Source Code Cross Referenced for FileInputStream.java in  » 6.0-JDK-Modules » j2me » java » io » Java Source Code / Java DocumentationJava Source Code and Java Documentation

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Java Source Code / Java Documentation » 6.0 JDK Modules » j2me » java.io 
Source Cross Referenced  Class Diagram Java Document (Java Doc) 


001:        /*
002:         * @(#)FileInputStream.java	1.60 06/10/10
003:         *
004:         * Copyright  1990-2006 Sun Microsystems, Inc. All Rights Reserved.  
005:         * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER  
006:         *   
007:         * This program is free software; you can redistribute it and/or  
008:         * modify it under the terms of the GNU General Public License version  
009:         * 2 only, as published by the Free Software Foundation.   
010:         *   
011:         * This program is distributed in the hope that it will be useful, but  
012:         * WITHOUT ANY WARRANTY; without even the implied warranty of  
013:         * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU  
014:         * General Public License version 2 for more details (a copy is  
015:         * included at /legal/license.txt).   
016:         *   
017:         * You should have received a copy of the GNU General Public License  
018:         * version 2 along with this work; if not, write to the Free Software  
019:         * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  
020:         * 02110-1301 USA   
021:         *   
022:         * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa  
023:         * Clara, CA 95054 or visit www.sun.com if you need additional  
024:         * information or have any questions. 
025:         *
026:         */
027:
028:        package java.io;
029:
030:        /**
031:         * A <code>FileInputStream</code> obtains input bytes
032:         * from a file in a file system. What files
033:         * are  available depends on the host environment.
034:         *
035:         * <p><code>FileInputStream</code> is meant for reading streams of raw bytes
036:         * such as image data. For reading streams of characters, consider using
037:         * <code>FileReader</code>.
038:         *
039:         * @version 1.45, 02/02/00
040:         * @see     java.io.File
041:         * @see     java.io.FileDescriptor
042:         * @see	    java.io.FileOutputStream
043:         * @since   JDK1.0
044:         */
045:        public class FileInputStream extends InputStream {
046:            /* File Descriptor - handle to the open file */
047:            private FileDescriptor fd;
048:
049:            /**
050:             * Creates a <code>FileInputStream</code> by
051:             * opening a connection to an actual file,
052:             * the file named by the path name <code>name</code>
053:             * in the file system.  A new <code>FileDescriptor</code>
054:             * object is created to represent this file
055:             * connection.
056:             * <p>
057:             * First, if there is a security
058:             * manager, its <code>checkRead</code> method
059:             * is called with the <code>name</code> argument
060:             * as its argument.
061:             * <p>
062:             * If the named file does not exist, is a directory rather than a regular
063:             * file, or for some other reason cannot be opened for reading then a
064:             * <code>FileNotFoundException</code> is thrown.
065:             *
066:             * @param      name   the system-dependent file name.
067:             * @exception  FileNotFoundException  if the file does not exist,
068:             *                   is a directory rather than a regular file,
069:             *                   or for some other reason cannot be opened for
070:             *                   reading.
071:             * @exception  SecurityException      if a security manager exists and its
072:             *               <code>checkRead</code> method denies read access
073:             *               to the file.
074:             * @see        java.lang.SecurityManager#checkRead(java.lang.String)
075:             */
076:            public FileInputStream(String name) throws FileNotFoundException {
077:                this (name != null ? new File(name) : null);
078:            }
079:
080:            /**
081:             * Creates a <code>FileInputStream</code> by
082:             * opening a connection to an actual file,
083:             * the file named by the <code>File</code>
084:             * object <code>file</code> in the file system.
085:             * A new <code>FileDescriptor</code> object
086:             * is created to represent this file connection.
087:             * <p>
088:             * First, if there is a security manager,
089:             * its <code>checkRead</code> method  is called
090:             * with the path represented by the <code>file</code>
091:             * argument as its argument.
