Java/File Input Output/Char Reader Writer
Версия от 18:01, 31 мая 2010; (обсуждение)
Содержание
Char Array IO
import java.io.CharArrayReader;
import java.io.CharArrayWriter;
import java.io.IOException;
public class CharArrayIOApp {
public static void main(String args[]) throws IOException {
CharArrayWriter outStream = new CharArrayWriter();
String s = "This is a test.";
for (int i = 0; i < s.length(); ++i)
outStream.write(s.charAt(i));
System.out.println("outstream: " + outStream);
System.out.println("size: " + outStream.size());
CharArrayReader inStream;
inStream = new CharArrayReader(outStream.toCharArray());
int ch = 0;
StringBuffer sb = new StringBuffer("");
while ((ch = inStream.read()) != -1)
sb.append((char) ch);
s = sb.toString();
System.out.println(s.length() + " characters were read");
System.out.println("They are: " + s);
}
}
Demonstrate CharArrayWriter.
import java.io.CharArrayWriter;
import java.io.FileWriter;
import java.io.IOException;
class CharArrayWriterDemo {
public static void main(String args[]) throws IOException {
CharArrayWriter f = new CharArrayWriter();
String s = "This should end up in the array";
char buf[] = new char[s.length()];
s.getChars(0, s.length(), buf, 0);
f.write(buf);
System.out.println(f.toString());
char c[] = f.toCharArray();
for (int i = 0; i < c.length; i++) {
System.out.print(c[i]);
}
FileWriter f2 = new FileWriter("test.txt");
f.writeTo(f2);
f2.close();
f.reset();
for (int i = 0; i < 3; i++)
f.write("X");
}
}
Safe UTF: 64K serialized size
/*
* JBoss, Home of Professional Open Source
* Copyright 2005, JBoss Inc., and individual contributors as indicated
* by the @authors tag. See the copyright.txt in the distribution for a
* full listing of individual contributors.
*
* This is free software; you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License as
* published by the Free Software Foundation; either version 2.1 of
* the License, or (at your option) any later version.
*
* This software 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this software; if not, write to the Free
* Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
* 02110-1301 USA, or see the FSF site: http://www.fsf.org.
*/
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
/**
*
* A SafeUTF
*
* @author
* @version $Revision: 1174 $
*
* $Id: SafeUTF.java 1174 2006-08-02 14:14:32Z timfox $
*
* There is a "bug" in JDK1.4 / 1.5 DataOutputStream.writeUTF()
* which means it does not work with Strings >= 64K serialized size.
* See http://bugs.sun.ru/bugdatabase/view_bug.do?bug_id=4806007
*
* We work around this by chunking larger strings into smaller pieces.
*
* Note we only support TextMessage and ObjectMessage bodies with serialized length >= 64K
* We DO NOT support Strings written to BytesMessages or StreamMessages or written as keys or values
* in MapMessages, or as String properties or other String fields having serialized length >= 64K
* This is for performance reasons since there is an overhead in coping with large
* Strings
*
*/
public class SafeUTF
{
//Default is 16K chunks
private static final int CHUNK_SIZE = 16 * 1024;
private static final byte NULL = 0;
private static final byte NOT_NULL = 1;
public static SafeUTF instance = new SafeUTF(CHUNK_SIZE);
private int chunkSize;
private int lastReadBufferSize;
public int getLastReadBufferSize()
{
return lastReadBufferSize;
}
public SafeUTF(int chunkSize)
{
this.chunkSize = chunkSize;
}
public void safeWriteUTF(DataOutputStream out, String str) throws IOException
{
if (str == null)
{
out.writeByte(NULL);
}
else
{
int len = str.length();
short numChunks;
if (len == 0)
{
numChunks = 0;
}
else
{
numChunks = (short)(((len - 1) / chunkSize) + 1);
}
out.writeByte(NOT_NULL);
out.writeShort(numChunks);
int i = 0;
while (len > 0)
{
int beginCopy = i * chunkSize;
int endCopy = len <= chunkSize ? beginCopy + len : beginCopy + chunkSize;
String theChunk = str.substring(beginCopy, endCopy);
out.writeUTF(theChunk);
len -= chunkSize;
i++;
}
}
}
public String safeReadUTF(DataInputStream in) throws IOException
{
boolean isNull = in.readByte() == NULL;
if (isNull)
{
return null;
}
short numChunks = in.readShort();
int bufferSize = chunkSize * numChunks;
// special handling for single chunk
if (numChunks == 1)
{
// The text size is likely to be much smaller than the chunkSize
// so set bufferSize to the min of the input stream available
// and the maximum buffer size. Since the input stream
// available() can be <= 0 we check for that and default to
// a small msg size of 256 bytes.
