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FREADDIR
INTRINSIC NUMBER 7
Reads a logical record located by its chronological record number from a
KSAM file to the user's stack.
IV LA IV DV
FREADDIR(filenum,target,tcount,recnum);
The FREADDIR intrinsic reads a specific logical record, or a portion of
such a record, from a KSAM file to the user's data stack. The particular
record read is specified by its chronological record number. This number
is determined by the order in which the record was written to the file;
it is not the logical record number determined by ascending key sequence.
When the file has fixed-length records, recnum is the actual record
number counting from the first record in the file. When the file has
variable-length records, recnum is a word pointer to the first word in
the record counting from the first word in the file, word zero.
After FREADDIR has been executed, the chronological record pointer
remains positioned at the record just read. FREADDIR does not change the
position of the logical record pointer.
PARAMETERS
filenum integer by value (required)
A word identifier supplying the file number of the file
to be read.
target logical array (required)
An array to which the record is to be transferred. This
array should be large enough to hold all of the
information to be transferred.
tcount integer by value (required)
An integer specifying the number of words or bytes to be
transferred. If this value is positive, it signifies
words; if negative, it signifies bytes; and if it is
zero, no transfer occurs.
If tcount is less than the size of the record, only the
first tcount words or bytes are read from the record.
If tcount is larger than the size of the logical record,
the transfer is limited to the length of the logical
record.
recnum double by value (required)
A double-word integer indicating the relative
chronological record number (or word number for
variable-length records) to which the chronological
pointer is positioned. Chronological record numbering
for fixed-length records starts with zero or one, as
specified in ksamparam or by FIRSTREC in BUILD.
CONDITION CODES
CCE The specified information was read.
CCG The end-of-data was encountered during reading.
CCL The information was not read because an error occurred.
SPECIAL CONSIDERATIONS
Split stack calls permitted.
USING FREADDIR
You can use the FREADDIR intrinsic to position to a particular record in
chronological sequence and then read that record. Following execution,
the record pointer remains positioned at the same record. This intrinsic
is similar in effect to the pair of intrinsics FPOINT and FREADC, with
one exception: FREADDIR does not skip records marked for deletion. You
might use FREADDIR to read one record and then reposition the pointer;
you might use FPOINT and FREADC to position to a particular record and
then continue reading in chronological order from that position.
You can use the FGETINFO intrinsic to determine the relative
chronological number of the record most recently accessed. This number
is returned in the FGETINFO parameter recpt. The example in Figure 4-10
determines the chronological record of each record as it is read in
sequence by primary key value. The chronological record number is
printed, and then FREADDIR uses this number to read the record to which
it points. The output shows the chronological record number followed by
the record to which it points. To see these records listed in
chronological order, refer to the output in example 4-9 illustrating
FREADC.
Note that execution of those intrinsics that position the KSAM data file
by means of the chronological record pointer (FPOINT, FREADC, FREADDIR),
do not access the key file. This type of access only affects the data
file. It is, therefore, much faster than those intrinsics that use key
sequence to position the data file and must access the key file.
_____________________________________________________________________
| |
| $CONTROL MAIN=JEXAMPL6 |
| <<******************************************************>> |
| <<* *>> |
| <<* EXAMPLE 6 *>> |
| <<* READ A KSAM FILE BY CHRONOLOGICAL RECORD NUMBER *>> |
| <<* *>> |
