Fix range handling for zero-length blobs

Author: nicktindall

test/fixtures/gcs-fixture/src/main/java/fixture/gcs/GoogleCloudStorageHttpHandler.java

@@ -129,35 +129,25 @@ public void handle(final HttpExchange exchange) throws IOException {
                 final MockGcsBlobStore.BlobVersion blob = mockGcsBlobStore.getBlob(path, ifGenerationMatch);
                 if (blob != null) {
                     final String rangeHeader = exchange.getRequestHeaders().getFirst("Range");
-                    final long offset;
-                    final long end;
+                    final BytesReference response;
                     if (rangeHeader == null) {
-                        offset = 0L;
-                        end = blob.contents().length() - 1;
+                        response = blob.contents();
                     } else {
                         final HttpHeaderParser.Range range = HttpHeaderParser.parseRangeHeader(rangeHeader);
                         if (range == null) {
                             throw new AssertionError("Range bytes header does not match expected format: " + rangeHeader);
                         }
-                        offset = range.start();
-                        end = range.end();
-                    }
 
-                    if (offset >= blob.contents().length()) {
-                        exchange.getResponseHeaders().add("Content-Type", "application/octet-stream");
-                        exchange.sendResponseHeaders(RestStatus.REQUESTED_RANGE_NOT_SATISFIED.getStatus(), -1);
-                        return;
-                    }
+                        if (range.start() >= blob.contents().length()) {
+                            exchange.getResponseHeaders().add("Content-Type", "application/octet-stream");
+                            exchange.sendResponseHeaders(RestStatus.REQUESTED_RANGE_NOT_SATISFIED.getStatus(), -1);
+                            return;
+                        }
 
-                    BytesReference response = blob.contents();
-                    exchange.getResponseHeaders().add("Content-Type", "application/octet-stream");
-                    final int bufferedLength = response.length();
-                    if (offset > 0 || bufferedLength > end) {
-                        response = response.slice(
-                            Math.toIntExact(offset),
-                            Math.toIntExact(Math.min(end + 1 - offset, bufferedLength - offset))
-                        );
+                        final long lastIndex = Math.min(range.end(), blob.contents().length() - 1);
+                        response = blob.contents().slice(Math.toIntExact(range.start()), Math.toIntExact(lastIndex - range.start() + 1));
                     }
+                    exchange.getResponseHeaders().add("Content-Type", "application/octet-stream");
                     exchange.sendResponseHeaders(RestStatus.OK.getStatus(), response.length());
                     response.writeTo(exchange.getResponseBody());
                 } else {

test/fixtures/gcs-fixture/src/test/java/fixture/gcs/GoogleCloudStorageHttpHandlerTests.java

@@ -186,6 +186,33 @@ public void testGetWithBytesRange() {
         );
     }
 
+    public void testZeroLengthObjectGets() {
+        final var bucket = randomIdentifier();
+        final var handler = new GoogleCloudStorageHttpHandler(bucket);
+        final var blobName = "blob_name_" + randomIdentifier();
+        final var blobBytes = BytesArray.EMPTY;
+
+        assertEquals(RestStatus.OK, executeMultipartUpload(handler, bucket, blobName, blobBytes, 0L).restStatus());
+
+        assertEquals(
+            "No Range",
+            new TestHttpResponse(RestStatus.OK, blobBytes, TestHttpExchange.EMPTY_HEADERS),
+            getBlobContents(handler, bucket, blobName, null, null)
+        );
+
+        assertEquals(
+            "Range 0-0",
+            new TestHttpResponse(RestStatus.REQUESTED_RANGE_NOT_SATISFIED, BytesArray.EMPTY, TestHttpExchange.EMPTY_HEADERS),
+            getBlobContents(handler, bucket, blobName, null, new HttpHeaderParser.Range(0, 0))
+        );
+
+        assertEquals(
+            "Random range x-y",
+            new TestHttpResponse(RestStatus.REQUESTED_RANGE_NOT_SATISFIED, BytesArray.EMPTY, TestHttpExchange.EMPTY_HEADERS),
+            getBlobContents(handler, bucket, blobName, null, new HttpHeaderParser.Range(randomIntBetween(0, 30), randomIntBetween(31, 100)))
+        );
+    }
+
     public void testResumableUpload() {
         final var bucket = randomIdentifier();
         final var handler = new GoogleCloudStorageHttpHandler(bucket);
@@ -545,7 +572,6 @@ private static TestHttpResponse executeUpload(
         BytesReference bytes,
         Long ifGenerationMatch
     ) {
-        assert bytes.length() > 20;
         if (randomBoolean()) {
             return executeResumableUpload(handler, bucket, blobName, bytes, ifGenerationMatch);
         } else {
@@ -560,6 +586,7 @@ private static TestHttpResponse executeResumableUpload(
         BytesReference bytes,
         Long ifGenerationMatch
     ) {
+        assert bytes.length() >= 2 : "We can't split anything smaller than two";
         final var createUploadResponse = handleRequest(
             handler,
             "POST",
@@ -572,7 +599,7 @@ private static TestHttpResponse executeResumableUpload(
         final var sessionURI = locationHeader.substring(locationHeader.indexOf(HOST) + HOST.length());
         assertEquals(RestStatus.OK, createUploadResponse.restStatus());
 
-        final int partBoundary = randomIntBetween(10, bytes.length() - 1);
+        final int partBoundary = randomIntBetween(1, bytes.length() - 1);
         final var part1 = bytes.slice(0, partBoundary);
         final var uploadPart1Response = handleRequest(handler, "PUT", sessionURI, part1, contentRangeHeader(0, partBoundary - 1, null));
         assertEquals(RESUME_INCOMPLETE, uploadPart1Response.status());