file io - Buffered RandomAccessFile java

Question

RandomAccessFile is quite slow for random access to a file. You often read about implementing a buffered layer over it, but code doing this isn't possible to find online.

So my question is: would you guys who know any opensource implementation of this class share a pointer or share your own implementation?

It would be nice if this question would turn out as a collection of useful links and code about this problem, which I'm sure, is shared by many and never addressed properly by SUN.

Please, no reference to MemoryMapping, as files can be way bigger than Integer.MAX_VALUE.

Answer 1

You can make a BufferedInputStream from a RandomAccessFile with code like,

 RandomAccessFile raf = ...
 FileInputStream fis = new FileInputStream(raf.getFD());
 BufferedInputStream bis = new BufferedInputStream(fis);

Some things to note

1. Closing the FileInputStream will close the RandomAccessFile and vice versa
2. The RandomAccessFile and FileInputStream point to the same position, so reading from the FileInputStream will advance the file pointer for the RandomAccessFile, and vice versa

Probably the way you want to use this would be something like,

RandomAccessFile raf = ...
FileInputStream fis = new FileInputStream(raf.getFD());
BufferedInputStream bis = new BufferedInputStream(fis);

//do some reads with buffer
bis.read(...);
bis.read(...);

//seek to a a different section of the file, so discard the previous buffer
raf.seek(...);
bis = new BufferedInputStream(fis);
bis.read(...);
bis.read(...);