com.larksuite.oapi.okio1_17.PeekSource Maven / Gradle / Ivy
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/*
* Copyright (C) 2018 Square, 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.larksuite.oapi.okio1_17;
import java.io.IOException;
/**
* A {@link Source} which peeks into an upstream {@link BufferedSource} and allows reading and
* expanding of the buffered data without consuming it. Does this by requesting additional data from
* the upstream source if needed and copying out of the internal buffer of the upstream source if
* possible.
*
* This source also maintains a snapshot of the starting location of the upstream buffer which it
* validates against on every read. If the upstream buffer is read from, this source will become
* invalid and throw {@link IllegalStateException} on any future reads.
*/
final class PeekSource implements Source {
private final BufferedSource upstream;
private final Buffer buffer;
private Segment expectedSegment;
private int expectedPos;
private boolean closed;
private long pos;
PeekSource(BufferedSource upstream) {
this.upstream = upstream;
this.buffer = upstream.buffer();
this.expectedSegment = buffer.head;
this.expectedPos = expectedSegment != null ? expectedSegment.pos : -1;
}
@Override public long read(Buffer sink, long byteCount) throws IOException {
if (closed) throw new IllegalStateException("closed");
// Source becomes invalid if there is an expected Segment and it and the expected position
// do not match the current head and head position of the upstream buffer
if (expectedSegment != null
&& (expectedSegment != buffer.head || expectedPos != buffer.head.pos)) {
throw new IllegalStateException("Peek source is invalid because upstream source was used");
}
upstream.request(pos + byteCount);
if (expectedSegment == null && buffer.head != null) {
// Only once the buffer actually holds data should an expected Segment and position be
// recorded. This allows reads from the peek source to repeatedly return -1 and for data to be
// added later. Unit tests depend on this behavior.
expectedSegment = buffer.head;
expectedPos = buffer.head.pos;
}
long toCopy = Math.min(byteCount, buffer.size - pos);
if (toCopy <= 0L) return -1L;
buffer.copyTo(sink, pos, toCopy);
pos += toCopy;
return toCopy;
}
@Override public Timeout timeout() {
return upstream.timeout();
}
@Override public void close() throws IOException {
closed = true;
}
}