rust/http2: box decompressor variants

These variants, in particular the Brotli one can be large at over 2500
bytes which is allocated no matter which decompressor is being used.

Gzip comes in at over 500 bytes.  Box deflate for consistency.

rust/src/http2/decompression.rs

@@ -76,9 +76,13 @@ impl Read for HTTP2cursor {
 
 pub enum HTTP2Decompresser {
     UNASSIGNED,
-    GZIP(GzDecoder<HTTP2cursor>),
-    BROTLI(brotli::Decompressor<HTTP2cursor>),
-    DEFLATE(DeflateDecoder<HTTP2cursor>),
+    // Box because large.
+    GZIP(Box<GzDecoder<HTTP2cursor>>),
+    // Box because large.
+    BROTLI(Box<brotli::Decompressor<HTTP2cursor>>),
+    // This one is not so large, at 88 bytes as of doing this, but box
+    // for consistency.
+    DEFLATE(Box<DeflateDecoder<HTTP2cursor>>),
 }
 
 impl std::fmt::Debug for HTTP2Decompresser {
@@ -170,16 +174,16 @@ impl HTTP2DecoderHalf {
         if self.encoding == HTTP2ContentEncoding::Unknown {
             if input == b"gzip" {
                 self.encoding = HTTP2ContentEncoding::Gzip;
-                self.decoder = HTTP2Decompresser::GZIP(GzDecoder::new(HTTP2cursor::new()));
+                self.decoder = HTTP2Decompresser::GZIP(Box::new(GzDecoder::new(HTTP2cursor::new())));
             } else if input == b"deflate" {
                 self.encoding = HTTP2ContentEncoding::Deflate;
-                self.decoder = HTTP2Decompresser::DEFLATE(DeflateDecoder::new(HTTP2cursor::new()));
+                self.decoder = HTTP2Decompresser::DEFLATE(Box::new(DeflateDecoder::new(HTTP2cursor::new())));
             } else if input == b"br" {
                 self.encoding = HTTP2ContentEncoding::Br;
-                self.decoder = HTTP2Decompresser::BROTLI(brotli::Decompressor::new(
+                self.decoder = HTTP2Decompresser::BROTLI(Box::new(brotli::Decompressor::new(
                     HTTP2cursor::new(),
                     HTTP2_DECOMPRESSION_CHUNK_SIZE,
-                ));
+                )));
             } else {
                 self.encoding = HTTP2ContentEncoding::Unrecognized;
             }
@@ -191,7 +195,7 @@ impl HTTP2DecoderHalf {
     ) -> io::Result<&'a [u8]> {
         match self.decoder {
             HTTP2Decompresser::GZIP(ref mut gzip_decoder) => {
-                let r = http2_decompress(gzip_decoder, input, output);
+                let r = http2_decompress(&mut *gzip_decoder.as_mut(), input, output);
                 match r {
                     Err(_) => {
                         self.decoder = HTTP2Decompresser::UNASSIGNED;
@@ -201,7 +205,7 @@ impl HTTP2DecoderHalf {
                 return r;
             }
             HTTP2Decompresser::BROTLI(ref mut br_decoder) => {
-                let r = http2_decompress(br_decoder, input, output);
+                let r = http2_decompress(&mut *br_decoder.as_mut(), input, output);
                 match r {
                     Err(_) => {
                         self.decoder = HTTP2Decompresser::UNASSIGNED;
@@ -211,7 +215,7 @@ impl HTTP2DecoderHalf {
                 return r;
             }
             HTTP2Decompresser::DEFLATE(ref mut df_decoder) => {
-                let r = http2_decompress(df_decoder, input, output);
+                let r = http2_decompress(&mut *df_decoder.as_mut(), input, output);
                 match r {
                     Err(_) => {
                         self.decoder = HTTP2Decompresser::UNASSIGNED;