1 package org.apache.lucene.store;
2
3 /**
4 * Licensed to the Apache Software Foundation (ASF) under one or more
5 * contributor license agreements. See the NOTICE file distributed with
6 * this work for additional information regarding copyright ownership.
7 * The ASF licenses this file to You under the Apache License, Version 2.0
8 * (the "License"); you may not use this file except in compliance with
9 * the License. You may obtain a copy of the License at
10 *
11 * http://www.apache.org/licenses/LICENSE-2.0
12 *
13 * Unless required by applicable law or agreed to in writing, software
14 * distributed under the License is distributed on an "AS IS" BASIS,
15 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
16 * See the License for the specific language governing permissions and
17 * limitations under the License.
18 */
19
20 import java.io.IOException;
21
22 /**
23 * A memory-resident {@link IndexOutput} implementation.
24 */
25
26 public class RAMOutputStream extends IndexOutput {
27 static final int BUFFER_SIZE = 1024;
28
29 private RAMFile file;
30
31 private byte[] currentBuffer;
32 private int currentBufferIndex;
33
34 private int bufferPosition;
35 private long bufferStart;
36 private int bufferLength;
37
38 /** Construct an empty output buffer. */
39 public RAMOutputStream() {
40 this(new RAMFile());
41 }
42
43 RAMOutputStream(RAMFile f) {
44 file = f;
45
46 // make sure that we switch to the
47 // first needed buffer lazily
48 currentBufferIndex = -1;
49 currentBuffer = null;
50 }
51
52 /** Copy the current contents of this buffer to the named output. */
53 public void writeTo(IndexOutput out) throws IOException {
54 flush();
55 final long end = file.length;
56 long pos = 0;
57 int buffer = 0;
58 while (pos < end) {
59 int length = BUFFER_SIZE;
60 long nextPos = pos + length;
61 if (nextPos > end) { // at the last buffer
62 length = (int)(end - pos);
63 }
64 out.writeBytes(file.getBuffer(buffer++), length);
65 pos = nextPos;
66 }
67 }
68
69 /** Resets this to an empty buffer. */
70 public void reset() {
71 try {
72 seek(0);
73 } catch (IOException e) { // should never happen
74 throw new RuntimeException(e.toString());
75 }
76
77 file.setLength(0);
78 }
79
80 @Override
81 public void close() throws IOException {
82 flush();
83 }
84
85 @Override
86 public void seek(long pos) throws IOException {
87 // set the file length in case we seek back
88 // and flush() has not been called yet
89 setFileLength();
90 if (pos < bufferStart || pos >= bufferStart + bufferLength) {
91 currentBufferIndex = (int) (pos / BUFFER_SIZE);
92 switchCurrentBuffer();
93 }
94
95 bufferPosition = (int) (pos % BUFFER_SIZE);
96 }
97
98 @Override
99 public long length() {
100 return file.length;
101 }
102
103 @Override
104 public void writeByte(byte b) throws IOException {
105 if (bufferPosition == bufferLength) {
106 currentBufferIndex++;
107 switchCurrentBuffer();
108 }
109 currentBuffer[bufferPosition++] = b;
110 }
111
112 @Override
113 public void writeBytes(byte[] b, int offset, int len) throws IOException {
114 assert b != null;
115 while (len > 0) {
116 if (bufferPosition == bufferLength) {
117 currentBufferIndex++;
118 switchCurrentBuffer();
119 }
120
121 int remainInBuffer = currentBuffer.length - bufferPosition;
122 int bytesToCopy = len < remainInBuffer ? len : remainInBuffer;
123 System.arraycopy(b, offset, currentBuffer, bufferPosition, bytesToCopy);
124 offset += bytesToCopy;
125 len -= bytesToCopy;
126 bufferPosition += bytesToCopy;
127 }
128 }
129
130 private final void switchCurrentBuffer() throws IOException {
131 if (currentBufferIndex == file.numBuffers()) {
132 currentBuffer = file.addBuffer(BUFFER_SIZE);
133 } else {
134 currentBuffer = file.getBuffer(currentBufferIndex);
135 }
136 bufferPosition = 0;
137 bufferStart = (long) BUFFER_SIZE * (long) currentBufferIndex;
138 bufferLength = currentBuffer.length;
139 }
140
141 private void setFileLength() {
142 long pointer = bufferStart + bufferPosition;
143 if (pointer > file.length) {
144 file.setLength(pointer);
145 }
146 }
147
148 @Override
149 public void flush() throws IOException {
150 file.setLastModified(System.currentTimeMillis());
151 setFileLength();
152 }
153
154 @Override
155 public long getFilePointer() {
156 return currentBufferIndex < 0 ? 0 : bufferStart + bufferPosition;
157 }
158
159 /** Returns byte usage of all buffers. */
160 public long sizeInBytes() {
161 return file.numBuffers() * BUFFER_SIZE;
162 }
163 }
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