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/*
* Copyright (C) 2014 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 io.prestosql.jdbc.$internal.okio;
import java.io.EOFException;
import java.io.IOException;
import java.util.zip.CRC32;
import java.util.zip.Inflater;
/**
* A source that uses GZIP to
* decompress data read from another source.
*/
public final class GzipSource implements Source {
private static final byte FHCRC = 1;
private static final byte FEXTRA = 2;
private static final byte FNAME = 3;
private static final byte FCOMMENT = 4;
private static final byte SECTION_HEADER = 0;
private static final byte SECTION_BODY = 1;
private static final byte SECTION_TRAILER = 2;
private static final byte SECTION_DONE = 3;
/** The current section. Always progresses forward. */
private int section = SECTION_HEADER;
/**
* Our source should yield a GZIP header (which we consume directly), followed
* by deflated bytes (which we consume via an InflaterSource), followed by a
* GZIP trailer (which we also consume directly).
*/
private final BufferedSource source;
/** The inflater used to decompress the deflated body. */
private final Inflater inflater;
/**
* The inflater source takes care of moving data between compressed source and
* decompressed sink buffers.
*/
private final InflaterSource inflaterSource;
/** Checksum used to check both the GZIP header and decompressed body. */
private final CRC32 crc = new CRC32();
public GzipSource(Source source) {
if (source == null) throw new IllegalArgumentException("source == null");
this.inflater = new Inflater(true);
this.source = Okio.buffer(source);
this.inflaterSource = new InflaterSource(this.source, inflater);
}
@Override public long read(Buffer sink, long byteCount) throws IOException {
if (byteCount < 0) throw new IllegalArgumentException("byteCount < 0: " + byteCount);
if (byteCount == 0) return 0;
// If we haven't consumed the header, we must consume it before anything else.
if (section == SECTION_HEADER) {
consumeHeader();
section = SECTION_BODY;
}
// Attempt to read at least a byte of the body. If we do, we're done.
if (section == SECTION_BODY) {
long offset = sink.size;
long result = inflaterSource.read(sink, byteCount);
if (result != -1) {
updateCrc(sink, offset, result);
return result;
}
section = SECTION_TRAILER;
}
// The body is exhausted; time to read the trailer. We always consume the
// trailer before returning a -1 exhausted result; that way if you read to
// the end of a GzipSource you guarantee that the CRC has been checked.
if (section == SECTION_TRAILER) {
consumeTrailer();
section = SECTION_DONE;
// Gzip streams self-terminate: they return -1 before their underlying
// source returns -1. Here we attempt to force the underlying stream to
// return -1 which may trigger it to release its resources. If it doesn't
// return -1, then our Gzip data finished prematurely!
if (!source.exhausted()) {
throw new IOException("gzip finished without exhausting source");
}
}
return -1;
}
private void consumeHeader() throws IOException {
// Read the 10-byte header. We peek at the flags byte first so we know if we
// need to CRC the entire header. Then we read the magic ID1ID2 sequence.
// We can skip everything else in the first 10 bytes.
// +---+---+---+---+---+---+---+---+---+---+
// |ID1|ID2|CM |FLG| MTIME |XFL|OS | (more-->)
// +---+---+---+---+---+---+---+---+---+---+
source.require(10);
byte flags = source.buffer().getByte(3);
boolean fhcrc = ((flags >> FHCRC) & 1) == 1;
if (fhcrc) updateCrc(source.buffer(), 0, 10);
short id1id2 = source.readShort();
checkEqual("ID1ID2", (short) 0x1f8b, id1id2);
source.skip(8);
// Skip optional extra fields.
// +---+---+=================================+
// | XLEN |...XLEN bytes of "extra field"...| (more-->)
// +---+---+=================================+
if (((flags >> FEXTRA) & 1) == 1) {
source.require(2);
if (fhcrc) updateCrc(source.buffer(), 0, 2);
int xlen = source.buffer().readShortLe();
source.require(xlen);
if (fhcrc) updateCrc(source.buffer(), 0, xlen);
source.skip(xlen);
}
// Skip an optional 0-terminated name.
// +=========================================+
// |...original file name, zero-terminated...| (more-->)
// +=========================================+
if (((flags >> FNAME) & 1) == 1) {
long index = source.indexOf((byte) 0);
if (index == -1) throw new EOFException();
if (fhcrc) updateCrc(source.buffer(), 0, index + 1);
source.skip(index + 1);
}
// Skip an optional 0-terminated comment.
// +===================================+
// |...file comment, zero-terminated...| (more-->)
// +===================================+
if (((flags >> FCOMMENT) & 1) == 1) {
long index = source.indexOf((byte) 0);
if (index == -1) throw new EOFException();
if (fhcrc) updateCrc(source.buffer(), 0, index + 1);
source.skip(index + 1);
}
// Confirm the optional header CRC.
// +---+---+
// | CRC16 |
// +---+---+
if (fhcrc) {
checkEqual("FHCRC", source.readShortLe(), (short) crc.getValue());
crc.reset();
}
}
private void consumeTrailer() throws IOException {
// Read the eight-byte trailer. Confirm the body's CRC and size.
// +---+---+---+---+---+---+---+---+
// | CRC32 | ISIZE |
// +---+---+---+---+---+---+---+---+
checkEqual("CRC", source.readIntLe(), (int) crc.getValue());
checkEqual("ISIZE", source.readIntLe(), (int) inflater.getBytesWritten());
}
@Override public Timeout timeout() {
return source.timeout();
}
@Override public void close() throws IOException {
inflaterSource.close();
}
/** Updates the CRC with the given bytes. */
private void updateCrc(Buffer buffer, long offset, long byteCount) {
// Skip segments that we aren't checksumming.
Segment s = buffer.head;
for (; offset >= (s.limit - s.pos); s = s.next) {
offset -= (s.limit - s.pos);
}
// Checksum one segment at a time.
for (; byteCount > 0; s = s.next) {
int pos = (int) (s.pos + offset);
int toUpdate = (int) Math.min(s.limit - pos, byteCount);
crc.update(s.data, pos, toUpdate);
byteCount -= toUpdate;
offset = 0;
}
}
private void checkEqual(String name, int expected, int actual) throws IOException {
if (actual != expected) {
throw new IOException(String.format(
"%s: actual 0x%08x != expected 0x%08x", name, actual, expected));
}
}
}
