Paul Duffin | 7fc0b45 | 2015-11-10 17:45:15 +0000 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (C) 2010 Google Inc. |
| 3 | * |
| 4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | * you may not use this file except in compliance with the License. |
| 6 | * You may obtain a copy of the License at |
| 7 | * |
| 8 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | * |
| 10 | * Unless required by applicable law or agreed to in writing, software |
| 11 | * distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | * See the License for the specific language governing permissions and |
| 14 | * limitations under the License. |
| 15 | */ |
| 16 | |
| 17 | package com.google.caliper.util; |
| 18 | |
| 19 | import com.google.gson.JsonParser; |
| 20 | |
| 21 | import java.io.BufferedReader; |
| 22 | import java.io.Closeable; |
| 23 | import java.io.IOException; |
| 24 | import java.io.Reader; |
| 25 | |
| 26 | /** |
| 27 | * Reads a stream containing inline JSON objects. Each JSON object is prefixed |
| 28 | * by a marker string and suffixed by a newline character. |
| 29 | */ |
| 30 | public final class InterleavedReader implements Closeable { |
| 31 | |
| 32 | /** |
| 33 | * The length of the scratch buffer to search for markers in. Also acts as an |
| 34 | * upper bound on the length of returned strings. Not used as an I/O buffer. |
| 35 | */ |
| 36 | private static final int BUFFER_LENGTH = 80; |
| 37 | |
| 38 | private final String marker; |
| 39 | private final BufferedReader reader; |
| 40 | private final JsonParser jsonParser = new JsonParser(); |
| 41 | |
| 42 | public static final String DEFAULT_MARKER = "//ZxJ/"; |
| 43 | |
| 44 | public InterleavedReader(Reader reader) { |
| 45 | this(DEFAULT_MARKER, reader); |
| 46 | } |
| 47 | |
| 48 | public InterleavedReader(String marker, Reader reader) { |
| 49 | if (marker.length() > BUFFER_LENGTH) { |
| 50 | throw new IllegalArgumentException("marker.length() > BUFFER_LENGTH"); |
| 51 | } |
| 52 | this.marker = marker; |
| 53 | this.reader = reader instanceof BufferedReader |
| 54 | ? (BufferedReader) reader |
| 55 | : new BufferedReader(reader); |
| 56 | } |
| 57 | |
| 58 | /** |
| 59 | * Returns the next value in the stream: either a String, a JsonElement, or |
| 60 | * null to indicate the end of the stream. Callers should use instanceof to |
| 61 | * inspect the return type. |
| 62 | */ |
| 63 | public Object read() throws IOException { |
| 64 | char[] buffer = new char[BUFFER_LENGTH]; |
| 65 | reader.mark(BUFFER_LENGTH); |
| 66 | int count = 0; |
| 67 | int textEnd; |
| 68 | |
| 69 | while (true) { |
| 70 | int r = reader.read(buffer, count, buffer.length - count); |
| 71 | |
| 72 | if (r == -1) { |
| 73 | // the input is exhausted; return the remaining characters |
| 74 | textEnd = count; |
| 75 | break; |
| 76 | } |
| 77 | |
| 78 | count += r; |
| 79 | int possibleMarker = findPossibleMarker(buffer, count); |
| 80 | |
| 81 | if (possibleMarker != 0) { |
| 82 | // return the characters that precede the marker |
| 83 | textEnd = possibleMarker; |
| 84 | break; |
| 85 | } |
| 86 | |
| 87 | if (count < marker.length()) { |
| 88 | // the buffer contains only the prefix of a marker so we must read more |
| 89 | continue; |
| 90 | } |
| 91 | |
| 92 | // we've read a marker so return the value that follows |
| 93 | reader.reset(); |
| 94 | String json = reader.readLine().substring(marker.length()); |
| 95 | return jsonParser.parse(json); |
| 96 | } |
| 97 | |
| 98 | if (count == 0) { |
| 99 | return null; |
| 100 | } |
| 101 | |
| 102 | // return characters |
| 103 | reader.reset(); |
| 104 | count = reader.read(buffer, 0, textEnd); |
| 105 | return new String(buffer, 0, count); |
| 106 | } |
| 107 | |
| 108 | @Override public void close() throws IOException { |
| 109 | reader.close(); |
| 110 | } |
| 111 | |
| 112 | /** |
| 113 | * Returns the index of marker in {@code chars}, stopping at {@code limit}. |
| 114 | * Should the chars end with a prefix of marker, the offset of that prefix |
| 115 | * is returned. |
| 116 | */ |
| 117 | int findPossibleMarker(char[] chars, int limit) { |
| 118 | search: |
| 119 | for (int i = 0; true; i++) { |
| 120 | for (int m = 0; m < marker.length() && i + m < limit; m++) { |
| 121 | if (chars[i + m] != marker.charAt(m)) { |
| 122 | continue search; |
| 123 | } |
| 124 | } |
| 125 | return i; |
| 126 | } |
| 127 | } |
| 128 | } |