org.flywaydb.core.internal.parser.UnboundedReadAheadReader Maven / Gradle / Ivy
/*
* Copyright (C) Red Gate Software Ltd 2010-2024
*
* Licensed 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.
*/
package org.flywaydb.core.internal.parser;
import java.io.FilterReader;
import java.io.IOException;
import java.io.Reader;
import java.util.ArrayList;
public class UnboundedReadAheadReader extends FilterReader {
protected ArrayList buffers = new ArrayList<>();
private int readIndex = 0;
private int markIndex = -1;
private int currentBuffersSize = 0;
private static final int bufferSize = 512;
protected UnboundedReadAheadReader(Reader in) {
super(in);
}
@Override
public void mark(int readAheadLimit) throws IOException {
markIndex = readIndex;
}
@Override
public void reset() throws IOException {
readIndex = markIndex;
freeBuffers();
markIndex = -1;
}
@Override
public int read() throws IOException {
if (readIndex < currentBuffersSize) {
return getValue(readIndex++);
}
int read = in.read();
if (markIndex != -1) {
setValue(read);
readIndex++;
currentBuffersSize++;
}
return read;
}
private int getValue(int index) {
int buffersIndex = index / bufferSize;
int buffersOffset = index - (buffersIndex * bufferSize);
return buffers.get(buffersIndex)[buffersOffset];
}
private void setValue(int value) {
int buffersIndex = readIndex / bufferSize;
int buffersOffset = readIndex - (buffersIndex * bufferSize);
if (buffersOffset == 0) {
buffers.add(new int[bufferSize]);
}
buffers.get(buffersIndex)[buffersOffset] = value;
}
private void freeBuffers() {
int buffersToRemove = (markIndex / bufferSize) - 1;
for (int i = 0; i < buffersToRemove; i++) {
buffers.remove(0);
readIndex -= bufferSize;
currentBuffersSize -= bufferSize;
}
}
}