improved reader close in tokenizer

Author: raydac

src/main/java/com/igormaznitsa/prologparser/PrologParser.java

@@ -75,6 +75,8 @@ public abstract class PrologParser implements Iterable<PrologTerm>, Closeable {
   private static final Koi7CharOpMap OPERATORS_SUBBLOCK;
   private static final Koi7CharOpMap OPERATORS_SUBBLOCK_CURLY;
 
+  private volatile boolean autoCloseReaderFlag;
+
   static {
     META_OP_MAP = ofOps();
 
@@ -106,6 +108,11 @@ public PrologParser(final Reader source, final ParserContext context) {
     this.parserFlags = context == null ? FLAG_NONE : context.getFlags();
   }
 
+  public PrologParser autoCloseReader(){
+    this.autoCloseReaderFlag = true;
+    return this;
+  }
+
   public static Op findBaseMetaOperator(final String text, final OpAssoc type) {
     if (text.length() != 1) {
       return null;
@@ -612,6 +619,6 @@ public Stream<PrologTerm> stream() {
 
   @Override
   public void close() throws IOException {
-    this.tokenizer.close();
+    this.tokenizer.close(this.autoCloseReaderFlag);
   }
 }

src/main/java/com/igormaznitsa/prologparser/tokenizer/Tokenizer.java

@@ -37,6 +37,7 @@
 import com.igormaznitsa.prologparser.utils.StringUtils;
 
 import java.io.IOException;
+import java.io.PushbackReader;
 import java.io.Reader;
 import java.math.BigInteger;
 
@@ -166,10 +167,21 @@ public void push(final char ch) {
     }
   }
 
-  public void close() throws IOException {
+  public void close(final boolean closeReader) throws IOException {
     this.lastPushedTerm = null;
-    this.strBuf.clear();
-    this.reader.close();
+    try {
+      if (this.reader instanceof PushbackReader) {
+        final PushbackReader pbReader = (PushbackReader) this.reader;
+        while (!this.strBuf.isEmpty()) {
+          pbReader.unread(this.strBuf.pop());
+        }
+      }
+    } finally {
+      this.strBuf.clear();
+      if (closeReader) {
+        this.reader.close();
+      }
+    }
   }
 
   public boolean hasOperatorStartsWith(final String operatorNameStartSubstring) {