uptake latest fast double parser code (#806)

Author: pjfanning

src/main/java/com/fasterxml/jackson/core/io/doubleparser/AbstractFloatValueParser.java

@@ -10,7 +10,7 @@
 package com.fasterxml.jackson.core.io.doubleparser;
 
 /**
- * Abstract base class for parsers that parse a {@code FloatValue} from a
+ * Abstract base class for parsers that parse a {@code FloatingPointLiteral} from a
  * character sequence ({@code str}).
  * <p>
  * This is a C++ to Java port of Daniel Lemire's fast_double_parser.
@@ -32,6 +32,20 @@
  * </dl>
  */
 abstract class AbstractFloatValueParser {
+    /**
+     * This return value indicates that the input value is not a legal
+     * production of the syntax rule for a float value.
+     * <p>
+     * The value is {@code -1L}.
+     * <p>
+     * Converting this value to a floating point number using
+     * {@code Double.longBitsToDouble(-1L)}, or
+     * {@code Float.intBitsToFloat((int) -1L)} yields a {@code NaN}.
+     * <p>
+     * Although this number yields {@code NaN}, the bit pattern of this value is
+     * intentionally different from {@link Double#NaN}, and {@link Float#NaN}.
+     */
+    final static long PARSE_ERROR = -1L;
     final static long MINIMAL_NINETEEN_DIGIT_INTEGER = 1000_00000_00000_00000L;
     /**
      * The decimal exponent of a double has a range of -324 to +308.
@@ -72,6 +86,4 @@ abstract class AbstractFloatValueParser {
             AbstractFloatValueParser.CHAR_TO_HEX_MAP[ch] = AbstractFloatValueParser.DECIMAL_POINT_CLASS;
         }
     }
-
-
 }