| // Copyright 2014 The Bazel Authors. All rights reserved. |
| // |
| // 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.devtools.build.lib.util.io; |
| |
| import static java.nio.charset.StandardCharsets.UTF_8; |
| |
| import java.io.IOException; |
| import java.io.OutputStream; |
| |
| /** |
| * A stream that writes to another one, emittig a prefix before every line |
| * it emits. This stream will also add a newline for every flush; so it's not |
| * useful for anything other than simple text data (e.g. log files). Here's |
| * an example which demonstrates how an explicit flush or a flush caused by |
| * a full buffer causes a newline to be added to the output. |
| * |
| * <code> |
| * foo bar |
| * baz ba[flush]ng |
| * boo |
| * </code> |
| * |
| * This results in this output being emitted: |
| * |
| * <code> |
| * my prefix: foo bar |
| * my prefix: ba |
| * my prefix: ng |
| * my prefix: boo |
| * </code> |
| */ |
| public final class LinePrefixingOutputStream extends LineFlushingOutputStream { |
| |
| private byte[] linePrefix; |
| private final OutputStream sink; |
| |
| public LinePrefixingOutputStream(String linePrefix, OutputStream sink) { |
| this.linePrefix = linePrefix.getBytes(UTF_8); |
| this.sink = sink; |
| } |
| |
| @Override |
| protected void flushingHook() throws IOException { |
| synchronized (sink) { |
| if (len == 0) { |
| sink.flush(); |
| return; |
| } |
| byte lastByte = buffer[len - 1]; |
| boolean lineIsIncomplete = lastByte != NEWLINE; |
| sink.write(linePrefix); |
| sink.write(buffer, 0, len); |
| if (lineIsIncomplete) { |
| sink.write(NEWLINE); |
| } |
| sink.flush(); |
| len = 0; |
| } |
| } |
| |
| } |