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java/javax/servlet/ServletInputStream.java

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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 javax.servlet;
+
+import java.io.IOException;
+import java.io.InputStream;
+
+/**
+ * Provides an input stream for reading binary data from a client request,
+ * including an efficient <code>readLine</code> method for reading data one line
+ * at a time. With some protocols, such as HTTP POST and PUT, a
+ * <code>ServletInputStream</code> object can be used to read data sent from the
+ * client.
+ * <p>
+ * A <code>ServletInputStream</code> object is normally retrieved via the
+ * {@link ServletRequest#getInputStream} method.
+ * <p>
+ * This is an abstract class that a servlet container implements. Subclasses of
+ * this class must implement the <code>java.io.InputStream.read()</code> method.
+ *
+ * @see ServletRequest
+ */
+public abstract class ServletInputStream extends InputStream {
+
+    /**
+     * Does nothing, because this is an abstract class.
+     */
+    protected ServletInputStream() {
+        // NOOP
+    }
+
+    /**
+     * Reads the input stream, one line at a time. Starting at an offset, reads
+     * bytes into an array, until it reads a certain number of bytes or reaches
+     * a newline character, which it reads into the array as well.
+     * <p>
+     * This method returns -1 if it reaches the end of the input stream before
+     * reading the maximum number of bytes.
+     *
+     * @param b
+     *            an array of bytes into which data is read
+     * @param off
+     *            an integer specifying the character at which this method
+     *            begins reading
+     * @param len
+     *            an integer specifying the maximum number of bytes to read
+     * @return an integer specifying the actual number of bytes read, or -1 if
+     *         the end of the stream is reached
+     * @exception IOException
+     *                if an input or output exception has occurred
+     */
+    public int readLine(byte[] b, int off, int len) throws IOException {
+
+        if (len <= 0) {
+            return 0;
+        }
+        int count = 0, c;
+
+        while ((c = read()) != -1) {
+            b[off++] = (byte) c;
+            count++;
+            if (c == '\n' || count == len) {
+                break;
+            }
+        }
+        return count > 0 ? count : -1;
+    }
+
+    /**
+     * Has the end of this InputStream been reached?
+     *
+     * @return <code>true</code> if all the data has been read from the stream,
+     * else <code>false</code>
+     *
+     * @since Servlet 3.1
+     */
+    public abstract boolean isFinished();
+
+    /**
+     * Can data be read from this InputStream without blocking?
+     * Returns  If this method is called and returns false, the container will
+     * invoke {@link ReadListener#onDataAvailable()} when data is available.
+     *
+     * @return <code>true</code> if data can be read without blocking, else
+     * <code>false</code>
+     *
+     * @since Servlet 3.1
+     */
+    public abstract boolean isReady();
+
+    /**
+     * Sets the {@link ReadListener} for this {@link ServletInputStream} and
+     * thereby switches to non-blocking IO. It is only valid to switch to
+     * non-blocking IO within async processing or HTTP upgrade processing.
+     *
+     * @param listener  The non-blocking IO read listener
+     *
+     * @throws IllegalStateException    If this method is called if neither
+     *                                  async nor HTTP upgrade is in progress or
+     *                                  if the {@link ReadListener} has already
+     *                                  been set
+     * @throws NullPointerException     If listener is null
+     *
+     * @since Servlet 3.1
+     */
+    public abstract void setReadListener(ReadListener listener);
+}