int inSize = in.available();
if (inSize <= 0)
{
inSize = 256;
}
bufferSize = Math.min(inSize, bufferSize);
lastReadBufferSize = bufferSize;
}
StringBuffer buff = new StringBuffer(bufferSize);
for (int i = 0; i < numChunks; i++)
{
String s = in.readUTF();
buff.append(s);
}
return buff.toString();
}
}
uses a pair of CharArrayReaders
import java.io.CharArrayReader;
import java.io.IOException;
public class CharArrayReaderDemo {
public static void main(String args[]) throws IOException {
String tmp = "abcdefghijklmnopqrstuvwxyz";
int length = tmp.length();
char c[] = new char[length];
tmp.getChars(0, length, c, 0);
CharArrayReader input1 = new CharArrayReader(c);
CharArrayReader input2 = new CharArrayReader(c, 0, 5);
int i;
while ((i = input1.read()) != -1) {
System.out.print((char) i);
}
while ((i = input2.read()) != -1) {
System.out.print((char) i);
}
}
}
UTF8 Reader
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
import java.io.InputStream;
import java.io.IOException;
import java.io.Reader;
import java.io.UTFDataFormatException;
/**
* @author Andy Clark, IBM
*
* @version $Id: UTF8Reader.java 515 2008-03-17 21:02:23Z jfrederic.clere@jboss.ru $
*/
public class UTF8Reader
extends Reader {
//
// Constants
//
/** Default byte buffer size (2048). */
public static final int DEFAULT_BUFFER_SIZE = 2048;
// debugging
/** Debug read. */
private static final boolean DEBUG_READ = false;
//
// Data
//
/** Input stream. */
protected InputStream fInputStream;
/** Byte buffer. */
protected byte[] fBuffer;
/** Offset into buffer. */
protected int fOffset;
/** Surrogate character. */
private int fSurrogate = -1;
//
// Constructors
//
/**
* Constructs a UTF-8 reader from the specified input stream,
* buffer size and MessageFormatter.
*
* @param inputStream The input stream.
* @param size The initial buffer size.
*/
public UTF8Reader(InputStream inputStream, int size) {
fInputStream = inputStream;
fBuffer = new byte[size];
}
//
// Reader methods
//
/**
* Read a single character. This method will block until a character is
* available, an I/O error occurs, or the end of the stream is reached.
*
* <p> Subclasses that intend to support efficient single-character input
* should override this method.
*
* @return The character read, as an integer in the range 0 to 16383
* (<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 {
// decode character
int c = fSurrogate;
if (fSurrogate == -1) {
// NOTE: We use the index into the buffer if there are remaining
// bytes from the last block read. -Ac
int index = 0;
// get first byte
int b0 = index == fOffset
? fInputStream.read() : fBuffer[index++] & 0x00FF;
if (b0 == -1) {
return -1;
}
// UTF-8: [0xxx xxxx]
// Unicode: [0000 0000] [0xxx xxxx]
if (b0 < 0x80) {
c = (char)b0;
}
// UTF-8: [110y yyyy] [10xx xxxx]
// Unicode: [0000 0yyy] [yyxx xxxx]
else if ((b0 & 0xE0) == 0xC0) {
int b1 = index == fOffset
? fInputStream.read() : fBuffer[index++] & 0x00FF;
if (b1 == -1) {
expectedByte(2, 2);
}
if ((b1 & 0xC0) != 0x80) {
invalidByte(2, 2, b1);
}
c = ((b0 << 6) & 0x07C0) | (b1 & 0x003F);
}
// UTF-8: [1110 zzzz] [10yy yyyy] [10xx xxxx]
// Unicode: [zzzz yyyy] [yyxx xxxx]
else if ((b0 & 0xF0) == 0xE0) {
int b1 = index == fOffset
? fInputStream.read() : fBuffer[index++] & 0x00FF;
if (b1 == -1) {
expectedByte(2, 3);
}
if ((b1 & 0xC0) != 0x80) {
