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Fix #5014: Implement java.io.BufferedWriter #5015

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Fix #5014: Implement java.io.BufferedWriter #5015

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26c47eb
Fix #5014: Implement java.io.BufferedWriter
ThijsBroersen Aug 16, 2024
9227086
feedback changes, todo: add more tests
ThijsBroersen Aug 18, 2024
00ce90d
fix write and extend tests
ThijsBroersen Aug 18, 2024
5030b9b
mimic jvm error scenarios
ThijsBroersen Aug 21, 2024
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77 changes: 77 additions & 0 deletions javalib/src/main/scala/java/io/BufferedWriter.scala
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Original file line number Diff line number Diff line change
@@ -0,0 +1,77 @@
// Ported from Scala-native

/*
* Scala.js (https://www.scala-js.org/)
*
* Copyright EPFL.
*
* Licensed under Apache License 2.0
* (https://www.apache.org/licenses/LICENSE-2.0).
*
* See the NOTICE file distributed with this work for
* additional information regarding copyright ownership.
*/

package java.io

class BufferedWriter(out: Writer, sz: Int) extends Writer {

if (sz <= 0) throw new IllegalArgumentException("Buffer size <= 0")

def this(out: Writer) = this(out, 4096)

private[this] val buffer: Array[Char] = new Array[Char](sz)
private[this] var pos: Int = 0
private[this] var closed: Boolean = false

def close(): Unit = if (!closed) {
flush()
out.close()
closed = true
}

def flush(): Unit = {
ensureOpen()
if (pos > 0) {
out.write(buffer, 0, pos)
out.flush()
pos = 0
}
}

def newLine(): Unit =
write(System.lineSeparator())

override def write(c: Int): Unit = {
buffer.update(pos, c.toChar)
pos += 1
if (pos == sz)
flush()
}

override def write(s: String, off: Int, len: Int): Unit =
write(s.toCharArray, off, len)

def write(cbuf: Array[Char], off: Int, len: Int): Unit = {
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From the JDK doc:

If the requested length is at least as large as the buffer, however, then this method will flush the buffer and write the characters directly to the underlying stream.

IIUC this behavior isn't implemented.

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I reimplemented the method

ensureOpen()

val cbufLength = cbuf.length
if (off < 0 || off + len > cbufLength)
throw new IndexOutOfBoundsException(s"Range [${off}, ${off + len}) out of bounds for length $cbufLength")

if (len > 0 && off + len > 0) {
val available = sz - pos
if (available > len) {
System.arraycopy(cbuf, off, buffer, pos, len)
pos += len
} else {
flush()
out.write(cbuf, off, len)
out.flush()
}
}
}

private def ensureOpen(): Unit =
if (closed) throw new IOException("Stream closed")
}
126 changes: 126 additions & 0 deletions test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/io/BufferedWriterTest.scala
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// Ported from Scala-native

/*
* Scala.js (https://www.scala-js.org/)
*
* Copyright EPFL.
*
* Licensed under Apache License 2.0
* (https://www.apache.org/licenses/LICENSE-2.0).
*
* See the NOTICE file distributed with this work for
* additional information regarding copyright ownership.
*/

package org.scalajs.testsuite.javalib.io

import java.io._

import org.junit.Ignore
import org.junit.Test
import org.junit.Assert._

import org.scalajs.testsuite.utils.AssertThrows.assertThrows

class BufferedWriterTest {
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We'll probably have to add more tests, notably (probably not a complete list, sorry):

  • operations on closed writers throw
  • index out of bounds use cases
  • corner cases pointed out in the implementation review (notably flushing behavior)
  • writing to a buffered writer multiple times (with different buffer boundary conditions).

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I have added more test cases.


@Test def creatingBufferedWriterWithBufferSizeZeroThrowsException(): Unit = {
val writer = new OutputStreamWriter(new ByteArrayOutputStream)
assertThrows(
classOf[IllegalArgumentException],
new BufferedWriter(writer, -1)
)
}

@Test def canWriteSmallChunksToBufferedWriter(): Unit = {
val stringWriter = new StringWriter()
val writer = new BufferedWriter(stringWriter)
val string = "Hello, world!"
writer.write(string)
assertTrue(stringWriter.toString == "")
writer.flush()
assertTrue(stringWriter.toString == string)
}

@Test def canWriteChunkLargerThanBufferSizeToBufferedWriter(): Unit = {
val stringWriter = new StringWriter()
val writer = new BufferedWriter(stringWriter, 1)
val string = "Hello, world!"
writer.write(string)
assertTrue(stringWriter.toString == string)
writer.flush()
assertTrue(stringWriter.toString == string)
}

@Test def canWriteInMultiplePartsToBufferedWriter(): Unit = {
val stringWriter = new StringWriter()
val writer = new BufferedWriter(stringWriter, 5)
writer.write("Hello,")
assertTrue(stringWriter.toString == "Hello,")
writer.write(" ")
assertTrue(stringWriter.toString == "Hello,")
writer.flush()
assertTrue(stringWriter.toString == "Hello, ")
writer.write("w")
assertTrue(stringWriter.toString == "Hello, ")
writer.write("orld!")
assertTrue(stringWriter.toString == "Hello, world!")
}

@Test def writeNegativeLengthWritesNothing(): Unit = {
val stringWriter = new StringWriter()
val writer = new BufferedWriter(stringWriter)
val string = "Hello, world!"
writer.write(string, 0, -1)
writer.flush()
assertTrue(stringWriter.toString == "")
}

@Ignore @Test def writeNegativeLengthThrowsIndexOutOfBound(): Unit = {
val stringWriter = new StringWriter()
val writer = new BufferedWriter(stringWriter)
val string = "Hello, world!"
assertThrows(classOf[IndexOutOfBoundsException], writer.write(string, 0, -1))
}

@Ignore @Test def writeNegativeOffsetPlusLengthWritesNothing(): Unit = {
val stringWriter = new StringWriter()
val writer = new BufferedWriter(stringWriter)
val string = "Hello, world!"
writer.write(string, -2, 1)
writer.flush()
assertTrue(stringWriter.toString == "")
}

@Test def writeNegativeOffsetPlusLengthThrowsIndexOutOfBound(): Unit = {
val stringWriter = new StringWriter()
val writer = new BufferedWriter(stringWriter)
val string = "Hello, world!"
assertThrows(classOf[IndexOutOfBoundsException], writer.write(string, -2, 1))
}

@Test def closedWritersThrow(): Unit = {
val stream = new ByteArrayOutputStream
val writer = new BufferedWriter(new OutputStreamWriter(stream))
writer.close()
assertThrows(classOf[IOException], writer.write("Hello, world!"))
}

@Test def closingTwiceIsHarmless(): Unit = {
val stream = new ByteArrayOutputStream
val writer = new BufferedWriter(new OutputStreamWriter(stream))
writer.close()
writer.close()
}

@Test def canWriteNewLineSeparator(): Unit = {
val stringWriter = new StringWriter()
val writer = new BufferedWriter(stringWriter)
writer.write("Hello")
writer.newLine()
writer.write("world!")
writer.flush()
val expectedResult = "Hello" + System.lineSeparator() + "world!"
assertTrue(stringWriter.toString == expectedResult)
}
}