测试代码
package com.lamole.nio;
import java.nio.ByteBuffer;
import java.nio.LongBuffer;
public class ByteBufferTest {
public static void main(String[] args) {
ByteBuffer byteBuffer = ByteBuffer.allocate(4 * 4);
byteBuffer.putInt(1);
byteBuffer.putInt(2);
byteBuffer.putInt(3);
byteBuffer.putInt(4);
byteBuffer.flip();
LongBuffer buffer = byteBuffer.asLongBuffer();
while(buffer.position() < buffer.limit()) {
System.out.println(Long.toBinaryString(buffer.get()));
}
}
}
输出结果
/*
* Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*/
// -- This file was mechanically generated: Do not edit! -- //
package java.nio;
/**
* A byte buffer.
*
* <p> This class defines six categories of operations upon
* byte buffers:
*
* <ul>
*
* <li><p> Absolute and relative {@link #get() <i>get</i>} and
* {@link #put(byte) <i>put</i>} methods that read and write
* single bytes; </p></li>
* 相对 & 绝对的put和get
*
* <li><p> Relative {@link #get(byte[]) <i>bulk get</i>}
* methods that transfer contiguous sequences of bytes from this buffer
* into an array; </p></li>
* 相对的get一个bulk块
*
* <li><p> Relative {@link #put(byte[]) <i>bulk put</i>}
* methods that transfer contiguous sequences of bytes from a
* byte array or some other byte
* buffer into this buffer; </p></li>
* 相对的put一个bulk块
*
*
* <li><p> Absolute and relative {@link #getChar() <i>get</i>}
* and {@link #putChar(char) <i>put</i>} methods that read and
* write values of other primitive types, translating them to and from
* sequences of bytes in a particular byte order; </p></li>
* 相对绝对的getChar & putChar
*
* <li><p> Methods for creating <i><a href="#views">view buffers</a></i>,
* which allow a byte buffer to be viewed as a buffer containing values of
* some other primitive type; and </p></li>
* 生成其他原始类型的buffer视图
*
*
*
* <li><p> Methods for {@link #compact compacting}, {@link
* #duplicate duplicating}, and {@link #slice slicing}
* a byte buffer. </p></li>
* 压缩、复制、切分
*
* </ul>
*
* <p> Byte buffers can be created either by {@link #allocate
* <i>allocation</i>}, which allocates space for the buffer's
*
*
* content, or by {@link #wrap(byte[]) <i>wrapping</i>} an
* existing byte array into a buffer.
* 两种创建方式allocate & 包装一个已有的
*
*
*
* <a name="direct"></a>
* <h2> Direct <i>vs.</i> non-direct buffers </h2>
*
* <p> A byte buffer is either <i>direct</i> or <i>non-direct</i>. Given a
* direct byte buffer, the Java virtual machine will make a best effort to
* perform native I/O operations directly upon it. That is, it will attempt to
* avoid copying the buffer's content to (or from) an intermediate buffer
* before (or after) each invocation of one of the underlying operating
* system's native I/O operations.
* 直接buffer不会在操作系统操作的时候copy来，copy去
*
*
* <p> A direct byte buffer may be created by invoking the {@link
* #allocateDirect(int) allocateDirect} factory method of this class. The
* buffers returned by this method typically have somewhat higher allocation
* and deallocation costs than non-direct buffers. The contents of direct
* buffers may reside outside of the normal garbage-collected heap, and so
* their impact upon the memory footprint of an application might not be
* obvious. It is therefore recommended that direct buffers be allocated
* primarily for large, long-lived buffers that are subject to the underlying
* system's native I/O operations. In general it is best to allocate direct
* buffers only when they yield a measureable gain in program performance.
* 直接内存的释放和申请的成本都很高，因为不在回收器内回收内存，所以对内存回收的影响不明显
* 大内存，长生命周期的buffer建议用直接内存
*
* <p> A direct byte buffer may also be created by {@link
* java.nio.channels.FileChannel#map mapping} a region of a file
* directly into memory. An implementation of the Java platform may optionally
* support the creation of direct byte buffers from native code via JNI. If an
* instance of one of these kinds of buffers refers to an inaccessible region
* of memory then an attempt to access that region will not change the buffer's
* content and will cause an unspecified exception to be thrown either at the
* time of the access or at some later time.
* 可以java.nio.channels.FileChannel#map 直接把文件的一个区域映射进来，通过JNI实现
* 但是后续操作的时候，如果这个区域不可访问会在后续操作的时候抛异常，不会立即抛出异常
*
* <p> Whether a byte buffer is direct or non-direct may be determined by
* invoking its {@link #isDirect isDirect} method. This method is provided so
* that explicit buffer management can be done in performance-critical code.
*
*
* <a name="bin"></a>
* <h2> Access to binary data </h2>
*
* <p> This class defines methods for reading and writing values of all other
* primitive types, except <tt>boolean</tt>. Primitive values are translated
* to (or from) sequences of bytes according to the buffer's current byte
* order, which may be retrieved and modified via the {@link #order order}
* methods. Specific byte orders are represented by instances of the {@link
* ByteOrder} class. The initial order of a byte buffer is always {@link
* ByteOrder#BIG_ENDIAN BIG_ENDIAN}.
* 高位编址，java本身采用高位编址，网络传输默认也是高位编址
*
* <p> For access to heterogeneous binary data, that is, sequences of values of
* different types, this class defines a family of absolute and relative
* <i>get</i> and <i>put</i> methods for each type. For 32-bit floating-point
* values, for example, this class defines:
* 为了访问各种各样的二进制数据，提供了一系列绝对 & 相对的get和put
* <blockquote><pre>
* float {@link #getFloat()}
* float {@link #getFloat(int) getFloat(int index)}
* void {@link #putFloat(float) putFloat(float f)}
* void {@link #putFloat(int,float) putFloat(int index, float f)}
* </pre></blockquote>
*
* <p> Corresponding methods are defined for the types <tt>char</tt>,
* <tt>short</tt>, <tt>int</tt>, <tt>long</tt>, and <tt>double</tt>. The index
* parameters of the absolute <i>get</i> and <i>put</i> methods are in terms of
* bytes rather than of the type being read or written.
