[PERF] BytesBackedLiteral: Size is known upon copy

Specifying the size enable a clean copy directly in the
resulting byte array, avoiding an extra copy to an
intermediate byte array.

Also avoids sizing issue of the byte array that yields
extra copies and.

Also prevent allocation of the copy buffer that might
have a non negligible impact for small payloads .

BytesBackedLiteral::copy was
responsible of 0.65% of total memory allocation.

Care needs to be taken to fully read the stream and
trigger the EOL check.

Author: chibenwa

protocols/imap/src/main/java/org/apache/james/imap/decode/ImapRequestStreamLineReader.java

@@ -83,9 +83,9 @@ public Literal read(int size, boolean extraCRLF) throws IOException {
         InputStream limited = ByteStreams.limit(input, size);
 
         if (extraCRLF) {
-            return BytesBackedLiteral.copy(new EolInputStream(this, limited));
+            return BytesBackedLiteral.copy(new EolInputStream(this, limited), size);
         } else {
-            return BytesBackedLiteral.copy(limited);
+            return BytesBackedLiteral.copy(limited, size);
         }
     }
 

protocols/imap/src/main/java/org/apache/james/imap/message/BytesBackedLiteral.java

@@ -24,13 +24,23 @@
 import java.io.IOException;
 import java.io.InputStream;
 
+import org.apache.commons.io.IOUtils;
+
 public class BytesBackedLiteral implements Literal {
     public static BytesBackedLiteral copy(InputStream stream) throws IOException {
         ByteArrayOutputStream out = new ByteArrayOutputStream();
         stream.transferTo(out);
         return of(out.toByteArray());
     }
 
+    public static BytesBackedLiteral copy(InputStream stream, int size) throws IOException {
+        byte[] buffer = IOUtils.toByteArray(stream, size);
+        if (stream.read() != -1) {
+            throw new IOException("Got a stream of the wrong size...");
+        }
+        return of(buffer);
+    }
+
     public static BytesBackedLiteral of(byte[] bytes) {
         return new BytesBackedLiteral(bytes);
     }

server/protocols/protocols-imap4/src/main/java/org/apache/james/imapserver/netty/NettyImapRequestLineReader.java

@@ -106,9 +106,9 @@ public Literal read(int size, boolean extraCRLF) throws DecodingException {
             // limit the size via commons-io as ByteBufInputStream size limiting is buggy
             InputStream in = new BoundedInputStream(new ByteBufInputStream(buffer), size);
             if (extraCRLF) {
-                return BytesBackedLiteral.copy(new EolInputStream(this, in));
+                return BytesBackedLiteral.copy(new EolInputStream(this, in), size);
             } else {
-                return BytesBackedLiteral.copy(in);
+                return BytesBackedLiteral.copy(in, size);
             }
         } catch (IOException e) {
             throw new DecodingException(HumanReadableText.SOCKET_IO_FAILURE, "Can not read literal", e);