Latin heap array fast path

Author: franz1981

bson/src/main/org/bson/io/OutputBuffer.java

@@ -196,11 +196,15 @@ public void writeLong(final long value) {
         writeInt64(value);
     }
 
-    private int writeCharacters(final String str, final boolean checkForNullCharacters) {
+    protected int writeCharacters(final String str, final boolean checkForNullCharacters) {
+        return writeCharacters(str, 0, checkForNullCharacters);
+    }
+
+    protected final int writeCharacters(final String str, int start, final boolean checkForNullCharacters) {
         int len = str.length();
         int total = 0;
 
-        for (int i = 0; i < len;) {
+        for (int i = start; i < len;) {
             int c = Character.codePointAt(str, i);
 
             if (checkForNullCharacters && c == 0x0) {

driver-core/src/main/com/mongodb/internal/connection/ByteBufferBsonOutput.java

@@ -16,6 +16,7 @@
 
 package com.mongodb.internal.connection;
 
+import org.bson.BsonSerializationException;
 import org.bson.ByteBuf;
 import org.bson.io.OutputBuffer;
 
@@ -27,6 +28,7 @@
 
 import static com.mongodb.assertions.Assertions.assertTrue;
 import static com.mongodb.assertions.Assertions.notNull;
+import static java.lang.String.format;
 
 /**
  * <p>This class is not part of the public API and may be removed or changed at any time</p>
@@ -273,6 +275,42 @@ public void close() {
         }
     }
 
+    @Override
+    protected int writeCharacters(final String str, final boolean checkForNullCharacters) {
+        ensureOpen();
+        ByteBuf buf = getCurrentByteBuffer();
+        byte[] array = buf.array();
+        int i = 0;
+        if (array != null && (buf.remaining() >= str.length() + 1)) {
+            int pos = buf.position();
+            int len = str.length();
+            for (;i < len; i++) {
+                char c = str.charAt(i);
+                if (checkForNullCharacters && c == 0x0) {
+                    throw new BsonSerializationException(format("BSON cstring '%s' is not valid because it contains a null character "
+                            + "at index %d", str, i));
+                }
+                if (c > 0x80) {
+                    break;
+                }
+                array[pos + i] = (byte) c;
+            }
+            if (i == len) {
+                int total = len + 1;
+                array[pos + len] = 0;
+                position += total;
+                buf.position(pos + total);
+                return len + 1;
+            }
+            // ith character is not ASCII
+            if (i > 0) {
+                position += i;
+                buf.position(pos + i);
+            }
+        }
+        return i + super.writeCharacters(str, i, checkForNullCharacters);
+    }
+
     private static final class BufferPositionPair {
         private final int bufferIndex;
         private int position;