BIN MEMO continued

Figure 1. Structure of Database Flies Used by BINMEMO.PRG.

Program BINMEMO operates on an arbitrary database file specified at

runtime by the user, storing binary disk files into its memo fields or

reiiieving them from its memo fieids and writing theni back to disk.

SYS.DBF and MEMOLIST.DBF are used by BINMEMO internally. In

between runs of the program, MEMOLIST.DBF is stored in a SYS.DBF

memo field named ML_DBF.

BINMEMO Is Based on

can be found in the FoxPro Help file, or

in Tom Rettig’s help file. For my part, I

the FoxPro Low-Level File

got simply copied the small code ex-

Functions

amples for these functions from Tom

The basic technique is not at all corn-

Rettig’s TRHELP file, and started twid-

pLicated. It employs the FoxPro low-level

dli. BINMEMO.PRG evolved as a

file functions. To create a disk file, you

housing around these functions.

use FCREATE ( ) to enable reading from

or writing to a file that already exists, use

How to Use BINMEMO

FOPENO. FREAD() and FWRITE()

perform the actual reads and writes. The

The operation of the program is as

syntax of their use is straightforward, and

follows: first, the user indicates what

database file has

the memo fields

s/he wants to work

Introduction to xBase Programming

with. FoxPro

makes it real easy to

Dialect-independent “hands-on” instruction in dBase

do this. The single

language programming for those wanting to work in Fox-

statement

base, FoxPro, dBase III +, dBase IV, Clipper, or other

USE?

“xBase” dialects,

takes care of it!

Next you tell the

Call for more information!

program whether

Greg Dunn Associates

you want to store a

file into a memo, or

(213) 371-6035

retrieve one from a

memo and write it

to disk. Note that I’ve included, just for

educational purposes, two different ways

to implement the little menu you choose

from; one is disarmed with comment

asterisks.

I’ve implemented a pop-up menu at

the GETwhere you indicate which memo

field in the tile you want to use. This

popup, displayed by way of an ON KEY

LABEL statement, presents the user

with a list of all the MEMO fields and

only the MEMO fields — in the database

s/he opened. Procedures PICKMEMO

and PICKMEMO2 build the memo field

list in MEMOLIST.DBF, the little

database file we keep tucked away in

SYS.DBF.2

The user selects the record s/he wants

to work with from a BROWSE window.

If s/he needs to add a record into the

database s/he can do it from that same

BROWSE window by pressing Ctrl-N. If

s/he wants to delete unwanted records,

Ctrl-T will take care of it. It would, of

course, be easy to assign more elegant

keys to these operations; I’ve stuck with

those native to FoxPro.

I’ve also thrown two other procedures

of interest into the soup. Function

YesNo displays buttons for the end user

at any binary branching point, returning a

"Y" or “N” depending on which button the

user “pushes”. You pass YesNo() a

numeric parameter to define the default

anwer.

Procedure ERRMSG allows you to

specify a message of arbitrary length, line-

by-line in an array. It then displays this

message, centered and giving you some

control over its placement, using the

MODIFY MEMO command with the

NOEDIT qualifier so the message can’t

be changed. (Come to think of it, the user

might enjoy being able to rewrite your

error message!)

Whenever we get a user group library

I’ll put the routines and other associated

files used with BINMEMO.PRG in it.

Meanwhile I’ll bring a few copies on disk

to the August meeting.

Enjoy!

2 You may note that I am ‘unpack-

ing: MEMOLIST.DBF at the beginning

of program BINMEMO, and deleting it

only at termination of the program. In

a networked application in a situation

requiring better security, you could un-

pack sensitive files only at the moment

of actual need, deleting them from the

disk immediately after use.

4

LA. FOX