Match HTTP/2 content-encoding with AsciiString constants instead of toLowerCase

client/src/main/java/org/asynchttpclient/netty/handler/Http2ContentDecompressor.java

@@ -23,11 +23,12 @@
 import io.netty.handler.codec.compression.DecompressionException;
 import io.netty.handler.codec.compression.JdkZlibDecoder;
 import io.netty.handler.codec.compression.ZlibWrapper;
+import io.netty.handler.codec.http.HttpHeaderNames;
+import io.netty.handler.codec.http.HttpHeaderValues;
 import io.netty.handler.codec.http2.DefaultHttp2DataFrame;
 import io.netty.handler.codec.http2.Http2DataFrame;
 import io.netty.handler.codec.http2.Http2HeadersFrame;
-
-import java.util.Locale;
+import io.netty.util.AsciiString;
 
 /**
  * HTTP/2 content decompressor that transparently decompresses gzip/deflate response bodies.
@@ -59,19 +60,20 @@ public Http2ContentDecompressor(boolean keepEncodingHeader, long maxDecompressed
     public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
         if (msg instanceof Http2HeadersFrame) {
             Http2HeadersFrame headersFrame = (Http2HeadersFrame) msg;
-            CharSequence contentEncoding = headersFrame.headers().get("content-encoding");
+            CharSequence contentEncoding = headersFrame.headers().get(HttpHeaderNames.CONTENT_ENCODING);
             if (contentEncoding != null) {
-                // Locale.ROOT: a default-locale toLowerCase() would mangle "GZIP" under the Turkish locale
-                // ("gzıp", dotless i), so the contains() checks below would miss it and the body would be
-                // forwarded still-compressed. Matches the toLowerCaseHeaderName idiom on the request path.
-                String enc = contentEncoding.toString().toLowerCase(Locale.ROOT);
-                if (enc.contains("gzip") || enc.contains("deflate")) {
-                    ZlibWrapper wrapper = enc.contains("gzip") ? ZlibWrapper.GZIP : ZlibWrapper.ZLIB_OR_NONE;
+                // Case-insensitive substring match against the AsciiString header-value constants in place,
+                // instead of allocating contentEncoding.toString().toLowerCase() per response. AsciiString
+                // case-folding is ASCII-only, hence locale-independent, so it also avoids the Turkish-locale
+                // hazard where a default-locale toLowerCase() would mangle "GZIP" and miss the match.
+                boolean gzip = AsciiString.containsIgnoreCase(contentEncoding, HttpHeaderValues.GZIP);
+                if (gzip || AsciiString.containsIgnoreCase(contentEncoding, HttpHeaderValues.DEFLATE)) {
+                    ZlibWrapper wrapper = gzip ? ZlibWrapper.GZIP : ZlibWrapper.ZLIB_OR_NONE;
                     decompressor = new EmbeddedChannel(false, new JdkZlibDecoder(wrapper));
                     if (!keepEncodingHeader) {
-                        headersFrame.headers().remove("content-encoding");
+                        headersFrame.headers().remove(HttpHeaderNames.CONTENT_ENCODING);
                     }
-                    headersFrame.headers().remove("content-length");
+                    headersFrame.headers().remove(HttpHeaderNames.CONTENT_LENGTH);
                 }
             }
             ctx.fireChannelRead(msg);

client/src/test/java/org/asynchttpclient/netty/handler/Http2ContentDecompressorTest.java

@@ -34,6 +34,7 @@
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertNull;
 import static org.junit.jupiter.api.Assertions.assertThrows;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
@@ -60,6 +61,50 @@ private static ByteBuf gzip(String s) throws Exception {
         return Unpooled.wrappedBuffer(gzipBytes(s));
     }
 
+    // Returns true iff the decompressor installed a decoder for the given content-encoding, detected by
+    // content-length being stripped (the code removes it only when it activates). Guards that the switch to
+    // AsciiString.containsIgnoreCase preserves the old toLowerCase().contains() activation set exactly.
+    private static boolean activatesDecompression(String contentEncoding) {
+        DefaultHttp2Headers headers = new DefaultHttp2Headers();
+        headers.status("200");
+        if (contentEncoding != null) {
+            headers.set("content-encoding", contentEncoding);
+        }
+        headers.set("content-length", "123");
+        EmbeddedChannel ch = new EmbeddedChannel(new Http2ContentDecompressor(false));
+        try {
+            ch.writeInbound(new DefaultHttp2HeadersFrame(headers, false));
+            Http2HeadersFrame out = ch.readInbound();
+            boolean clRemoved = !out.headers().contains("content-length");
+            if (clRemoved) {
+                assertNull(out.headers().get("content-encoding"),
+                        "content-encoding must be stripped when decompression activates and keepEncodingHeader=false");
+            }
+            return clRemoved;
+        } finally {
+            ch.finishAndReleaseAll();
+        }
+    }
+
+    @Test
+    public void activatesForGzipDeflateCaseInsensitivelyAndSubstrings() {
+        // Case-insensitive substring match, identical to the old contains() logic.
+        assertTrue(activatesDecompression("gzip"));
+        assertTrue(activatesDecompression("GZIP"));
+        assertTrue(activatesDecompression("x-gzip"));
+        assertTrue(activatesDecompression("deflate"));
+        assertTrue(activatesDecompression("DEFLATE"));
+        assertTrue(activatesDecompression("gzip, deflate"));
+    }
+
+    @Test
+    public void doesNotActivateForOtherOrAbsentEncodings() {
+        assertFalse(activatesDecompression(null), "no content-encoding -> no decompression");
+        assertFalse(activatesDecompression("br"), "brotli is not handled by this decompressor");
+        assertFalse(activatesDecompression("zstd"), "zstd is not handled by this decompressor");
+        assertFalse(activatesDecompression("identity"));
+    }
+
     @Test
     public void decompressesValidGzipBodyAndReleasesFrames() throws Exception {
         EmbeddedChannel ch = new EmbeddedChannel(new Http2ContentDecompressor(false));