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package java.io
import scala.annotation.tailrec
import java.nio._
import java.nio.charset._
class InputStreamReader(private[this] var in: InputStream,
private[this] var decoder: CharsetDecoder) extends Reader {
private[this] var closed: Boolean = false
/** Buffer in which to read bytes from the underlying input stream.
*
* Class invariant: contains bytes already read from `in` but not yet
* decoded.
*/
private[this] var inBuf: ByteBuffer = ByteBuffer.allocate(4096)
inBuf.limit(0)
/** Tells whether the end of the underlying input stream has been reached.
* Class invariant: if true, then `in.read()` has returned -1.
*/
private[this] var endOfInput: Boolean = false
/** Buffer in which to decode bytes into chars.
* Usually, it is not used, because we try to decode directly to the
* destination array. So as long as we do not really need one, we share
* an empty buffer.
*
* Class invariant: contains chars already decoded but not yet *read* by
* the user of this instance.
*/
private[this] var outBuf: CharBuffer = InputStreamReader.CommonEmptyCharBuffer
def this(in: InputStream, charset: Charset) =
this(in,
charset.newDecoder
.onMalformedInput(CodingErrorAction.REPLACE)
.onUnmappableCharacter(CodingErrorAction.REPLACE))
def this(in: InputStream) =
this(in, Charset.defaultCharset)
def this(in: InputStream, charsetName: String) =
this(in, Charset.forName(charsetName))
def close(): Unit = {
closed = true
in = null
decoder = null
inBuf = null
outBuf = null
}
def getEncoding(): String =
if (closed) null else decoder.charset.name
override def read(): Int = {
ensureOpen()
if (outBuf.hasRemaining) outBuf.get()
else super.read()
}
def read(cbuf: Array[Char], off: Int, len: Int): Int = {
ensureOpen()
if (off < 0 || len < 0 || len > cbuf.length - off)
throw new IndexOutOfBoundsException
if (len == 0) 0
else if (outBuf.hasRemaining) {
// Reuse chars decoded last time
val available = Math.min(outBuf.remaining, len)
outBuf.get(cbuf, off, available)
available
} else {
// Try and decode directly into the destination array
val directOut = CharBuffer.wrap(cbuf, off, len)
val result = readImpl(directOut)
if (result != InputStreamReader.Overflow) {
result
} else {
/* There's not enough space in the destination array to receive even
* a tiny bit of output from the decoder. We need to decode to the
* outBuf instead.
* This happens typically when the next code point to decode is a
* supplementary character, and the given `len` is 1.
*/
readMoreThroughOutBuf(cbuf, off, len)
}
}
}
// In a separate method because this is (hopefully) not a common case
private def readMoreThroughOutBuf(cbuf: Array[Char], off: Int, len: Int): Int = {
// Return outBuf to its full capacity
outBuf.limit(outBuf.capacity)
outBuf.position(0)
@tailrec // but not inline, this is not a common path
def loopWithOutBuf(desiredOutBufSize: Int): Int = {
if (outBuf.capacity < desiredOutBufSize)
outBuf = CharBuffer.allocate(desiredOutBufSize)
val charsRead = readImpl(outBuf)
if (charsRead == InputStreamReader.Overflow)
loopWithOutBuf(desiredOutBufSize*2)
else
charsRead
}
val charsRead = loopWithOutBuf(2*len)
assert(charsRead != 0) // can be -1, though
outBuf.flip()
if (charsRead == -1) -1
else {
val available = Math.min(charsRead, len)
outBuf.get(cbuf, off, available)
available
}
}
@tailrec
private def readImpl(out: CharBuffer): Int = {
val initPos = out.position
val result = decoder.decode(inBuf, out, endOfInput)
if (out.position != initPos) {
/* Good, we made progress, so we can return.
* Note that the `result` does not matter. Whether it's an underflow,
* an overflow, or even an error, if we read *something*, we can return
* that.
* The next invocation of read() will cause a new invocation of decode(),
* which will necessarily return the same result (but without advancing
* at all), which will cause one of the following cases to be handled.
*/
out.position - initPos
} else if (result.isUnderflow) {
if (endOfInput) {
assert(!inBuf.hasRemaining,
"CharsetDecoder.decode() should not have returned UNDERFLOW when "+
"both endOfInput and inBuf.hasRemaining are true. It should have "+
"returned a MalformedInput error instead.")
// Flush
if (decoder.flush(out).isOverflow)
InputStreamReader.Overflow
else {
// Done
if (out.position == initPos) -1
else out.position - initPos
}
} else {
// We need to read more from the underlying input stream
if (inBuf.limit == inBuf.capacity) {
inBuf.compact()
if (!inBuf.hasRemaining) {
throw new AssertionError(
"Scala.js implementation restriction: " +
inBuf.capacity + " bytes do not seem to be enough for " +
getEncoding + " to decode a single code point. " +
"Please report this as a bug.")
}
inBuf.limit(inBuf.position)
inBuf.position(0)
}
/* Note that this stores the new data after the limit of the buffer.
* Further, note that we may read more bytes than strictly necessary,
* according to the specification of InputStreamReader.
*/
val bytesRead =
in.read(inBuf.array, inBuf.limit, inBuf.capacity - inBuf.limit)
if (bytesRead == -1)
endOfInput = true
else
inBuf.limit(inBuf.limit + bytesRead)
readImpl(out)
}
} else if (result.isOverflow) {
InputStreamReader.Overflow
} else {
result.throwException()
throw new AssertionError("should not get here")
}
}
/* In theory, `in.available() > 0` is incorrect. We should return true only
* if there are enough bytes available to read at least one code point.
* However, this is how the JDK behaves, and even the JavaDoc suggests this
* is the expected behavior.
*/
override def ready(): Boolean =
outBuf.hasRemaining || in.available() > 0
private def ensureOpen(): Unit = {
if (closed)
throw new IOException("Stream closed")
}
}
object InputStreamReader {
private final val Overflow = -2
/** Empty CharBuffer shared by all InputStreamReaders as long as they do
* not really need one.
* Since we do not use `mark()`, it is fine to share them, because `mark()`
* is the only piece of mutable state for an empty buffer. Everything else
* is effectively immutable (e.g., position and limit must always be 0).
*/
private val CommonEmptyCharBuffer = CharBuffer.allocate(0)
}
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