* 相关的类型有short, int, long, double, char。绝对的get和put的index指的是byte的，
* 不是类型的
*
* <a name="views"></a>
*
* <p> For access to homogeneous binary data, that is, sequences of values of
* the same type, this class defines methods that can create <i>views</i> of a
* given byte buffer. A <i>view buffer</i> is simply another buffer whose
* content is backed by the byte buffer. Changes to the byte buffer's content
* will be visible in the view buffer, and vice versa; the two buffers'
* position, limit, and mark values are independent. The {@link
* #asFloatBuffer() asFloatBuffer} method, for example, creates an instance of
* the {@link FloatBuffer} class that is backed by the byte buffer upon which
* the method is invoked. Corresponding view-creation methods are defined for
* the types <tt>char</tt>, <tt>short</tt>, <tt>int</tt>, <tt>long</tt>, and
* <tt>double</tt>.
* 视图缓冲区, 底层数据共享，position、limit、mark不共享
*
* <p> View buffers have three important advantages over the families of
* type-specific <i>get</i> and <i>put</i> methods described above:
*
* <ul>
*
* <li><p> A view buffer is indexed not in terms of bytes but rather in terms
* of the type-specific size of its values; </p></li>
* 索引是基于类型的
*
* <li><p> A view buffer provides relative bulk <i>get</i> and <i>put</i>
* methods that can transfer contiguous sequences of values between a buffer
* and an array or some other buffer of the same type; and </p></li>
* 提供了基于类型的bulk操作
*
* <li><p> A view buffer is potentially much more efficient because it will
* be direct if, and only if, its backing byte buffer is direct. </p></li>
* 可以根据是不是direct来判断自己的类型，更有效率
*
* </ul>
*
* <p> The byte order of a view buffer is fixed to be that of its byte buffer
* at the time that the view is created. </p>
* 视图buffer的顺序和创建时，buffer的顺序一致
*
*
*
* <h2> Invocation chaining </h2>
* 支持链式调用
* <p> Methods in this class that do not otherwise have a value to return are
* specified to return the buffer upon which they are invoked. This allows
* method invocations to be chained.
*
*
* The sequence of statements
*
* <blockquote><pre>
* bb.putInt(0xCAFEBABE);
* bb.putShort(3);
* bb.putShort(45);</pre></blockquote>
*
* can, for example, be replaced by the single statement
*
* <blockquote><pre>
* bb.putInt(0xCAFEBABE).putShort(3).putShort(45);</pre></blockquote>
*
*
*
* @author Mark Reinhold
* @author JSR-51 Expert Group
* @since 1.4
*/
public abstract class ByteBuffer
extends Buffer
implements Comparable<ByteBuffer>
{
// These fields are declared here rather than in Heap-X-Buffer in order to
// reduce the number of virtual method invocations needed to access these
// values, which is especially costly when coding small buffers.
//
final byte[] hb; // Non-null only for heap buffers
final int offset;
boolean isReadOnly; // Valid only for heap buffers
// Creates a new buffer with the given mark, position, limit, capacity,
// backing array, and array offset
//
ByteBuffer(int mark, int pos, int lim, int cap, // package-private
byte[] hb, int offset)
{
super(mark, pos, lim, cap);
this.hb = hb;
this.offset = offset;
}
// Creates a new buffer with the given mark, position, limit, and capacity
//
ByteBuffer(int mark, int pos, int lim, int cap) { // package-private
this(mark, pos, lim, cap, null, 0);
}
/**
* Allocates a new direct byte buffer.
*
* <p> The new buffer's position will be zero, its limit will be its
* capacity, its mark will be undefined, and each of its elements will be
* initialized to zero. Whether or not it has a
* {@link #hasArray backing array} is unspecified.
*
* @param capacity
* The new buffer's capacity, in bytes
*
* @return The new byte buffer
*
* @throws IllegalArgumentException
* If the <tt>capacity</tt> is a negative integer
*/
public static ByteBuffer allocateDirect(int capacity) {
return new DirectByteBuffer(capacity);
}
/**
* Allocates a new byte buffer.
*
* <p> The new buffer's position will be zero, its limit will be its
* capacity, its mark will be undefined, and each of its elements will be
* initialized to zero. It will have a {@link #array backing array},
* and its {@link #arrayOffset array offset} will be zero.
*
* @param capacity
* The new buffer's capacity, in bytes
*
* @return The new byte buffer
*
* @throws IllegalArgumentException
* If the <tt>capacity</tt> is a negative integer
*/
public static ByteBuffer allocate(int capacity) {
if (capacity < 0)
throw new IllegalArgumentException();
return new HeapByteBuffer(capacity, capacity);
}
/**
* Wraps a byte array into a buffer.
*
* <p> The new buffer will be backed by the given byte array;
* that is, modifications to the buffer will cause the array to be modified
* and vice versa. The new buffer's capacity will be
* <tt>array.length</tt>, its position will be <tt>offset</tt>, its limit
* will be <tt>offset + length</tt>, and its mark will be undefined. Its
* {@link #array backing array} will be the given array, and
* its {@link #arrayOffset array offset} will be zero. </p>
*
* @param array
* The array that will back the new buffer
*
* @param offset
* The offset of the subarray to be used; must be non-negative and
* no larger than <tt>array.length</tt>. The new buffer's position
* will be set to this value.
