Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.sys.acorn.programmer > #2007

Re: Reading text files with cr / lf line terminators

Show all headers | View raw

In article <mpro.m8dugr003qcq900zk.vinceh@softrock.co.uk>,
   Vince M Hudd <vinceh@softrock.co.uk> wrote:
> Vince M Hudd <vinceh@softrock.co.uk> wrote:
> > Dave Stratford <daves@orpheusmail.co.uk> wrote:

> [...]

> > I don't think you'll be able to get the terminator from the actual line
> > returned by GET$, but you should be able to read it from the file, so you
> > could probably do something like:

> Typical, you post, and it isn't until you read your own post when you think
> "D'oh!"

> Why bother checking the line ending on every line? Why not just check the
> line ending (and that of the previous line) when a blank line is
> encountered?

> ----8<----
> REM Your line to read a line from the file
> line$ = GET$#file%

> REM [re]initialise validblank% every time

> REM If it's blank, check if it's validly so
> IF line$ = "" THEN validblank% = FN_IsItReallyBlank(file%)


> REM rest of your code, and somewhere, this function
> DEF FN_IsItReallyBlank(handle%)
> LOCAL oldterm%, newterm%

> REM Go back two bytes in the file
> PTR#handle% = (PTR#handle%)-2

> REM Read those two bytes as the old terminator and new terminator
> oldterm%=BGET#Handle%
> newterm%=BGET#Handle%

> REM Compare them, return TRUE if they're the same, FALSE if not
> IF oldterm%=newterm% THEN =TRUE ELSE =FALSE
> ----8<----

> The outcome is the same - you have a variable, validblank% containing TRUE
> if a blank line is a valid one, FALSE if it's the result of a mixed
> terminator. The advantage is far fewer additional byte reads from the file
> when the file only has single line terminators.

> (Again, untested in the usual tradition of usenet, etc)

By itself this doesn't work, as it wouldn't catch validly empty blank
lines with a PC/DOS style CRLF line terminator, but with a small tweak it
worked fine:

=== 8< ===

DEF FN_CheckBlank(handle%)
LOCAL oldterm%, newterm%, prev1%, prev2%, curr1%, curr2%

REM Go back two bytes in the file
PTR#handle% = (PTR#handle%)-2

REM Read those two bytes as the old terminator and new terminator
oldterm%=BGET#handle%
newterm%=BGET#handle%

IF (oldterm%=10 AND newterm%=13) OR (oldterm%=13 AND newterm%=10) THEN
REM here we have a cr/lf terminator, so go back another two characters to
see if they too were a cr/lf terminator for a pc/dos style end of line.
PTR#handle% = (PTR#handle%)-4

  prev1%=BGET#handle%
  prev2%=BGET#handle%
  curr1%=BGET#handle%
  curr2%=BGET#handle%

  IF prev1% = curr1% AND prev2% = curr2% THEN =TRUE ELSE =FALSE
ELSE
  IF oldterm%=newterm% THEN =TRUE ELSE =FALSE
ENDIF

=== 8< ===

Many thanks,

Dave


-- 
    _                     _________________________________________
   / \._._ |_  _     _  /'       Orpheus Internet Services
   \_/| |_)| |(/_|_|_> /          'Internet for Everyone'
_______ | ___________./       http://www.orpheusinternet.co.uk

Back to comp.sys.acorn.programmer | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

Reading text files with cr / lf line terminators Dave Stratford <daves@orpheusmail.co.uk> - 2012-08-07 09:05 +0100
  Re: Reading text files with cr / lf line terminators Vince M Hudd <vinceh@softrock.co.uk> - 2012-08-07 12:11 +0100
    Re: Reading text files with cr / lf line terminators Vince M Hudd <vinceh@softrock.co.uk> - 2012-08-07 12:26 +0100
      Re: Reading text files with cr / lf line terminators Dave Stratford <daves@orpheusmail.co.uk> - 2012-08-07 14:52 +0100
  Re: Reading text files with cr / lf line terminators Ron <beeb@woosh.co.nz> - 2012-08-07 23:35 +1200
    Re: Reading text files with cr / lf line terminators Alan Adams <alan@adamshome.org.uk> - 2012-08-07 14:21 +0100
      Re: Reading text files with cr / lf line terminators Jeremy Nicoll - news posts <jn.nntp.scrap007@wingsandbeaks.org.uk> - 2012-08-07 15:09 +0100
      Re: Reading text files with cr / lf line terminators Ron <beeb@woosh.co.nz> - 2012-08-08 03:01 +1200
        Re: Reading text files with cr / lf line terminators Ron <beeb@woosh.co.nz> - 2012-08-08 04:13 +1200
  Re: Reading text files with cr / lf line terminators Jeremy Nicoll - news posts <jn.nntp.scrap007@wingsandbeaks.org.uk> - 2012-08-07 15:20 +0100
  Re: Reading text files with cr / lf line terminators jgh@arcade.demon.co.uk (Jonathan Graham Harston) - 2012-08-08 22:41 +0100

csiph-web