Re: Efficient writable character buffers in Java
- From: "Matt Humphrey" <matth@xxxxxxxxxxxxxx>
- Date: Fri, 30 Jun 2006 13:15:52 -0400
<yay_frogs@xxxxxxxxx> wrote in message
news:1151685824.501525.319580@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
My problem: I need to create a buffer that needs a capacity sufficient
to hold a row of 80 characters that will be written out to a file, then
modified, then written out to a file again. In C, this could be done
like:
char linebuf[81];
/* code to insert chars in linebuf; as an example: */
linebuf[0] = 'H';
linebuf[1] = 'i';
linebuf[2] = 0; /* null char to terminate string */
/* write the line */
printf("%s\n", linebuf); // "Hi" is written out followed by a
newline.
/* modify line buffer again; no need to allocate/delete memory */
linebuf[0] = 'Y';
linebuf[1] = 'o';
linebuf[2] = '!';
linebuf[3] = 0;
/* write the line */
printf("%s\n", linebuf); // "Yo!" is written out followed by a
newline.
Now my problem is that in Java, I can't figure out how to do this
without allocating new objects. If a use a StringBuffer/StringBuilder
that has a length of 80 characters, there doesn't seem to be a way to
efficiently print only the number of characters that the current row
actually has. (The setLength method creates a new object.) If I use a
char[] in Java then the output routines ignore the terminating null
byte.
I'll skip the standard warning against premature optimization because you
seem determined that allocating memory is implicitly inefficient. A key
problem with null-terminated strings, of course, is that you have to keep
iterating to find the end.
What's wrong with
char [] buffer = new char [81];
// Fill out the buffer
writer.write (buffer, 0, lastIndexWritten + 1);
OR
writer.write (buffer, 0, positionOfZero(buffer) + 1);
You either already know the length in advance and simply use it when writing
data or you have a little iterator utility function that figures out where
the zero is. Or just wrap the ordinary write (char) in a loop that stops
after the zero.
Cheers,
Matt Humphrey matth@xxxxxxxxxxxxxx http://www.iviz.com/
.
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- Efficient writable character buffers in Java
- From: yay_frogs
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