gzip-sample.scala

import java.io._
import java.util.zip._

val pi = new PipedInputStream        
val po = new PipedOutputStream(pi)
val zo = new GZIPOutputStream(po)
val zi = new GZIPInputStream(pi)
val w  = new PrintWriter(zo)
val r  = new BufferedReader(new InputStreamReader(zi))

pw.println("Hello, world.")
pw.close

println(r.readLine)

gzip.scala

import java.io._
import java.util.zip._

/** Gzcat
 */
object gzcat extends App {
  private val buf = new Array[Byte](1024)

  try {
    for (path <- args) {
      try {
	var in = new GZIPInputStream(new FileInputStream(path))
	var n = in.read(buf)
	while (n >= 0) {
	  System.out.write(buf, 0, n)
	  n = in.read(buf)
	}
      }
      catch {
	case _:FileNotFoundException =>
	  System.err.printf("File Not Found: %s", path)
	case _:SecurityException =>
	  System.err.printf("Permission Denied: %s", path)
      }
    }
  }
  finally {
    System.out.flush
  }
}


/** gzip
 */
object gzip {

  def gzip(path: String) {
    val src = new File(path)
    val dst = new File(path ++ ".gz")
    val buf = new Array[Byte](1024)

    try {
      val in  = new BufferedInputStream(new FileInputStream(src))
      try {
	val out = new GZIPOutputStream(new FileOutputStream(dst))
	try {
	  var n = in.read(buf)
	  while (n >= 0) {
	    out.write(buf, 0, n)
	    n = in.read(buf)
	  }
	}
	finally {
	  out.flush
	}
      } catch {
	case _:FileNotFoundException =>
	  System.err.printf("Permission Denied: %s", path ++ ".gz")
	case _:SecurityException =>
	  System.err.printf("Permission Denied: %s", path ++ ".gz")
      }
    } catch {
      case _: FileNotFoundException =>
	System.err.printf("File Not Found: %s", path)
      case _: SecurityException =>
	System.err.printf("Permission Denied: %s", path)
    }
  }

  def main(filenames: Array[String]) {
    if (filenames.length == 0) {
      System.err.println("Usage: scala gzip file...")
      System.exit(1)
    }
    else {
      filenames.foreach(gzip(_))
    }
  }
}


object gunzip {
  private val buf = new Array[Byte](1024)

  /**
   * gunzip
   *
   * @param PATH: the path name without the extentson ".gz"
   *   You have to check if there is no file named as PATH
   * before you invode this method, or the file is going
   * to be overwritten.
   */
  def gunzip(path: String) {
    val src = new File(path ++ ".gz")
    val dst = new File(path)

    try {
      val in  = new GZIPInputStream(new FileInputStream(src))
      try {
	val out = new BufferedOutputStream(new FileOutputStream(dst))
	try {
	  var n = in.read(buf)
	  while (n >= 0) {
	    out.write(buf, 0, n)
	    n = in.read(buf)
	  }
	}
	finally {
	  out.flush
	}
      } catch {
	case _:FileNotFoundException =>
	  System.err.printf("Permission Denied: %s", path)
	case _:SecurityException =>
	  System.err.printf("Permission Denied: %s", path)
      }
    } catch {
      case _: FileNotFoundException =>
	System.err.printf("File Not Found: %s", path ++ ".gz")
      case _: SecurityException =>
	System.err.printf("Permission Denied: %s", path ++ ".gz")
    }
  }

  def main(filenames: Array[String]) {
    if (filenames.length == 0) {
      System.err.println("Usage: scala gunzip gz-file...")
      System.exit(1)
    }
    else {
      val eitherNames = 
	for (name <- filenames)
	  yield if (name.endsWith(".gz")) {
		    val noExtension = name.drop(3)
		    val src = new File(name)
		    val dst = new File(noExtension)
		    if (! src.exists)
		      Left(new FileNotFoundException(name))
		    else if (dst.exists)
		      Left(new IOException("file already exists: " + noExtension))
		    else
		      Right(noExtension)
	        } else {
		  Left(new IOException("file is not gzip: " + name))
		}
      if (eitherNames.forall {_.isRight}) {
	for (Right(noExt) <- eitherNames) {
	  gunzip(noExt)
	}
      }
      else {
	for (Left(e) <- eitherNames)
	  throw e
      }
    }
  }
}