*
* @param length
* The length of the subarray to be used;
* must be non-negative and no larger than
* <tt>array.length - offset</tt>.
* The new buffer's limit will be set to <tt>offset + length</tt>.
*
* @return The new byte buffer
*
* @throws IndexOutOfBoundsException
* If the preconditions on the <tt>offset</tt> and <tt>length</tt>
* parameters do not hold
*/
public static ByteBuffer wrap(byte[] array,
int offset, int length)
{
try {
return new HeapByteBuffer(array, offset, length);
} catch (IllegalArgumentException x) {
throw new IndexOutOfBoundsException();
}
}
/**
* Wraps a byte array into a buffer.
*
* <p> The new buffer will be backed by the given byte array;
* that is, modifications to the buffer will cause the array to be modified
* and vice versa. The new buffer's capacity and limit will be
* <tt>array.length</tt>, its position will be zero, and its mark will be
* undefined. Its {@link #array backing array} will be the
* given array, and its {@link #arrayOffset array offset>} will
* be zero. </p>
*
* @param array
* The array that will back this buffer
*
* @return The new byte buffer
*/
public static ByteBuffer wrap(byte[] array) {
return wrap(array, 0, array.length);
}
/**
* Creates a new byte buffer whose content is a shared subsequence of
* this buffer's content.
*
* <p> The content of the new buffer will start at this buffer's current
* position. Changes to this buffer's content will be visible in the new
* buffer, and vice versa; the two buffers' position, limit, and mark
* values will be independent.
*
* <p> The new buffer's position will be zero, its capacity and its limit
* will be the number of bytes remaining in this buffer, and its mark
* will be undefined. The new buffer will be direct if, and only if, this
* buffer is direct, and it will be read-only if, and only if, this buffer
* is read-only. </p>
*
* @return The new byte buffer
*/
public abstract ByteBuffer slice();
/**
* Creates a new byte buffer that shares this buffer's content.
*
* <p> The content of the new buffer will be that of this buffer. Changes
* to this buffer's content will be visible in the new buffer, and vice
* versa; the two buffers' position, limit, and mark values will be
* independent.
*
* <p> The new buffer's capacity, limit, position, and mark values will be
* identical to those of this buffer. The new buffer will be direct if,
* and only if, this buffer is direct, and it will be read-only if, and
* only if, this buffer is read-only. </p>
*
* @return The new byte buffer
*/
public abstract ByteBuffer duplicate();
/**
* Creates a new, read-only byte buffer that shares this buffer's
* content.
*
* <p> The content of the new buffer will be that of this buffer. Changes
* to this buffer's content will be visible in the new buffer; the new
* buffer itself, however, will be read-only and will not allow the shared
* content to be modified. The two buffers' position, limit, and mark
* values will be independent.
*
* <p> The new buffer's capacity, limit, position, and mark values will be
* identical to those of this buffer.
*
* <p> If this buffer is itself read-only then this method behaves in
* exactly the same way as the {@link #duplicate duplicate} method. </p>
*
* @return The new, read-only byte buffer
*/
public abstract ByteBuffer asReadOnlyBuffer();
// -- Singleton get/put methods --
/**
* Relative <i>get</i> method. Reads the byte at this buffer's
* current position, and then increments the position.
*
* @return The byte at the buffer's current position
*
* @throws BufferUnderflowException
* If the buffer's current position is not smaller than its limit
*/
public abstract byte get();
/**
* Relative <i>put</i> method <i>(optional operation)</i>.
*
* <p> Writes the given byte into this buffer at the current
* position, and then increments the position. </p>
*
* @param b
* The byte to be written
*
* @return This buffer
*
* @throws BufferOverflowException
* If this buffer's current position is not smaller than its limit
*
* @throws ReadOnlyBufferException
* If this buffer is read-only
*/
public abstract ByteBuffer put(byte b);
/**
* Absolute <i>get</i> method. Reads the byte at the given
* index.
*
* @param index
* The index from which the byte will be read
*
* @return The byte at the given index
*
* @throws IndexOutOfBoundsException
* If <tt>index</tt> is negative
* or not smaller than the buffer's limit
*/
public abstract byte get(int index);
/**
* Absolute <i>put</i> method <i>(optional operation)</i>.
*
* <p> Writes the given byte into this buffer at the given
* index. </p>
*
* @param index
* The index at which the byte will be written
*
* @param b
* The byte value to be written
*
* @return This buffer
*
* @throws IndexOutOfBoundsException
* If <tt>index</tt> is negative
* or not smaller than the buffer's limit
*
* @throws ReadOnlyBufferException
* If this buffer is read-only
*/
public abstract ByteBuffer put(int index, byte b);
// -- Bulk get operations --
/**
* Relative bulk <i>get</i> method.
*
* <p> This method transfers bytes from this buffer into the given
* destination array. If there are fewer bytes remaining in the
* buffer than are required to satisfy the request, that is, if
* <tt>length</tt> <tt>></tt> <tt>remaining()</tt>, then no
* bytes are transferred and a {@link BufferUnderflowException} is
* thrown.
*
* <p> Otherwise, this method copies <tt>length</tt> bytes from this
* buffer into the given array, starting at the current position of this
* buffer and at the given offset in the array. The position of this
* buffer is then incremented by <tt>length</tt>.
*
* <p> In other words, an invocation of this method of the form
* <tt>src.get(dst, off, len)</tt> has exactly the same effect as
* the loop
*
* <pre>{@code
* for (int i = off; i < off + len; i++)
* dst[i] = src.get():
* }</pre>
*
* except that it first checks that there are sufficient bytes in
* this buffer and it is potentially much more efficient.
