/*
 * Copyright (c) 1996, 2017, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
 *
 *
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 */

package java.io;


import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.Spliterator;
import java.util.Spliterators;
import java.util.stream.Stream;
import java.util.stream.StreamSupport;

/**
 * Reads text from a character-input stream, buffering characters so as to
 * provide for the efficient reading of characters, arrays, and lines.
 *
 * <p> The buffer size may be specified, or the default size may be used. The
 * default is large enough for most purposes.
 *
 * <p> In general, each read request made of a Reader causes a corresponding
 * read request to be made of the underlying character or byte stream. It is
 * therefore advisable to wrap a BufferedReader around any Reader whose read()
 * operations may be costly, such as FileReaders and InputStreamReaders. For
 * example,
 *
 * <pre>
 * BufferedReader in
 * = new BufferedReader(new FileReader("foo.in"));
 * </pre>
 *
 * will buffer the input from the specified file. Without buffering, each
 * invocation of read() or readLine() could cause bytes to be read from the
 * file, converted into characters, and then returned, which can be very
 * inefficient.
 *
 * <p> Programs that use DataInputStreams for textual input can be localized by
 * replacing each DataInputStream with an appropriate BufferedReader.
 *
 * @see FileReader
 * @see InputStreamReader
 * @see java.nio.file.Files#newBufferedReader
 *
 * @author Mark Reinhold
 * @since 1.1
 */

public class BufferedReader extends Reader {

 private Reader in;

 private char cb[];
 private int nChars, nextChar;

 private static final int INVALIDATED = -2;
 private static final int UNMARKED = -1;
 private int markedChar = UNMARKED;
 private int readAheadLimit = 0; /* Valid only when markedChar > 0 */

 /** If the next character is a line feed, skip it */
 private boolean skipLF = false;

 /** The skipLF flag when the mark was set */
 private boolean markedSkipLF = false;

 private static int defaultCharBufferSize = 8192;
 private static int defaultExpectedLineLength = 80;

 /**
 * Creates a buffering character-input stream that uses an input buffer of
 * the specified size.
 *
 * @param in A Reader
 * @param sz Input-buffer size
 *
 * @exception IllegalArgumentException If {@code sz <= 0}
 */
 public BufferedReader(Reader in, int sz) {
 super(in);
 if (sz <= 0)
 throw new IllegalArgumentException("Buffer size <= 0");
 this.in = in;
 cb = new char[sz];
 nextChar = nChars = 0;
 }

 /**
 * Creates a buffering character-input stream that uses a default-sized
 * input buffer.
 *
 * @param in A Reader
 */
 public BufferedReader(Reader in) {
 this(in, defaultCharBufferSize);
 }

 /** Checks to make sure that the stream has not been closed */
 private void ensureOpen() throws IOException {
 if (in == null)
 throw new IOException("Stream closed");
 }

 /**
 * Fills the input buffer, taking the mark into account if it is valid.
 */
 private void fill() throws IOException {
 int dst;
 if (markedChar <= UNMARKED) {
 /* No mark */
 dst = 0;
 } else {
 /* Marked */
 int delta = nextChar - markedChar;
 if (delta >= readAheadLimit) {
 /* Gone past read-ahead limit: Invalidate mark */
 markedChar = INVALIDATED;
 readAheadLimit = 0;
 dst = 0;
 } else {
 if (readAheadLimit <= cb.length) {
 /* Shuffle in the current buffer */
 System.arraycopy(cb, markedChar, cb, 0, delta);
 markedChar = 0;
 dst = delta;
 } else {
 /* Reallocate buffer to accommodate read-ahead limit */
 char ncb[] = new char[readAheadLimit];
 System.arraycopy(cb, markedChar, ncb, 0, delta);
 cb = ncb;
 markedChar = 0;
 dst = delta;
 }
 nextChar = nChars = delta;
 }
 }

 int n;
 do {
 n = in.read(cb, dst, cb.length - dst);
 } while (n == 0);
 if (n > 0) {
 nChars = dst + n;
 nextChar = dst;
 }
 }

