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/*
* Copyright (C) 2007 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.base.Preconditions.checkPositionIndex;
import static com.google.common.base.Preconditions.checkPositionIndexes;
import static java.lang.Math.max;
import static java.lang.Math.min;
import com.google.common.annotations.GwtIncompatible;
import com.google.common.annotations.J2ktIncompatible;
import com.google.common.math.IntMath;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.DataInput;
import java.io.DataInputStream;
import java.io.DataOutput;
import java.io.DataOutputStream;
import java.io.EOFException;
import java.io.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.channels.ReadableByteChannel;
import java.nio.channels.WritableByteChannel;
import java.util.ArrayDeque;
import java.util.Arrays;
import java.util.Queue;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.Nullable;
/**
* Provides utility methods for working with byte arrays and I/O streams.
*
* @author Chris Nokleberg
* @author Colin Decker
* @since 1.0
*/
@J2ktIncompatible
@GwtIncompatible
@ElementTypesAreNonnullByDefault
public final class ByteStreams {
private static final int BUFFER_SIZE = 8192;
/** Creates a new byte array for buffering reads or writes. */
static byte[] createBuffer() {
return new byte[BUFFER_SIZE];
}
/**
* There are three methods to implement {@link FileChannel#transferTo(long, long,
* WritableByteChannel)}:
*
*
* - Use sendfile(2) or equivalent. Requires that both the input channel and the output
* channel have their own file descriptors. Generally this only happens when both channels
* are files or sockets. This performs zero copies - the bytes never enter userspace.
*
- Use mmap(2) or equivalent. Requires that either the input channel or the output channel
* have file descriptors. Bytes are copied from the file into a kernel buffer, then directly
* into the other buffer (userspace). Note that if the file is very large, a naive
* implementation will effectively put the whole file in memory. On many systems with paging
* and virtual memory, this is not a problem - because it is mapped read-only, the kernel
* can always page it to disk "for free". However, on systems where killing processes
* happens all the time in normal conditions (i.e., android) the OS must make a tradeoff
* between paging memory and killing other processes - so allocating a gigantic buffer and
* then sequentially accessing it could result in other processes dying. This is solvable
* via madvise(2), but that obviously doesn't exist in java.
*
- Ordinary copy. Kernel copies bytes into a kernel buffer, from a kernel buffer into a
* userspace buffer (byte[] or ByteBuffer), then copies them from that buffer into the
* destination channel.
*
*
* This value is intended to be large enough to make the overhead of system calls negligible,
* without being so large that it causes problems for systems with atypical memory management if
* approaches 2 or 3 are used.
*/
private static final int ZERO_COPY_CHUNK_SIZE = 512 * 1024;
private ByteStreams() {}
/**
* Copies all bytes from the input stream to the output stream. Does not close or flush either
* stream.
*
* Java 9 users and later: this method should be treated as deprecated; use the
* equivalent {@link InputStream#transferTo} method instead.
*
* @param from the input stream to read from
* @param to the output stream to write to
* @return the number of bytes copied
* @throws IOException if an I/O error occurs
*/
@CanIgnoreReturnValue
public static long copy(InputStream from, OutputStream to) throws IOException {
checkNotNull(from);
checkNotNull(to);
byte[] buf = createBuffer();
long total = 0;
while (true) {
int r = from.read(buf);
if (r == -1) {
break;
}
to.write(buf, 0, r);
total += r;
}
return total;
}
/**
* Copies all bytes from the readable channel to the writable channel. Does not close or flush
* either channel.