invalidByte(2, 3, b1);
}
int b2 = index == fOffset
? fInputStream.read() : fBuffer[index++] & 0x00FF;
if (b2 == -1) {
expectedByte(3, 3);
}
if ((b2 & 0xC0) != 0x80) {
invalidByte(3, 3, b2);
}
c = ((b0 << 12) & 0xF000) | ((b1 << 6) & 0x0FC0) |
(b2 & 0x003F);
}
// UTF-8: [1111 0uuu] [10uu zzzz] [10yy yyyy] [10xx xxxx]*
// Unicode: [1101 10ww] [wwzz zzyy] (high surrogate)
// [1101 11yy] [yyxx xxxx] (low surrogate)
// * uuuuu = wwww + 1
else if ((b0 & 0xF8) == 0xF0) {
int b1 = index == fOffset
? fInputStream.read() : fBuffer[index++] & 0x00FF;
if (b1 == -1) {
expectedByte(2, 4);
}
if ((b1 & 0xC0) != 0x80) {
invalidByte(2, 3, b1);
}
int b2 = index == fOffset
? fInputStream.read() : fBuffer[index++] & 0x00FF;
if (b2 == -1) {
expectedByte(3, 4);
}
if ((b2 & 0xC0) != 0x80) {
invalidByte(3, 3, b2);
}
int b3 = index == fOffset
? fInputStream.read() : fBuffer[index++] & 0x00FF;
if (b3 == -1) {
expectedByte(4, 4);
}
if ((b3 & 0xC0) != 0x80) {
invalidByte(4, 4, b3);
}
int uuuuu = ((b0 << 2) & 0x001C) | ((b1 >> 4) & 0x0003);
if (uuuuu > 0x10) {
invalidSurrogate(uuuuu);
}
int wwww = uuuuu - 1;
int hs = 0xD800 |
((wwww << 6) & 0x03C0) | ((b1 << 2) & 0x003C) |
((b2 >> 4) & 0x0003);
int ls = 0xDC00 | ((b2 << 6) & 0x03C0) | (b3 & 0x003F);
c = hs;
fSurrogate = ls;
}
// error
else {
invalidByte(1, 1, b0);
}
}
// use surrogate
else {
fSurrogate = -1;
}
return c;
} // read():int
/**
* Read characters into a portion of an array. This method will block
* until some input is available, an I/O error occurs, or the end of the
* stream is reached.
*
* @param ch Destination buffer
* @param offset Offset at which to start storing characters
* @param length 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 ch[], int offset, int length) throws IOException {
// handle surrogate
int out = offset;
if (fSurrogate != -1) {
ch[offset + 1] = (char)fSurrogate;
fSurrogate = -1;
length--;
out++;
}
// read bytes
int count = 0;
if (fOffset == 0) {
// adjust length to read
if (length > fBuffer.length) {
length = fBuffer.length;
}
// perform read operation
count = fInputStream.read(fBuffer, 0, length);
if (count == -1) {
return -1;
}
count += out - offset;
}
// skip read; last character was in error
// NOTE: Having an offset value other than zero means that there was
// an error in the last character read. In this case, we have
// skipped the read so we don"t consume any bytes past the
// error. By signalling the error on the next block read we
// allow the method to return the most valid characters that
// it can on the previous block read. -Ac
else {
count = fOffset;
fOffset = 0;
}
// convert bytes to characters
final int total = count;
for (int in = 0; in < total; in++) {
int b0 = fBuffer[in] & 0x00FF;
// UTF-8: [0xxx xxxx]
// Unicode: [0000 0000] [0xxx xxxx]
if (b0 < 0x80) {
ch[out++] = (char)b0;
continue;
}
// UTF-8: [110y yyyy] [10xx xxxx]
// Unicode: [0000 0yyy] [yyxx xxxx]
if ((b0 & 0xE0) == 0xC0) {
int b1 = -1;
if (++in < total) {
b1 = fBuffer[in] & 0x00FF;
}
else {
b1 = fInputStream.read();
if (b1 == -1) {
if (out > offset) {
fBuffer[0] = (byte)b0;
fOffset = 1;
return out - offset;
}
expectedByte(2, 2);
}
count++;
}
if ((b1 & 0xC0) != 0x80) {
if (out > offset) {
fBuffer[0] = (byte)b0;
fBuffer[1] = (byte)b1;
fOffset = 2;
return out - offset;
}
invalidByte(2, 2, b1);
}