 /**
 * Reads a single character.
 *
 * @return The character read, as an integer in the range
 * 0 to 65535 ({@code 0x00-0xffff}), or -1 if the
 * end of the stream has been reached
 * @exception IOException If an I/O error occurs
 */
 public int read() throws IOException {
 synchronized (lock) {
 ensureOpen();
 for (;;) {
 if (nextChar >= nChars) {
 fill();
 if (nextChar >= nChars)
 return -1;
 }
 if (skipLF) {
 skipLF = false;
 if (cb[nextChar] == '\n') {
 nextChar++;
 continue;
 }
 }
 return cb[nextChar++];
 }
 }
 }

 /**
 * Reads characters into a portion of an array, reading from the underlying
 * stream if necessary.
 */
 private int read1(char[] cbuf, int off, int len) throws IOException {
 if (nextChar >= nChars) {
 /* If the requested length is at least as large as the buffer, and
 if there is no mark/reset activity, and if line feeds are not
 being skipped, do not bother to copy the characters into the
 local buffer. In this way buffered streams will cascade
 harmlessly. */
 if (len >= cb.length && markedChar <= UNMARKED && !skipLF) {
 return in.read(cbuf, off, len);
 }
 fill();
 }
 if (nextChar >= nChars) return -1;
 if (skipLF) {
 skipLF = false;
 if (cb[nextChar] == '\n') {
 nextChar++;
 if (nextChar >= nChars)
 fill();
 if (nextChar >= nChars)
 return -1;
 }
 }
 int n = Math.min(len, nChars - nextChar);
 System.arraycopy(cb, nextChar, cbuf, off, n);
 nextChar += n;
 return n;
 }

 /**
 * Reads characters into a portion of an array.
 *
 * <p> This method implements the general contract of the corresponding
 * <code>{@link Reader#read(char[], int, int) read}</code> method of the
 * <code>{@link Reader}</code> class. As an additional convenience, it
 * attempts to read as many characters as possible by repeatedly invoking
 * the <code>read</code> method of the underlying stream. This iterated
 * <code>read</code> continues until one of the following conditions becomes
 * true: <ul>
 *
 * <li> The specified number of characters have been read,
 *
 * <li> The <code>read</code> method of the underlying stream returns
 * <code>-1</code>, indicating end-of-file, or
 *
 * <li> The <code>ready</code> method of the underlying stream
 * returns <code>false</code>, indicating that further input requests
 * would block.
 *
 * </ul> If the first <code>read</code> on the underlying stream returns
 * <code>-1</code> to indicate end-of-file then this method returns
 * <code>-1</code>. Otherwise this method returns the number of characters
 * actually read.
 *
 * <p> Subclasses of this class are encouraged, but not required, to
 * attempt to read as many characters as possible in the same fashion.
 *
 * <p> Ordinarily this method takes characters from this stream's character
 * buffer, filling it from the underlying stream as necessary. If,
 * however, the buffer is empty, the mark is not valid, and the requested
 * length is at least as large as the buffer, then this method will read
 * characters directly from the underlying stream into the given array.
 * Thus redundant <code>BufferedReader</code>s will not copy data
 * unnecessarily.
 *
 * @param cbuf Destination buffer
 * @param off Offset at which to start storing characters
 * @param len Maximum number of characters to read
 *
 * @return The number of characters read, or -1 if the end of the
 * stream has been reached
 *
 * @exception IOException If an I/O error occurs
 * @exception IndexOutOfBoundsException {@inheritDoc}
 */
 public int read(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 0;
 }

 int n = read1(cbuf, off, len);
 if (n <= 0) return n;
 while ((n < len) && in.ready()) {
 int n1 = read1(cbuf, off + n, len - n);
 if (n1 <= 0) break;
 n += n1;
 }
 return n;
 }
 }

