
/*     REASON TO KNOW, OR, IN FACT, SHALL KNOW OF THE POSSIBILITY. */

/*     RECIPIENT BEARS ALL RISK RELATING TO QUALITY AND PERFORMANCE OF */
/*     THE SOFTWARE AND ANY RELATED MATERIALS, AND AGREES TO INDEMNIFY */
/*     CALTECH AND NASA FOR ALL THIRD-PARTY CLAIMS RESULTING FROM THE */
/*     ACTIONS OF RECIPIENT IN THE USE OF THE SOFTWARE. */


/*     Include Section:  EK Column Descriptor Parameters */

/*        ekcoldsc.inc Version 6    23-AUG-1995 (NJB) */


/*     Note:  The column descriptor size parameter CDSCSZ  is */
/*     declared separately in the include section CDSIZE$INC.FOR. */

/*     Offset of column descriptors, relative to start of segment */
/*     integer address range.  This number, when added to the last */
/*     integer address preceding the segment, yields the DAS integer */
/*     base address of the first column descriptor.  Currently, this */
/*     offset is exactly the size of a segment descriptor.  The */
/*     parameter SDSCSZ, which defines the size of a segment descriptor, */
/*     is declared in the include file eksegdsc.inc. */


/*     Size of column descriptor */


/*     Indices of various pieces of column descriptors: */


/*     CLSIDX is the index of the column's class code.  (We use the */
/*     word `class' to distinguish this item from the column's data */
/*     type.) */


/*     TYPIDX is the index of the column's data type code (CHR, INT, DP, */
/*     or TIME).  The type is actually implied by the class, but it */
/*     will frequently be convenient to look up the type directly. */



/*     LENIDX is the index of the column's string length value, if the */
/*     column has character type.  A value of IFALSE in this element of */
/*     the descriptor indicates that the strings have variable length. */


/*     SIZIDX is the index of the column's element size value.  This */
/*     descriptor element is meaningful for columns with fixed-size */
/*     entries.  For variable-sized columns, this value is IFALSE. */


/*     NAMIDX is the index of the base address of the column's name. */


/*     IXTIDX is the data type of the column's index.  IXTIDX */
/*     contains a type value only if the column is indexed. For columns */
/*     that are not indexed, the location IXTIDX contains the boolean */
/*     value IFALSE. */


/*     IXPIDX is a pointer to the column's index.  IXTPDX contains a */
/*     meaningful value only if the column is indexed.  The */
/*     interpretation of the pointer depends on the data type of the */
/*     index. */


/*     NFLIDX is the index of a flag indicating whether nulls are */
/*     permitted in the column.  The value at location NFLIDX is */
/*     ITRUE if nulls are permitted and IFALSE otherwise. */


/*     ORDIDX is the index of the column's ordinal position in the */
/*     list of columns belonging to the column's parent segment. */


/*     METIDX is the index of the column's integer metadata pointer. */
/*     This pointer is a DAS integer address. */


/*     The last position in the column descriptor is reserved.  No */
/*     parameter is defined to point to this location. */


/*     End Include Section:  EK Column Descriptor Parameters */

/* $ Disclaimer */

/*     THIS SOFTWARE AND ANY RELATED MATERIALS WERE CREATED BY THE */
/*     CALIFORNIA INSTITUTE OF TECHNOLOGY (CALTECH) UNDER A U.S. */
/*     GOVERNMENT CONTRACT WITH THE NATIONAL AERONAUTICS AND SPACE */
/*     ADMINISTRATION (NASA). THE SOFTWARE IS TECHNOLOGY AND SOFTWARE */
/*     PUBLICLY AVAILABLE UNDER U.S. EXPORT LAWS AND IS PROVIDED "AS-IS" */
/*     TO THE RECIPIENT WITHOUT WARRANTY OF ANY KIND, INCLUDING ANY */
/*     WARRANTIES OF PERFORMANCE OR MERCHANTABILITY OR FITNESS FOR A */
/*     PARTICULAR USE OR PURPOSE (AS SET FORTH IN UNITED STATES UCC */
/*     SECTIONS 2312-2313) OR FOR ANY PURPOSE WHATSOEVER, FOR THE */
/*     SOFTWARE AND RELATED MATERIALS, HOWEVER USED. */

