6631046: BufferedInputStream.available() reports negative int on very large inputstream

Reviewed-by: dholmes, alanb, mduigou

src/share/classes/java/io/BufferedInputStream.java

@@ -395,7 +395,11 @@ class BufferedInputStream extends FilterInputStream {
      *                          or an I/O error occurs.
      */
     public synchronized int available() throws IOException {
-        return getInIfOpen().available() + (count - pos);
+        int n = count - pos;
+        int avail = getInIfOpen().available();
+        return n > (Integer.MAX_VALUE - avail)
+                    ? Integer.MAX_VALUE
+                    : n + avail;
     }
 
     /**

src/share/classes/java/io/PushbackInputStream.java

@@ -273,7 +273,11 @@ class PushbackInputStream extends FilterInputStream {
      */
     public int available() throws IOException {
         ensureOpen();
-        return (buf.length - pos) + super.available();
+        int n = buf.length - pos;
+        int avail = super.available();
+        return n > (Integer.MAX_VALUE - avail)
+                    ? Integer.MAX_VALUE
+                    : n + avail;
     }
 
     /**