export sub openfile(filename$, recordlength, numberoffields)
// specify the record(block) length and number of fields for the file
// returns the filehandle number used for other subs
static numfiles
x=open(filename$, "a")
if x=0 return 0 // error opening the file
close x
numfiles=numfiles+1
dim f$(numfiles,50,2) // f$(numfile,1-50=fieldname$
dim f(numfiles,52)
f$(numfiles,0,0)=filename$
f(numfiles,51)=recordlength
f(numfiles,52)=numberoffields

return numfiles
end sub


export sub Field( filehandle,fieldnumber, fieldname$, fieldlength)
//specify the field name and length for the field numbered fieldnumber
if fieldnumber <= f(filehandle,52) then
f$(filehandle,fieldnumber,0)=fieldname$
f(filehandle,fieldnumber)=fieldlength
f$(filehandle,fieldnumber,1)=blank$(f(filehandle,fieldnumber))
return 1
endif
return 0
end sub



export sub lset(filehandle,fieldname$,data$)
//sets data$ on the left end of the field, truncates the string if it is longer than the fieldlength
//use this to prepare the record for writing

l=len(data$)
x=0
for x=1 to 50

b$=f$(filehandle,x,0)
if (b$ = fieldname$) then
	lf=f(filehandle,x)
	dt$=data$
	
	if( l > lf )dt$=left$(dt$,lf)
	a$=blank$(lf-l)
	if l<lf dt$=dt$+a$

f$(filehandle,x,1) = dt$

end if

next


end sub

export sub rset(filehandle,fieldname$,data$)
//sets data$ on the right end of the field, truncates the string if it is longer than the fieldlength
//use this to prepare the record for writing

l=len(data$)
x=0
for x=1 to 50

b$=f$(filehandle,x,0)
if (b$ = fieldname$) then
	lf=f(filehandle,x)
	dt$=data$
	
	if( l > lf )dt$=left$(dt$,lf)
	
	a$=blank$(lf-l)
	if l<lf dt$=a$+dt$

f$(filehandle,x,1) = dt$

end if

next




end sub

export sub readfield$(File, fieldname$)
//returns the data held in fieldname$
local x
for x=1 to 50
	if f$(File,x,0)=fieldname$ then
	
	return f$(File,x,1)
end if
next

end sub

export sub write_block(recordnumber, filehandle)
// Writes all the fields to the file at this record location
// Uses seek recordnumber*recordlength before the write
// Clears the field data
// Recordnumbers start at 0. ie the first record is 0, the second is 1 etc.

filename$=f$(filehandle,0,0)
x=open(filename$, "r+")
if x=0 print "error":return 0 // error opening the file
if recordnumber = -1 then
	seek x, 0, "end" // append data to the file
else
	seek x, ((f(filehandle,51) +1) * (recordnumber))
endif
printstring$=""
for y=1 to f(filehandle,52)
	printstring$=printstring$+f$(filehandle,y,1)
next
l=len(printstring$)
for y=1 to l
	a$=left$(printstring$,1)
	printstring$=right$(printstring$,len(printstring$)-1)
	poke x, a$
next
poke x ,"\n"
for y=1 to f(filehandle,52)
	f$(filehandle,y,1)=blank$(f(filehandle,y))
next
close x
end sub

export sub read_block(recordnumber, filehandle)
// Reads the data at this record, or the next record if recordnumber is -1
// Ffills the fields with the data
// Recordnumbers start at 0. ie the first record is 0, the second is 1 etc.
static rec
File=open(filename$, "rb")
if File=0 print "error":return -1 // error opening the file
if (recordnumber <> -1) then
rec = recordnumber
seek File, ((f(filehandle,51) +1) * (rec))
endif
a$=""
for z=1 to f(filehandle,51)
y=peek(File)
a$=a$+chr$(y) 
next

for y=0 to f(filehandle,52)
	f$(filehandle,y,1)= left$(a$,f(filehandle,y))
	a$=right$(a$,len(a$)-f(filehandle,y))
next
rec=rec+1
return rec
end sub

export sub lof(filehandle)  // alias for numberofrecords()
local x
filename$=f$(filehandle,0,0)
x=open(filename$) 
seek #x, 0, "end"
ret=tell(#x)
if ret=0 return ret

ret= ret/(f(filehandle,51)+1)
ret=int(ret)
return ret
end sub

export sub numberofrecords(filehandle) // alias for lof()
fh=filehandle
rtn=lof(fh)
return rtn
end sub




sub blank$(num)
local s$
local x
s$=""
for x=1 to num
s$=s$+" "
next
return s$ 
end sub