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/*
* Copyright (C) 2010 Google Inc.
*
* 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 com.google.caliper.util;
import com.google.gson.JsonParser;
import java.io.BufferedReader;
import java.io.Closeable;
import java.io.IOException;
import java.io.Reader;
/**
* Reads a stream containing inline JSON objects. Each JSON object is prefixed
* by a marker string and suffixed by a newline character.
*/
public final class InterleavedReader implements Closeable {
/**
* The length of the scratch buffer to search for markers in. Also acts as an
* upper bound on the length of returned strings. Not used as an I/O buffer.
*/
private static final int BUFFER_LENGTH = 80;
private final String marker;
private final BufferedReader reader;
private final JsonParser jsonParser = new JsonParser();
public static final String DEFAULT_MARKER = "//ZxJ/";
public InterleavedReader(Reader reader) {
this(DEFAULT_MARKER, reader);
}
public InterleavedReader(String marker, Reader reader) {
if (marker.length() > BUFFER_LENGTH) {
throw new IllegalArgumentException("marker.length() > BUFFER_LENGTH");
}
this.marker = marker;
this.reader = reader instanceof BufferedReader
? (BufferedReader) reader
: new BufferedReader(reader);
}
/**
* Returns the next value in the stream: either a String, a JsonElement, or
* null to indicate the end of the stream. Callers should use instanceof to
* inspect the return type.
*/
public Object read() throws IOException {
char[] buffer = new char[BUFFER_LENGTH];
reader.mark(BUFFER_LENGTH);
int count = 0;
int textEnd;
while (true) {
int r = reader.read(buffer, count, buffer.length - count);
if (r == -1) {
// the input is exhausted; return the remaining characters
textEnd = count;
break;
}
count += r;
int possibleMarker = findPossibleMarker(buffer, count);
if (possibleMarker != 0) {
// return the characters that precede the marker
textEnd = possibleMarker;
break;
}
if (count < marker.length()) {
// the buffer contains only the prefix of a marker so we must read more
continue;
}
// we've read a marker so return the value that follows
reader.reset();
String json = reader.readLine().substring(marker.length());
return jsonParser.parse(json);
}
if (count == 0) {
return null;
}
// return characters
reader.reset();
count = reader.read(buffer, 0, textEnd);
return new String(buffer, 0, count);
}
@Override public void close() throws IOException {
reader.close();
}
/**
* Returns the index of marker in {@code chars}, stopping at {@code limit}.
* Should the chars end with a prefix of marker, the offset of that prefix
* is returned.
*/
int findPossibleMarker(char[] chars, int limit) {
search:
for (int i = 0; true; i++) {
for (int m = 0; m < marker.length() && i + m < limit; m++) {
if (chars[i + m] != marker.charAt(m)) {
continue search;
}
}
return i;
}
}
}
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