*
* @param from the readable channel to read from
* @param to the writable channel to write to
* @return the number of bytes copied
* @throws IOException if an I/O error occurs
*/
@CanIgnoreReturnValue
public static long copy(ReadableByteChannel from, WritableByteChannel to) throws IOException {
checkNotNull(from);
checkNotNull(to);
if (from instanceof FileChannel) {
FileChannel sourceChannel = (FileChannel) from;
long oldPosition = sourceChannel.position();
long position = oldPosition;
long copied;
do {
copied = sourceChannel.transferTo(position, ZERO_COPY_CHUNK_SIZE, to);
position += copied;
sourceChannel.position(position);
} while (copied > 0 || position < sourceChannel.size());
return position - oldPosition;
}
ByteBuffer buf = ByteBuffer.wrap(createBuffer());
long total = 0;
while (from.read(buf) != -1) {
Java8Compatibility.flip(buf);
while (buf.hasRemaining()) {
total += to.write(buf);
}
Java8Compatibility.clear(buf);
}
return total;
}
/** Max array length on JVM. */
private static final int MAX_ARRAY_LEN = Integer.MAX_VALUE - 8;
/** Large enough to never need to expand, given the geometric progression of buffer sizes. */
private static final int TO_BYTE_ARRAY_DEQUE_SIZE = 20;
/**
* Returns a byte array containing the bytes from the buffers already in {@code bufs} (which have
* a total combined length of {@code totalLen} bytes) followed by all bytes remaining in the given
* input stream.
*/
private static byte[] toByteArrayInternal(InputStream in, Queue bufs, int totalLen)
throws IOException {
// Roughly size to match what has been read already. Some file systems, such as procfs, return 0
// as their length. These files are very small, so it's wasteful to allocate an 8KB buffer.
int initialBufferSize = min(BUFFER_SIZE, max(128, Integer.highestOneBit(totalLen) * 2));
// Starting with an 8k buffer, double the size of each successive buffer. Smaller buffers
// quadruple in size until they reach 8k, to minimize the number of small reads for longer
// streams. Buffers are retained in a deque so that there's no copying between buffers while
// reading and so all of the bytes in each new allocated buffer are available for reading from
// the stream.
for (int bufSize = initialBufferSize;
totalLen < MAX_ARRAY_LEN;
bufSize = IntMath.saturatedMultiply(bufSize, bufSize < 4096 ? 4 : 2)) {
byte[] buf = new byte[min(bufSize, MAX_ARRAY_LEN - totalLen)];
bufs.add(buf);
int off = 0;
while (off < buf.length) {
// always OK to fill buf; its size plus the rest of bufs is never more than MAX_ARRAY_LEN
int r = in.read(buf, off, buf.length - off);
if (r == -1) {
return combineBuffers(bufs, totalLen);
}
off += r;
totalLen += r;
}
}
// read MAX_ARRAY_LEN bytes without seeing end of stream
if (in.read() == -1) {
// oh, there's the end of the stream
return combineBuffers(bufs, MAX_ARRAY_LEN);
} else {
throw new OutOfMemoryError("input is too large to fit in a byte array");
}
}
private static byte[] combineBuffers(Queue bufs, int totalLen) {
if (bufs.isEmpty()) {
return new byte[0];
}
byte[] result = bufs.remove();
if (result.length == totalLen) {
return result;
}
int remaining = totalLen - result.length;
result = Arrays.copyOf(result, totalLen);
while (remaining > 0) {
byte[] buf = bufs.remove();
int bytesToCopy = min(remaining, buf.length);
int resultOffset = totalLen - remaining;
System.arraycopy(buf, 0, result, resultOffset, bytesToCopy);
remaining -= bytesToCopy;
}
return result;
}
/**
* Reads all bytes from an input stream into a byte array. Does not close the stream.
*
* Java 9+ users: use {@code in#readAllBytes()} instead.
*
* @param in the input stream to read from
* @return a byte array containing all the bytes from the stream
* @throws IOException if an I/O error occurs
*/
public static byte[] toByteArray(InputStream in) throws IOException {
checkNotNull(in);
return toByteArrayInternal(in, new ArrayDeque(TO_BYTE_ARRAY_DEQUE_SIZE), 0);
}
/**
* Reads all bytes from an input stream into a byte array. The given expected size is used to
* create an initial byte array, but if the actual number of bytes read from the stream differs,
* the correct result will be returned anyway.
