Make HtmlInputStreamReader sniffing limit settable

This change makes the sniffing limit in HtmlInputStreamReader settable.

Without this change, the HtmlInputStreamReader sniffing limit is
hardcoded to 1024 — and in the context of testing, that has the effect
of limiting HtmlInputStreamReader to only being useful for testing
expected output of the meta prescan.

So this change makes it possible for HtmlInputStreamReader to also be
used for testing the results for the state where the expected character
encoding is not limited to what can be determined by checking the first
1024 bytes of the input stream.

src/nu/validator/htmlparser/io/HtmlInputStreamReader.java

@@ -1,6 +1,6 @@
 /*
  * Copyright (c) 2007 Henri Sivonen
- * Copyright (c) 2013 Mozilla Foundation
+ * Copyright (c) 2013-2020 Mozilla Foundation
  *
  * Permission is hereby granted, free of charge, to any person obtaining a 
  * copy of this software and associated documentation files (the "Software"), 
@@ -61,7 +61,7 @@
 public final class HtmlInputStreamReader extends Reader implements
         ByteReadable, Locator, Locator2 {
 
-    private static final int SNIFFING_LIMIT = 1024;
+    private int sniffingLimit = 1024;
 
     private final InputStream inputStream;
 
@@ -87,11 +87,9 @@ public final class HtmlInputStreamReader extends Reader implements
 
     private boolean charsetBoundaryPassed = false;
 
-    private final byte[] byteArray = new byte[4096]; // Length must be >=
+    private byte[] byteArray = new byte[4096]; // Length must be >= sniffingLimit
 
-    // SNIFFING_LIMIT
-
-    private final ByteBuffer byteBuffer = ByteBuffer.wrap(byteArray);
+    private ByteBuffer byteBuffer = ByteBuffer.wrap(byteArray);
 
     private boolean needToNotifyTokenizer = false;
 
@@ -112,18 +110,27 @@ public final class HtmlInputStreamReader extends Reader implements
     /**
      * @param inputStream
      * @param errorHandler
-     * @param locator
+     * @param tokenizer
+     * @param driver
+     * @param heuristics
+     * @param sniffingLimit
      * @throws IOException
      * @throws SAXException
      */
     public HtmlInputStreamReader(InputStream inputStream,
             ErrorHandler errorHandler, Tokenizer tokenizer, Driver driver,
-            Heuristics heuristics) throws SAXException, IOException {
+            Heuristics heuristics, int sniffingLimit)
+            throws SAXException, IOException {
         this.inputStream = inputStream;
         this.errorHandler = errorHandler;
         this.tokenizer = tokenizer;
         this.driver = driver;
         this.sniffing = true;
+        if (sniffingLimit != -1) {
+            this.sniffingLimit = sniffingLimit;
+            this.byteArray = new byte[sniffingLimit];
+            this.byteBuffer = ByteBuffer.wrap(byteArray);
+        }
         Encoding encoding = (new BomSniffer(this)).sniff();
         if (encoding == null) {
             position = 0;
@@ -178,6 +185,12 @@ public HtmlInputStreamReader(InputStream inputStream,
         initDecoder();
     }
 
+    public HtmlInputStreamReader(InputStream inputStream,
+            ErrorHandler errorHandler, Tokenizer tokenizer, Driver driver,
+            Heuristics heuristics) throws SAXException, IOException {
+        this(inputStream, errorHandler, tokenizer, driver, heuristics, -1);
+    }
+
     /**
      * 
      */
@@ -237,7 +250,7 @@ public HtmlInputStreamReader(InputStream inputStream,
                 if (charsetBoundaryPassed) {
                     readLen = byteArray.length - oldLimit;
                 } else {
-                    readLen = SNIFFING_LIMIT - oldLimit;
+                    readLen = sniffingLimit - oldLimit;
                 }
                 int num = inputStream.read(byteArray, oldLimit, readLen);
                 if (num == -1) {
@@ -261,7 +274,7 @@ public HtmlInputStreamReader(InputStream inputStream,
                 } else if (cr == CoderResult.UNDERFLOW) {
                     int remaining = byteBuffer.remaining();
                     if (!charsetBoundaryPassed) {
-                        if (bytesRead + remaining >= SNIFFING_LIMIT) {
+                        if (bytesRead + remaining >= sniffingLimit) {
                             needToNotifyTokenizer = true;
                             charsetBoundaryPassed = true;
                         }
@@ -389,12 +402,12 @@ public int readByte() throws IOException {
             throw new IllegalStateException(
                     "readByte() called when not in the sniffing state.");
         }
-        if (position == SNIFFING_LIMIT) {
+        if (position == sniffingLimit) {
             return -1;
         } else if (position < limit) {
             return byteArray[position++] & 0xFF;
         } else {
-            int num = inputStream.read(byteArray, limit, SNIFFING_LIMIT - limit);
+            int num = inputStream.read(byteArray, limit, sniffingLimit - limit);
             if (num == -1) {
                 return -1;
             } else {