*
* @param dst
* The array into which bytes are to be written
*
* @param offset
* The offset within the array of the first byte to be
* written; must be non-negative and no larger than
* <tt>dst.length</tt>
*
* @param length
* The maximum number of bytes to be written to the given
* array; must be non-negative and no larger than
* <tt>dst.length - offset</tt>
*
* @return This buffer
*
* @throws BufferUnderflowException
* If there are fewer than <tt>length</tt> bytes
* remaining in this buffer
*
* @throws IndexOutOfBoundsException
* If the preconditions on the <tt>offset</tt> and <tt>length</tt>
* parameters do not hold
*/
public ByteBuffer get(byte[] dst, int offset, int length) {
checkBounds(offset, length, dst.length);
if (length > remaining())
throw new BufferUnderflowException();
int end = offset + length;
for (int i = offset; i < end; i++)
dst[i] = get();
return this;
}
/**
* Relative bulk <i>get</i> method.
*
* <p> This method transfers bytes from this buffer into the given
* destination array. An invocation of this method of the form
* <tt>src.get(a)</tt> behaves in exactly the same way as the invocation
*
* <pre>
* src.get(a, 0, a.length) </pre>
*
* @param dst
* The destination array
*
* @return This buffer
*
* @throws BufferUnderflowException
* If there are fewer than <tt>length</tt> bytes
* remaining in this buffer
*/
public ByteBuffer get(byte[] dst) {
return get(dst, 0, dst.length);
}
// -- Bulk put operations --
/**
* Relative bulk <i>put</i> method <i>(optional operation)</i>.
*
* <p> This method transfers the bytes remaining in the given source
* buffer into this buffer. If there are more bytes remaining in the
* source buffer than in this buffer, that is, if
* <tt>src.remaining()</tt> <tt>></tt> <tt>remaining()</tt>,
* then no bytes are transferred and a {@link
* BufferOverflowException} is thrown.
*
* <p> Otherwise, this method copies
* <i>n</i> = <tt>src.remaining()</tt> bytes from the given
* buffer into this buffer, starting at each buffer's current position.
* The positions of both buffers are then incremented by <i>n</i>.
*
* <p> In other words, an invocation of this method of the form
* <tt>dst.put(src)</tt> has exactly the same effect as the loop
*
* <pre>
* while (src.hasRemaining())
* dst.put(src.get()); </pre>
*
* except that it first checks that there is sufficient space in this
* buffer and it is potentially much more efficient.
*
* @param src
* The source buffer from which bytes are to be read;
* must not be this buffer
*
* @return This buffer
*
* @throws BufferOverflowException
* If there is insufficient space in this buffer
* for the remaining bytes in the source buffer
*
* @throws IllegalArgumentException
* If the source buffer is this buffer
*
* @throws ReadOnlyBufferException
* If this buffer is read-only
*/
public ByteBuffer put(ByteBuffer src) {
if (src == this)
throw new IllegalArgumentException();
if (isReadOnly())
throw new ReadOnlyBufferException();
int n = src.remaining();
if (n > remaining())
throw new BufferOverflowException();
for (int i = 0; i < n; i++)
put(src.get());
return this;
}
/**
* Relative bulk <i>put</i> method <i>(optional operation)</i>.
*
* <p> This method transfers bytes into this buffer from the given
* source array. If there are more bytes to be copied from the array
* than remain in this buffer, that is, if
* <tt>length</tt> <tt>></tt> <tt>remaining()</tt>, then no
* bytes are transferred and a {@link BufferOverflowException} is
* thrown.
*
* <p> Otherwise, this method copies <tt>length</tt> bytes from the
* given array into this buffer, starting at the given offset in the array
* and at the current position of this buffer. The position of this buffer
* is then incremented by <tt>length</tt>.
*
* <p> In other words, an invocation of this method of the form
* <tt>dst.put(src, off, len)</tt> has exactly the same effect as
* the loop
*
* <pre>{@code
* for (int i = off; i < off + len; i++)
* dst.put(a[i]);
* }</pre>
*
* except that it first checks that there is sufficient space in this
* buffer and it is potentially much more efficient.
*
* @param src
* The array from which bytes are to be read
*
* @param offset
* The offset within the array of the first byte to be read;
* must be non-negative and no larger than <tt>array.length</tt>
*
* @param length
* The number of bytes to be read from the given array;
* must be non-negative and no larger than
* <tt>array.length - offset</tt>
*
* @return This buffer
*
* @throws BufferOverflowException
* If there is insufficient space in this buffer
*
* @throws IndexOutOfBoundsException
* If the preconditions on the <tt>offset</tt> and <tt>length</tt>
* parameters do not hold
*
* @throws ReadOnlyBufferException
* If this buffer is read-only
*/
public ByteBuffer put(byte[] src, int offset, int length) {
checkBounds(offset, length, src.length);
if (length > remaining())
throw new BufferOverflowException();
int end = offset + length;
for (int i = offset; i < end; i++)
this.put(src[i]);
return this;
}
/**
* Relative bulk <i>put</i> method <i>(optional operation)</i>.
*
* <p> This method transfers the entire content of the given source
* byte array into this buffer. An invocation of this method of the
* form <tt>dst.put(a)</tt> behaves in exactly the same way as the
* invocation
*
* <pre>
* dst.put(a, 0, a.length) </pre>
*
* @param src
* The source array
*
* @return This buffer
*
* @throws BufferOverflowException
* If there is insufficient space in this buffer
*
* @throws ReadOnlyBufferException
* If this buffer is read-only
*/
public final ByteBuffer put(byte[] src) {
return put(src, 0, src.length);
}
// -- Other stuff --
/**
* Tells whether or not this buffer is backed by an accessible byte
* array.
*
* <p> If this method returns <tt>true</tt> then the {@link #array() array}
* and {@link #arrayOffset() arrayOffset} methods may safely be invoked.