*/
static byte[] toByteArray(InputStream in, long expectedSize) throws IOException {
checkArgument(expectedSize >= 0, "expectedSize (%s) must be non-negative", expectedSize);
if (expectedSize > MAX_ARRAY_LEN) {
throw new OutOfMemoryError(expectedSize + " bytes is too large to fit in a byte array");
}
byte[] bytes = new byte[(int) expectedSize];
int remaining = (int) expectedSize;
while (remaining > 0) {
int off = (int) expectedSize - remaining;
int read = in.read(bytes, off, remaining);
if (read == -1) {
// end of stream before reading expectedSize bytes
// just return the bytes read so far
return Arrays.copyOf(bytes, off);
}
remaining -= read;
}
// bytes is now full
int b = in.read();
if (b == -1) {
return bytes;
}
// the stream was longer, so read the rest normally
Queue bufs = new ArrayDeque<>(TO_BYTE_ARRAY_DEQUE_SIZE + 2);
bufs.add(bytes);
bufs.add(new byte[] {(byte) b});
return toByteArrayInternal(in, bufs, bytes.length + 1);
}
/**
* Reads and discards data from the given {@code InputStream} until the end of the stream is
* reached. Returns the total number of bytes read. Does not close the stream.
*
* @since 20.0
*/
@CanIgnoreReturnValue
public static long exhaust(InputStream in) throws IOException {
long total = 0;
long read;
byte[] buf = createBuffer();
while ((read = in.read(buf)) != -1) {
total += read;
}
return total;
}
/**
* Returns a new {@link ByteArrayDataInput} instance to read from the {@code bytes} array from the
* beginning.
*/
public static ByteArrayDataInput newDataInput(byte[] bytes) {
return newDataInput(new ByteArrayInputStream(bytes));
}
/**
* Returns a new {@link ByteArrayDataInput} instance to read from the {@code bytes} array,
* starting at the given position.
*
* @throws IndexOutOfBoundsException if {@code start} is negative or greater than the length of
* the array
*/
public static ByteArrayDataInput newDataInput(byte[] bytes, int start) {
checkPositionIndex(start, bytes.length);
return newDataInput(new ByteArrayInputStream(bytes, start, bytes.length - start));
}
/**
* Returns a new {@link ByteArrayDataInput} instance to read from the given {@code
* ByteArrayInputStream}. The given input stream is not reset before being read from by the
* returned {@code ByteArrayDataInput}.
*
* @since 17.0
*/
public static ByteArrayDataInput newDataInput(ByteArrayInputStream byteArrayInputStream) {
return new ByteArrayDataInputStream(checkNotNull(byteArrayInputStream));
}
private static class ByteArrayDataInputStream implements ByteArrayDataInput {
final DataInput input;
ByteArrayDataInputStream(ByteArrayInputStream byteArrayInputStream) {
this.input = new DataInputStream(byteArrayInputStream);
}
@Override
public void readFully(byte b[]) {
try {
input.readFully(b);
} catch (IOException e) {
throw new IllegalStateException(e);
}
}
@Override
public void readFully(byte b[], int off, int len) {
try {
input.readFully(b, off, len);
} catch (IOException e) {
throw new IllegalStateException(e);
}
}
@Override
public int skipBytes(int n) {
try {
return input.skipBytes(n);
} catch (IOException e) {
throw new IllegalStateException(e);
}
}
@Override
public boolean readBoolean() {
try {
return input.readBoolean();
} catch (IOException e) {
throw new IllegalStateException(e);
}
}
@Override
public byte readByte() {
try {
return input.readByte();
} catch (EOFException e) {
throw new IllegalStateException(e);
} catch (IOException impossible) {
throw new AssertionError(impossible);
}
}
@Override
public int readUnsignedByte() {
try {
return input.readUnsignedByte();
} catch (IOException e) {
throw new IllegalStateException(e);
}
}
@Override
public short readShort() {
try {
return input.readShort();
} catch (IOException e) {
throw new IllegalStateException(e);
}
}
@Override
public int readUnsignedShort() {
try {
return input.readUnsignedShort();
} catch (IOException e) {
throw new IllegalStateException(e);
}
}
@Override
public char readChar() {
try {
return input.readChar();
} catch (IOException e) {
throw new IllegalStateException(e);
}
}
@Override
public int readInt() {
try {
return input.readInt();
} catch (IOException e) {
throw new IllegalStateException(e);
}
}
@Override
public long readLong() {
try {
return input.readLong();
} catch (IOException e) {
throw new IllegalStateException(e);
}
}
@Override
public float readFloat() {
try {
return input.readFloat();
} catch (IOException e) {
throw new IllegalStateException(e);
}
}
@Override
public double readDouble() {
try {
return input.readDouble();
} catch (IOException e) {
throw new IllegalStateException(e);
}
}
@Override
@CheckForNull
public String readLine() {
try {
return input.readLine();
} catch (IOException e) {
throw new IllegalStateException(e);
}
}
@Override
public String readUTF() {
try {
return input.readUTF();
} catch (IOException e) {
throw new IllegalStateException(e);
}
}
}
/** Returns a new {@link ByteArrayDataOutput} instance with a default size. */
public static ByteArrayDataOutput newDataOutput() {
return newDataOutput(new ByteArrayOutputStream());
}
/**
* Returns a new {@link ByteArrayDataOutput} instance sized to hold {@code size} bytes before
* resizing.
