/*

  * Copyright (c) 1996, 2011, Oracle and/or its affiliates. All rights reserved.

  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

  *

  * This code is free software; you can redistribute it and/or modify it

  * under the terms of the GNU General Public License version 2 only, as

  * published by the Free Software Foundation.  Oracle designates this

  * particular file as subject to the "Classpath" exception as provided

  * by Oracle in the LICENSE file that accompanied this code.

  *

  * This code is distributed in the hope that it will be useful, but WITHOUT

  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

  * version 2 for more details (a copy is included in the LICENSE file that

  * accompanied this code).

  *

  * You should have received a copy of the GNU General Public License version

  * 2 along with this work; if not, write to the Free Software Foundation,

  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

  *

  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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  */

 package java.io;

 /**

  * 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       JDK1.1

  */

 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 sz is <= 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 (<tt>0x00-0xffff</tt>), 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

      */

     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'), or a carriage return

      * followed immediately by a linefeed.

      *

      * @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

      *

      * @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'), or a carriage return

      * followed immediately by a linefeed.

      *

      * @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

      *

      * @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 readAheadLimit is < 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;

             in.close();

             in = null;

             cb = null;

         }

     }

 }