 /**
 * Reads a line of text. A line is considered to be terminated by any one
 * of a line feed ('\n'), a carriage return ('\r'), a carriage return
 * followed immediately by a line feed, or by reaching the end-of-file
 * (EOF).
 *
 * @param ignoreLF If true, the next '\n' will be skipped
 *
 * @return A String containing the contents of the line, not including
 * any line-termination characters, or null if the end of the
 * stream has been reached without reading any characters
 *
 * @see java.io.LineNumberReader#readLine()
 *
 * @exception IOException If an I/O error occurs
 */
 String readLine(boolean ignoreLF) throws IOException {
 StringBuffer s = null;
 int startChar;

 synchronized (lock) {
 ensureOpen();
 boolean omitLF = ignoreLF || skipLF;

 bufferLoop:
 for (;;) {

 if (nextChar >= nChars)
 fill();
 if (nextChar >= nChars) { /* EOF */
 if (s != null && s.length() > 0)
 return s.toString();
 else
 return null;
 }
 boolean eol = false;
 char c = 0;
 int i;

 /* Skip a leftover '\n', if necessary */
 if (omitLF && (cb[nextChar] == '\n'))
 nextChar++;
 skipLF = false;
 omitLF = false;

 charLoop:
 for (i = nextChar; i < nChars; i++) {
 c = cb[i];
 if ((c == '\n') || (c == '\r')) {
 eol = true;
 break charLoop;
 }
 }

 startChar = nextChar;
 nextChar = i;

 if (eol) {
 String str;
 if (s == null) {
 str = new String(cb, startChar, i - startChar);
 } else {
 s.append(cb, startChar, i - startChar);
 str = s.toString();
 }
 nextChar++;
 if (c == '\r') {
 skipLF = true;
 }
 return str;
 }

 if (s == null)
 s = new StringBuffer(defaultExpectedLineLength);
 s.append(cb, startChar, i - startChar);
 }
 }
 }

 /**
 * Reads a line of text. A line is considered to be terminated by any one
 * of a line feed ('\n'), a carriage return ('\r'), a carriage return
 * followed immediately by a line feed, or by reaching the end-of-file
 * (EOF).
 *
 * @return A String containing the contents of the line, not including
 * any line-termination characters, or null if the end of the
 * stream has been reached without reading any characters
 *
 * @exception IOException If an I/O error occurs
 *
 * @see java.nio.file.Files#readAllLines
 */
 public String readLine() throws IOException {
 return readLine(false);
 }

 /**
 * Skips characters.
 *
 * @param n The number of characters to skip
 *
 * @return The number of characters actually skipped
 *
 * @exception IllegalArgumentException If <code>n</code> is negative.
 * @exception IOException If an I/O error occurs
 */
 public long skip(long n) throws IOException {
 if (n < 0L) {
 throw new IllegalArgumentException("skip value is negative");
 }
 synchronized (lock) {
 ensureOpen();
 long r = n;
 while (r > 0) {
 if (nextChar >= nChars)
 fill();
 if (nextChar >= nChars) /* EOF */
 break;
 if (skipLF) {
 skipLF = false;
 if (cb[nextChar] == '\n') {
 nextChar++;
 }
 }
 long d = nChars - nextChar;
 if (r <= d) {
 nextChar += r;
 r = 0;
 break;
 }
 else {
 r -= d;
 nextChar = nChars;
 }
 }
 return n - r;
 }
 }

 /**
 * Tells whether this stream is ready to be read. A buffered character
 * stream is ready if the buffer is not empty, or if the underlying
 * character stream is ready.
 *
 * @exception IOException If an I/O error occurs
 */
 public boolean ready() throws IOException {
 synchronized (lock) {
 ensureOpen();

