ByteSource.java
/*
* Copyright (C) 2012 The Guava Authors
*
* 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.common.io;
import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.io.ByteStreams.createBuffer;
import static com.google.common.io.ByteStreams.skipUpTo;
import com.google.common.annotations.Beta;
import com.google.common.annotations.GwtIncompatible;
import com.google.common.base.Ascii;
import com.google.common.base.Optional;
import com.google.common.collect.ImmutableList;
import com.google.common.hash.Funnels;
import com.google.common.hash.HashCode;
import com.google.common.hash.HashFunction;
import com.google.common.hash.Hasher;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import java.io.BufferedInputStream;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.Reader;
import java.nio.charset.Charset;
import java.util.Arrays;
import java.util.Collection;
import java.util.Iterator;
import org.checkerframework.checker.nullness.qual.Nullable;
/**
* A readable source of bytes, such as a file. Unlike an {@link InputStream}, a {@code ByteSource}
* is not an open, stateful stream for input that can be read and closed. Instead, it is an
* immutable <i>supplier</i> of {@code InputStream} instances.
*
* <p>{@code ByteSource} provides two kinds of methods:
*
* <ul>
* <li><b>Methods that return a stream:</b> These methods should return a <i>new</i>, independent
* instance each time they are called. The caller is responsible for ensuring that the
* returned stream is closed.
* <li><b>Convenience methods:</b> These are implementations of common operations that are
* typically implemented by opening a stream using one of the methods in the first category,
* doing something and finally closing the stream that was opened.
* </ul>
*
* <p><b>Note:</b> In general, {@code ByteSource} is intended to be used for "file-like" sources
* that provide streams that are:
*
* <ul>
* <li><b>Finite:</b> Many operations, such as {@link #size()} and {@link #read()}, will either
* block indefinitely or fail if the source creates an infinite stream.
* <li><b>Non-destructive:</b> A <i>destructive</i> stream will consume or otherwise alter the
* bytes of the source as they are read from it. A source that provides such streams will not
* be reusable, and operations that read from the stream (including {@link #size()}, in some
* implementations) will prevent further operations from completing as expected.
* </ul>
*
* @since 14.0
* @author Colin Decker
*/
@GwtIncompatible
@ElementTypesAreNonnullByDefault
public abstract class ByteSource {
/** Constructor for use by subclasses. */
protected ByteSource() {}
/**
* Returns a {@link CharSource} view of this byte source that decodes bytes read from this source
* as characters using the given {@link Charset}.
*
* <p>If {@link CharSource#asByteSource} is called on the returned source with the same charset,
* the default implementation of this method will ensure that the original {@code ByteSource} is
* returned, rather than round-trip encoding. Subclasses that override this method should behave
* the same way.
*/
public CharSource asCharSource(Charset charset) {
return new AsCharSource(charset);
}
/**
* Opens a new {@link InputStream} for reading from this source. This method returns a new,
* independent stream each time it is called.
*
* <p>The caller is responsible for ensuring that the returned stream is closed.
*
* @throws IOException if an I/O error occurs while opening the stream
*/
public abstract InputStream openStream() throws IOException;
/**
* Opens a new buffered {@link InputStream} for reading from this source. The returned stream is
* not required to be a {@link BufferedInputStream} in order to allow implementations to simply
* delegate to {@link #openStream()} when the stream returned by that method does not benefit from
* additional buffering (for example, a {@code ByteArrayInputStream}). This method returns a new,
* independent stream each time it is called.
*
* <p>The caller is responsible for ensuring that the returned stream is closed.
*
* @throws IOException if an I/O error occurs while opening the stream
* @since 15.0 (in 14.0 with return type {@link BufferedInputStream})
*/
public InputStream openBufferedStream() throws IOException {
InputStream in = openStream();
return (in instanceof BufferedInputStream)
? (BufferedInputStream) in
: new BufferedInputStream(in);
}
/**
* Returns a view of a slice of this byte source that is at most {@code length} bytes long
* starting at the given {@code offset}. If {@code offset} is greater than the size of this
* source, the returned source will be empty. If {@code offset + length} is greater than the size
* of this source, the returned source will contain the slice starting at {@code offset} and
* ending at the end of this source.
*
* @throws IllegalArgumentException if {@code offset} or {@code length} is negative
*/
public ByteSource slice(long offset, long length) {
return new SlicedByteSource(offset, length);
}
/**
* Returns whether the source has zero bytes. The default implementation first checks {@link
* #sizeIfKnown}, returning true if it's known to be zero and false if it's known to be non-zero.
