ByteArrayInputStreamはInputStreamからバイト配列としてデータを読み込むためのクラスである。byte型の配列としてbufというインスタンス変数が，次の読込位置を示すint型のインスタンス変数posが定義されている。
コンストラクタは，以下のようなものが定義されている。一つ目のものは与えられたバイト配列をすべて読み込む。２つ目のコンストラクタは与えられたバイト配列のうち，指定されたオフセットから指定された長さだけを読み込む。
- ByteArrayInputStream(byte buf[])
- ByteArrayInputStream(byte buf[], int offset, int length)
int read()メソッドは次のバイトを読込み，int型で返す。実装は0xFFとの積を計算している。int read(byte b[], int off, int len)メソッドでは引数で与えられたbyte型配列b[]に読み込んだデータをSystem.arraycopy()メソッドを使ってコピーしている。
readAllBytes()メソッドはストリームからすべてのデータをbyte型配列へ読み込んで返す。readNBytes(byte[] b, int off, int len)メソッドは指定のオフセットから指定の長さだけbyte型配列に読み込む。skip(long n)メソッドは，指定した長さだけストリームをスキップする。available()メソッドは残りのバイト数を返す。メソッド名と戻り値の内容にややずれがある印象だ。close()メソッドは実装されているものの，空である。
/*
* Copyright (c) 1994, 2018, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
package java.io;
import java.util.Arrays;
import java.util.Objects;
public class ByteArrayInputStream extends InputStream {
protected byte buf[];
protected int pos;
protected int mark = 0;
protected int count;
public ByteArrayInputStream(byte buf[]) {
this.buf = buf;
this.pos = 0;
this.count = buf.length;
}
public ByteArrayInputStream(byte buf[], int offset, int length) {
this.buf = buf;
this.pos = offset;
this.count = Math.min(offset + length, buf.length);
this.mark = offset;
}
public synchronized int read() {
return (pos < count) ? (buf[pos++] & 0xff) : -1;
}
public synchronized int read(byte b[], int off, int len) {
Objects.checkFromIndexSize(off, len, b.length);
if (pos >= count) {
return -1;
}
int avail = count – pos;
if (len > avail) {
len = avail;
}
if (len <= 0) {
return 0;
}
System.arraycopy(buf, pos, b, off, len);
pos += len;
return len;
}
public synchronized byte[] readAllBytes() {
byte[] result = Arrays.copyOfRange(buf, pos, count);
pos = count;
return result;
}
public int readNBytes(byte[] b, int off, int len) {
int n = read(b, off, len);
return n == -1 ? 0 : n;
}
public synchronized long transferTo(OutputStream out) throws IOException {
int len = count – pos;
out.write(buf, pos, len);
pos = count;
return len;
}
public synchronized long skip(long n) {
long k = count – pos;
if (n < k) {
k = n < 0 ? 0 : n;
}
pos += k;
return k;
}
public synchronized int available() {
return count – pos;
}
public boolean markSupported() {
return true;
}
public void mark(int readAheadLimit) {
mark = pos;
}
public synchronized void reset() {
pos = mark;
}
public void close() throws IOException {
}
}
* Copyright (c) 1994, 2018, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
package java.io;
import java.util.Arrays;
import java.util.Objects;
public class ByteArrayInputStream extends InputStream {
protected byte buf[];
protected int pos;
protected int mark = 0;
protected int count;
public ByteArrayInputStream(byte buf[]) {
this.buf = buf;
this.pos = 0;
this.count = buf.length;
}
public ByteArrayInputStream(byte buf[], int offset, int length) {
this.buf = buf;
this.pos = offset;
this.count = Math.min(offset + length, buf.length);
this.mark = offset;
}
public synchronized int read() {
return (pos < count) ? (buf[pos++] & 0xff) : -1;
}
public synchronized int read(byte b[], int off, int len) {
Objects.checkFromIndexSize(off, len, b.length);
if (pos >= count) {
return -1;
}
int avail = count – pos;
if (len > avail) {
len = avail;
}
if (len <= 0) {
return 0;
}
System.arraycopy(buf, pos, b, off, len);
pos += len;
return len;
}
public synchronized byte[] readAllBytes() {
byte[] result = Arrays.copyOfRange(buf, pos, count);
pos = count;
return result;
}
public int readNBytes(byte[] b, int off, int len) {
int n = read(b, off, len);
return n == -1 ? 0 : n;
}
public synchronized long transferTo(OutputStream out) throws IOException {
int len = count – pos;
out.write(buf, pos, len);
pos = count;
return len;
}
public synchronized long skip(long n) {
long k = count – pos;
if (n < k) {
k = n < 0 ? 0 : n;
}
pos += k;
return k;
}
public synchronized int available() {
return count – pos;
}
public boolean markSupported() {
return true;
}
public void mark(int readAheadLimit) {
mark = pos;
}
public synchronized void reset() {
pos = mark;
}
public void close() throws IOException {
}
}
ＪＹ情報システムズ 