/*     IN NO EVENT SHALL CALTECH, ITS JET PROPULSION LABORATORY, OR NASA */
/*     BE LIABLE FOR ANY DAMAGES AND/OR COSTS, INCLUDING, BUT NOT */
/*     LIMITED TO, INCIDENTAL OR CONSEQUENTIAL DAMAGES OF ANY KIND, */
/*     INCLUDING ECONOMIC DAMAGE OR INJURY TO PROPERTY AND LOST PROFITS, */
/*     REGARDLESS OF WHETHER CALTECH, JPL, OR NASA BE ADVISED, HAVE */
/*     REASON TO KNOW, OR, IN FACT, SHALL KNOW OF THE POSSIBILITY. */

/*     RECIPIENT BEARS ALL RISK RELATING TO QUALITY AND PERFORMANCE OF */
/*     THE SOFTWARE AND ANY RELATED MATERIALS, AND AGREES TO INDEMNIFY */
/*     CALTECH AND NASA FOR ALL THIRD-PARTY CLAIMS RESULTING FROM THE */
/*     ACTIONS OF RECIPIENT IN THE USE OF THE SOFTWARE. */


/*     Include Section:  EK Operator Codes */

/*        ekopcd.inc  Version 1  30-DEC-1994 (NJB) */


/*     Within the EK system, operators used in EK queries are */
/*     represented by integer codes.  The codes and their meanings are */
/*     listed below. */

/*     Relational expressions in EK queries have the form */

/*        <column name> <operator> <value> */

/*     For columns containing numeric values, the operators */

/*        EQ,  GE,  GT,  LE,  LT,  NE */

/*     may be used; these operators have the same meanings as their */
/*     Fortran counterparts.  For columns containing character values, */
/*     the list of allowed operators includes those in the above list, */
/*     and in addition includes the operators */

/*        LIKE,  UNLIKE */

/*     which are used to compare strings to a template.  In the character */
/*     case, the meanings of the parameters */

/*        GE,  GT,  LE,  LT */

/*     match those of the Fortran lexical functions */

/*        LGE, LGT, LLE, LLT */


/*     The additional unary operators */

/*        ISNULL, NOTNUL */

/*     are used to test whether a value of any type is null. */



/*     End Include Section:  EK Operator Codes */

/* $ Disclaimer */

/*     THIS SOFTWARE AND ANY RELATED MATERIALS WERE CREATED BY THE */
/*     CALIFORNIA INSTITUTE OF TECHNOLOGY (CALTECH) UNDER A U.S. */
/*     GOVERNMENT CONTRACT WITH THE NATIONAL AERONAUTICS AND SPACE */
/*     ADMINISTRATION (NASA). THE SOFTWARE IS TECHNOLOGY AND SOFTWARE */
/*     PUBLICLY AVAILABLE UNDER U.S. EXPORT LAWS AND IS PROVIDED "AS-IS" */
/*     TO THE RECIPIENT WITHOUT WARRANTY OF ANY KIND, INCLUDING ANY */
/*     WARRANTIES OF PERFORMANCE OR MERCHANTABILITY OR FITNESS FOR A */
/*     PARTICULAR USE OR PURPOSE (AS SET FORTH IN UNITED STATES UCC */
/*     SECTIONS 2312-2313) OR FOR ANY PURPOSE WHATSOEVER, FOR THE */
/*     SOFTWARE AND RELATED MATERIALS, HOWEVER USED. */

/*     IN NO EVENT SHALL CALTECH, ITS JET PROPULSION LABORATORY, OR NASA */
/*     BE LIABLE FOR ANY DAMAGES AND/OR COSTS, INCLUDING, BUT NOT */
/*     LIMITED TO, INCIDENTAL OR CONSEQUENTIAL DAMAGES OF ANY KIND, */
/*     INCLUDING ECONOMIC DAMAGE OR INJURY TO PROPERTY AND LOST PROFITS, */
/*     REGARDLESS OF WHETHER CALTECH, JPL, OR NASA BE ADVISED, HAVE */
/*     REASON TO KNOW, OR, IN FACT, SHALL KNOW OF THE POSSIBILITY. */

