lib,zlib: fix brotli flush range

Refs: nodejs#38407

Author: XadillaX

lib/zlib.js

@@ -89,7 +89,7 @@ const {
   BROTLI_DECODE, BROTLI_ENCODE,
   // Brotli operations (~flush levels)
   BROTLI_OPERATION_PROCESS, BROTLI_OPERATION_FLUSH,
-  BROTLI_OPERATION_FINISH
+  BROTLI_OPERATION_FINISH, BROTLI_OPERATION_EMIT_METADATA,
 } = constants;
 
 // Translation table for return codes.
@@ -238,8 +238,15 @@ const checkRangesOrGetDefault = hideStackFrames(
   }
 );
 
+function isBrotliHandle(handle) {
+  return (handle instanceof binding.BrotliEncoder) ||
+    (handle instanceof binding.BrotliDecoder);
+}
+
 // The base class for all Zlib-style streams.
 function ZlibBase(opts, mode, handle, { flush, finishFlush, fullFlush }) {
+  const isBrotli = isBrotliHandle(handle);
+
   let chunkSize = Z_DEFAULT_CHUNK;
   let maxOutputLength = kMaxLength;
   // The ZlibBase class is not exported to user land, the mode should only be
@@ -256,13 +263,27 @@ function ZlibBase(opts, mode, handle, { flush, finishFlush, fullFlush }) {
                                  `>= ${Z_MIN_CHUNK}`, chunkSize);
     }
 
-    flush = checkRangesOrGetDefault(
-      opts.flush, 'options.flush',
-      Z_NO_FLUSH, Z_BLOCK, flush);
+    if (!isBrotli) {
+      flush = checkRangesOrGetDefault(
+        opts.flush, 'options.flush',
+        Z_NO_FLUSH, Z_BLOCK, flush);
 
-    finishFlush = checkRangesOrGetDefault(
-      opts.finishFlush, 'options.finishFlush',
-      Z_NO_FLUSH, Z_BLOCK, finishFlush);
+      finishFlush = checkRangesOrGetDefault(
+        opts.finishFlush, 'options.finishFlush',
+        Z_NO_FLUSH, Z_BLOCK, finishFlush);
+    } else {
+      flush = checkRangesOrGetDefault(
+        opts.flush, 'options.flush',
+        BROTLI_OPERATION_PROCESS, BROTLI_OPERATION_EMIT_METADATA, flush);
+
+      finishFlush = checkRangesOrGetDefault(
+        opts.finishFlush, 'options.finishFlush',
+        BROTLI_OPERATION_PROCESS, BROTLI_OPERATION_EMIT_METADATA, finishFlush);
+
+      fullFlush = checkRangesOrGetDefault(
+        opts.finishFlush, 'options.finishFlush',
+        BROTLI_OPERATION_PROCESS, BROTLI_OPERATION_EMIT_METADATA, finishFlush);
+    }
 
     maxOutputLength = checkRangesOrGetDefault(
       opts.maxOutputLength, 'options.maxOutputLength',