* </p>
*
* @return <tt>true</tt> if, and only if, this buffer
* is backed by an array and is not read-only
*/
public final boolean hasArray() {
return (hb != null) && !isReadOnly;
}
/**
* Returns the byte array that backs this
* buffer <i>(optional operation)</i>.
*
* <p> Modifications to this buffer's content will cause the returned
* array's content to be modified, and vice versa.
*
* <p> Invoke the {@link #hasArray hasArray} method before invoking this
* method in order to ensure that this buffer has an accessible backing
* array. </p>
*
* @return The array that backs this buffer
*
* @throws ReadOnlyBufferException
* If this buffer is backed by an array but is read-only
*
* @throws UnsupportedOperationException
* If this buffer is not backed by an accessible array
*/
public final byte[] array() {
if (hb == null)
throw new UnsupportedOperationException();
if (isReadOnly)
throw new ReadOnlyBufferException();
return hb;
}
/**
* Returns the offset within this buffer's backing array of the first
* element of the buffer <i>(optional operation)</i>.
*
* <p> If this buffer is backed by an array then buffer position <i>p</i>
* corresponds to array index <i>p</i> + <tt>arrayOffset()</tt>.
*
* <p> Invoke the {@link #hasArray hasArray} method before invoking this
* method in order to ensure that this buffer has an accessible backing
* array. </p>
*
* @return The offset within this buffer's array
* of the first element of the buffer
*
* @throws ReadOnlyBufferException
* If this buffer is backed by an array but is read-only
*
* @throws UnsupportedOperationException
* If this buffer is not backed by an accessible array
*/
public final int arrayOffset() {
if (hb == null)
throw new UnsupportedOperationException();
if (isReadOnly)
throw new ReadOnlyBufferException();
return offset;
}
/**
* Compacts this buffer <i>(optional operation)</i>.
*
* <p> The bytes between the buffer's current position and its limit,
* if any, are copied to the beginning of the buffer. That is, the
* byte at index <i>p</i> = <tt>position()</tt> is copied
* to index zero, the byte at index <i>p</i> + 1 is copied
* to index one, and so forth until the byte at index
* <tt>limit()</tt> - 1 is copied to index
* <i>n</i> = <tt>limit()</tt> - <tt>1</tt> - <i>p</i>.
* The buffer's position is then set to <i>n+1</i> and its limit is set to
* its capacity. The mark, if defined, is discarded.
*
* <p> The buffer's position is set to the number of bytes copied,
* rather than to zero, so that an invocation of this method can be
* followed immediately by an invocation of another relative <i>put</i>
* method. </p>
*
*
* <p> Invoke this method after writing data from a buffer in case the
* write was incomplete. The following loop, for example, copies bytes
* from one channel to another via the buffer <tt>buf</tt>:
*
* <blockquote><pre>{@code
* buf.clear(); // Prepare buffer for use
* while (in.read(buf) >= 0 || buf.position != 0) {
* buf.flip();
* out.write(buf);
* buf.compact(); // In case of partial write
* }
* }</pre></blockquote>
*
*
* @return This buffer
*
* @throws ReadOnlyBufferException
* If this buffer is read-only
*/
public abstract ByteBuffer compact();
/**
* Tells whether or not this byte buffer is direct.
*
* @return <tt>true</tt> if, and only if, this buffer is direct
*/
public abstract boolean isDirect();
/**
* Returns a string summarizing the state of this buffer.
*
* @return A summary string
*/
public String toString() {
StringBuffer sb = new StringBuffer();
sb.append(getClass().getName());
sb.append("[pos=");
sb.append(position());
sb.append(" lim=");
sb.append(limit());
sb.append(" cap=");
sb.append(capacity());
sb.append("]");
return sb.toString();
}
/**
* Returns the current hash code of this buffer.
*
* <p> The hash code of a byte buffer depends only upon its remaining
* elements; that is, upon the elements from <tt>position()</tt> up to, and
* including, the element at <tt>limit()</tt> - <tt>1</tt>.
*
* <p> Because buffer hash codes are content-dependent, it is inadvisable
* to use buffers as keys in hash maps or similar data structures unless it
* is known that their contents will not change. </p>
*
* @return The current hash code of this buffer
*/
public int hashCode() {
int h = 1;
int p = position();
for (int i = limit() - 1; i >= p; i--)
h = 31 * h + (int)get(i);
return h;
}
/**
* Tells whether or not this buffer is equal to another object.
*
* <p> Two byte buffers are equal if, and only if,
*
* <ol>
*
* <li><p> They have the same element type, </p></li>
*
* <li><p> They have the same number of remaining elements, and
* </p></li>
*
* <li><p> The two sequences of remaining elements, considered
* independently of their starting positions, are pointwise equal.
* </p></li>
*
* </ol>
*
* <p> A byte buffer is not equal to any other type of object. </p>
*
* @param ob The object to which this buffer is to be compared
*
* @return <tt>true</tt> if, and only if, this buffer is equal to the
* given object
*/
public boolean equals(Object ob) {
if (this == ob)
return true;
if (!(ob instanceof ByteBuffer))
return false;
ByteBuffer that = (ByteBuffer)ob;
if (this.remaining() != that.remaining())
return false;
int p = this.position();
for (int i = this.limit() - 1, j = that.limit() - 1; i >= p; i--, j--)
if (!equals(this.get(i), that.get(j)))
return false;
return true;
}
private static boolean equals(byte x, byte y) {
return x == y;
}
/**
* Compares this buffer to another.
*
* <p> Two byte buffers are compared by comparing their sequences of
* remaining elements lexicographically, without regard to the starting
* position of each sequence within its corresponding buffer.
* Pairs of {@code byte} elements are compared as if by invoking
* {@link Byte#compare(byte,byte)}.