/*     RECIPIENT BEARS ALL RISK RELATING TO QUALITY AND PERFORMANCE OF */
/*     THE SOFTWARE AND ANY RELATED MATERIALS, AND AGREES TO INDEMNIFY */
/*     CALTECH AND NASA FOR ALL THIRD-PARTY CLAIMS RESULTING FROM THE */
/*     ACTIONS OF RECIPIENT IN THE USE OF THE SOFTWARE. */


/*     Include Section:  EK Segment Descriptor Parameters */

/*        eksegdsc.inc  Version 8  06-NOV-1995 (NJB) */


/*     All `base addresses' referred to below are the addresses */
/*     *preceding* the item the base applies to.  This convention */
/*     enables simplied address calculations in many cases. */

/*     Size of segment descriptor.  Note:  the include file ekcoldsc.inc */
/*     must be updated if this parameter is changed.  The parameter */
/*     CDOFF in that file should be kept equal to SDSCSZ. */


/*     Index of the segment type code: */


/*     Index of the segment's number.  This number is the segment's */
/*     index in the list of segments contained in the EK to which */
/*     the segment belongs. */


/*     Index of the DAS integer base address of the segment's integer */
/*     meta-data: */


/*     Index of the DAS character base address of the table name: */


/*     Index of the segment's column count: */


/*     Index of the segment's record count: */


/*     Index of the root page number of the record tree: */


/*     Index of the root page number of the character data page tree: */


/*     Index of the root page number of the double precision data page */
/*     tree: */


/*     Index of the root page number of the integer data page tree: */


/*     Index of the `modified' flag: */


/*     Index of the `initialized' flag: */


/*     Index of the shadowing flag: */


/*     Index of the companion file handle: */


/*     Index of the companion segment number: */


/*     The next three items are, respectively, the page numbers of the */
/*     last character, d.p., and integer data pages allocated by the */
/*     segment: */


/*     The next three items are, respectively, the page-relative */
/*     indices of the last DAS word in use in the segment's */
/*     last character, d.p., and integer data pages: */


/*     Index of the DAS character base address of the column name list: */


/*     The last descriptor element is reserved for future use.  No */
/*     parameter is defined to point to this location. */


/*     End Include Section:  EK Segment Descriptor Parameters */

/* $ Disclaimer */

/*     THIS SOFTWARE AND ANY RELATED MATERIALS WERE CREATED BY THE */
/*     CALIFORNIA INSTITUTE OF TECHNOLOGY (CALTECH) UNDER A U.S. */
/*     GOVERNMENT CONTRACT WITH THE NATIONAL AERONAUTICS AND SPACE */
/*     ADMINISTRATION (NASA). THE SOFTWARE IS TECHNOLOGY AND SOFTWARE */
/*     PUBLICLY AVAILABLE UNDER U.S. EXPORT LAWS AND IS PROVIDED "AS-IS" */
/*     TO THE RECIPIENT WITHOUT WARRANTY OF ANY KIND, INCLUDING ANY */
/*     WARRANTIES OF PERFORMANCE OR MERCHANTABILITY OR FITNESS FOR A */
/*     PARTICULAR USE OR PURPOSE (AS SET FORTH IN UNITED STATES UCC */
/*     SECTIONS 2312-2313) OR FOR ANY PURPOSE WHATSOEVER, FOR THE */
/*     SOFTWARE AND RELATED MATERIALS, HOWEVER USED. */

/*     IN NO EVENT SHALL CALTECH, ITS JET PROPULSION LABORATORY, OR NASA */
/*     BE LIABLE FOR ANY DAMAGES AND/OR COSTS, INCLUDING, BUT NOT */
/*     LIMITED TO, INCIDENTAL OR CONSEQUENTIAL DAMAGES OF ANY KIND, */
/*     INCLUDING ECONOMIC DAMAGE OR INJURY TO PROPERTY AND LOST PROFITS, */
/*     REGARDLESS OF WHETHER CALTECH, JPL, OR NASA BE ADVISED, HAVE */
/*     REASON TO KNOW, OR, IN FACT, SHALL KNOW OF THE POSSIBILITY. */

