com.google.gwt.emul.java.io.Reader Maven / Gradle / Ivy
/*
* Copyright 2018 Google Inc.
*
* Licensed 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 java.io;
/**
* Reads a stream of characters.
*/
public abstract class Reader {
/**
* The maximum buffer size to incrementally read in {@link #skip}.
*/
private static final int MAX_SKIP_BUFFER_SIZE = 1024;
/**
* Closes the reader, and releases any associated resources.
*/
public abstract void close() throws IOException;
/**
* Marks the present position in the stream. Until {@code readAheadLimit} more
* characters have been read, the current point in the stream will be stored
* as the mark. Calls to {@link #reset} will reposition the point in the
* stream to the mark.
*
* @throws IOException If the stream does not support mark().
*/
public void mark(int readAheadLimit) throws IOException {
throw new IOException("Not supported");
}
/**
* Returns whether {@link #mark} is implemented.
*/
public boolean markSupported() {
return false;
}
/**
* Reads a single character, or -1 if we are at the end of the stream.
*/
public int read() throws IOException {
char chr[] = new char[1];
return (read(chr) == -1) ? -1 : chr[0];
}
/**
* Attempts to fill {@code buf} with characters up to the size of the array.
*/
public int read(char[] buf) {
return read(buf, 0, buf.length);
}
/**
* Attempts to fill {@code buf} with up to {@code len} characters. Characters
* will be stored in {@code buf} starting at index {@code off}.
*/
public abstract int read(char[] buf, int off, int len);
/**
* Returns whether the stream is ready for reading characters.
*/
public boolean ready() throws IOException {
return false;
}
/**
* Attempts to reset the stream to the previous mark.
*/
public void reset() throws IOException {
throw new IOException("Not supported");
}
/**
* Skips {@code n} characters, returning the number of characters that were actually skipped.
*/
public long skip(long n) throws IOException {
long remaining = n;
int bufferSize = Math.min((int) n, MAX_SKIP_BUFFER_SIZE);
char[] skipBuffer = new char[bufferSize];
while (remaining > 0) {
long numRead = read(skipBuffer, 0, (int) remaining);
if (numRead < 0) {
break;
}
remaining -= numRead;
}
return n - remaining;
}
}