int c = ((b0 << 6) & 0x07C0) | (b1 & 0x003F);
ch[out++] = (char)c;
count -= 1;
continue;
}
// UTF-8: [1110 zzzz] [10yy yyyy] [10xx xxxx]
// Unicode: [zzzz yyyy] [yyxx xxxx]
if ((b0 & 0xF0) == 0xE0) {
int b1 = -1;
if (++in < total) {
b1 = fBuffer[in] & 0x00FF;
}
else {
b1 = fInputStream.read();
if (b1 == -1) {
if (out > offset) {
fBuffer[0] = (byte)b0;
fOffset = 1;
return out - offset;
}
expectedByte(2, 3);
}
count++;
}
if ((b1 & 0xC0) != 0x80) {
if (out > offset) {
fBuffer[0] = (byte)b0;
fBuffer[1] = (byte)b1;
fOffset = 2;
return out - offset;
}
invalidByte(2, 3, b1);
}
int b2 = -1;
if (++in < total) {
b2 = fBuffer[in] & 0x00FF;
}
else {
b2 = fInputStream.read();
if (b2 == -1) {
if (out > offset) {
fBuffer[0] = (byte)b0;
fBuffer[1] = (byte)b1;
fOffset = 2;
return out - offset;
}
expectedByte(3, 3);
}
count++;
}
if ((b2 & 0xC0) != 0x80) {
if (out > offset) {
fBuffer[0] = (byte)b0;
fBuffer[1] = (byte)b1;
fBuffer[2] = (byte)b2;
fOffset = 3;
return out - offset;
}
invalidByte(3, 3, b2);
}
int c = ((b0 << 12) & 0xF000) | ((b1 << 6) & 0x0FC0) |
(b2 & 0x003F);
ch[out++] = (char)c;
count -= 2;
continue;
}
// UTF-8: [1111 0uuu] [10uu zzzz] [10yy yyyy] [10xx xxxx]*
// Unicode: [1101 10ww] [wwzz zzyy] (high surrogate)
// [1101 11yy] [yyxx xxxx] (low surrogate)
// * uuuuu = wwww + 1
if ((b0 & 0xF8) == 0xF0) {
int b1 = -1;
if (++in < total) {
b1 = fBuffer[in] & 0x00FF;
}
else {
b1 = fInputStream.read();
if (b1 == -1) {
if (out > offset) {
fBuffer[0] = (byte)b0;
fOffset = 1;
return out - offset;
}
expectedByte(2, 4);
}
count++;
}
if ((b1 & 0xC0) != 0x80) {
if (out > offset) {
fBuffer[0] = (byte)b0;
fBuffer[1] = (byte)b1;
fOffset = 2;
return out - offset;
}
invalidByte(2, 4, b1);
}
int b2 = -1;
if (++in < total) {
b2 = fBuffer[in] & 0x00FF;
}
else {
b2 = fInputStream.read();
if (b2 == -1) {
if (out > offset) {
fBuffer[0] = (byte)b0;
fBuffer[1] = (byte)b1;
fOffset = 2;
return out - offset;
}
expectedByte(3, 4);
}
count++;
}
if ((b2 & 0xC0) != 0x80) {
if (out > offset) {
fBuffer[0] = (byte)b0;
fBuffer[1] = (byte)b1;
fBuffer[2] = (byte)b2;
fOffset = 3;
return out - offset;
}
invalidByte(3, 4, b2);
}
int b3 = -1;
if (++in < total) {
b3 = fBuffer[in] & 0x00FF;
}
else {
b3 = fInputStream.read();
if (b3 == -1) {
if (out > offset) {
fBuffer[0] = (byte)b0;
fBuffer[1] = (byte)b1;
fBuffer[2] = (byte)b2;
fOffset = 3;
return out - offset;
}
expectedByte(4, 4);
}
count++;
}
if ((b3 & 0xC0) != 0x80) {
if (out > offset) {
fBuffer[0] = (byte)b0;
fBuffer[1] = (byte)b1;
fBuffer[2] = (byte)b2;
fBuffer[3] = (byte)b3;
fOffset = 4;
return out - offset;
}
invalidByte(4, 4, b2);
}
// decode bytes into surrogate characters
int uuuuu = ((b0 << 2) & 0x001C) | ((b1 >> 4) & 0x0003);
if (uuuuu > 0x10) {
invalidSurrogate(uuuuu);
}
int wwww = uuuuu - 1;
int zzzz = b1 & 0x000F;
int yyyyyy = b2 & 0x003F;
int xxxxxx = b3 & 0x003F;
int hs = 0xD800 | ((wwww << 6) & 0x03C0) | (zzzz << 2) | (yyyyyy >> 4);
int ls = 0xDC00 | ((yyyyyy << 6) & 0x03C0) | xxxxxx;
// set characters
ch[out++] = (char)hs;
ch[out++] = (char)ls;
count -= 2;
continue;
}
// error
if (out > offset) {
fBuffer[0] = (byte)b0;
fOffset = 1;
return out - offset;
}
invalidByte(1, 1, b0);
}
return count;
} // read(char[],int,int)
/**
* Skip characters. This method will block until some characters are
* available, an I/O error occurs, or the end of the stream is reached.
