scalaz-stream的膨胀的用法示例

Question

In the following usage example of scalaz-stream (taken from the documentation ), what do I need to change if the input and/or output is a gzipped file? In other words, how do I use compress ?

import scalaz.stream._
import scalaz.concurrent.Task

val converter: Task[Unit] =
  io.linesR("testdata/fahrenheit.txt")
    .filter(s => !s.trim.isEmpty && !s.startsWith("//"))
    .map(line => fahrenheitToCelsius(line.toDouble).toString)
    .intersperse("\n")
    .pipe(text.utf8Encode)
    .to(io.fileChunkW("testdata/celsius.txt"))
    .run

// at the end of the universe...
val u: Unit = converter.run

Answer 1

Compressing the output is easy. Since compress.deflate() is a Process1[ByteVector, ByteVector] you need to plug it into your pipeline where you are emitting ByteVector s (that is right after text.utf8Encode which is a Process1[String, ByteVector] ):

val converter: Task[Unit] =
  io.linesR("testdata/fahrenheit.txt")
    .filter(s => !s.trim.isEmpty && !s.startsWith("//"))
    .map(line => fahrenheitToCelsius(line.toDouble).toString)
    .intersperse("\n")
    .pipe(text.utf8Encode)
    .pipe(compress.deflate())
    .to(io.fileChunkW("testdata/celsius.zip"))
    .run

For inflate you can't use io.linesR to read the compressed file. You need a process that produces ByteVector s instead of String s in order to pipe them into inflate . (You could use io.fileChunkR for that.) The next step would be decoding the uncompressed data to String s (with text.utf8Decode for example) and then using text.lines() to emit the text line by line. Something like this should do the trick:

val converter: Task[Unit] =
  Process.constant(4096).toSource
    .through(io.fileChunkR("testdata/fahrenheit.zip"))
    .pipe(compress.inflate())
    .pipe(text.utf8Decode)
    .pipe(text.lines())
    .filter(s => !s.trim.isEmpty && !s.startsWith("//"))
    .map(line => fahrenheitToCelsius(line.toDouble).toString)
    .intersperse("\n")
    .pipe(text.utf8Encode)
    .to(io.fileChunkW("testdata/celsius.txt"))
    .run