Optimize GoogleCloudStorageHttpHandler (elastic#49677)

Removing a lot of needless buffering and array creation
to reduce the significant memory usage of tests using this.
The incoming stream from the `exchange` is already buffered
so there is no point in adding a ton of additional buffers
everywhere.

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

@@ -161,7 +161,7 @@ public void handle(final HttpExchange exchange) throws IOException {
                 // Batch https://cloud.google.com/storage/docs/json_api/v1/how-tos/batch
                 final String uri = "/storage/v1/b/" + bucket + "/o/";
                 final StringBuilder batch = new StringBuilder();
-                for (String line : Streams.readAllLines(new BufferedInputStream(wrappedRequest))) {
+                for (String line : Streams.readAllLines(wrappedRequest)) {
                     if (line.length() == 0 || line.startsWith("--") || line.toLowerCase(Locale.ROOT).startsWith("content")) {
                         batch.append(line).append('\n');
                     } else if (line.startsWith("DELETE")) {
@@ -225,8 +225,13 @@ public void handle(final HttpExchange exchange) throws IOException {
                 final int start = getContentRangeStart(range);
                 final int end = getContentRangeEnd(range);
 
-                final ByteArrayOutputStream out = new ByteArrayOutputStream();
-                long bytesRead = Streams.copy(wrappedRequest, out);
+                final ByteArrayOutputStream out = new ByteArrayOutputStream() {
+                    @Override
+                    public byte[] toByteArray() {
+                        return buf;
+                    }
+                };
+                long bytesRead = Streams.copy(wrappedRequest, out, new byte[128]);
                 int length = Math.max(end + 1, limit != null ? limit : 0);
                 if ((int) bytesRead > length) {
                     throw new AssertionError("Requesting more bytes than available for blob");
@@ -266,56 +271,62 @@ private String httpServerUrl(final HttpExchange exchange) {
         return "http://" + InetAddresses.toUriString(address.getAddress()) + ":" + address.getPort();
     }
 
+    private static final Pattern NAME_PATTERN = Pattern.compile("\"name\":\"([^\"]*)\"");
+
     public static Optional<Tuple<String, BytesArray>> parseMultipartRequestBody(final InputStream requestBody) throws IOException {
         Tuple<String, BytesArray> content = null;
         try (BufferedInputStream in = new BufferedInputStream(new GZIPInputStream(requestBody))) {
             String name = null;
             int read;
+            ByteArrayOutputStream out = new ByteArrayOutputStream() {
+                @Override
+                public byte[] toByteArray() {
+                    return buf;
+                }
+            };
             while ((read = in.read()) != -1) {
+                out.reset();
                 boolean markAndContinue = false;
-                try (ByteArrayOutputStream out = new ByteArrayOutputStream()) {
-                    do { // search next consecutive {carriage return, new line} chars and stop
-                        if ((char) read == '\r') {
-                            int next = in.read();
-                            if (next != -1) {
-                                if (next == '\n') {
-                                    break;
-                                }
-                                out.write(read);
-                                out.write(next);
-                                continue;
+                do { // search next consecutive {carriage return, new line} chars and stop
+                    if ((char) read == '\r') {
+                        int next = in.read();
+                        if (next != -1) {
+                            if (next == '\n') {
+                                break;
                             }
-                        }
-                        out.write(read);
-                    } while ((read = in.read()) != -1);
-
-                    final String line = new String(out.toByteArray(), UTF_8);
-                    if (line.length() == 0 || line.equals("\r\n") || line.startsWith("--")
-                        || line.toLowerCase(Locale.ROOT).startsWith("content")) {
-                        markAndContinue = true;
-                    } else if (line.startsWith("{\"bucket\":")) {
-                        markAndContinue = true;
-                        Matcher matcher = Pattern.compile("\"name\":\"([^\"]*)\"").matcher(line);
-                        if (matcher.find()) {
-                            name = matcher.group(1);
+                            out.write(read);
+                            out.write(next);
+                            continue;
                         }
                     }
-                    if (markAndContinue) {
-                        in.mark(Integer.MAX_VALUE);
-                        continue;
+                    out.write(read);
+                } while ((read = in.read()) != -1);
+                final String bucketPrefix = "{\"bucket\":";
+                final String start = new String(out.toByteArray(), 0, Math.min(out.size(), bucketPrefix.length()), UTF_8);
+                if (start.length() == 0 || start.equals("\r\n") || start.startsWith("--")
+                    || start.toLowerCase(Locale.ROOT).startsWith("content")) {
+                    markAndContinue = true;
+                } else if (start.startsWith(bucketPrefix)) {
+                    markAndContinue = true;
+                    final String line = new String(out.toByteArray(), bucketPrefix.length(), out.size() - bucketPrefix.length(), UTF_8);
+                    Matcher matcher = NAME_PATTERN.matcher(line);
+                    if (matcher.find()) {
+                        name = matcher.group(1);
                     }
                 }
+                if (markAndContinue) {
+                    in.mark(Integer.MAX_VALUE);
+                    continue;
+                }
                 if (name != null) {
                     in.reset();
-                    try (ByteArrayOutputStream binary = new ByteArrayOutputStream()) {
-                        while ((read = in.read()) != -1) {
-                            binary.write(read);
-                        }
-                        binary.flush();
-                        byte[] tmp = binary.toByteArray();
-                        // removes the trailing end "\r\n--__END_OF_PART__--\r\n" which is 23 bytes long
-                        content = Tuple.tuple(name, new BytesArray(Arrays.copyOf(tmp, tmp.length - 23)));
+                    out.reset();
+                    while ((read = in.read()) != -1) {
+                        out.write(read);
                     }
+                    // removes the trailing end "\r\n--__END_OF_PART__--\r\n" which is 23 bytes long
+                    content = Tuple.tuple(name, new BytesArray(Arrays.copyOf(out.toByteArray(), out.size() - 23)));
+                    break;
                 }
             }
         }