*
* @param n The number of characters to skip
*
* @return The number of characters actually skipped
*
* @exception IOException If an I/O error occurs
*/
public long skip(long n) throws IOException {
long remaining = n;
final char[] ch = new char[fBuffer.length];
do {
int length = ch.length < remaining ? ch.length : (int)remaining;
int count = read(ch, 0, length);
if (count > 0) {
remaining -= count;
}
else {
break;
}
} while (remaining > 0);
long skipped = n - remaining;
return skipped;
} // skip(long):long
/**
* Tell whether this stream is ready to be read.
*
* @return True if the next read() is guaranteed not to block for input,
* false otherwise. Note that returning false does not guarantee that the
* next read will block.
*
* @exception IOException If an I/O error occurs
*/
public boolean ready() throws IOException {
return false;
} // ready()
/**
* Tell whether this stream supports the mark() operation.
*/
public boolean markSupported() {
return false;
} // markSupported()
/**
* Mark the present position in the stream. Subsequent calls to reset()
* will attempt to reposition the stream to this point. Not all
* character-input streams support the mark() operation.
*
* @param readAheadLimit Limit on the number of characters that may be
* read while still preserving the mark. After
* reading this many characters, attempting to
* reset the stream may fail.
*
* @exception IOException If the stream does not support mark(),
* or if some other I/O error occurs
*/
public void mark(int readAheadLimit) throws IOException {
throw new IOException("operationNotSupported");
}
/**
* Reset the stream. If the stream has been marked, then attempt to
* reposition it at the mark. If the stream has not been marked, then
* attempt to reset it in some way appropriate to the particular stream,
* for example by repositioning it to its starting point. Not all
* character-input streams support the reset() operation, and some support
* reset() without supporting mark().
*
* @exception IOException If the stream has not been marked,
* or if the mark has been invalidated,
* or if the stream does not support reset(),
* or if some other I/O error occurs
*/
public void reset() throws IOException {
fOffset = 0;
fSurrogate = -1;
} // reset()
/**
* Close the stream. Once a stream has been closed, further read(),
* ready(), mark(), or reset() invocations will throw an IOException.
* Closing a previously-closed stream, however, has no effect.
*
* @exception IOException If an I/O error occurs
*/
public void close() throws IOException {
fInputStream.close();
} // close()
//
// Private methods
//
/** Throws an exception for expected byte. */
private void expectedByte(int position, int count)
throws UTFDataFormatException {
throw new UTFDataFormatException("expectedByte");
} // expectedByte(int,int,int)
/** Throws an exception for invalid byte. */
private void invalidByte(int position, int count, int c)
throws UTFDataFormatException {
throw new UTFDataFormatException("invalidByte");
} // invalidByte(int,int,int,int)
/** Throws an exception for invalid surrogate bits. */
private void invalidSurrogate(int uuuuu) throws UTFDataFormatException {
throw new UTFDataFormatException("invalidHighSurrogate");
} // invalidSurrogate(int)
} // class UTF8Reader