/*     RECIPIENT BEARS ALL RISK RELATING TO QUALITY AND PERFORMANCE OF */
/*     THE SOFTWARE AND ANY RELATED MATERIALS, AND AGREES TO INDEMNIFY */
/*     CALTECH AND NASA FOR ALL THIRD-PARTY CLAIMS RESULTING FROM THE */
/*     ACTIONS OF RECIPIENT IN THE USE OF THE SOFTWARE. */


/*     Include Section:  EK Data Types */

/*        ektype.inc Version 1  27-DEC-1994 (NJB) */


/*     Within the EK system, data types of EK column contents are */
/*     represented by integer codes.  The codes and their meanings */
/*     are listed below. */

/*     Integer codes are also used within the DAS system to indicate */
/*     data types; the EK system makes no assumptions about compatibility */
/*     between the codes used here and those used in the DAS system. */


/*     Character type: */


/*     Double precision type: */


/*     Integer type: */


/*     `Time' type: */

/*     Within the EK system, time values are represented as ephemeris */
/*     seconds past J2000 (TDB), and double precision numbers are used */
/*     to store these values.  However, since time values require special */
/*     treatment both on input and output, and since the `TIME' column */
/*     has a special role in the EK specification and code, time values */
/*     are identified as a type distinct from double precision numbers. */


/*     End Include Section:  EK Data Types */

/* $ Brief_I/O */

/*     Variable  I/O  Description */
/*     --------  ---  -------------------------------------------------- */
/*     HANDLE     I   File handle. */
/*     SEGDSC     I   Segment descriptor. */
/*     COLDSC     I   Column descriptor. */
/*     IKEY       I   Integer key. */
/*     PRVLOC     O   Ordinal position of predecessor of IKEY. */
/*     PRVPTR     O   Pointer to record containing predecessor of IKEY. */

/* $ Detailed_Input */

/*     HANDLE         is an EK file handle.  The file may be open for */
/*                    reading or writing. */

/*     SEGDSC         is the segment descriptor of the segment */
/*                    containing the column specified by COLDSC. */

/*     COLDSC         is the column descriptor of the column to be */
/*                    searched. */

/*     IKEY           is an integer key.  The last column entry */
/*                    less than this key is sought. */

/* $ Detailed_Output */

/*     PRVLOC         is the ordinal position, according to the order */
/*                    relation implied by the column's index, of the */
/*                    record containing the last element less than IKEY. */

/*                    If all elements of the column are greater than */
/*                    or equal to IKEY, PRVLOC is set to zero. */

/*     PRVPTR         is a pointer to the record containing the element */
/*                    whose ordinal position is PRVLOC. */

/*                    If all elements of the column are greater than */
/*                    or equal to IKEY, PRVPTR is set to zero. */

/* $ Parameters */

/*     None. */

/* $ Exceptions */

/*     1)  If HANDLE is invalid, the error will be diagnosed by routines */
/*         called by this routine. */

/*     2)  If the data type of the input column is not character, */
/*         the error SPICE(INVALIDTYPE) is signalled. */

/*     3)  If the input column is not indexed, the error */
/*         SPICE(NOTINDEXED) is signalled. */

/*     4)  If the index type of the input column is not recognized, */
/*         the error will be diagnosed by routines called by this */
/*         routine. */

/*     5)  If an I/O error occurs while reading or writing the indicated */
/*         file, the error will be diagnosed by routines called by this */
/*         routine. */

/* $ Files */

/*     See the EK Required Reading for a discussion of the EK file */
/*     format. */

/* $ Particulars */

/*     This routine finds the last column element less than a specified */
/*     integer key, within a specified segment and column. */

/*     In order to support the capability of creating an index for a */
/*     column that has already been populated with data, this routine */
/*     does not require that number of elements referenced by the */
/*     input column's index match the number of elements in the column; */
/*     the index is allowed to reference fewer elements.  However, */
/*     every record referenced by the index must be populated with data. */