*
* <p> A byte buffer is not comparable to any other type of object.
*
* @return A negative integer, zero, or a positive integer as this buffer
* is less than, equal to, or greater than the given buffer
*/
public int compareTo(ByteBuffer that) {
int n = this.position() + Math.min(this.remaining(), that.remaining());
for (int i = this.position(), j = that.position(); i < n; i++, j++) {
int cmp = compare(this.get(i), that.get(j));
if (cmp != 0)
return cmp;
}
return this.remaining() - that.remaining();
}
private static int compare(byte x, byte y) {
return Byte.compare(x, y);
}
// -- Other char stuff --
// -- Other byte stuff: Access to binary data --
boolean bigEndian // package-private
= true;
boolean nativeByteOrder // package-private
= (Bits.byteOrder() == ByteOrder.BIG_ENDIAN);
/**
* Retrieves this buffer's byte order.
*
* <p> The byte order is used when reading or writing multibyte values, and
* when creating buffers that are views of this byte buffer. The order of
* a newly-created byte buffer is always {@link ByteOrder#BIG_ENDIAN
* BIG_ENDIAN}. </p>
*
* @return This buffer's byte order
*/
public final ByteOrder order() {
return bigEndian ? ByteOrder.BIG_ENDIAN : ByteOrder.LITTLE_ENDIAN;
}
/**
* Modifies this buffer's byte order.
*
* @param bo
* The new byte order,
* either {@link ByteOrder#BIG_ENDIAN BIG_ENDIAN}
* or {@link ByteOrder#LITTLE_ENDIAN LITTLE_ENDIAN}
*
* @return This buffer
*/
public final ByteBuffer order(ByteOrder bo) {
bigEndian = (bo == ByteOrder.BIG_ENDIAN);
nativeByteOrder =
(bigEndian == (Bits.byteOrder() == ByteOrder.BIG_ENDIAN));
return this;
}
// Unchecked accessors, for use by ByteBufferAs-X-Buffer classes
//
abstract byte _get(int i); // package-private
abstract void _put(int i, byte b); // package-private
/**
* Relative <i>get</i> method for reading a char value.
*
* <p> Reads the next two bytes at this buffer's current position,
* composing them into a char value according to the current byte order,
* and then increments the position by two. </p>
*
* @return The char value at the buffer's current position
*
* @throws BufferUnderflowException
* If there are fewer than two bytes
* remaining in this buffer
*/
public abstract char getChar();
/**
* Relative <i>put</i> method for writing a char
* value <i>(optional operation)</i>.
*
* <p> Writes two bytes containing the given char value, in the
* current byte order, into this buffer at the current position, and then
* increments the position by two. </p>
*
* @param value
* The char value to be written
*
* @return This buffer
*
* @throws BufferOverflowException
* If there are fewer than two bytes
* remaining in this buffer
*
* @throws ReadOnlyBufferException
* If this buffer is read-only
*/
public abstract ByteBuffer putChar(char value);
/**
* Absolute <i>get</i> method for reading a char value.
*
* <p> Reads two bytes at the given index, composing them into a
* char value according to the current byte order. </p>
*
* @param index
* The index from which the bytes will be read
*
* @return The char value at the given index
*
* @throws IndexOutOfBoundsException
* If <tt>index</tt> is negative
* or not smaller than the buffer's limit,
* minus one
*/
public abstract char getChar(int index);
/**
* Absolute <i>put</i> method for writing a char
* value <i>(optional operation)</i>.
*
* <p> Writes two bytes containing the given char value, in the
* current byte order, into this buffer at the given index. </p>
*
* @param index
* The index at which the bytes will be written
*
* @param value
* The char value to be written
*
* @return This buffer
*
* @throws IndexOutOfBoundsException
* If <tt>index</tt> is negative
* or not smaller than the buffer's limit,
* minus one
*
* @throws ReadOnlyBufferException
* If this buffer is read-only
*/
public abstract ByteBuffer putChar(int index, char value);
/**
* Creates a view of this byte buffer as a char buffer.
*
* <p> The content of the new buffer will start at this buffer's current
* position. Changes to this buffer's content will be visible in the new
* buffer, and vice versa; the two buffers' position, limit, and mark
* values will be independent.
*
* <p> The new buffer's position will be zero, its capacity and its limit
* will be the number of bytes remaining in this buffer divided by
* two, and its mark will be undefined. The new buffer will be direct
* if, and only if, this buffer is direct, and it will be read-only if, and
* only if, this buffer is read-only. </p>
*
* @return A new char buffer
*/
public abstract CharBuffer asCharBuffer();
/**
* Relative <i>get</i> method for reading a short value.
*
* <p> Reads the next two bytes at this buffer's current position,
* composing them into a short value according to the current byte order,
* and then increments the position by two. </p>
*
* @return The short value at the buffer's current position
*
* @throws BufferUnderflowException
* If there are fewer than two bytes
* remaining in this buffer
*/
public abstract short getShort();
/**
* Relative <i>put</i> method for writing a short
* value <i>(optional operation)</i>.
*
* <p> Writes two bytes containing the given short value, in the
* current byte order, into this buffer at the current position, and then
* increments the position by two. </p>
*
* @param value
* The short value to be written
*
* @return This buffer
*
* @throws BufferOverflowException
* If there are fewer than two bytes
* remaining in this buffer
*
* @throws ReadOnlyBufferException
* If this buffer is read-only
*/
public abstract ByteBuffer putShort(short value);
/**
* Absolute <i>get</i> method for reading a short value.
*
* <p> Reads two bytes at the given index, composing them into a
* short value according to the current byte order. </p>
*
* @param index
* The index from which the bytes will be read
*
* @return The short value at the given index
*
* @throws IndexOutOfBoundsException
* If <tt>index</tt> is negative
* or not smaller than the buffer's limit,
* minus one
*/
public abstract short getShort(int index);
/**
* Absolute <i>put</i> method for writing a short
* value <i>(optional operation)</i>.