* If the size is not known, it falls back to opening a stream and checking for EOF.
*
* <p>Note that, in cases where {@code sizeIfKnown} returns zero, it is <i>possible</i> that bytes
* are actually available for reading. (For example, some special files may return a size of 0
* despite actually having content when read.) This means that a source may return {@code true}
* from {@code isEmpty()} despite having readable content.
*
* @throws IOException if an I/O error occurs
* @since 15.0
*/
public boolean isEmpty() throws IOException {
Optional<Long> sizeIfKnown = sizeIfKnown();
if (sizeIfKnown.isPresent()) {
return sizeIfKnown.get() == 0L;
}
Closer closer = Closer.create();
try {
InputStream in = closer.register(openStream());
return in.read() == -1;
} catch (Throwable e) {
throw closer.rethrow(e);
} finally {
closer.close();
}
}
/**
* Returns the size of this source in bytes, if the size can be easily determined without actually
* opening the data stream.
*
* <p>The default implementation returns {@link Optional#absent}. Some sources, such as a file,
* may return a non-absent value. Note that in such cases, it is <i>possible</i> that this method
* will return a different number of bytes than would be returned by reading all of the bytes (for
* example, some special files may return a size of 0 despite actually having content when read).
*
* <p>Additionally, for mutable sources such as files, a subsequent read may return a different
* number of bytes if the contents are changed.
*
* @since 19.0
*/
@Beta
public Optional<Long> sizeIfKnown() {
return Optional.absent();
}
/**
* Returns the size of this source in bytes, even if doing so requires opening and traversing an
* entire stream. To avoid a potentially expensive operation, see {@link #sizeIfKnown}.
*
* <p>The default implementation calls {@link #sizeIfKnown} and returns the value if present. If
* absent, it will fall back to a heavyweight operation that will open a stream, read (or {@link
* InputStream#skip(long) skip}, if possible) to the end of the stream and return the total number
* of bytes that were read.
*
* <p>Note that for some sources that implement {@link #sizeIfKnown} to provide a more efficient
* implementation, it is <i>possible</i> that this method will return a different number of bytes
* than would be returned by reading all of the bytes (for example, some special files may return
* a size of 0 despite actually having content when read).
*
* <p>In either case, for mutable sources such as files, a subsequent read may return a different
* number of bytes if the contents are changed.
*
* @throws IOException if an I/O error occurs while reading the size of this source
*/
public long size() throws IOException {
Optional<Long> sizeIfKnown = sizeIfKnown();
if (sizeIfKnown.isPresent()) {
return sizeIfKnown.get();
}
Closer closer = Closer.create();
try {
InputStream in = closer.register(openStream());
return countBySkipping(in);
} catch (IOException e) {
// skip may not be supported... at any rate, try reading
} finally {
closer.close();
}
closer = Closer.create();
try {
InputStream in = closer.register(openStream());
return ByteStreams.exhaust(in);
} catch (Throwable e) {
throw closer.rethrow(e);
} finally {
closer.close();
}
}
/** Counts the bytes in the given input stream using skip if possible. */
private long countBySkipping(InputStream in) throws IOException {
long count = 0;
long skipped;
while ((skipped = skipUpTo(in, Integer.MAX_VALUE)) > 0) {
count += skipped;
}
return count;
}
/**
* Copies the contents of this byte source to the given {@code OutputStream}. Does not close
* {@code output}.
*
* @return the number of bytes copied
* @throws IOException if an I/O error occurs while reading from this source or writing to {@code
* output}
*/
@CanIgnoreReturnValue
public long copyTo(OutputStream output) throws IOException {
checkNotNull(output);
Closer closer = Closer.create();
try {
InputStream in = closer.register(openStream());
return ByteStreams.copy(in, output);
} catch (Throwable e) {
throw closer.rethrow(e);
} finally {
closer.close();
}
}
/**
* Copies the contents of this byte source to the given {@code ByteSink}.
*
* @return the number of bytes copied
* @throws IOException if an I/O error occurs while reading from this source or writing to {@code
* sink}
*/
@CanIgnoreReturnValue
public long copyTo(ByteSink sink) throws IOException {
checkNotNull(sink);
Closer closer = Closer.create();
try {
InputStream in = closer.register(openStream());
OutputStream out = closer.register(sink.openStream());
return ByteStreams.copy(in, out);
} catch (Throwable e) {
throw closer.rethrow(e);
} finally {
closer.close();
}
}
/**
* Reads the full contents of this byte source as a byte array.
