IO流小问题 - 黑马程序员技术交流社区

public class StreamEncoder extends Writer
{
private static final int DEFAULT_BYTE_BUFFER_SIZE = 8192;
private volatile boolean isOpen = true;
private void ensureOpen() throws IOException {
if (!isOpen)
throw new IOException("Stream closed");
}
public static StreamEncoder forOutputStreamWriter(OutputStream out,
Object lock,
String charsetName)
throws UnsupportedEncodingException
{
String csn = charsetName;
if (csn == null)
csn = Charset.defaultCharset().name();
try {
if (Charset.isSupported(csn))
return new StreamEncoder(out, lock, Charset.forName(csn));
} catch (IllegalCharsetNameException x) { }
throw new UnsupportedEncodingException (csn);
}
public static StreamEncoder forOutputStreamWriter(OutputStream out,
Object lock,
Charset cs)
{
return new StreamEncoder(out, lock, cs);
}
public static StreamEncoder forOutputStreamWriter(OutputStream out,
Object lock,
CharsetEncoder enc)
{
return new StreamEncoder(out, lock, enc);
}
public static StreamEncoder forEncoder(WritableByteChannel ch,
CharsetEncoder enc,
int minBufferCap)
{
return new StreamEncoder(ch, enc, minBufferCap);
}
public String getEncoding() {
if (isOpen())
return encodingName();
return null;
}
public void flushBuffer() throws IOException {
synchronized (lock) {
if (isOpen())
implFlushBuffer();
else
throw new IOException("Stream closed");
}
}
public void write(int c) throws IOException {
char cbuf[] = new char[1];
cbuf[0] = (char) c;
write(cbuf, 0, 1);
}
public void write(char cbuf[], int off, int len) throws IOException {
synchronized (lock) {
ensureOpen();
if ((off < 0) || (off > cbuf.length) || (len < 0) ||
((off + len) > cbuf.length) || ((off + len) < 0)) {
throw new IndexOutOfBoundsException();
} else if (len == 0) {
return;
}
implWrite(cbuf, off, len);
}
}
public void write(String str, int off, int len) throws IOException {
/* Check the len before creating a char buffer */
if (len < 0)
throw new IndexOutOfBoundsException();
char cbuf[] = new char[len];
str.getChars(off, off + len, cbuf, 0);
write(cbuf, 0, len);
}
public void flush() throws IOException {
synchronized (lock) {
ensureOpen();
implFlush();
}
}
public void close() throws IOException {
synchronized (lock) {
if (!isOpen)
return;
implClose();
isOpen = false;
}
}
private boolean isOpen() {
return isOpen;
}
private Charset cs;
private CharsetEncoder encoder;
private ByteBuffer bb;
private final OutputStream out;
private WritableByteChannel ch;
private boolean haveLeftoverChar = false;
private char leftoverChar;
private CharBuffer lcb = null;
private StreamEncoder(OutputStream out, Object lock, Charset cs) {
this(out, lock,
cs.newEncoder()
.onMalformedInput(CodingErrorAction.REPLACE)
.onUnmappableCharacter(CodingErrorAction.REPLACE));
}
private StreamEncoder(OutputStream out, Object lock, CharsetEncoder enc) {
super(lock);
this.out = out;
this.ch = null;
this.cs = enc.charset();
this.encoder = enc;
// This path disabled until direct buffers are faster
if (false && out instanceof FileOutputStream) {
ch = ((FileOutputStream)out).getChannel();
if (ch != null)
bb = ByteBuffer.allocateDirect(DEFAULT_BYTE_BUFFER_SIZE);
}
if (ch == null) {
bb = ByteBuffer.allocate(DEFAULT_BYTE_BUFFER_SIZE);
}
}
private StreamEncoder(WritableByteChannel ch, CharsetEncoder enc, int mbc) {
this.out = null;
this.ch = ch;
this.cs = enc.charset();
this.encoder = enc;
this.bb = ByteBuffer.allocate(mbc < 0
? DEFAULT_BYTE_BUFFER_SIZE
: mbc);
}
private void writeBytes() throws IOException {
bb.flip();
int lim = bb.limit();
int pos = bb.position();
assert (pos <= lim);
int rem = (pos <= lim ? lim - pos : 0);
if (rem > 0) {
if (ch != null) {
if (ch.write(bb) != rem)
assert false : rem;
} else {
out.write(bb.array(), bb.arrayOffset() + pos, rem);
}
}
bb.clear();
}
private void flushLeftoverChar(CharBuffer cb, boolean endOfInput)
throws IOException
{
if (!haveLeftoverChar && !endOfInput)
return;
if (lcb == null)
lcb = CharBuffer.allocate(2);
else
lcb.clear();
if (haveLeftoverChar)
lcb.put(leftoverChar);
if ((cb != null) && cb.hasRemaining())
lcb.put(cb.get());
lcb.flip();
while (lcb.hasRemaining() || endOfInput) {
CoderResult cr = encoder.encode(lcb, bb, endOfInput);
if (cr.isUnderflow()) {
if (lcb.hasRemaining()) {
leftoverChar = lcb.get();
if (cb != null && cb.hasRemaining())
flushLeftoverChar(cb, endOfInput);
return;
}
break;
}
if (cr.isOverflow()) {
assert bb.position() > 0;
writeBytes();
continue;
}
cr.throwException();
}
haveLeftoverChar = false;
}
void implWrite(char cbuf[], int off, int len)
throws IOException
{
CharBuffer cb = CharBuffer.wrap(cbuf, off, len);
if (haveLeftoverChar)
flushLeftoverChar(cb, false);
while (cb.hasRemaining()) {
CoderResult cr = encoder.encode(cb, bb, false);/
if (cr.isUnderflow()) {
assert (cb.remaining() <= 1) : cb.remaining();、
if (cb.remaining() == 1) {
haveLeftoverChar = true;
leftoverChar = cb.get();
}
break;
}
if (cr.isOverflow()) {
assert bb.position() > 0;
writeBytes();
continue;
}
cr.throwException();
}
void implFlushBuffer() throws IOException {
if (bb.position() > 0)
writeBytes();
}
void implFlush() throws IOException {
implFlushBuffer();
if (out != null)
out.flush();}
void implClose() throws IOException {
flushLeftoverChar(null, true);
try {
for (;;) {
CoderResult cr = encoder.flush(bb);
if (cr.isUnderflow())
break;
if (cr.isOverflow()) {
assert bb.position() > 0;
writeBytes();
continue;
}
cr.throwException();
}
if (bb.position() > 0)
writeBytes();
if (ch != null)
ch.close();
else
out.close();
} catch (IOException x) {
encoder.reset();
throw x;
}
}
String encodingName() {
return ((cs instanceof HistoricallyNamedCharset)
? ((HistoricallyNamedCharset)cs).historicalName()
: cs.name());
}
}
这是StreamEncoder源码

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