001: package com.quadcap.sql.file;
002:
003: /* Copyright 1997 - 2003 Quadcap Software. All rights reserved.
004: *
005: * This software is distributed under the Quadcap Free Software License.
006: * This software may be used or modified for any purpose, personal or
007: * commercial. Open Source redistributions are permitted. Commercial
008: * redistribution of larger works derived from, or works which bundle
009: * this software requires a "Commercial Redistribution License"; see
010: * http://www.quadcap.com/purchase.
011: *
012: * Redistributions qualify as "Open Source" under one of the following terms:
013: *
014: * Redistributions are made at no charge beyond the reasonable cost of
015: * materials and delivery.
016: *
017: * Redistributions are accompanied by a copy of the Source Code or by an
018: * irrevocable offer to provide a copy of the Source Code for up to three
019: * years at the cost of materials and delivery. Such redistributions
020: * must allow further use, modification, and redistribution of the Source
021: * Code under substantially the same terms as this license.
022: *
023: * Redistributions of source code must retain the copyright notices as they
024: * appear in each source code file, these license terms, and the
025: * disclaimer/limitation of liability set forth as paragraph 6 below.
026: *
027: * Redistributions in binary form must reproduce this Copyright Notice,
028: * these license terms, and the disclaimer/limitation of liability set
029: * forth as paragraph 6 below, in the documentation and/or other materials
030: * provided with the distribution.
031: *
032: * The Software is provided on an "AS IS" basis. No warranty is
033: * provided that the Software is free of defects, or fit for a
034: * particular purpose.
035: *
036: * Limitation of Liability. Quadcap Software shall not be liable
037: * for any damages suffered by the Licensee or any third party resulting
038: * from use of the Software.
039: */
040:
041: import java.io.InputStream;
042: import java.io.IOException;
043:
044: import com.quadcap.util.Debug;
045:
046: /**
047: * An input stream attached to a <code>RandomAccess</code> object.
048: *
049: * @author Stan Bailes
050: */
051: public class RandomAccessInputStream extends InputStream {
052: RandomAccess ra;
053: int position;
054: byte[] buf1 = new byte[1];
055:
056: public RandomAccessInputStream(RandomAccess ra) {
057: this .ra = ra;
058: this .position = 0;
059: }
060:
061: public int getPosition() {
062: return position;
063: }
064:
065: public void setPosition(int p) {
066: position = p;
067: }
068:
069: /**
070: * Reads the next byte of data from this input stream. The value
071: * byte is returned as an <code>int</code> in the range
072: * <code>0</code> to <code>255</code>. If no byte is available
073: * because the end of the stream has been reached, the value
074: * <code>-1</code> is returned.
075: *
076: * @return the next byte of data, or <code>-1</code> if the end of the
077: * stream is reached.
078: * @exception IOException if an I/O error occurs.
079: */
080: public int read() throws IOException {
081: if (position >= ra.size())
082: return -1;
083:
084: ra.read(position, buf1, 0, 1);
085: position++;
086: return buf1[0] & 0xff;
087: }
088:
089: /**
090: * Reads up to <code>len</code> bytes of data from this input stream
091: * into an array of bytes. This method blocks until some input is
092: * available. If the first argument is <code>null,</code> up to
093: * <code>len</code> bytes are read and discarded.
094: *
095: * @param b the buffer into which the data is read.
096: * @param off the start offset of the data.
097: * @param len the maximum number of bytes read.
098: * @return the total number of bytes read into the buffer, or
099: * <code>-1</code> if there is no more data because the end of
100: * the stream has been reached.
101: * @exception IOException if an I/O error occurs.
102: */
103: public int read(byte b[], int off, int len) throws IOException {
104: if (position >= ra.size())
105: return -1;
106: if (ra.size() - position < len)
107: len = (int) (ra.size() - position);
108:
109: if (b != null)
110: ra.read(position, b, off, len);
111: position += len;
112: return len;
113: }
114:
115: /**
116: * Skips over and discards <code>n</code> bytes of data from this
117: * input stream. The <code>skip</code> method may, for a variety of
118: * reasons, end up skipping over some smaller number of bytes,
119: * possibly <code>0</code>. The actual number of bytes skipped is
120: * returned.
121: * <p>
122: * The <code>skip</code> method of <code>InputStream</code> creates
123: * a byte array of length <code>n</code> and then reads into it until
124: * <code>n</code> bytes have been read or the end of the stream has
125: * been reached. Subclasses are encouraged to provide a more
126: * efficient implementation of this method.
127: *
128: * @param n the number of bytes to be skipped.
129: * @return the actual number of bytes skipped.
130: * @exception IOException if an I/O error occurs.
131: * @since JDK1.0
132: */
133: public long skip(long n) throws IOException {
134: return read(null, 0, (int) n);
135: }
136:
137: /**
138: * Returns the number of bytes that can be read from this input
139: * stream without blocking. The available method of
140: * <code>InputStream</code> returns <code>0</code>. This method
141: * <B>should</B> be overridden by subclasses.
142: *
143: * @return the number of bytes that can be read from this input stream
144: * without blocking.
145: * @exception IOException if an I/O error occurs.
146: */
147: public int available() throws IOException {
148: return (int) (ra.size() - position);
149: }
150:
151: /**
152: * Closes this input stream and releases any system resources
153: * associated with the stream.
154: *
155: * @exception IOException if an I/O error occurs.
156: */
157: public void close() throws IOException {
158: ra.close();
159: }
160:
161: }
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