1 files changed, 167 insertions, 0 deletions
diff --git a/java/src/json/ext/ByteListTranscoder.java b/java/src/json/ext/ByteListTranscoder.java
new file mode 100644
index 0000000..ed9e54b
--- /dev/null
+++ b/java/src/json/ext/ByteListTranscoder.java
@@ -0,0 +1,167 @@
+/*
+ * This code is copyrighted work by Daniel Luz <dev at mernen dot com>.
+ *
+ * Distributed under the Ruby and GPLv2 licenses; see COPYING and GPL files
+ * for details.
+ */
+package json.ext;
+
+import org.jruby.exceptions.RaiseException;
+import org.jruby.runtime.ThreadContext;
+import org.jruby.util.ByteList;
+
+/**
+ * A class specialized in transcoding a certain String format into another,
+ * using UTF-8 ByteLists as both input and output.
+ */
+abstract class ByteListTranscoder {
+    protected final ThreadContext context;
+
+    protected ByteList src;
+    protected int srcEnd;
+    /** Position where the last read character started */
+    protected int charStart;
+    /** Position of the next character to read */
+    protected int pos;
+
+    private ByteList 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
+     * the sequence of characters that can be copied ends.
+     *
+     * <p>The variable stores -1 when not in a plain sequence.
+     */
+    private int quoteStart = -1;
+
+    protected ByteListTranscoder(ThreadContext context) {
+        this.context = context;
+    }
+
+    protected void init(ByteList src, ByteList out) {
+        this.init(src, 0, src.length(), out);
+    }
+
+    protected void init(ByteList src, int start, int end, ByteList out) {
+        this.src = src;
+        this.pos = start;
+        this.charStart = start;
+        this.srcEnd = end;
+        this.out = out;
+    }
+
+    /**
+     * Returns whether there are any characters left to be read.
+     */
+    protected boolean hasNext() {
+        return pos < srcEnd;
+    }
+
+    /**
+     * Returns the next character in the buffer.
+     */
+    private char next() {
+        return src.charAt(pos++);
+    }
+
+    /**
+     * Reads an UTF-8 character from the input and returns its code point,
+     * while advancing the input position.
+     *
+     * <p>Raises an {@link #invalidUtf8()} exception if an invalid byte
+     * is found.
+     */
+    protected int readUtf8Char() {
+        charStart = pos;
+        char head = next();
+        if (head <= 0x7f) { // 0b0xxxxxxx (ASCII)
+            return head;
+        }
+        if (head <= 0xbf) { // 0b10xxxxxx
+            throw invalidUtf8(); // tail byte with no head
+        }
+        if (head <= 0xdf) { // 0b110xxxxx
+            ensureMin(1);
+            int cp = ((head  & 0x1f) << 6)
+                     | nextPart();
+            if (cp < 0x0080) throw invalidUtf8();
+            return cp;
+        }
+        if (head <= 0xef) { // 0b1110xxxx
+            ensureMin(2);
+            int cp = ((head & 0x0f) << 12)
+                     | (nextPart()  << 6)
+                     | nextPart();
+            if (cp < 0x0800) throw invalidUtf8();
+            return cp;
+        }
+        if (head <= 0xf7) { // 0b11110xxx
+            ensureMin(3);
+            int cp = ((head & 0x07) << 18)
+                     | (nextPart()  << 12)
+                     | (nextPart()  << 6)
+                     | nextPart();
+            if (!Character.isValidCodePoint(cp)) throw invalidUtf8();
+            return cp;
+        }
+        // 0b11111xxx?
+        throw invalidUtf8();
+    }
+
+    /**
+     * Throws a GeneratorError if the input list doesn't have at least this
+     * many bytes left.
+     */
+    protected void ensureMin(int n) {
+        if (pos + n > srcEnd) throw incompleteUtf8();
+    }
+
+    /**
+     * Reads the next byte of a multi-byte UTF-8 character and returns its
+     * contents (lower 6 bits).
+     *
+     * <p>Throws a GeneratorError if the byte is not a valid tail.
+     */
+    private int nextPart() {
+        char c = next();
+        // tail bytes must be 0b10xxxxxx
+        if ((c & 0xc0) != 0x80) throw invalidUtf8();
+        return c & 0x3f;
+    }
+
+
+    protected void quoteStart() {
+        if (quoteStart == -1) quoteStart = charStart;
+    }
+
+    /**
+     * When in a sequence of characters that can be copied directly,
+     * interrupts the sequence and copies it to the output buffer.
+     *
+     * @param endPos The offset until which the direct character quoting should
+     *               occur. You may pass {@link #pos} to quote until the most
+     *               recently read character, or {@link #charStart} to quote
+     *               until the character before it.
+     */
+    protected void quoteStop(int endPos) {
+        if (quoteStart != -1) {
+            out.append(src, quoteStart, endPos - quoteStart);
+            quoteStart = -1;
+        }
+    }
+
+    protected void append(int b) {
+        out.append(b);
+    }
+
+    protected void append(byte[] origin, int start, int length) {
+        out.append(origin, start, length);
+    }
+
+
+    protected abstract RaiseException invalidUtf8();
+
+    protected RaiseException incompleteUtf8() {
+        return invalidUtf8();
+    }
+}