FREAD/FREADSTR

[John Gillen]

Prior to converting a dBASE application, I need to confirm that the FREAD or FREADSTR function can be configured to read a string from a file and stop at CR/LF or \n. This is a critical need for the application, as it reads through large text files separated into paragraphs with CR/LF or \n.

Reading x number of characters will not work as the number will, of course, vary by paragraph.

Any thoughts on this will help.

Thanks,

John

[Pete]

Hello,

On Tuesday, 23 August 2022 at 08:54:32 UTC+3 johna...@gmail.com wrote:

Any thoughts on this will help.

If what you want to do is to read your text files line-by-line and process each one (or some) of those lines,
then you could look at and utilize other than FREAD** functions, more appropriate for the purpose.
In any case, to get useful  suggestions, I think you must supply more details about the task
(it'd be good also to be more specific about the "largeness" of the text files in question).

regards,
Pete



 

 

[AL67]

Maybe use HBMISC  library.

SAMPLE1:

***********************

#require "hbmisc"
#include "fileio.ch"
PROCEDURE Main( cFile )
   hb_default( @cFile, __FILE__ )
   // open a text file here
   IF hb_FUse( cFile, FO_READ ) > 1
      DO WHILE ! hb_FAtEof()
         ? "line " + Str( hb_FRecNo(), 2 ) + " " + hb_FReadLn()
         hb_FSkip( 1 )
      ENDDO
      ?
      my_goto( 18 )
      my_goto( 2 )
      hb_FGoBottom()
      ?
      ? "after hb_FGoBottom() now in line # " + hb_ntos( hb_FRecNo() )
      hb_FGoTop()
      ?
      ? "after hb_FGoTop() now in line # " + hb_ntos( hb_FRecNo() )
      ?
      ? "hb_FLastRec() = " + hb_ntos( hb_FLastRec() )
      // close the file
      hb_FUse()
   ENDIF
   RETURN

STATIC PROCEDURE my_goto( n_go )
   hb_FGoto( n_go )
   ?
   ? "after hb_FGoto( " + hb_ntos( n_go ) + " )"
   ? "line " + hb_ntos( hb_FRecNo() ) + " is " + LTrim( hb_FReadLn() )
   RETURN

***************************************

SAMPLE2:

*******************

#require "hbmisc"
PROCEDURE Main( cFile )
   LOCAL oFile := TFileRead():New( cFile )
   oFile:Open()
   IF oFile:Error()
      ? oFile:ErrorMsg( "FileRead:" )
   ELSE
      DO WHILE oFile:MoreToRead()
         ? oFile:ReadLine()
      ENDDO
      oFile:Close()
   ENDIF
   RETURN

*****************

Adam

[d s]

You can try this:

*
#define CRLF CHR(13)+CHR(10)
*
FUNCTION ReadCsv ()  // reading Csv file
*
LOCAL i
LOCAL cLine,nHandle,cFile
*
cFile:="somefile.csv"
IF ! FILE(cFile)
   RETURN (.F.)
ENDIF
*
nHandle:=FOPEN(cFile)
IF nHandle == -1
   RETURN (.F.)
ENDIF
*
i:=0
DO WHILE GreadR1(@cLine,nHandle)
   i++
   IF i==1   // if you have and do not need first header line
      LOOP
   ENDIF
   *
   * now you have line data in cLine
   * do what you want with cLine from somefile.csv
   *
   * get next line in loop
ENDDO
FCLOSE(nHandle)
*
RETURN (.T.)
*
*EOF-----------------------------------------------------------------

*
FUNCTION GreadR1(cstring, nhandle)
*
LOCAL ret_val := .T.
LOCAL buffer,ptr,bytes
LOCAL bufsize := 4000
LOCAL tempstring
*
cstring := []
buffer := SPACE(bufsize)
*
DO WHILE .T.
   bytes := FREAD(nhandle, @buffer, bufsize)
   tempstring := LEFT(buffer, bytes)
   IF ( ptr := AT(CRLF, tempstring) ) > 0
      cstring:=cstring+SUBSTR(tempstring, 1, ptr - 1)
      FSEEK(nhandle, -(bytes - (ptr + 1)), FS_RELATIVE)
      EXIT
   ELSE
      cstring:=cstring+tempstring
      IF bytes < bufsize
         ret_val := .F.
         EXIT
      ENDIF
   ENDIF
ENDDO
*
RETURN ret_val
*
*--------------------------------------------------GreadR1-----------
*

 Best Regards,

Simo.

[Bob Burns]

Hi John

When I have had to work with programming languages that did not have a "read line" function I have written a low level routine to read in x characters at a time, build a temporary string and look for the CR/LF end of line marker in order to terminate the string building process for each line. Not too difficult to achieve but does add a time overhead as string handling can be quite slow.

Clipper's FREADSTR function reads in a specified number of characters up to a maximum of 65535 from which you can extract / build each line of text.

If you cannot find a satisfactory solution take a look at:

https://github.com/vszakats/hb/blob/096e855/contrib/hbmisc/fileread.prg#L17

Regards

Bob

Bob F Burns G3OOU, G-QRP 6907, @BobFBurns
Crystal Palace Radio & Electronics Club: https://cprec.chessck.co.uk/
Admin/sales site: http://www.g3oou.co.uk/
Technical site: www.qsl.net/g3oou

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[Auge & Ohr]

hi

how big is you File to read ?

i do use MEMOREAD(), MLCOUNT() and MEMOLINE().

if your File is > 2 GB than you need a "special Reader"

Jimmy

[Bernard Mouille]

* FREADLINE.ch - Lecture d'une ligne d'un fichier binaire.
* --------------------------------------------------------
*
*  Function: GFReadLine()
*  Author:   Greg Lief
*  Copyright (c) 1990 Grumpfish, Inc. - All Rights Reserved
*
*  Purpose:  Read in the next string from the text file
*            (i.e., up to the next CR/LF combo)
*
*  Syntax:   GFReadLine(@<string>, <handle>)
*
*  Parameters:  <string> is the character variable which will
*               will hold the string.  NOTE: this must be
*               passed by reference (preceded by a "@")!!
*
*               <handle> is the file handle to read the string
*               from.  This would have been returned from either
*               FOPEN() or FCREATE().
*
*  Returns:  Logical value: .T. if successful, .F. if EOF()
*
* Le 5 février 2012, j'ai modifié pour la mettre sans warning.
*
*******************************************
FUNCTION FREADLINE( mstring, handle, nFin )
*******************************************
*
LOCAL ptr
LOCAL bytes
LOCAL tempstring
LOCAL bufsize := 255
LOCAL buffer  := SPACE( bufsize )
LOCAL crlf    := CHR( 13 ) + CHR( 10 )
LOCAL ret_val := .T.
LOCAL nFinSeek := 1
*
mstring := []
*
IF nFin <> NIL          && Fichier avec fin de ligne LF
 crlf := CHR( 10 )
 nFinSeek := 0
ENDIF
*
DO WHILE .T.
 bytes      := FREAD( handle, @buffer, bufsize )
 tempstring := LEFT( buffer, bytes )
 ptr        := AT( crlf, tempstring )
 *
 IF ptr > 0
  mstring := mstring + substr( tempstring, 1, ptr - 1 )
  fseek( handle, -( bytes - ( ptr + nFinSeek ) ), 1 )
  EXIT
 ELSE
  mstring := mstring + tempstring
  **

  IF bytes < bufsize
   ret_val := .F.
    EXIT
  ENDIF

  **
 ENDIF
 *
ENDDO
*
RETURN ret_val

Regards,

Bernard.