*
* @throws IllegalArgumentException if {@code size} is negative
*/
public static ByteArrayDataOutput newDataOutput(int size) {
// When called at high frequency, boxing size generates too much garbage,
// so avoid doing that if we can.
if (size < 0) {
throw new IllegalArgumentException(String.format("Invalid size: %s", size));
}
return newDataOutput(new ByteArrayOutputStream(size));
}
/**
* Returns a new {@link ByteArrayDataOutput} instance which writes to the given {@code
* ByteArrayOutputStream}. The given output stream is not reset before being written to by the
* returned {@code ByteArrayDataOutput} and new data will be appended to any existing content.
*
* Note that if the given output stream was not empty or is modified after the {@code
* ByteArrayDataOutput} is created, the contract for {@link ByteArrayDataOutput#toByteArray} will
* not be honored (the bytes returned in the byte array may not be exactly what was written via
* calls to {@code ByteArrayDataOutput}).
*
* @since 17.0
*/
public static ByteArrayDataOutput newDataOutput(ByteArrayOutputStream byteArrayOutputStream) {
return new ByteArrayDataOutputStream(checkNotNull(byteArrayOutputStream));
}
private static class ByteArrayDataOutputStream implements ByteArrayDataOutput {
final DataOutput output;
final ByteArrayOutputStream byteArrayOutputStream;
ByteArrayDataOutputStream(ByteArrayOutputStream byteArrayOutputStream) {
this.byteArrayOutputStream = byteArrayOutputStream;
output = new DataOutputStream(byteArrayOutputStream);
}
@Override
public void write(int b) {
try {
output.write(b);
} catch (IOException impossible) {
throw new AssertionError(impossible);
}
}
@Override
public void write(byte[] b) {
try {
output.write(b);
} catch (IOException impossible) {
throw new AssertionError(impossible);
}
}
@Override
public void write(byte[] b, int off, int len) {
try {
output.write(b, off, len);
} catch (IOException impossible) {
throw new AssertionError(impossible);
}
}
@Override
public void writeBoolean(boolean v) {
try {
output.writeBoolean(v);
} catch (IOException impossible) {
throw new AssertionError(impossible);
}
}
@Override
public void writeByte(int v) {
try {
output.writeByte(v);
} catch (IOException impossible) {
throw new AssertionError(impossible);
}
}
@Override
public void writeBytes(String s) {
try {
output.writeBytes(s);
} catch (IOException impossible) {
throw new AssertionError(impossible);
}
}
@Override
public void writeChar(int v) {
try {
output.writeChar(v);
} catch (IOException impossible) {
throw new AssertionError(impossible);
}
}
@Override
public void writeChars(String s) {
try {
output.writeChars(s);
} catch (IOException impossible) {
throw new AssertionError(impossible);
}
}
@Override
public void writeDouble(double v) {
try {
output.writeDouble(v);
} catch (IOException impossible) {
throw new AssertionError(impossible);
}
}
@Override
public void writeFloat(float v) {
try {
output.writeFloat(v);
} catch (IOException impossible) {
throw new AssertionError(impossible);
}
}
@Override
public void writeInt(int v) {
try {
output.writeInt(v);
} catch (IOException impossible) {
throw new AssertionError(impossible);
}
}
@Override
public void writeLong(long v) {
try {
output.writeLong(v);
} catch (IOException impossible) {
throw new AssertionError(impossible);
}
}
@Override
public void writeShort(int v) {
try {
output.writeShort(v);
} catch (IOException impossible) {
throw new AssertionError(impossible);
}
}
@Override
public void writeUTF(String s) {
try {
output.writeUTF(s);
} catch (IOException impossible) {
throw new AssertionError(impossible);
}
}
@Override
public byte[] toByteArray() {
return byteArrayOutputStream.toByteArray();
}
}
private static final OutputStream NULL_OUTPUT_STREAM =
new OutputStream() {
/** Discards the specified byte. */
@Override
public void write(int b) {}
/** Discards the specified byte array. */
@Override
public void write(byte[] b) {
checkNotNull(b);
}
/** Discards the specified byte array. */
@Override
public void write(byte[] b, int off, int len) {
checkNotNull(b);
checkPositionIndexes(off, off + len, b.length);
}
@Override
public String toString() {
return "ByteStreams.nullOutputStream()";
}
};
/**
* Returns an {@link OutputStream} that simply discards written bytes.
