java.nio.BufferUnderflowException when processing files in Scala

Question

I got a similar problem to this guy while processing 4MB log file. Actually I'm processing multiple files simultaneously but since I keep getting this exception, I decide to just test it for a single file:

val temp = Source.fromFile("./datasource/input.txt")
val dummy = new PrintWriter("test.txt")
var itr = 0
println("Default Buffer size: " + Source.DefaultBufSize)
try {
    for( chr <- temp) {
        dummy.print(chr.toChar)
        itr += 1
        if(itr == 75703) println("Passed line 85")
        if(itr % 256 == 0){ print("..." + itr); temp.reset; System.gc; }
        if(itr == 75703) println("Passed line 87")
        if(itr % 2048 == 0) println("")
        if(itr == 75703) println("Passed line 89")
    }
} finally {
    println("\nFalied at itr = " + itr)
}

What I always get is that it will fails at itr = 75703, while my output file will always be 64KB (65536 Bytes exact). No matter where I put temp.reset or System.gc, all experiments ends up the same.

It seems like the problem relies on some memory allocation but I cannot find any useful information on this problem. Any idea on how to solve this one?

All your helps are greatly appreciated

EDIT: Actually I want to process it as binary files, so this technique is not a good solution, many had recommend me to use BufferedInputStream instead.

Answer 1

Why are you calling reset on the Source before it has finished iterating thru the file?

val temp = Source.fromFile("./datasource/input.txt")
try {
  for (line <- tem p.getLines) {
    //whatever
  }
finally temp.reset

Should work just fine with no underflows. See also this question