Fix response truncation

If the response is an exact multiple of the buffer size it is being
truncated.

Fixes #22973

extensions/resteasy-classic/resteasy-jackson/deployment/src/test/java/io/quarkus/resteasy/jackson/LargeResource.java

@@ -0,0 +1,39 @@
+package io.quarkus.resteasy.jackson;
+
+import java.util.HashMap;
+import java.util.Map;
+
+import javax.ws.rs.GET;
+import javax.ws.rs.Path;
+import javax.ws.rs.Produces;
+import javax.ws.rs.core.MediaType;
+
+@Produces(MediaType.APPLICATION_JSON)
+@Path("/large")
+public class LargeResource {
+
+    @GET
+    @Path("/bufmult")
+    public Map<String, String> hello() {
+        Map<String, String> ret = new HashMap<>();
+        for (int i = 0; i < 830; ++i) {
+            if (i == 0) {
+                //hack to make this exactly 2 * 8191 bytes long, as tested by trial and error
+                ret.put("key00", "value" + i);
+            } else {
+                ret.put("key" + i, "value" + i);
+            }
+        }
+        return ret;
+    }
+
+    @GET
+    @Path("/huge")
+    public Map<String, String> huge() {
+        Map<String, String> ret = new HashMap<>();
+        for (int i = 0; i < 1280; ++i) {
+            ret.put("key" + i, "value" + i);
+        }
+        return ret;
+    }
+}

extensions/resteasy-classic/resteasy-jackson/deployment/src/test/java/io/quarkus/resteasy/jackson/LargeResponseTest.java

@@ -0,0 +1,32 @@
+package io.quarkus.resteasy.jackson;
+
+import static org.hamcrest.Matchers.equalTo;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.RegisterExtension;
+
+import io.quarkus.test.QuarkusUnitTest;
+import io.restassured.RestAssured;
+
+public class LargeResponseTest {
+
+    @RegisterExtension
+    static QuarkusUnitTest TEST = new QuarkusUnitTest()
+            .withApplicationRoot((jar) -> jar
+                    .addClasses(LargeResource.class));
+
+    @Test
+    public void testLargeResponseMultipleOfBuffer() {
+        RestAssured.get("/large/bufmult").then()
+                .statusCode(200)
+                .body("key500", equalTo("value500"));
+    }
+
+    @Test
+    public void testLargeResponse() {
+        RestAssured.get("/large/huge").then()
+                .statusCode(200)
+                .body("key500", equalTo("value500"));
+    }
+
+}

extensions/resteasy-classic/resteasy/runtime/src/main/java/io/quarkus/resteasy/runtime/standalone/VertxOutputStream.java

@@ -3,12 +3,14 @@
 import java.io.IOException;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.CompletionStage;
+import java.util.function.BiConsumer;
 
 import javax.ws.rs.core.HttpHeaders;
 
 import org.jboss.resteasy.spi.AsyncOutputStream;
 
 import io.netty.buffer.ByteBuf;
+import io.netty.buffer.Unpooled;
 
 public class VertxOutputStream extends AsyncOutputStream {
 
@@ -160,36 +162,38 @@ public CompletionStage<Void> asyncWrite(final byte[] b, final int off, final int
             return ret;
         }
 
-        CompletionStage<Void> ret = CompletableFuture.completedFuture(null);
-        int bufferSize = allocator.getBufferSize();
-        int bufferCount = len / bufferSize;
-        int remainder = len % bufferSize;
-        if (remainder != 0) {
-            bufferCount = bufferCount + 1;
-        }
+        CompletableFuture<Void> ret = CompletableFuture.completedFuture(null);
 
-        if (bufferCount == 1) {
-            if (pooledBuffer == null) {
-                pooledBuffer = allocator.allocateBuffer();
-            }
-            pooledBuffer.writeBytes(b, 0, len);
-        } else {
-            for (int i = 0; i < bufferCount - 1; i++) {
-                int bufferIndex = i;
-                ret = ret.thenCompose(v -> {
-                    ByteBuf tmpBuf = null;
-                    if ((bufferIndex == 0) && ((pooledBuffer != null))) {
-                        tmpBuf = pooledBuffer;
+        ByteBuf wrappedBuffer = Unpooled.wrappedBuffer(b, off, len);
+        if (pooledBuffer == null) {
+            pooledBuffer = allocator.allocateBuffer();
+        }
+        pooledBuffer.writeBytes(wrappedBuffer, Math.min(pooledBuffer.writableBytes(), wrappedBuffer.readableBytes()));
+        if (pooledBuffer.writableBytes() == 0) {
+            CompletableFuture<Void> cf = new CompletableFuture<>();
+            ret = cf;
+            ByteBuf filled = pooledBuffer;
+            pooledBuffer = null;
+            response.writeNonBlocking(filled, false).whenComplete(new BiConsumer<Void, Throwable>() {
+                @Override
+                public void accept(Void unused, Throwable throwable) {
+                    if (throwable != null) {
+                        cf.completeExceptionally(throwable);
+                        return;
                     }
-                    if (tmpBuf == null) {
-                        tmpBuf = allocator.allocateBuffer();
+                    pooledBuffer = allocator.allocateBuffer();
+                    pooledBuffer.writeBytes(wrappedBuffer,
+                            Math.min(pooledBuffer.writableBytes(), wrappedBuffer.readableBytes()));
+
+                    if (pooledBuffer.writableBytes() == 0) {
+                        ByteBuf filled = pooledBuffer;
+                        pooledBuffer = null;
+                        response.writeNonBlocking(filled, false).whenComplete(this);
+                    } else {
+                        cf.complete(null);
                     }
-                    tmpBuf.writeBytes(b, bufferIndex * bufferSize, bufferSize);
-                    return response.writeNonBlocking(tmpBuf, false);
-                });
-            }
-            pooledBuffer = allocator.allocateBuffer();
-            pooledBuffer.writeBytes(b, (bufferCount - 1) * bufferSize, remainder);
+                }
+            });
         }
 
         return ret.thenCompose(v -> asyncUpdateWritten(len));