092:             * <p>
093:             * If the named file does not exist, is a directory rather than a regular
094:             * file, or for some other reason cannot be opened for reading then a
095:             * <code>FileNotFoundException</code> is thrown.
096:             *
097:             * @param      file   the file to be opened for reading.
098:             * @exception  FileNotFoundException  if the file does not exist,
099:             *                   is a directory rather than a regular file,
100:             *                   or for some other reason cannot be opened for
101:             *                   reading.
102:             * @exception  SecurityException      if a security manager exists and its
103:             *               <code>checkRead</code> method denies read access to the file.
104:             * @see        java.io.File#getPath()
105:             * @see        java.lang.SecurityManager#checkRead(java.lang.String)
106:             */
107:            public FileInputStream(File file) throws FileNotFoundException {
108:                String name = (file != null ? file.getPath() : null);
109:                SecurityManager security = System.getSecurityManager();
110:                if (security != null) {
111:                    security.checkRead(name);
112:                }
113:                if (name == null) {
114:                    throw new NullPointerException();
115:                }
116:                fd = new FileDescriptor();
117:                open(name);
118:            }
119:
120:            /**
121:             * Creates a <code>FileInputStream</code> by using the file descriptor
122:             * <code>fdObj</code>, which represents an existing connection to an
123:             * actual file in the file system.
124:             * <p>
125:             * If there is a security manager, its <code>checkRead</code> method is
126:             * called with the file descriptor <code>fdObj</code> as its argument to
127:             * see if it's ok to read the file descriptor. If read access is denied
128:             * to the file descriptor a <code>SecurityException</code> is thrown.
129:             * <p>
130:             * If <code>fdObj</code> is null then a <code>NullPointerException</code>
131:             * is thrown.
132:             *
133:             * @param      fdObj   the file descriptor to be opened for reading.
134:             * @throws     SecurityException      if a security manager exists and its
135:             *                 <code>checkRead</code> method denies read access to the
136:             *                 file descriptor.
137:             * @see        SecurityManager#checkRead(java.io.FileDescriptor)
138:             */
139:            public FileInputStream(FileDescriptor fdObj) {
140:                SecurityManager security = System.getSecurityManager();
141:                if (fdObj == null) {
142:                    throw new NullPointerException();
143:                }
144:                if (security != null) {
145:                    security.checkRead(fdObj);
146:                }
147:                fd = fdObj;
148:            }
149:
150:            /**
151:             * Opens the specified file for reading.
152:             * @param name the name of the file
153:             */
154:            private native void open(String name) throws FileNotFoundException;
155:
156:            /**
157:             * Reads a byte of data from this input stream. This method blocks
158:             * if no input is yet available.
159:             *
160:             * @return     the next byte of data, or <code>-1</code> if the end of the
161:             *             file is reached.
162:             * @exception  IOException  if an I/O error occurs.
163:             */
164:            public native int read() throws IOException;
165:
166:            /**
167:             * Reads a subarray as a sequence of bytes.
168:             * @param b the data to be written
169:             * @param off the start offset in the data
170:             * @param len the number of bytes that are written
171:             * @exception IOException If an I/O error has occurred.
172:             */
173:            private native int readBytes(byte b[], int off, int len)
174:                    throws IOException;
175:
176:            /**
177:             * Reads up to <code>b.length</code> bytes of data from this input
178:             * stream into an array of bytes. This method blocks until some input
179:             * is available.
180:             *
181:             * @param      b   the buffer into which the data is read.
182:             * @return     the total number of bytes read into the buffer, or
183:             *             <code>-1</code> if there is no more data because the end of
184:             *             the file has been reached.
185:             * @exception  IOException  if an I/O error occurs.
186:             */
187:            public int read(byte b[]) throws IOException {
188:                return readBytes(b, 0, b.length);
189:            }
190:
191:            /**
192:             * Reads up to <code>len</code> bytes of data from this input stream
193:             * into an array of bytes. This method blocks until some input is
194:             * available.