*
* @throws IOException if an I/O error occurs while reading from this source
*/
public byte[] read() throws IOException {
Closer closer = Closer.create();
try {
InputStream in = closer.register(openStream());
Optional<Long> size = sizeIfKnown();
return size.isPresent()
? ByteStreams.toByteArray(in, size.get())
: ByteStreams.toByteArray(in);
} catch (Throwable e) {
throw closer.rethrow(e);
} finally {
closer.close();
}
}
/**
* Reads the contents of this byte source using the given {@code processor} to process bytes as
* they are read. Stops when all bytes have been read or the consumer returns {@code false}.
* Returns the result produced by the processor.
*
* @throws IOException if an I/O error occurs while reading from this source or if {@code
* processor} throws an {@code IOException}
* @since 16.0
*/
@Beta
@CanIgnoreReturnValue // some processors won't return a useful result
public <T extends @Nullable Object> T read(ByteProcessor<T> processor) throws IOException {
checkNotNull(processor);
Closer closer = Closer.create();
try {
InputStream in = closer.register(openStream());
return ByteStreams.readBytes(in, processor);
} catch (Throwable e) {
throw closer.rethrow(e);
} finally {
closer.close();
}
}
/**
* Hashes the contents of this byte source using the given hash function.
*
* @throws IOException if an I/O error occurs while reading from this source
*/
public HashCode hash(HashFunction hashFunction) throws IOException {
Hasher hasher = hashFunction.newHasher();
copyTo(Funnels.asOutputStream(hasher));
return hasher.hash();
}
/**
* Checks that the contents of this byte source are equal to the contents of the given byte
* source.
*
* @throws IOException if an I/O error occurs while reading from this source or {@code other}
*/
public boolean contentEquals(ByteSource other) throws IOException {
checkNotNull(other);
byte[] buf1 = createBuffer();
byte[] buf2 = createBuffer();
Closer closer = Closer.create();
try {
InputStream in1 = closer.register(openStream());
InputStream in2 = closer.register(other.openStream());
while (true) {
int read1 = ByteStreams.read(in1, buf1, 0, buf1.length);
int read2 = ByteStreams.read(in2, buf2, 0, buf2.length);
if (read1 != read2 || !Arrays.equals(buf1, buf2)) {
return false;
} else if (read1 != buf1.length) {
return true;
}
}
} catch (Throwable e) {
throw closer.rethrow(e);
} finally {
closer.close();
}
}
/**
* Concatenates multiple {@link ByteSource} instances into a single source. Streams returned from
* the source will contain the concatenated data from the streams of the underlying sources.
*
* <p>Only one underlying stream will be open at a time. Closing the concatenated stream will
* close the open underlying stream.
*
* @param sources the sources to concatenate
* @return a {@code ByteSource} containing the concatenated data
* @since 15.0
*/
public static ByteSource concat(Iterable<? extends ByteSource> sources) {
return new ConcatenatedByteSource(sources);
}
/**
* Concatenates multiple {@link ByteSource} instances into a single source. Streams returned from
* the source will contain the concatenated data from the streams of the underlying sources.
*
* <p>Only one underlying stream will be open at a time. Closing the concatenated stream will
* close the open underlying stream.
*
* <p>Note: The input {@code Iterator} will be copied to an {@code ImmutableList} when this method
* is called. This will fail if the iterator is infinite and may cause problems if the iterator
* eagerly fetches data for each source when iterated (rather than producing sources that only
* load data through their streams). Prefer using the {@link #concat(Iterable)} overload if
* possible.
*
* @param sources the sources to concatenate
* @return a {@code ByteSource} containing the concatenated data
* @throws NullPointerException if any of {@code sources} is {@code null}
* @since 15.0
*/
public static ByteSource concat(Iterator<? extends ByteSource> sources) {
return concat(ImmutableList.copyOf(sources));
}
/**
* Concatenates multiple {@link ByteSource} instances into a single source. Streams returned from
* the source will contain the concatenated data from the streams of the underlying sources.
*
* <p>Only one underlying stream will be open at a time. Closing the concatenated stream will
* close the open underlying stream.
