Plumb OutputStream through generators

When an IO is given, we should try to write directly to it. This
patch moves that direction by always doing JSON dumping into an
OutputStream, which can be implemented on top of a given IO or by
producing a ByteList via a ByteArrayOutputStream.

Rakefile

@@ -161,7 +161,7 @@ if defined?(RUBY_ENGINE) and RUBY_ENGINE == 'jruby'
   file JRUBY_PARSER_JAR => :compile do
     cd 'java/src' do
       parser_classes = FileList[
-        "json/ext/ByteListTranscoder*.class",
+        "json/ext/ByteList*.class",
         "json/ext/OptionsReader*.class",
         "json/ext/Parser*.class",
         "json/ext/RuntimeInfo*.class",
@@ -179,7 +179,7 @@ if defined?(RUBY_ENGINE) and RUBY_ENGINE == 'jruby'
   file JRUBY_GENERATOR_JAR => :compile do
     cd 'java/src' do
       generator_classes = FileList[
-        "json/ext/ByteListTranscoder*.class",
+        "json/ext/ByteList*.class",
         "json/ext/OptionsReader*.class",
         "json/ext/Generator*.class",
         "json/ext/RuntimeInfo*.class",

java/src/json/ext/ByteListDirectOutputStream.java

@@ -0,0 +1,16 @@
+package json.ext;
+
+import org.jcodings.Encoding;
+import org.jruby.util.ByteList;
+
+import java.io.ByteArrayOutputStream;
+
+public class ByteListDirectOutputStream extends ByteArrayOutputStream {
+    ByteListDirectOutputStream(int size) {
+        super(size);
+    }
+
+    public ByteList toByteListDirect(Encoding encoding) {
+        return new ByteList(buf, 0, count, encoding, false);
+    }
+}

java/src/json/ext/ByteListTranscoder.java

@@ -9,6 +9,9 @@
 import org.jruby.runtime.ThreadContext;
 import org.jruby.util.ByteList;
 
+import java.io.IOException;
+import java.io.OutputStream;
+
 /**
  * A class specialized in transcoding a certain String format into another,
  * using UTF-8 ByteLists as both input and output.
@@ -23,7 +26,7 @@ abstract class ByteListTranscoder {
     /** Position of the next character to read */
     protected int pos;
 
-    private ByteList out;
+    private OutputStream out;
     /**
      * When a character that can be copied straight into the output is found,
      * its index is stored on this variable, and copying is delayed until
@@ -37,11 +40,11 @@ protected ByteListTranscoder(ThreadContext context) {
         this.context = context;
     }
 
-    protected void init(ByteList src, ByteList out) {
+    protected void init(ByteList src, OutputStream out) {
         this.init(src, 0, src.length(), out);
     }
 
-    protected void init(ByteList src, int start, int end, ByteList out) {
+    protected void init(ByteList src, int start, int end, OutputStream out) {
         this.src = src;
         this.pos = start;
         this.charStart = start;
@@ -142,19 +145,19 @@ protected void quoteStart() {
      *               recently read character, or {@link #charStart} to quote
      *               until the character before it.
      */
-    protected void quoteStop(int endPos) {
+    protected void quoteStop(int endPos) throws IOException {
         if (quoteStart != -1) {
-            out.append(src, quoteStart, endPos - quoteStart);
+            out.write(src.bytes(), quoteStart, endPos - quoteStart);
             quoteStart = -1;
         }
     }
 
-    protected void append(int b) {
-        out.append(b);
+    protected void append(int b) throws IOException {
+        out.write(b);
     }
 
-    protected void append(byte[] origin, int start, int length) {
-        out.append(origin, start, length);
+    protected void append(byte[] origin, int start, int length) throws IOException {
+        out.write(origin, start, length);
     }