195:             *
196:             * @param      b     the buffer into which the data is read.
197:             * @param      off   the start offset of the data.
198:             * @param      len   the maximum number of bytes read.
199:             * @return     the total number of bytes read into the buffer, or
200:             *             <code>-1</code> if there is no more data because the end of
201:             *             the file has been reached.
202:             * @exception  IOException  if an I/O error occurs.
203:             */
204:            public int read(byte b[], int off, int len) throws IOException {
205:                return readBytes(b, off, len);
206:            }
207:
208:            /**
209:             * Skips over and discards <code>n</code> bytes of data from the
210:             * input stream. The <code>skip</code> method may, for a variety of
211:             * reasons, end up skipping over some smaller number of bytes,
212:             * possibly <code>0</code>. The actual number of bytes skipped is returned.
213:             *
214:             * @param      n   the number of bytes to be skipped.
215:             * @return     the actual number of bytes skipped.
216:             * @exception  IOException  if an I/O error occurs.
217:             */
218:            public native long skip(long n) throws IOException;
219:
220:            /**
221:             * Returns the number of bytes that can be read from this file input
222:             * stream without blocking.
223:             *
224:             * @return     the number of bytes that can be read from this file input
225:             *             stream without blocking.
226:             * @exception  IOException  if an I/O error occurs.
227:             */
228:            public native int available() throws IOException;
229:
230:            /**
231:             * Closes this file input stream and releases any system resources
232:             * associated with the stream.
233:             *
234:             * <p> If this stream has an associated channel then the channel is closed
235:             * as well.
236:             *
237:             * @exception  IOException  if an I/O error occurs.
238:             *
239:             * @revised 1.4
240:             * @spec JSR-51
241:             */
242:            public void close() throws IOException {
243:                close0();
244:            }
245:
246:            /**
247:             * Returns the <code>FileDescriptor</code>
248:             * object  that represents the connection to
249:             * the actual file in the file system being
250:             * used by this <code>FileInputStream</code>.
251:             *
252:             * @return     the file descriptor object associated with this stream.
253:             * @exception  IOException  if an I/O error occurs.
254:             * @see        java.io.FileDescriptor
255:             */
256:            public final FileDescriptor getFD() throws IOException {
257:                if (fd != null)
258:                    return fd;
259:                throw new IOException();
260:            }
261:
262:            /**
263:             * Returns the unique {@link java.nio.channels.FileChannel FileChannel}
264:             * object associated with this file input stream.
265:             *
266:             * <p> The initial {@link java.nio.channels.FileChannel#position()
267:             * </code>position<code>} of the returned channel will be equal to the
268:             * number of bytes read from the file so far.  Reading bytes from this
269:             * stream will increment the channel's position.  Changing the channel's
270:             * position, either explicitly or by reading, will change this stream's
271:             * file position.
272:             *
273:             * @return  the file channel associated with this file input stream
274:             *
275:             * @since 1.4
276:             * @spec JSR-51
277:             */
278:            /* Comment out due to no NIO in CDC
279:            public FileChannel getChannel() {        
280:            synchronized (this) {
281:                if (channel == null)
282:            	channel = FileChannelImpl.open(fd, true, false, this);
283:                return channel;
284:            }
285:            }
286:             */
287:
288:            private static native void initIDs();
289:
290:            private native void close0() throws IOException;
291:
292:            static {
293:                initIDs();
294:            }
295:
296:            /**
297:             * Ensures that the <code>close</code> method of this file input stream is
298:             * called when there are no more references to it.
299:             *
300:             * @exception  IOException  if an I/O error occurs.
301:             * @see        java.io.FileInputStream#close()
302:             */
303:            protected void finalize() throws IOException {
304:                if (fd != null) {
305:                    if (fd != fd.in) {
306:                        close();
307:                    }
308:                }
309:            }
310:        }
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