*
* <p> Writes two bytes containing the given short value, in the
* current byte order, into this buffer at the given index. </p>
*
* @param index
* The index at which the bytes will be written
*
* @param value
* The short value to be written
*
* @return This buffer
*
* @throws IndexOutOfBoundsException
* If <tt>index</tt> is negative
* or not smaller than the buffer's limit,
* minus one
*
* @throws ReadOnlyBufferException
* If this buffer is read-only
*/
public abstract ByteBuffer putShort(int index, short value);
/**
* Creates a view of this byte buffer as a short buffer.
*
* <p> The content of the new buffer will start at this buffer's current
* position. Changes to this buffer's content will be visible in the new
* buffer, and vice versa; the two buffers' position, limit, and mark
* values will be independent.
*
* <p> The new buffer's position will be zero, its capacity and its limit
* will be the number of bytes remaining in this buffer divided by
* two, and its mark will be undefined. The new buffer will be direct
* if, and only if, this buffer is direct, and it will be read-only if, and
* only if, this buffer is read-only. </p>
*
* @return A new short buffer
*/
public abstract ShortBuffer asShortBuffer();
/**
* Relative <i>get</i> method for reading an int value.
*
* <p> Reads the next four bytes at this buffer's current position,
* composing them into an int value according to the current byte order,
* and then increments the position by four. </p>
*
* @return The int value at the buffer's current position
*
* @throws BufferUnderflowException
* If there are fewer than four bytes
* remaining in this buffer
*/
public abstract int getInt();
/**
* Relative <i>put</i> method for writing an int
* value <i>(optional operation)</i>.
*
* <p> Writes four bytes containing the given int value, in the
* current byte order, into this buffer at the current position, and then
* increments the position by four. </p>
*
* @param value
* The int value to be written
*
* @return This buffer
*
* @throws BufferOverflowException
* If there are fewer than four bytes
* remaining in this buffer
*
* @throws ReadOnlyBufferException
* If this buffer is read-only
*/
public abstract ByteBuffer putInt(int value);
/**
* Absolute <i>get</i> method for reading an int value.
*
* <p> Reads four bytes at the given index, composing them into a
* int value according to the current byte order. </p>
*
* @param index
* The index from which the bytes will be read
*
* @return The int value at the given index
*
* @throws IndexOutOfBoundsException
* If <tt>index</tt> is negative
* or not smaller than the buffer's limit,
* minus three
*/
public abstract int getInt(int index);
/**
* Absolute <i>put</i> method for writing an int
* value <i>(optional operation)</i>.
*
* <p> Writes four bytes containing the given int value, in the
* current byte order, into this buffer at the given index. </p>
*
* @param index
* The index at which the bytes will be written
*
* @param value
* The int value to be written
*
* @return This buffer
*
* @throws IndexOutOfBoundsException
* If <tt>index</tt> is negative
* or not smaller than the buffer's limit,
* minus three
*
* @throws ReadOnlyBufferException
* If this buffer is read-only
*/
public abstract ByteBuffer putInt(int index, int value);
/**
* Creates a view of this byte buffer as an int buffer.
*
* <p> The content of the new buffer will start at this buffer's current
* position. Changes to this buffer's content will be visible in the new
* buffer, and vice versa; the two buffers' position, limit, and mark
* values will be independent.
*
* <p> The new buffer's position will be zero, its capacity and its limit
* will be the number of bytes remaining in this buffer divided by
* four, and its mark will be undefined. The new buffer will be direct
* if, and only if, this buffer is direct, and it will be read-only if, and
* only if, this buffer is read-only. </p>
*
* @return A new int buffer
*/
public abstract IntBuffer asIntBuffer();
/**
* Relative <i>get</i> method for reading a long value.
*
* <p> Reads the next eight bytes at this buffer's current position,
* composing them into a long value according to the current byte order,
* and then increments the position by eight. </p>
*
* @return The long value at the buffer's current position
*
* @throws BufferUnderflowException
* If there are fewer than eight bytes
* remaining in this buffer
*/
public abstract long getLong();
/**
* Relative <i>put</i> method for writing a long
* value <i>(optional operation)</i>.
*
* <p> Writes eight bytes containing the given long value, in the
* current byte order, into this buffer at the current position, and then
* increments the position by eight. </p>
*
* @param value
* The long value to be written
*
* @return This buffer
*
* @throws BufferOverflowException
* If there are fewer than eight bytes
* remaining in this buffer
*
* @throws ReadOnlyBufferException
* If this buffer is read-only
*/
public abstract ByteBuffer putLong(long value);
/**
* Absolute <i>get</i> method for reading a long value.
*
* <p> Reads eight bytes at the given index, composing them into a
* long value according to the current byte order. </p>
*
* @param index
* The index from which the bytes will be read
*
* @return The long value at the given index
*
* @throws IndexOutOfBoundsException
* If <tt>index</tt> is negative
* or not smaller than the buffer's limit,
* minus seven
*/
public abstract long getLong(int index);
/**
* Absolute <i>put</i> method for writing a long
* value <i>(optional operation)</i>.
*
* <p> Writes eight bytes containing the given long value, in the
* current byte order, into this buffer at the given index. </p>
*
* @param index
* The index at which the bytes will be written
*
* @param value
* The long value to be written
*
* @return This buffer
*
* @throws IndexOutOfBoundsException
* If <tt>index</tt> is negative
* or not smaller than the buffer's limit,
* minus seven
*
* @throws ReadOnlyBufferException
* If this buffer is read-only
*/
public abstract ByteBuffer putLong(int index, long value);
/**
* Creates a view of this byte buffer as a long buffer.
