Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!sdd.hp.com!uakari.primate.wisc.edu!aplcen!haven!adm!news
From: CDCKAB%EMUVM1.BITNET@cunyvm.cuny.edu ( Karl Brendel)
Newsgroups: comp.lang.pascal
Subject: (R)Blockread/write problem
Message-ID: <24336@adm.BRL.MIL>
Date: 29 Aug 90 16:49:50 GMT
Sender: news@adm.BRL.MIL
Lines: 41


In article <9008290754.aa22853@VIM.BRL.MIL>, Edwin Groothuis
<S89405079%HSEPM1.HSE.NL> writes

>  assign(fil1,'FILE.1');reset(fil1);    {Sourcefile}
>  assign(fil2,'TEMP');rewrite(fil2);    {Targetfile}
>  repeat
>    blockread(fil1,buffer,bufsize,recsread);
>    blockwrite(fil2,buffer,recsread);
>    writeln(recsread:5,' blocks written.');
>  until recsread=0;

>1. When I run this program, I don't get the whole file copied (I miss
>   several bytes).
>
>   FILE.1  TEMP   missing bytes:
>   7056    7040    16

Carefully read the procedure BlockRead documentation in the RefGuide.
The "result" variable (your recsread) returns the number of _complete_
"records" written. Since you opened the file with the default record
size of 128 bytes, the final bytes (filesize mod 128) are not being
written. "...a possible last partial record is not included in result."

As suggested by others, open the file with a record size of 1. Your file
I/O speed will not be affected.

>2. When I reset a read-only file, why does TurboPascal then say that it
>   is impossible to open the file<>

Refer to the FileMode variable documentation in the RefGuide. Altho
sometimes a nuisance, this behavior is not a bug, is well-documented,
and is easily dealt with.

+-------------------------------------------------------------------------+
| Karl Brendel                                Centers for Disease Control |
| phone 404/639-2709                          Epidemiology Program Office |
| fts       236-2709                          Atlanta, GA                 |
|                                                                         |
|                        Home of Epi Info 5.0                             |
+-------------------------------------------------------------------------+