*
* @param sources the sources to concatenate
* @return a {@code ByteSource} containing the concatenated data
* @throws NullPointerException if any of {@code sources} is {@code null}
* @since 15.0
*/
public static ByteSource concat(ByteSource... sources) {
return concat(ImmutableList.copyOf(sources));
}
/**
* Returns a view of the given byte array as a {@link ByteSource}. To view only a specific range
* in the array, use {@code ByteSource.wrap(b).slice(offset, length)}.
*
* <p>Note that the given byte array may be passed directly to methods on, for example, {@code
* OutputStream} (when {@code copyTo(OutputStream)} is called on the resulting {@code
* ByteSource}). This could allow a malicious {@code OutputStream} implementation to modify the
* contents of the array, but provides better performance in the normal case.
*
* @since 15.0 (since 14.0 as {@code ByteStreams.asByteSource(byte[])}).
*/
public static ByteSource wrap(byte[] b) {
return new ByteArrayByteSource(b);
}
/**
* Returns an immutable {@link ByteSource} that contains no bytes.
*
* @since 15.0
*/
public static ByteSource empty() {
return EmptyByteSource.INSTANCE;
}
/**
* A char source that reads bytes from this source and decodes them as characters using a charset.
*/
class AsCharSource extends CharSource {
final Charset charset;
AsCharSource(Charset charset) {
this.charset = checkNotNull(charset);
}
@Override
public ByteSource asByteSource(Charset charset) {
if (charset.equals(this.charset)) {
return ByteSource.this;
}
return super.asByteSource(charset);
}
@Override
public Reader openStream() throws IOException {
return new InputStreamReader(ByteSource.this.openStream(), charset);
}
@Override
public String read() throws IOException {
// Reading all the data as a byte array is more efficient than the default read()
// implementation because:
// 1. the string constructor can avoid an extra copy most of the time by correctly sizing the
// internal char array (hard to avoid using StringBuilder)
// 2. we avoid extra copies into temporary buffers altogether
// The downside is that this will cause us to store the file bytes in memory twice for a short
// amount of time.
return new String(ByteSource.this.read(), charset);
}
@Override
public String toString() {
return ByteSource.this.toString() + ".asCharSource(" + charset + ")";
}
}
/** A view of a subsection of the containing byte source. */
private final class SlicedByteSource extends ByteSource {
final long offset;
final long length;
SlicedByteSource(long offset, long length) {
checkArgument(offset >= 0, "offset (%s) may not be negative", offset);
checkArgument(length >= 0, "length (%s) may not be negative", length);
this.offset = offset;
this.length = length;
}
@Override
public InputStream openStream() throws IOException {
return sliceStream(ByteSource.this.openStream());
}
@Override
public InputStream openBufferedStream() throws IOException {
return sliceStream(ByteSource.this.openBufferedStream());
}
private InputStream sliceStream(InputStream in) throws IOException {
if (offset > 0) {
long skipped;
try {
skipped = ByteStreams.skipUpTo(in, offset);
} catch (Throwable e) {
Closer closer = Closer.create();
closer.register(in);
try {
throw closer.rethrow(e);
} finally {
closer.close();
}
}
if (skipped < offset) {
// offset was beyond EOF
in.close();
return new ByteArrayInputStream(new byte[0]);
}
}
return ByteStreams.limit(in, length);
}
@Override
public ByteSource slice(long offset, long length) {
checkArgument(offset >= 0, "offset (%s) may not be negative", offset);
checkArgument(length >= 0, "length (%s) may not be negative", length);
long maxLength = this.length - offset;
return maxLength <= 0
? ByteSource.empty()
: ByteSource.this.slice(this.offset + offset, Math.min(length, maxLength));
}
@Override
public boolean isEmpty() throws IOException {
return length == 0 || super.isEmpty();
}
@Override
public Optional<Long> sizeIfKnown() {
Optional<Long> optionalUnslicedSize = ByteSource.this.sizeIfKnown();
if (optionalUnslicedSize.isPresent()) {
long unslicedSize = optionalUnslicedSize.get();
long off = Math.min(offset, unslicedSize);
return Optional.of(Math.min(length, unslicedSize - off));
}
return Optional.absent();
}
@Override
public String toString() {
return ByteSource.this.toString() + ".slice(" + offset + ", " + length + ")";
}
}
private static class ByteArrayByteSource extends ByteSource {
final byte[] bytes;
final int offset;
final int length;
ByteArrayByteSource(byte[] bytes) {
this(bytes, 0, bytes.length);
}
// NOTE: Preconditions are enforced by slice, the only non-trivial caller.
