/*
* 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.facebook.common.internal;
import java.io.ByteArrayOutputStream;
import java.io.DataInput;
import java.io.EOFException;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Arrays;
import static com.facebook.common.internal.Preconditions.checkNotNull;
/**
* Provides utility methods for working with byte arrays and I/O streams.
*
* @author Chris Nokleberg
* @author Colin Decker
* @since 1.0
*/
public final class ByteStreams {
private static final int BUF_SIZE = 0x1000; // 4K
private ByteStreams() {
}
/**
* Copies all bytes from the input stream to the output stream. Does not close or flush either
* stream.
*
* @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
*/
public static long copy(InputStream from, OutputStream to)
throws IOException {
checkNotNull(from);
checkNotNull(to);
byte[] buf = new byte[BUF_SIZE];
long total = 0;
while (true) {
int r = from.read(buf);
if (r == -1) {
break;
}
to.write(buf, 0, r);
total += r;
}
return total;
}
/**
* 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.
*
* <p>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.
*
* <p>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
*/
public static int read(InputStream in, byte[] b, int off, int len)
throws IOException {
checkNotNull(in);
checkNotNull(b);
if (len < 0) {
throw new IndexOutOfBoundsException("len is negative");
}
int total = 0;
while (total < len) {
int result = in.read(b, off + total, len - total);
if (result == -1) {
break;
}
total += result;
}
return total;
}
/**
* Reads all bytes from an input stream into a byte array.
* Does not close the stream.
*
* @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 {
ByteArrayOutputStream out = new ByteArrayOutputStream();
copy(in, out);
return out.toByteArray();
}
/**
* 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.
*/
public static byte[] toByteArray(
InputStream in,
int expectedSize) throws IOException {
byte[] bytes = new byte[expectedSize];
int remaining = expectedSize;
while (remaining > 0) {
int off = 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
FastByteArrayOutputStream out = new FastByteArrayOutputStream();
out.write(b); // write the byte we read when testing for end of stream
copy(in, out);
byte[] result = new byte[bytes.length + out.size()];
System.arraycopy(bytes, 0, result, 0, bytes.length);
out.writeTo(result, bytes.length);
return result;
}
/**
* BAOS that provides limited access to its internal byte array.
*/
private static final class FastByteArrayOutputStream
extends ByteArrayOutputStream {
/**
* Writes the contents of the internal buffer to the given array starting
* at the given offset. Assumes the array has space to hold count bytes.
*/
void writeTo(byte[] b, int off) {
System.arraycopy(buf, 0, b, off, count);
}
}
/**
* 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");
}
}
}