*
* <p> The content of the new buffer will start at this buffer's current
* position. Changes to this buffer's content will be visible in the new
* buffer, and vice versa; the two buffers' position, limit, and mark
* values will be independent.
*
* <p> The new buffer's position will be zero, its capacity and its limit
* will be the number of bytes remaining in this buffer divided by
* eight, and its mark will be undefined. The new buffer will be direct
* if, and only if, this buffer is direct, and it will be read-only if, and
* only if, this buffer is read-only. </p>
*
* @return A new long buffer
*/
public abstract LongBuffer asLongBuffer();
/**
* Relative <i>get</i> method for reading a float value.
*
* <p> Reads the next four bytes at this buffer's current position,
* composing them into a float value according to the current byte order,
* and then increments the position by four. </p>
*
* @return The float value at the buffer's current position
*
* @throws BufferUnderflowException
* If there are fewer than four bytes
* remaining in this buffer
*/
public abstract float getFloat();
/**
* Relative <i>put</i> method for writing a float
* value <i>(optional operation)</i>.
*
* <p> Writes four bytes containing the given float value, in the
* current byte order, into this buffer at the current position, and then
* increments the position by four. </p>
*
* @param value
* The float value to be written
*
* @return This buffer
*
* @throws BufferOverflowException
* If there are fewer than four bytes
* remaining in this buffer
*
* @throws ReadOnlyBufferException
* If this buffer is read-only
*/
public abstract ByteBuffer putFloat(float value);
/**
* Absolute <i>get</i> method for reading a float value.
*
* <p> Reads four bytes at the given index, composing them into a
* float value according to the current byte order. </p>
*
* @param index
* The index from which the bytes will be read
*
* @return The float value at the given index
*
* @throws IndexOutOfBoundsException
* If <tt>index</tt> is negative
* or not smaller than the buffer's limit,
* minus three
*/
public abstract float getFloat(int index);
/**
* Absolute <i>put</i> method for writing a float
* value <i>(optional operation)</i>.
*
* <p> Writes four bytes containing the given float value, in the
* current byte order, into this buffer at the given index. </p>
*
* @param index
* The index at which the bytes will be written
*
* @param value
* The float value to be written
*
* @return This buffer
*
* @throws IndexOutOfBoundsException
* If <tt>index</tt> is negative
* or not smaller than the buffer's limit,
* minus three
*
* @throws ReadOnlyBufferException
* If this buffer is read-only
*/
public abstract ByteBuffer putFloat(int index, float value);
/**
* Creates a view of this byte buffer as a float buffer.
*
* <p> The content of the new buffer will start at this buffer's current
* position. Changes to this buffer's content will be visible in the new
* buffer, and vice versa; the two buffers' position, limit, and mark
* values will be independent.
*
* <p> The new buffer's position will be zero, its capacity and its limit
* will be the number of bytes remaining in this buffer divided by
* four, and its mark will be undefined. The new buffer will be direct
* if, and only if, this buffer is direct, and it will be read-only if, and
* only if, this buffer is read-only. </p>
*
* @return A new float buffer
*/
public abstract FloatBuffer asFloatBuffer();
/**
* Relative <i>get</i> method for reading a double value.
*
* <p> Reads the next eight bytes at this buffer's current position,
* composing them into a double value according to the current byte order,
* and then increments the position by eight. </p>
*
* @return The double value at the buffer's current position
*
* @throws BufferUnderflowException
* If there are fewer than eight bytes
* remaining in this buffer
*/
public abstract double getDouble();
/**
* Relative <i>put</i> method for writing a double
* value <i>(optional operation)</i>.
*
* <p> Writes eight bytes containing the given double value, in the
* current byte order, into this buffer at the current position, and then
* increments the position by eight. </p>
*
* @param value
* The double value to be written
*
* @return This buffer
*
* @throws BufferOverflowException
* If there are fewer than eight bytes
* remaining in this buffer
*
* @throws ReadOnlyBufferException
* If this buffer is read-only
*/
public abstract ByteBuffer putDouble(double value);
/**
* Absolute <i>get</i> method for reading a double value.
*
* <p> Reads eight bytes at the given index, composing them into a
* double value according to the current byte order. </p>
*
* @param index
* The index from which the bytes will be read
*
* @return The double value at the given index
*
* @throws IndexOutOfBoundsException
* If <tt>index</tt> is negative
* or not smaller than the buffer's limit,
* minus seven
*/
public abstract double getDouble(int index);
/**
* Absolute <i>put</i> method for writing a double
* value <i>(optional operation)</i>.
*
* <p> Writes eight bytes containing the given double value, in the
* current byte order, into this buffer at the given index. </p>
*
* @param index
* The index at which the bytes will be written
*
* @param value
* The double value to be written
*
* @return This buffer
*
* @throws IndexOutOfBoundsException
* If <tt>index</tt> is negative
* or not smaller than the buffer's limit,
* minus seven
*
* @throws ReadOnlyBufferException
* If this buffer is read-only
*/
public abstract ByteBuffer putDouble(int index, double value);
/**
* Creates a view of this byte buffer as a double buffer.
*
* <p> The content of the new buffer will start at this buffer's current
* position. Changes to this buffer's content will be visible in the new
* buffer, and vice versa; the two buffers' position, limit, and mark
* values will be independent.
*
* <p> The new buffer's position will be zero, its capacity and its limit
* will be the number of bytes remaining in this buffer divided by
* eight, and its mark will be undefined. The new buffer will be direct
* if, and only if, this buffer is direct, and it will be read-only if, and
* only if, this buffer is read-only. </p>
*
* @return A new double buffer
*/
public abstract DoubleBuffer asDoubleBuffer();
}
