Properly handles an empty input stream by keeping the internal state …

…of a GrowingBufferData consistent. (#8694)

Signed-off-by: Santiago Pericas-Geertsen <[email protected]>

common/buffers/src/main/java/io/helidon/common/buffers/GrowingBufferData.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2022 Oracle and/or its affiliates.
+ * Copyright (c) 2022, 2024 Oracle and/or its affiliates.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -74,7 +74,9 @@ public void writeTo(OutputStream out) {
     public int readFrom(InputStream in) {
         try {
             int read = in.read(bytes, writePosition, bytes.length - writePosition);
-            writePosition += read;
+            if (read > 0) {
+                writePosition += read;
+            }
             return read;
         } catch (IOException e) {
             throw new UncheckedIOException(e);

common/buffers/src/test/java/io/helidon/common/buffers/BufferDataTest.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2022 Oracle and/or its affiliates.
+ * Copyright (c) 2022, 2024 Oracle and/or its affiliates.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,6 +16,7 @@
 
 package io.helidon.common.buffers;
 
+import java.io.InputStream;
 import java.util.HexFormat;
 import java.util.stream.Stream;
 
@@ -285,6 +286,20 @@ void testHexOutput(TestContext context) {
         assertThat(bd.debugDataHex(true), is(expected));
     }
 
+    @ParameterizedTest
+    @MethodSource("initParams")
+    void emptyInputStream(TestContext context) {
+        BufferData b = context.bufferData();
+        assertThat(b.available(), is(0));
+        b.readFrom(new InputStream() {
+            @Override
+            public int read() {
+                return -1;      // no data
+            }
+        });
+        assertThat(b.available(), is(0));
+    }
+
     BufferData dataFromHex(String hexEncoded) {
         byte[] bytes = HexFormat.of().parseHex(hexEncoded.replace(" ", ""));
         return BufferData.create(bytes);