 /*
 * If newline needs to be skipped and the next char to be read
 * is a newline character, then just skip it right away.
 */
 if (skipLF) {
 /* Note that in.ready() will return true if and only if the next
 * read on the stream will not block.
 */
 if (nextChar >= nChars && in.ready()) {
 fill();
 }
 if (nextChar < nChars) {
 if (cb[nextChar] == '\n')
 nextChar++;
 skipLF = false;
 }
 }
 return (nextChar < nChars) || in.ready();
 }
 }

 /**
 * Tells whether this stream supports the mark() operation, which it does.
 */
 public boolean markSupported() {
 return true;
 }

 /**
 * Marks the present position in the stream. Subsequent calls to reset()
 * will attempt to reposition the stream to this point.
 *
 * @param readAheadLimit Limit on the number of characters that may be
 * read while still preserving the mark. An attempt
 * to reset the stream after reading characters
 * up to this limit or beyond may fail.
 * A limit value larger than the size of the input
 * buffer will cause a new buffer to be allocated
 * whose size is no smaller than limit.
 * Therefore large values should be used with care.
 *
 * @exception IllegalArgumentException If {@code readAheadLimit < 0}
 * @exception IOException If an I/O error occurs
 */
 public void mark(int readAheadLimit) throws IOException {
 if (readAheadLimit < 0) {
 throw new IllegalArgumentException("Read-ahead limit < 0");
 }
 synchronized (lock) {
 ensureOpen();
 this.readAheadLimit = readAheadLimit;
 markedChar = nextChar;
 markedSkipLF = skipLF;
 }
 }

 /**
 * Resets the stream to the most recent mark.
 *
 * @exception IOException If the stream has never been marked,
 * or if the mark has been invalidated
 */
 public void reset() throws IOException {
 synchronized (lock) {
 ensureOpen();
 if (markedChar < 0)
 throw new IOException((markedChar == INVALIDATED)
 ? "Mark invalid"
 : "Stream not marked");
 nextChar = markedChar;
 skipLF = markedSkipLF;
 }
 }

 public void close() throws IOException {
 synchronized (lock) {
 if (in == null)
 return;
 try {
 in.close();
 } finally {
 in = null;
 cb = null;
 }
 }
 }

 /**
 * Returns a {@code Stream}, the elements of which are lines read from
 * this {@code BufferedReader}. The {@link Stream} is lazily populated,
 * i.e., read only occurs during the
 * <a href="../util/stream/package-summary.html#StreamOps">terminal
 * stream operation</a>.
 *
 * <p> The reader must not be operated on during the execution of the
 * terminal stream operation. Otherwise, the result of the terminal stream
 * operation is undefined.
 *
 * <p> After execution of the terminal stream operation there are no
 * guarantees that the reader will be at a specific position from which to
 * read the next character or line.
 *
 * <p> If an {@link IOException} is thrown when accessing the underlying
 * {@code BufferedReader}, it is wrapped in an {@link
 * UncheckedIOException} which will be thrown from the {@code Stream}
 * method that caused the read to take place. This method will return a
 * Stream if invoked on a BufferedReader that is closed. Any operation on
 * that stream that requires reading from the BufferedReader after it is
 * closed, will cause an UncheckedIOException to be thrown.
 *
 * @return a {@code Stream<String>} providing the lines of text
 * described by this {@code BufferedReader}
 *
 * @since 1.8
 */
 public Stream<String> lines() {
 Iterator<String> iter = new Iterator<>() {
 String nextLine = null;

 @Override
 public boolean hasNext() {
 if (nextLine != null) {
 return true;
 } else {
 try {
 nextLine = readLine();
 return (nextLine != null);
 } catch (IOException e) {
 throw new UncheckedIOException(e);
 }
 }
 }

 @Override
 public String next() {
 if (nextLine != null || hasNext()) {
 String line = nextLine;
 nextLine = null;
 return line;
 } else {
 throw new NoSuchElementException();
 }
 }
 };
 return StreamSupport.stream(Spliterators.spliteratorUnknownSize(
 iter, Spliterator.ORDERED | Spliterator.NONNULL), false);
 }
}