Re: In need of something like RandomAccessFile.read(char[] cAr, int off, int len)

From:
lbrtchx@gmail.com
Newsgroups:
comp.lang.java.programmer
Date:
Fri, 14 Mar 2008 16:35:44 -0700 (PDT)
Message-ID:
<f36fbb2d-f31b-411e-8586-6abb2bc142f8@t54g2000hsg.googlegroups.com>

... are these files written with a Java program?

~
 No necessarily. They are mostly texts downloaded from the Internet
~

... If there were an InputStream

~
 option as an argument to a RandomAccessFile ctor then things were
easier, but I think, and I may be wrong, that there is a fundamental
problem here.
~
 InputStreams and RandomAccessFiles should not be mixed because when
you go:
~
 RandomAccessFiles.seek((long) lThere)
~
 you can not be absolutely sure that:
~
 1) you will land at the start of a byte sequence conforming a
character,
~
 2) belonging to the encoding you specified in the InputStream
~
 3) at, ... where actually? lThere? the API says:
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 http://java.sun.com/j2se/1.5.0/docs/api/java/io/RandomAccessFile.html#seek(long)
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<API>
 seek: public void seek(long pos) throws IOException
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 Sets the file-pointer offset, measured from the beginning of this
file, at which the next read or write occurs. The offset may be set
beyond the end of the file. Setting the offset beyond the end of the
file does not change the file length. The file length will change only
by writing after the offset has been set beyond the end of the file.
 Parameters: pos - the offset position, measured in bytes from the
beginning of the file, at which to set the file pointer.
 Throws: IOException - if pos is less than 0 or if an I/O error
occurs.
</API>
~
 The unclear bit is "measured from the beginning of this file" how
exactly is it measured? Why not simply saying in "bytes"?
~
 I think that java should let the programmer do something like what I
illustrate with a piece of pseudo code below
~
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
// __
  int iChrsRd, iChrBfrSz = 4096;
  char[] cChrAr = new char[iChrBfrSz];
  RandomAccessFile RAxFl;
  String aEnc = ...; // "UTF8", "ISO-8859-1", "" or whatever encoding
your text are written in
// __
  try{
   FileInputStream FIS = new FileInputStream(IFl);
   InputStreamReader ISRdr = new InputStreamReader(FIS, aEnc);
   RAxFl = new RandomAccessFile(ISRdr);
// . . .
   RAxFl.seek(lThere);
   iChrsRd = RAxFl.read(cChrAr, 0, iChrBfrSz); // reading iChrsRd into
cChrAr provided iChrBfrSz can fully take them
// . . .
   RAxFl.close();
  }catch(FileNotFoundException FlNtFX){ FlNtFX.printStackTrace(); }
    catch(IOException IOX){ IOX.printStackTrace(); }
// __
  finally{
   if(RAxFl != null){ try{ RAxFl.close(); }catch(IOException IOXcptn)
{ ; }}
  }
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
~
 Dealing with Java's I/O and internationalization is not exactly easy
~
 lbrtchx

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