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java.nio.ByteBuffer源码是什么

发表于：2024-09-22 作者：千家信息网编辑

千家信息网最后更新 2024年09月22日，本篇内容介绍了"java.nio.ByteBuffer源码是什么"的有关知识，在实际案例的操作过程中，不少人都会遇到这样的困境，接下来就让小编带领大家学习一下如何处理这些情况吧！希望大家仔细阅读，能够

千家信息网最后更新 2024年09月22日java.nio.ByteBuffer源码是什么

本篇内容介绍了"java.nio.ByteBuffer源码是什么"的有关知识，在实际案例的操作过程中，不少人都会遇到这样的困境，接下来就让小编带领大家学习一下如何处理这些情况吧！希望大家仔细阅读，能够学有所成！

版本：JDK7

package java.nio;

public abstract class ByteBuffer extends Buffer implements Comparable {

// 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 buffersfinal int offset;boolean isReadOnly;                 // Valid only for heap buffersByteBuffer(int mark, int pos, int lim, int cap, byte[] hb, int offset) {    super(mark, pos, lim, cap);    this.hb = hb;    this.offset = offset;}ByteBuffer(int mark, int pos, int lim, int cap) { // package-private    this(mark, pos, lim, cap, null, 0);}// 创建一个容量为capacity的ByteBuffer对象public static ByteBuffer allocateDirect(int capacity) {    return new DirectByteBuffer(capacity);}// 创建一个容量为capacity的ByteBuffer对象public static ByteBuffer allocate(int capacity) {    if (capacity < 0) throw new IllegalArgumentException();    return new HeapByteBuffer(capacity, capacity);}public static ByteBuffer wrap(byte[] array, int offset, int length) {    try {        return new HeapByteBuffer(array, offset, length);    } catch (IllegalArgumentException x) {        throw new IndexOutOfBoundsException();    }}public static ByteBuffer wrap(byte[] array) {    return wrap(array, 0, array.length);}public abstract ByteBuffer slice();public abstract ByteBuffer duplicate();public abstract ByteBuffer asReadOnlyBuffer();/** * Reads the byte at this buffer's position, and then increments the position. */// 读取单个字节，并将position自增1public abstract byte get();/** * Writes the given byte into this buffer at the current position, and then increments the position.  */// 将给定的单个字节写入缓冲区的当前位置，并将position自增1public abstract ByteBuffer put(byte b);// 读取指定位置的字节，注意：不会改变positionpublic abstract byte get(int index);// 将给定的单个字节写入缓冲区的index位置，注意：不会改变positionpublic abstract ByteBuffer put(int index, byte b);// -- Bulk get operations --/** * This method transfers bytes from this buffer into the given destination array.  */// (从Buffer中)读取多个字节(从索引offset开始,读取length长度的数据)到dst中，如果Buffer剩余的空间小于length，则抛异常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;}/** * This method transfers bytes from this buffer into the given destination array. */// 批量读取dst.length个字节到dst中，如果Buffer剩余的空间小于dst的length，则抛异常public ByteBuffer get(byte[] dst) {    return get(dst, 0, dst.length);}// -- Bulk put operations --/** * 将src中的数据写入Buffer的当前位置 */public ByteBuffer put(ByteBuffer src) {    if (src == this)        throw new IllegalArgumentException();    int n = src.remaining();    if (n > remaining())        throw new BufferOverflowException();    for (int i = 0; i < n; i++)        put(src.get());    return this;}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;}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. * *  If this method returns true then the {[@link](https://my.oschina.net/u/393) #array() array} * and {[@link](https://my.oschina.net/u/393) #arrayOffset() arrayOffset} methods may safely be invoked. * 
 * * [@return](https://my.oschina.net/u/556800)  true 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  (optional operation). * *  Modifications to this buffer's content will cause the returned * array's content to be modified, and vice versa. * * 
 Invoke the {[@link](https://my.oschina.net/u/393) #hasArray hasArray} method before invoking this * method in order to ensure that this buffer has an accessible backing * array.  
 * * [@return](https://my.oschina.net/u/556800)  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  (optional operation). * *  If this buffer is backed by an array then buffer position p * corresponds to array index p + arrayOffset(). * * 
 Invoke the {@link #hasArray hasArray} method before invoking this * method in order to ensure that this buffer has an accessible backing * array.  
 * * @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. 压缩并整理Buffer。 * * 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 p=position() is copied to index zero,  * the byte at index p+1 is copied to index one,  * and so forth until the byte at index limit()-1 is copied to index n=limit()-1-p  * The buffer's position is then set to n+1 and its limit is set to its capacity.  The mark, if defined, is discarded. *  * 即：将所有未读的数据拷贝到Buffer的起始处，然后将position设到最后一个未读元素的后面 * limit设置为capacity，此时，如果向Buffer中写数据，则不会覆盖之前未读的数据！ * 与clear()方法的比较： *            如果Buffer中存在未读的数据，调用clear()方法后，这些未读的数据将会被"遗忘"，因为在clear之后，position的值为0，故无法确定未读数据的位置。 */public abstract ByteBuffer compact();/** * Tells whether or not this byte buffer is direct. 
 */public abstract boolean isDirect();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. */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. * * They have the same element type, * They have the same number of remaining elements, * and The two sequences of remaining elements,  * considered independently of their starting positions, are pointwise equal. *  * 即：Buffer中元素的类型相同，并且剩余的元素完全相同，则返回true * 注意：并不是比较Buffer的所有数据，只是比较Buffer中的剩余数据。 */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. * * 比较两个Buffer的剩余元素 * 一个Buffer"小于"另一个Buffer的场景： *            第一个不相等的元素小于另一个Buffer中对应的元素 *            所有元素都相等，但是第一个Buffer的元素个数小于另一个Buffer的个数 */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 = true;                                  // package-private    boolean nativeByteOrder = (Bits.byteOrder() == ByteOrder.BIG_ENDIAN);  // package-private   /** * Retrieves this buffer's byte order. * *  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}.  
 * * @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-privateabstract void _put(int i, byte b);                  // package-private/** * Relative get method for reading an int value. * *  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.  
 * * @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 put method for writing an int * value  (optional operation). * *  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.  
 * * @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 get method for reading an int value. * *  Reads four bytes at the given index, composing them into a * int value according to the current byte order.  
 * * @param  index *         The index from which the bytes will be read * * @return  The int value at the given index * * @throws  IndexOutOfBoundsException *          If index is negative *          or not smaller than the buffer's limit, *          minus three */public abstract int getInt(int index);/** * Absolute put method for writing an int * value  (optional operation). * *  Writes four bytes containing the given int value, in the * current byte order, into this buffer at the given index.  
 * * @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 index 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. * *  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. * * 
 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.  
 * * @return  A new int buffer */public abstract IntBuffer asIntBuffer();// ...