/* $ Examples */

/*     See ZZEKILLT. */

/* $ Restrictions */

/*     None. */

/* $ Literature_References */

/*     None. */

/* $ Author_and_Institution */

/*     N.J. Bachman   (JPL) */

/* $ Version */

/* -    Beta Version 1.0.0, 09-NOV-1995 (NJB) */

/* -& */

/*     Non-SPICELIB functions */


/*     Local variables */


/*     Use discovery check-in. */

/*     If the column's not indexed, we have no business being here. */

    indexd = coldsc[5] != -1;
    if (! indexd) {
	zzekcnam_(handle, coldsc, column, (ftnlen)32);
	chkin_("ZZEKLLTI", (ftnlen)8);
	setmsg_("Column # is not indexed.", (ftnlen)24);
	errch_("#", column, (ftnlen)1, (ftnlen)32);
	sigerr_("SPICE(NOTINDEXED)", (ftnlen)17);
	chkout_("ZZEKLLTI", (ftnlen)8);
	return 0;
    }

/*     Check the column's data type. */

    dtype = coldsc[1];
    if (dtype != 3) {
	zzekcnam_(handle, coldsc, column, (ftnlen)32);
	chkin_("ZZEKLLTI", (ftnlen)8);
	setmsg_("Column # should be INT but has type #.", (ftnlen)38);
	errch_("#", column, (ftnlen)1, (ftnlen)32);
	errint_("#", &dtype, (ftnlen)1);
	sigerr_("SPICE(INVALIDTYPE)", (ftnlen)18);
	chkout_("ZZEKLLTI", (ftnlen)8);
	return 0;
    }

/*     Handle the case of an empty segment gracefully. */

    nrows = segdsc[5];
    if (nrows == 0) {
	*prvloc = 0;
	*prvptr = 0;
	return 0;
    }

/*     The algorithm used here is very like unto that used in LSTLTD. */

    begin = 1;
    end = nrows;

/*     Get the record pointers BEGPTR and ENDPTR of the least and */
/*     greatest elements in the column. */

    zzekixlk_(handle, coldsc, &begin, &begptr);
    zzekixlk_(handle, coldsc, &end, &endptr);
    if (zzekscmp_(&c__2, handle, segdsc, coldsc, &begptr, &c__1, &c__3, " ", &
	    c_b17, ikey, &c_false, (ftnlen)1)) {

/*        The smallest entry of the column is greater than or equal to */
/*        the input value of the same data type, so none of the entries */
/*        are less than the input value. */

	*prvloc = 0;
	*prvptr = 0;
    } else if (zzekscmp_(&c__5, handle, segdsc, coldsc, &endptr, &c__1, &c__3,
	     " ", &c_b17, ikey, &c_false, (ftnlen)1)) {

/*        The last element of the array is less than the input value of */
/*        the same data type, so it's the last item less than the input */
/*        value. */

	*prvloc = nrows;
	zzekixlk_(handle, coldsc, prvloc, prvptr);
    } else {

/*        The input value lies between some pair of column entries. */
/*        The value is greater than the smallest column entry and */
/*        less than or equal to the greatest entry. */

	while(end > begin + 1) {

/*           Find the address of the element whose ordinal position */
/*           is halfway between BEGIN and END. */

	    middle = (begin + end) / 2;
	    zzekixlk_(handle, coldsc, &middle, &midptr);
	    if (zzekscmp_(&c__5, handle, segdsc, coldsc, &midptr, &c__1, &
		    c__3, " ", &c_b17, ikey, &c_false, (ftnlen)1)) {

/*              The middle value is less than the input value of the */
/*              same data type. */

		begin = middle;
	    } else {
		end = middle;
	    }

/*           The input value is greater than the element having ordinal */
/*           position BEGIN and less than or equal to the element having */
/*           ordinal position END. */

	}
	*prvloc = begin;
	zzekixlk_(handle, coldsc, prvloc, prvptr);
    }
    return 0;
} /* zzekllti_ */

