--- /dev/null
+/*
+ * Copyright (C) 2012 The Android Open Source Project
+ *
+ * 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 org.lineageos.eleven.cache.disklrucache;
+
+import java.io.ByteArrayOutputStream;
+import java.io.Closeable;
+import java.io.EOFException;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.UnsupportedEncodingException;
+import java.nio.charset.Charset;
+
+/**
+ * Buffers input from an {@link InputStream} for reading lines.
+ *
+ * <p>This class is used for buffered reading of lines. For purposes of this class, a line ends
+ * with "\n" or "\r\n". End of input is reported by throwing {@code EOFException}. Unterminated
+ * line at end of input is invalid and will be ignored, the caller may use {@code
+ * hasUnterminatedLine()} to detect it after catching the {@code EOFException}.
+ *
+ * <p>This class is intended for reading input that strictly consists of lines, such as line-based
+ * cache entries or cache journal. Unlike the {@link java.io.BufferedReader} which in conjunction
+ * with {@link java.io.InputStreamReader} provides similar functionality, this class uses different
+ * end-of-input reporting and a more restrictive definition of a line.
+ *
+ * <p>This class supports only charsets that encode '\r' and '\n' as a single byte with value 13
+ * and 10, respectively, and the representation of no other character contains these values.
+ * We currently check in constructor that the charset is one of US-ASCII, UTF-8 and ISO-8859-1.
+ * The default charset is US_ASCII.
+ */
+class StrictLineReader implements Closeable {
+ private static final byte CR = (byte) '\r';
+ private static final byte LF = (byte) '\n';
+
+ private final InputStream in;
+ private final Charset charset;
+
+ /*
+ * Buffered data is stored in {@code buf}. As long as no exception occurs, 0 <= pos <= end
+ * and the data in the range [pos, end) is buffered for reading. At end of input, if there is
+ * an unterminated line, we set end == -1, otherwise end == pos. If the underlying
+ * {@code InputStream} throws an {@code IOException}, end may remain as either pos or -1.
+ */
+ private byte[] buf;
+ private int pos;
+ private int end;
+
+ /**
+ * Constructs a new {@code LineReader} with the specified charset and the default capacity.
+ *
+ * @param in the {@code InputStream} to read data from.
+ * @param charset the charset used to decode data. Only US-ASCII, UTF-8 and ISO-8859-1 are
+ * supported.
+ * @throws NullPointerException if {@code in} or {@code charset} is null.
+ * @throws IllegalArgumentException if the specified charset is not supported.
+ */
+ public StrictLineReader(InputStream in, Charset charset) {
+ this(in, 8192, charset);
+ }
+
+ /**
+ * Constructs a new {@code LineReader} with the specified capacity and charset.
+ *
+ * @param in the {@code InputStream} to read data from.
+ * @param capacity the capacity of the buffer.
+ * @param charset the charset used to decode data. Only US-ASCII, UTF-8 and ISO-8859-1 are
+ * supported.
+ * @throws NullPointerException if {@code in} or {@code charset} is null.
+ * @throws IllegalArgumentException if {@code capacity} is negative or zero
+ * or the specified charset is not supported.
+ */
+ public StrictLineReader(InputStream in, int capacity, Charset charset) {
+ if (in == null || charset == null) {
+ throw new NullPointerException();
+ }
+ if (capacity < 0) {
+ throw new IllegalArgumentException("capacity <= 0");
+ }
+ if (!(charset.equals(Util.US_ASCII))) {
+ throw new IllegalArgumentException("Unsupported encoding");
+ }
+
+ this.in = in;
+ this.charset = charset;
+ buf = new byte[capacity];
+ }
+
+ /**
+ * Closes the reader by closing the underlying {@code InputStream} and
+ * marking this reader as closed.
+ *
+ * @throws IOException for errors when closing the underlying {@code InputStream}.
+ */
+ public void close() throws IOException {
+ synchronized (in) {
+ if (buf != null) {
+ buf = null;
+ in.close();
+ }
+ }
+ }
+
+ /**
+ * Reads the next line. A line ends with {@code "\n"} or {@code "\r\n"},
+ * this end of line marker is not included in the result.
+ *
+ * @return the next line from the input.
+ * @throws IOException for underlying {@code InputStream} errors.
+ * @throws EOFException for the end of source stream.
+ */
+ public String readLine() throws IOException {
+ synchronized (in) {
+ if (buf == null) {
+ throw new IOException("LineReader is closed");
+ }
+
+ // Read more data if we are at the end of the buffered data.
+ // Though it's an error to read after an exception, we will let {@code fillBuf()}
+ // throw again if that happens; thus we need to handle end == -1 as well as end == pos.
+ if (pos >= end) {
+ fillBuf();
+ }
+ // Try to find LF in the buffered data and return the line if successful.
+ for (int i = pos; i != end; ++i) {
+ if (buf[i] == LF) {
+ int lineEnd = (i != pos && buf[i - 1] == CR) ? i - 1 : i;
+ String res = new String(buf, pos, lineEnd - pos, charset.name());
+ pos = i + 1;
+ return res;
+ }
+ }
+
+ // Let's anticipate up to 80 characters on top of those already read.
+ ByteArrayOutputStream out = new ByteArrayOutputStream(end - pos + 80) {
+ @Override
+ public String toString() {
+ int length = (count > 0 && buf[count - 1] == CR) ? count - 1 : count;
+ try {
+ return new String(buf, 0, length, charset.name());
+ } catch (UnsupportedEncodingException e) {
+ throw new AssertionError(e); // Since we control the charset this will never happen.
+ }
+ }
+ };
+
+ while (true) {
+ out.write(buf, pos, end - pos);
+ // Mark unterminated line in case fillBuf throws EOFException or IOException.
+ end = -1;
+ fillBuf();
+ // Try to find LF in the buffered data and return the line if successful.
+ for (int i = pos; i != end; ++i) {
+ if (buf[i] == LF) {
+ if (i != pos) {
+ out.write(buf, pos, i - pos);
+ }
+ pos = i + 1;
+ return out.toString();
+ }
+ }
+ }
+ }
+ }
+
+ public boolean hasUnterminatedLine() {
+ return end == -1;
+ }
+
+ /**
+ * Reads new input data into the buffer. Call only with pos == end or end == -1,
+ * depending on the desired outcome if the function throws.
+ */
+ private void fillBuf() throws IOException {
+ int result = in.read(buf, 0, buf.length);
+ if (result == -1) {
+ throw new EOFException();
+ }
+ pos = 0;
+ end = result;
+ }
+}
+
OSDN Git Service
