Merge pull request #16 from cschanck/PushbackReader

Add pushback reader, keeps position in Reader stream

Author: cschanck

src/main/java/org/sfj/ChiseledMap.java

@@ -498,6 +498,18 @@ public synchronized boolean ioSet(K key, V v) throws IOException {
  return map.put(key, newAddr) != null;
  }
 
+ public synchronized V ioGetSet(K key, V v) throws IOException {
+ Objects.requireNonNull(v);
+ Long addr = map.get(key);
+ V ret = null;
+ if (addr != null) {
+ ret = fetch(addr, false, null).getValue();
+ }
+ long newAddr = append(key, v);
+ map.put(key, newAddr);
+ return ret;
+ }
+
  /**
  * Copy only live entries to another file. Blocks writes to this map
  * while snapshotting.
@@ -542,11 +554,9 @@ public boolean set(K key, V value) {
  }
 
  @Override
- public synchronized V put(K key, V value) {
+ public V put(K key, V value) {
  try {
- V p = ioGet(key);
- ioSet(key, value);
- return p;
+ return ioGetSet(key, value);
  } catch (IOException e) {
  throw new RuntimeIOException(e);
  }

src/main/java/org/sfj/PositionalPushbackReader.java

@@ -0,0 +1,241 @@
+/*
+ * Copyright 2020 C. Schanck
+ *
+ * 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.sfj;
+
+import java.io.IOException;
+import java.io.LineNumberReader;
+import java.io.Reader;
+import java.io.StringReader;
+import java.nio.CharBuffer;
+
+/**
+ * This is a basically an infinite pushback Reader, which handles line endings
+ * resiliently. It will not be super fast, as all calls end up going through
+ * the single char read() method, but it will keep line/column position properly
+ * across line endings, across character and line endings being pushed back, etc.
+ * <p>Since it is inifinite, it keeps track of the line lengths of all read lines in
+ * a humpty-dumpty linked list, so when newlines are pushed back, the column position
+ * is maintained. A similarly linked list is used for pushback chars. I am not certain
+ * of the need for a hand rolled linked list for this, but the overhead of boxing
+ * seems blah.
+ * <p>End-of-line is denoted by newlines only, and only newlines should be pushed back.
+ * <p>It would have been nice to fit this into PegLeg, as it would be much
+ * more efficient for parsing.
+ */
+public class PositionalPushbackReader extends LineNumberReader {
+
+ private static class IntNode {
+ IntNode next;
+ int val;
+
+ public IntNode(int val) {
+ this.val = val;
+ }
+ }
+
+ private static class IntQueue {
+ private IntNode head = null;
+ private IntNode tail = null;
+
+ public void clear() {
+ head = tail = null;
+ }
+
+ void push(int val) {
+ IntNode p = new IntNode(val);
+ if (head == null) {
+ head = tail = p;
+ } else if (head == tail) {
+ p.next = tail;
+ head = p;
+ } else {
+ p.next = head;
+ head = p;
+ }
+ }
+
+ int pop() {
+ if (head == null) {
+ throw new IllegalStateException();
+ }
+ int ret = head.val;
+ if (head == tail) {
+ head = tail = null;
+ } else {
+ head = head.next;
+ }
+ return ret;
+ }
+
+ boolean isEmpty() {
+ return head == null;
+ }
+ }
+
+ private final IntQueue pushback = new IntQueue();
+ private final IntQueue lineLengths = new IntQueue();
+ private int latestReadPosInLine = 0;
+ private int latestReadLineNumber = 0;
+ private boolean lastReadWasNewline = false;
+
+ public PositionalPushbackReader(String source) {
+ this(new StringReader(source));
+ }
+
+ public PositionalPushbackReader(Reader r) {
+ super(r);
+ }
+
+ /**
+ * Core method. Reads a char, possibly from pushback, return a char, or -1
+ * on end of input.
+ * @return char as int, or -1 on end of input.
+ * @throws IOException
+ */
+ public int read() throws IOException {
+ int ch = pushback.isEmpty() ? super.read() : pushback.pop();
+ if (ch == -1) { return -1; }
+ if (lastReadWasNewline) {
+ lastReadWasNewline = false;
+ latestReadPosInLine = 0;
+ latestReadLineNumber++;
+ }
+ if (ch == '\n') {
+ lastReadWasNewline = true;
+ latestReadPosInLine++;
+ lineLengths.push(latestReadPosInLine);
+ } else {
+ lastReadWasNewline = false;
+ latestReadPosInLine++;
+ }
+ return ch;
+ }
+
+ /**
+ * Pushback a character. Use '\n' newline for end of line. If you
+ * pushback a char that was not read, the line number/column position
+ * maintanence behavior is undefined.
+ * @param ch char to pushback.
+ */
+ public void pushback(int ch) {
+ if (ch == -1) { throw new IllegalArgumentException(); }
+ if (--latestReadPosInLine == 0) {
+ latestReadLineNumber--;
+ latestReadPosInLine = lineLengths.pop();
+ lastReadWasNewline = true;
+ } else {
+ lastReadWasNewline = false;
+ }
+ pushback.push(ch);
+ }
+
+ @Override
+ public long skip(long n) throws IOException {
+ int cnt = 0;
+ while (cnt < n) {
+ int ch = read();
+ if (ch == -1) { break; }
+ cnt++;
+ }
+ return cnt;
+ }
+
+ @Override
+ public boolean ready() throws IOException {
+ return !pushback.isEmpty() || super.ready();
+ }
+
+ @Override
+ public void reset() throws IOException {
+ pushback.clear();
+ latestReadLineNumber = 0;
+ latestReadPosInLine = 0;
+ super.reset();
+ }
+
+ @Override
+ public int read(CharBuffer target) throws IOException {
+ return super.read(target);
+ }
+
+ @Override
+ public int read(char[] cbuf) throws IOException {
+ return read(cbuf, 0, cbuf.length);
+ }
+
+ @Override
+ public boolean markSupported() {
+ return false;
+ }
+
+ @Override
+ public void mark(int readAheadLimit) {
+ throw new UnsupportedOperationException();
+ }
+
+ @Override
+ public int read(char[] cbuf, int off, int len) throws IOException {
+ int cnt = 0;
+ while (cnt < len) {
+ int ch = read();
+ if (ch == -1) { break; }
+ cnt++;
+ cbuf[off + cnt] = (char) ch;
+ }
+ return cnt;
+ }
+
+ @Override
+ public void close() throws IOException {
+ pushback.clear();
+ super.close();
+ }
+
+ /**
+ * Position of last read character in the current line. 1 is the first position.
+ * @return position
+ */
+ public int getColumnPosition() {
+ return latestReadPosInLine;
+ }
+
+ /**
+ * Line number of last read character. 1 indexed.
+ * @return line number
+ */
+ public int getLineNumber() {
+ return latestReadLineNumber + 1;
+ }
+
+ @Override
+ public void setLineNumber(int lineNumber) {
+ throw new UnsupportedOperationException();
+ }
+
+ @Override
+ public String readLine() throws IOException {
+ StringBuilder sb = new StringBuilder();
+
+ int ch = read();
+ if (ch == -1) {
+ return null;
+ }
+ for (; ch != -1 && ((char) ch != '\n'); ch = read()) {
+ sb.append(ch);
+ }
+ return sb.toString();
+ }
+}