*
* @since 14.0 (since 1.0 as com.google.common.io.NullOutputStream)
*/
public static OutputStream nullOutputStream() {
return NULL_OUTPUT_STREAM;
}
/**
* Wraps a {@link InputStream}, limiting the number of bytes which can be read.
*
* @param in the input stream to be wrapped
* @param limit the maximum number of bytes to be read
* @return a length-limited {@link InputStream}
* @since 14.0 (since 1.0 as com.google.common.io.LimitInputStream)
*/
public static InputStream limit(InputStream in, long limit) {
return new LimitedInputStream(in, limit);
}
private static final class LimitedInputStream extends FilterInputStream {
private long left;
private long mark = -1;
LimitedInputStream(InputStream in, long limit) {
super(in);
checkNotNull(in);
checkArgument(limit >= 0, "limit must be non-negative");
left = limit;
}
@Override
public int available() throws IOException {
return (int) Math.min(in.available(), left);
}
// it's okay to mark even if mark isn't supported, as reset won't work
@Override
public synchronized void mark(int readLimit) {
in.mark(readLimit);
mark = left;
}
@Override
public int read() throws IOException {
if (left == 0) {
return -1;
}
int result = in.read();
if (result != -1) {
--left;
}
return result;
}
@Override
public int read(byte[] b, int off, int len) throws IOException {
if (left == 0) {
return -1;
}
len = (int) Math.min(len, left);
int result = in.read(b, off, len);
if (result != -1) {
left -= result;
}
return result;
}
@Override
public synchronized void reset() throws IOException {
if (!in.markSupported()) {
throw new IOException("Mark not supported");
}
if (mark == -1) {
throw new IOException("Mark not set");
}
in.reset();
left = mark;
}
@Override
public long skip(long n) throws IOException {
n = Math.min(n, left);
long skipped = in.skip(n);
left -= skipped;
return skipped;
}
}
/**
* Attempts to read enough bytes from the stream to fill the given byte array, with the same
* behavior as {@link DataInput#readFully(byte[])}. Does not close the stream.
*
* @param in the input stream to read from.
* @param b the buffer into which the data is read.
* @throws EOFException if this stream reaches the end before reading all the bytes.
* @throws IOException if an I/O error occurs.
*/
public static void readFully(InputStream in, byte[] b) throws IOException {
readFully(in, b, 0, b.length);
}
/**
* Attempts to read {@code len} bytes from the stream into the given array starting at {@code
* off}, with the same behavior as {@link DataInput#readFully(byte[], int, int)}. Does not close
* the stream.
*
* @param in the input stream to read from.
* @param b the buffer into which the data is read.
* @param off an int specifying the offset into the data.
* @param len an int specifying the number of bytes to read.
* @throws EOFException if this stream reaches the end before reading all the bytes.
* @throws IOException if an I/O error occurs.
*/
public static void readFully(InputStream in, byte[] b, int off, int len) throws IOException {
int read = read(in, b, off, len);
if (read != len) {
throw new EOFException(
"reached end of stream after reading " + read + " bytes; " + len + " bytes expected");
}
}
/**
* Discards {@code n} bytes of data from the input stream. This method will block until the full
* amount has been skipped. Does not close the stream.