ByteArrayByteSource(byte[] bytes, int offset, int length) {
this.bytes = bytes;
this.offset = offset;
this.length = length;
}
@Override
public InputStream openStream() {
return new ByteArrayInputStream(bytes, offset, length);
}
@Override
public InputStream openBufferedStream() throws IOException {
return openStream();
}
@Override
public boolean isEmpty() {
return length == 0;
}
@Override
public long size() {
return length;
}
@Override
public Optional<Long> sizeIfKnown() {
return Optional.of((long) length);
}
@Override
public byte[] read() {
return Arrays.copyOfRange(bytes, offset, offset + length);
}
@SuppressWarnings("CheckReturnValue") // it doesn't matter what processBytes returns here
@Override
@ParametricNullness
public <T extends @Nullable Object> T read(ByteProcessor<T> processor) throws IOException {
processor.processBytes(bytes, offset, length);
return processor.getResult();
}
@Override
public long copyTo(OutputStream output) throws IOException {
output.write(bytes, offset, length);
return length;
}
@Override
public HashCode hash(HashFunction hashFunction) throws IOException {
return hashFunction.hashBytes(bytes, offset, length);
}
@Override
public ByteSource slice(long offset, long length) {
checkArgument(offset >= 0, "offset (%s) may not be negative", offset);
checkArgument(length >= 0, "length (%s) may not be negative", length);
offset = Math.min(offset, this.length);
length = Math.min(length, this.length - offset);
int newOffset = this.offset + (int) offset;
return new ByteArrayByteSource(bytes, newOffset, (int) length);
}
@Override
public String toString() {
return "ByteSource.wrap("
+ Ascii.truncate(BaseEncoding.base16().encode(bytes, offset, length), 30, "...")
+ ")";
}
}
private static final class EmptyByteSource extends ByteArrayByteSource {
static final EmptyByteSource INSTANCE = new EmptyByteSource();
EmptyByteSource() {
super(new byte[0]);
}
@Override
public CharSource asCharSource(Charset charset) {
checkNotNull(charset);
return CharSource.empty();
}
@Override
public byte[] read() {
return bytes; // length is 0, no need to clone
}
@Override
public String toString() {
return "ByteSource.empty()";
}
}
private static final class ConcatenatedByteSource extends ByteSource {
final Iterable<? extends ByteSource> sources;
ConcatenatedByteSource(Iterable<? extends ByteSource> sources) {
this.sources = checkNotNull(sources);
}
@Override
public InputStream openStream() throws IOException {
return new MultiInputStream(sources.iterator());
}
@Override
public boolean isEmpty() throws IOException {
for (ByteSource source : sources) {
if (!source.isEmpty()) {
return false;
}
}
return true;
}
@Override
public Optional<Long> sizeIfKnown() {
if (!(sources instanceof Collection)) {
// Infinite Iterables can cause problems here. Of course, it's true that most of the other
// methods on this class also have potential problems with infinite Iterables. But unlike
// those, this method can cause issues even if the user is dealing with a (finite) slice()
// of this source, since the slice's sizeIfKnown() method needs to know the size of the
// underlying source to know what its size actually is.
return Optional.absent();
}
long result = 0L;
for (ByteSource source : sources) {
Optional<Long> sizeIfKnown = source.sizeIfKnown();
if (!sizeIfKnown.isPresent()) {
return Optional.absent();
}
result += sizeIfKnown.get();
if (result < 0) {
// Overflow (or one or more sources that returned a negative size, but all bets are off in
// that case)
// Can't represent anything higher, and realistically there probably isn't anything that
// can actually be done anyway with the supposed 8+ exbibytes of data the source is
// claiming to have if we get here, so just stop.
return Optional.of(Long.MAX_VALUE);
}
}
return Optional.of(result);
}
@Override
public long size() throws IOException {
long result = 0L;
for (ByteSource source : sources) {
result += source.size();
if (result < 0) {
// Overflow (or one or more sources that returned a negative size, but all bets are off in
// that case)
// Can't represent anything higher, and realistically there probably isn't anything that
// can actually be done anyway with the supposed 8+ exbibytes of data the source is
// claiming to have if we get here, so just stop.
return Long.MAX_VALUE;
}
}
return result;
}
@Override
public String toString() {
return "ByteSource.concat(" + sources + ")";
}
}
}