| <<******************************************************>> |
| INTEGER FILNUM; |
| INTEGER ERRORCODE; |
| INTEGER LENGTH; |
| BYTE ARRAY FILNAME(0:9):="JEXAMFIL "; |
| ARRAY MESSAGE(0:35); |
| ARRAY INPUT(0:39); |
| ARRAY OUTPUT(*)=INPUT; |
| DOUBLE RECPTR; |
| INTRINSIC FOPEN,FCLOSE,FREAD,FGETINFO,FREADDIR, |
| PRTNT,TERMINATE,DASCII,FCHECK,FERRMSG; |
| <<*************************>> |
| <<* OPEN THE KSAM FILE *>> |
| <<*************************>> |
| FILNUM,=FOPEN(FILNAME,3); <<OPEN THE KSAM FILE>> |
| IF FILNUM=0 |
| THEN BEGIN <<CANNOT OPEN KSAM FILE>> |
| MOVE MESSAGE:="CANNOT OPEN KSAM FILE"; |
| PRINT(MESSAGE,-21,0); |
| FCHECK(FILNUM,ERRORCODE); <<GET ERROR NUMBER>> |
| FERRMSG(ERRORCODE,MESSAGE,LENGTH);<<CONVERT TO STRING>>|
| PRINT(MESSAGE,-LENGTH,0); <<PRTNTOUT ERROR MESSAGE>> |
| TERMINATE; |
| END; |
| <<*****************************************************>> |
| <<* READ KSAM SEQUENTIALLY *>> |
| <<****************#************************************>> |
| L1: |
| FREAD(FILNUM,INPUT,-72); |
| IF > |
| THEN BEGIN |
| FCLOSE(FILNUM,0,0); <<CLOSE THE KSAM FILE>> |
| IF <> THEN |
| BEGIN |
| MOVE MESSAGE:="CANNOT CLOSE THE KSAM FILE"; |
| PRINT(MESSAGE,-22,0); |
_____________________________________________________________________
Figure 4-10. FREADDIR Example
____________________________________________________________________________
| |
| FCHECK(FILNUM,ERRORCOOE); <<GET ERROR NUMBER>> |
| FFRRMSG(ERRORCODE,MESSAGE,LENGTH);<<CONVERT TO STRING>> |
| PRINT(MESSAGE,-LENGTH,0); <<PRINTOUT ERROR MESSAGE>> |
| END; |
| TERMINATE; |
| END; |
| IF < |
| THEN BEGIN |
| MOVE MESSAGE:="ERROR OCCURRED WHILE READING KSAM FILE"; |
| PRINT(MESSAGE,-37,0); |
| FCHECK(FILNUM,ERRORCODE); <<GET ERROR NUMBER>> |
| FERRMSG(ERRORCODE,MESSAGE,LENGTH);<<CONVERT TO STRING>> |
| PRINT(MESSAGE,-LENGTH,0); <<PRINTOUT ERROR MESSAGE>> |
| TERMINATE; |
| END; |
| <<*****************************************************>> |
| <<* TO FIND OUT RECORD NUMBER OF THE RECORD JUST READ *>> |
| <<*****************************************************>> |
| FGETINFO(FINUM,,,,,,,,RECPTR); |
| MOVE MESSAGE:="RECORD# = "; |
| DASCII(RECPTR,10,MESSAGE(5)); |
| PRINT(MESSAGE,-14,0); |
| <<**********************************************>> |
| <<* READ THE KSAM FILE BY USING RECORD NUMBER *>> |
| <<**********************************************>> |
| FREADDIR(FILNUM,INPUT,-72,RECPTR); |
| IF <> |
| THEN BEGIN |
| MOVE MESSAGE:="ERROR OCCURRED DURING FREADDIR"; |
| PRINT(MESSAGE,-30,0); |
| FCHECK(FILNUM,ERRORCODE); <<GET ERROR NUMBER>> |
| FERRMSG(ERRORCODE,MESSAGE,LENGTH);<<CONVERT TO STRING>>>|
| PRINT(MESSAGE,-LENGTH,0); <<PRINTOUT ERROR MESSAGE>> |
| TERMINATE; |
| END; |
| <<***********************************************>> |
| <<* WRITE THE DATA JUST READ BY FREADDIR *>> |
| <<***********************************************>> |
| PRINT(OUTPUT,-72,0); |
| <<**********************************>> |
| <<* GO BACK TO GET ANOTHER RECORD *>> |
| <<**********************************>> |
| GO TO L1; |
| END; |
____________________________________________________________________________
Figure 4-10. FREADDIR Example (continued)
_____________________________________________________________________
| |
| Output from Program Execution: |
| |
| RECORD# = 4 |
| CARDIN RICK 578-7018 11100 WOLFE ROAD CUPERTINO CA. 94053 |
| RECORD# = 3 |
| ECKSTEIN LEO 287-5137 5303 STEVENS CREEK SANTA CLARA CA. 95050|
| RECORD# = 2 |
| HOSODA JOE 227-8214 1180 SAINT PETER CT. LOS ALTOS CA. 94022 |
| RECORD# = 1 |
| NOLAN JACK 923-4975 967 REED AVE. SUNNYVALE CA. 94087 |
| RECORD# = 5 |
| PASBY LINDA 295-1187 TOWN & CNTRY VILLAGE SAN JOSE CA. 94102 |
| RECORD# = 7 |
| ROBERT GERRY 259-5535 12345 TELEGRAPH AVE. BERKELEY CA. 90871 |
| RECORD# = 6 |
| SEELY HENRY 293-4220 1144 LEBERTY ST. EL CERRITO CA. 94053 |
| RECORD# = 8 |
| TURNEWR IVAN 984-8498 22905 EMERSON ST. OAKLAND CA. 98234 |
| RECORD# = 10 |
| WESTER ELDER 287-4598 1256 KINGFISHER ST. SUNNYVALE CA. 43098 |
| RECORD# = 9 |
| WHITE GORDON 398-0301 4350 ASHBY AVE. BERKELEY CA. 91234 |
| |
| END OF PROGRAM |
_____________________________________________________________________
Figure 4-10. FREADDIR Example (continued)