Fix RUBY-2436 Write ByteBuffer gets length reset to 0 after to_s conversion in JRuby (#224)

Co-authored-by: Oleg Pudeyev <[email protected]>

Author: p-mongo

ext/bson/init.c

@@ -276,7 +276,7 @@ void Init_bson_native()
 
   /*
    * call-seq:
-   *   buffer.put_hash(hash) -> ByteBuffer
+   *   buffer.put_hash(hash, validating_keys) -> ByteBuffer
    *
    * Writes a Hash into the byte buffer.
    *
@@ -329,6 +329,10 @@ void Init_bson_native()
    *
    * Returns the contents of the buffer as a binary string.
    *
+   * If the buffer is used for reading, the returned contents is the data
+   * that was not yet read. If the buffer is used for writing, the returned
+   * contents is the complete data that has been written so far.
+   *
    * Note: this method copies the buffer's contents into a newly allocated
    * +String+ instance. It does not return a reference to the data stored in
    * the buffer itself.

spec/bson/byte_buffer_spec.rb

@@ -65,6 +65,37 @@
         expect(buffer.length).to eq(1)
       end
     end
+
+    context 'after the byte buffer was converted to string' do
+
+      shared_examples 'returns the total buffer length' do
+        it 'returns the total buffer length' do
+          expect(buffer.length).to eq(5)
+          buffer.to_s.length.should == 5
+          expect(buffer.length).to eq(5)
+        end
+      end
+
+      context 'read buffer' do
+
+        let(:buffer) do
+          described_class.new({}.to_bson.to_s)
+        end
+
+        include_examples 'returns the total buffer length'
+      end
+
+      context 'write buffer' do
+
+        let(:buffer) do
+          described_class.new.tap do |buffer|
+            buffer.put_bytes('hello')
+          end
+        end
+
+        include_examples 'returns the total buffer length'
+      end
+    end
   end
 
   describe '#rewind!' do
@@ -160,4 +191,40 @@
       end
     end
   end
+
+  describe '#to_s' do
+    context 'read buffer' do
+      let(:buffer) do
+        described_class.new("\x18\x00\x00\x00*\x00\x00\x00")
+      end
+
+      it 'returns the data' do
+        buffer.to_s.should == "\x18\x00\x00\x00*\x00\x00\x00"
+      end
+
+      it 'returns the remaining buffer contents after a read' do
+        buffer.to_s.should == "\x18\x00\x00\x00*\x00\x00\x00"
+        buffer.get_int32.should == 24
+        buffer.to_s.should == "*\x00\x00\x00"
+      end
+    end
+
+    context 'write buffer' do
+      let(:buffer) do
+        described_class.new.tap do |buffer|
+          buffer.put_int32(24)
+        end
+      end
+
+      it 'returns the data' do
+        buffer.to_s.should == "\x18\x00\x00\x00".force_encoding('binary')
+      end
+
+      it 'returns the complete buffer contents after a write' do
+        buffer.to_s.should == "\x18\x00\x00\x00".force_encoding('binary')
+        buffer.put_int32(42)
+        buffer.to_s.should == "\x18\x00\x00\x00*\x00\x00\x00".force_encoding('binary')
+      end
+    end
+  end
 end

src/main/org/bson/ByteBuf.java

@@ -152,11 +152,15 @@ public IRubyObject initialize(final RubyString value) {
    * @version 4.0.0
    */
   @JRubyMethod(name = "length")
-  public RubyFixnum getLength() {
+  public RubyFixnum getLength(ThreadContext context) {
+    return new RubyFixnum(context.runtime, getLengthInternal());
+  }
+  
+  private int getLengthInternal() {
     if (this.mode == Mode.WRITE) {
-      return getWritePosition();
+      return this.writePosition;
     } else {
-      return new RubyFixnum(getRuntime(), this.buffer.remaining());
+      return this.buffer.remaining();
     }
   }
 
@@ -168,8 +172,8 @@ public RubyFixnum getLength() {
    * @version 4.0.0
    */
   @JRubyMethod(name = "read_position")
-  public RubyFixnum getReadPosition() {
-    return new RubyFixnum(getRuntime(), this.readPosition);
+  public RubyFixnum getReadPosition(ThreadContext context) {
+    return new RubyFixnum(context.runtime, this.readPosition);
   }
 
   /**
@@ -180,8 +184,8 @@ public RubyFixnum getReadPosition() {
    * @version 4.0.0
    */
   @JRubyMethod(name = "write_position")
-  public RubyFixnum getWritePosition() {
-    return new RubyFixnum(getRuntime(), this.writePosition);
+  public RubyFixnum getWritePosition(ThreadContext context) {
+    return new RubyFixnum(context.runtime, this.writePosition);
   }
 
  /**
@@ -207,11 +211,16 @@ public ByteBuf rewind() {
    * @version 4.0.0
    */
   @JRubyMethod(name = "to_s")
-  public RubyString toRubyString() {
-    ensureBsonRead();
-    byte[] bytes = new byte[this.writePosition];
-    this.buffer.get(bytes, 0, this.writePosition);
-    return RubyString.newString(getRuntime(), bytes);
+  public RubyString toRubyString(ThreadContext context) {
+    ByteBuffer buffer_copy = this.buffer.duplicate();
+    if (this.mode == Mode.WRITE) {
+      buffer_copy.flip();
+    }
+    int length = this.getLengthInternal();
+    byte[] bytes = new byte[length];
+    buffer_copy.get(bytes, 0, length);
+    
+    return RubyString.newString(context.runtime, bytes);
   }
 
   /**