*
* @param in the input stream to read from
* @param n the number of bytes to skip
* @throws EOFException if this stream reaches the end before skipping all the bytes
* @throws IOException if an I/O error occurs, or the stream does not support skipping
*/
public static void skipFully(InputStream in, long n) throws IOException {
long skipped = skipUpTo(in, n);
if (skipped < n) {
throw new EOFException(
"reached end of stream after skipping " + skipped + " bytes; " + n + " bytes expected");
}
}
/**
* Discards up to {@code n} bytes of data from the input stream. This method will block until
* either the full amount has been skipped or until the end of the stream is reached, whichever
* happens first. Returns the total number of bytes skipped.
*/
static long skipUpTo(InputStream in, long n) throws IOException {
long totalSkipped = 0;
// A buffer is allocated if skipSafely does not skip any bytes.
byte[] buf = null;
while (totalSkipped < n) {
long remaining = n - totalSkipped;
long skipped = skipSafely(in, remaining);
if (skipped == 0) {
// Do a buffered read since skipSafely could return 0 repeatedly, for example if
// in.available() always returns 0 (the default).
int skip = (int) Math.min(remaining, BUFFER_SIZE);
if (buf == null) {
// Allocate a buffer bounded by the maximum size that can be requested, for
// example an array of BUFFER_SIZE is unnecessary when the value of remaining
// is smaller.
buf = new byte[skip];
}
if ((skipped = in.read(buf, 0, skip)) == -1) {
// Reached EOF
break;
}
}
totalSkipped += skipped;
}
return totalSkipped;
}
/**
* Attempts to skip up to {@code n} bytes from the given input stream, but not more than {@code
* in.available()} bytes. This prevents {@code FileInputStream} from skipping more bytes than
* actually remain in the file, something that it {@linkplain java.io.FileInputStream#skip(long)
* specifies} it can do in its Javadoc despite the fact that it is violating the contract of
* {@code InputStream.skip()}.
*/
private static long skipSafely(InputStream in, long n) throws IOException {
int available = in.available();
return available == 0 ? 0 : in.skip(Math.min(available, n));
}
/**
* Process the bytes of the given input stream using the given processor.
*
* @param input the input stream to process
* @param processor the object to which to pass the bytes of the stream
* @return the result of the byte processor
* @throws IOException if an I/O error occurs
* @since 14.0
*/
@CanIgnoreReturnValue // some processors won't return a useful result
@ParametricNullness
public static T readBytes(
InputStream input, ByteProcessor processor) throws IOException {
checkNotNull(input);
checkNotNull(processor);
byte[] buf = createBuffer();
int read;
do {
read = input.read(buf);
} while (read != -1 && processor.processBytes(buf, 0, read));
return processor.getResult();
}
/**
* Reads some bytes from an input stream and stores them into the buffer array {@code b}. This
* method blocks until {@code len} bytes of input data have been read into the array, or end of
* file is detected. The number of bytes read is returned, possibly zero. Does not close the
* stream.
*
* A caller can detect EOF if the number of bytes read is less than {@code len}. All subsequent
* calls on the same stream will return zero.
*
*
If {@code b} is null, a {@code NullPointerException} is thrown. If {@code off} is negative,
* or {@code len} is negative, or {@code off+len} is greater than the length of the array {@code
* b}, then an {@code IndexOutOfBoundsException} is thrown. If {@code len} is zero, then no bytes
* are read. Otherwise, the first byte read is stored into element {@code b[off]}, the next one
* into {@code b[off+1]}, and so on. The number of bytes read is, at most, equal to {@code len}.
*
* @param in the input stream to read from
* @param b the buffer into which the data is read
* @param off an int specifying the offset into the data
* @param len an int specifying the number of bytes to read
* @return the number of bytes read
* @throws IOException if an I/O error occurs
* @throws IndexOutOfBoundsException if {@code off} is negative, if {@code len} is negative, or if
* {@code off + len} is greater than {@code b.length}
*/
@CanIgnoreReturnValue
// Sometimes you don't care how many bytes you actually read, I guess.
// (You know that it's either going to read len bytes or stop at EOF.)
public static int read(InputStream in, byte[] b, int off, int len) throws IOException {
checkNotNull(in);
checkNotNull(b);
if (len < 0) {
throw new IndexOutOfBoundsException(String.format("len (%s) cannot be negative", len));
}
checkPositionIndexes(off, off + len, b.length);
int total = 0;
while (total < len) {
int result = in.read(b, off + total, len - total);
if (result == -1) {
break;
}
total += result;
}
return total;
}
}