Buffer.java
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上传日期:2018-01-08
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- /**
- * Licensed to the Apache Software Foundation (ASF) under one
- * or more contributor license agreements. See the NOTICE file
- * distributed with this work for additional information
- * regarding copyright ownership. The ASF licenses this file
- * to you 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 org.apache.hadoop.record;
- import java.io.UnsupportedEncodingException;
- /**
- * A byte sequence that is used as a Java native type for buffer.
- * It is resizable and distinguishes between the count of the seqeunce and
- * the current capacity.
- *
- */
- public class Buffer implements Comparable, Cloneable {
- /** Number of valid bytes in this.bytes. */
- private int count;
- /** Backing store for Buffer. */
- private byte[] bytes = null;
- /**
- * Create a zero-count sequence.
- */
- public Buffer() {
- this.count = 0;
- }
- /**
- * Create a Buffer using the byte array as the initial value.
- *
- * @param bytes This array becomes the backing storage for the object.
- */
- public Buffer(byte[] bytes) {
- this.bytes = bytes;
- this.count = (bytes == null) ? 0 : bytes.length;
- }
-
- /**
- * Create a Buffer using the byte range as the initial value.
- *
- * @param bytes Copy of this array becomes the backing storage for the object.
- * @param offset offset into byte array
- * @param length length of data
- */
- public Buffer(byte[] bytes, int offset, int length) {
- copy(bytes, offset, length);
- }
-
-
- /**
- * Use the specified bytes array as underlying sequence.
- *
- * @param bytes byte sequence
- */
- public void set(byte[] bytes) {
- this.count = (bytes == null) ? 0 : bytes.length;
- this.bytes = bytes;
- }
-
- /**
- * Copy the specified byte array to the Buffer. Replaces the current buffer.
- *
- * @param bytes byte array to be assigned
- * @param offset offset into byte array
- * @param length length of data
- */
- public final void copy(byte[] bytes, int offset, int length) {
- if (this.bytes == null || this.bytes.length < length) {
- this.bytes = new byte[length];
- }
- System.arraycopy(bytes, offset, this.bytes, 0, length);
- this.count = length;
- }
-
- /**
- * Get the data from the Buffer.
- *
- * @return The data is only valid between 0 and getCount() - 1.
- */
- public byte[] get() {
- if (bytes == null) {
- bytes = new byte[0];
- }
- return bytes;
- }
-
- /**
- * Get the current count of the buffer.
- */
- public int getCount() {
- return count;
- }
-
- /**
- * Get the capacity, which is the maximum count that could handled without
- * resizing the backing storage.
- *
- * @return The number of bytes
- */
- public int getCapacity() {
- return this.get().length;
- }
-
- /**
- * Change the capacity of the backing storage.
- * The data is preserved if newCapacity >= getCount().
- * @param newCapacity The new capacity in bytes.
- */
- public void setCapacity(int newCapacity) {
- if (newCapacity < 0) {
- throw new IllegalArgumentException("Invalid capacity argument "+newCapacity);
- }
- if (newCapacity == 0) {
- this.bytes = null;
- this.count = 0;
- return;
- }
- if (newCapacity != getCapacity()) {
- byte[] data = new byte[newCapacity];
- if (newCapacity < count) {
- count = newCapacity;
- }
- if (count != 0) {
- System.arraycopy(this.get(), 0, data, 0, count);
- }
- bytes = data;
- }
- }
-
- /**
- * Reset the buffer to 0 size
- */
- public void reset() {
- setCapacity(0);
- }
-
- /**
- * Change the capacity of the backing store to be the same as the current
- * count of buffer.
- */
- public void truncate() {
- setCapacity(count);
- }
-
- /**
- * Append specified bytes to the buffer.
- *
- * @param bytes byte array to be appended
- * @param offset offset into byte array
- * @param length length of data
- */
- public void append(byte[] bytes, int offset, int length) {
- setCapacity(count+length);
- System.arraycopy(bytes, offset, this.get(), count, length);
- count = count + length;
- }
-
- /**
- * Append specified bytes to the buffer
- *
- * @param bytes byte array to be appended
- */
- public void append(byte[] bytes) {
- append(bytes, 0, bytes.length);
- }
-
- // inherit javadoc
- public int hashCode() {
- int hash = 1;
- byte[] b = this.get();
- for (int i = 0; i < count; i++)
- hash = (31 * hash) + (int)b[i];
- return hash;
- }
-
- /**
- * Define the sort order of the Buffer.
- *
- * @param other The other buffer
- * @return Positive if this is bigger than other, 0 if they are equal, and
- * negative if this is smaller than other.
- */
- public int compareTo(Object other) {
- Buffer right = ((Buffer) other);
- byte[] lb = this.get();
- byte[] rb = right.get();
- for (int i = 0; i < count && i < right.count; i++) {
- int a = (lb[i] & 0xff);
- int b = (rb[i] & 0xff);
- if (a != b) {
- return a - b;
- }
- }
- return count - right.count;
- }
-
- // inherit javadoc
- public boolean equals(Object other) {
- if (other instanceof Buffer && this != other) {
- return compareTo(other) == 0;
- }
- return (this == other);
- }
-
- // inheric javadoc
- public String toString() {
- StringBuffer sb = new StringBuffer(2*count);
- for(int idx = 0; idx < count; idx++) {
- sb.append(Character.forDigit((bytes[idx] & 0xF0) >> 4, 16));
- sb.append(Character.forDigit(bytes[idx] & 0x0F, 16));
- }
- return sb.toString();
- }
-
- /**
- * Convert the byte buffer to a string an specific character encoding
- *
- * @param charsetName Valid Java Character Set Name
- */
- public String toString(String charsetName)
- throws UnsupportedEncodingException {
- return new String(this.get(), 0, this.getCount(), charsetName);
- }
-
- // inherit javadoc
- public Object clone() throws CloneNotSupportedException {
- Buffer result = (Buffer) super.clone();
- result.copy(this.get(), 0, this.getCount());
- return result;
- }
- }