From 40ffea2367b3838a07739dc97442971b0c3916c9 Mon Sep 17 00:00:00 2001
From: Tyler Gregg <greggt@amazon.com>
Date: Tue, 24 Oct 2023 16:00:57 -0700
Subject: [PATCH] Ensures that the binary reader can handle a
 ByteArrayInputStream that returns a negative number from available().

---
 src/com/amazon/ion/impl/IonCursorBinary.java          |  5 ++++-
 .../impl/IonReaderContinuableTopLevelBinaryTest.java  | 11 +++++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/src/com/amazon/ion/impl/IonCursorBinary.java b/src/com/amazon/ion/impl/IonCursorBinary.java
index 1f25bbec9..cfa2740e7 100644
--- a/src/com/amazon/ion/impl/IonCursorBinary.java
+++ b/src/com/amazon/ion/impl/IonCursorBinary.java
@@ -389,7 +389,10 @@ private static IonBufferConfiguration getFixedSizeConfigurationFor(
         ByteArrayInputStream inputStream,
         int alreadyReadLen
     ) {
-        int fixedBufferSize = inputStream.available();
+        // Note: ByteArrayInputStream.available() can return a negative number because its constructor does
+        // not validate that the offset and length provided are actually within range of the provided byte array.
+        // Setting the result to 0 in this case avoids an error when looking up the fixed sized configuration.
+        int fixedBufferSize = Math.max(0, inputStream.available());
         if (alreadyReadLen > 0) {
             fixedBufferSize += alreadyReadLen;
         }
diff --git a/test/com/amazon/ion/impl/IonReaderContinuableTopLevelBinaryTest.java b/test/com/amazon/ion/impl/IonReaderContinuableTopLevelBinaryTest.java
index 1318cc55a..3bf42d28b 100644
--- a/test/com/amazon/ion/impl/IonReaderContinuableTopLevelBinaryTest.java
+++ b/test/com/amazon/ion/impl/IonReaderContinuableTopLevelBinaryTest.java
@@ -3321,6 +3321,17 @@ public void concatenatedAfterMissingGZIPTrailer() throws Exception {
         assertEquals(1, oversizedCounter.get());
     }
 
+    @Test
+    public void shouldNotFailWhenProvidedWithAnEmptyByteArrayInputStream() throws Exception {
+        reader = IonReaderBuilder.standard().build(new ByteArrayInputStream(new byte[]{}));
+        assertSequence(next(null));
+        reader.close();
+        // The following ByteArrayInputStream is weird, but not disallowed. Its available() method will return -1.
+        reader = IonReaderBuilder.standard().build(new ByteArrayInputStream(new byte[]{}, 1, 1));
+        assertSequence(next(null));
+        reader.close();
+    }
+
     @ParameterizedTest(name = "constructFromBytes={0}")
     @ValueSource(booleans = {true, false})
     public void incompleteContainerNonContinuable(boolean constructFromBytes) throws Exception {