C and Pure parser accept invalid UTF-8 strings, the Java parser doesn't.

先复现 Ruby 示例，然后阅读 java/src/json/ext/ByteListTranscoder.java，并比较 C、Pure 和 Java 解析器对无效 UTF-8 的行为。在修改解析器之前，明确哪种行为应与 MRI 一致；当各实现对该输入得出一致且达成共识的结果时，即视为完成。

I know, I know...if it's bad content it's bad content. But this represents a difference from MRI.

Here's the case, again a reduced version of one I got from @rkh:

# encoding: utf-8
require 'json'
x = "{\"foo\":\"\xC3\"}"
h = JSON.parse(x)
p h['foo']
p h['foo'].encoding

So basically there's a bad byte in a UTF-8 string, and the MRI version walks right by it and allows it to come through to the resulting parsed json structure.

I have a totally broken patch for this:

diff --git a/java/src/json/ext/ByteListTranscoder.java b/java/src/json/ext/ByteListTranscoder.java
index ed9e54b..a7e42ba 100644
--- a/java/src/json/ext/ByteListTranscoder.java
+++ b/java/src/json/ext/ByteListTranscoder.java
@@ -78,9 +78,10 @@ abstract class ByteListTranscoder {
             return head;
         }
         if (head <= 0xbf) { // 0b10xxxxxx
-            throw invalidUtf8(); // tail byte with no head
+            return head; //throw invalidUtf8(); // tail byte with no head
         }
         if (head <= 0xdf) { // 0b110xxxxx
+            if (pos + 1 > srcEnd) return head;
             ensureMin(1);
             int cp = ((head  & 0x1f) << 6)
                      | nextPart();

Again, I'm not sure this is actually something that needs to be fixed, but because the MRI version of json does not blow up on this content, there's something to be addressed.