Rename PerMessageDeflateExtension maxFrameSize to maxFragmentSize

The PerMessageDeflationExtension's optional maxFrameSize constructor
parameter is applied to the size of a fragment while decompressing, and
not to the complete frame size (that size is checked after passing the
decompressed fragment), so rename the parameter to what it actually is.

Add Javadoc to the full-parameter constructor method.

Author: robert-s-ubi

src/main/java/org/java_websocket/extensions/permessage_deflate/PerMessageDeflateExtension.java

@@ -82,7 +82,7 @@ public class PerMessageDeflateExtension extends CompressionExtension {
   private static final int TRANSFER_CHUNK_SIZE = 8192;
 
   private final int compressionLevel;
-  private final int maxFrameSize;
+  private final int maxFragmentSize;
   private final Deflater compressor;
   private final Inflater decompressor;
 
@@ -107,9 +107,16 @@ public PerMessageDeflateExtension(int compressionLevel) {
     this(compressionLevel, Integer.MAX_VALUE);
   }
 
-  public PerMessageDeflateExtension(int compressionLevel, int maxFrameSize) {
+  /**
+   * Constructs the RFC 7692 permessage-deflate extension with a specific compression level and a
+   * maximum decompressed fragment size.
+   *
+   * @param compressionLevel the compression level to use, see {@link Deflater}
+   * @param maxFragmentSize the maximum allowed fragment size after decompression
+   */
+  public PerMessageDeflateExtension(int compressionLevel, int maxFragmentSize) {
     this.compressionLevel = compressionLevel;
-    this.maxFrameSize = maxFrameSize;
+    this.maxFragmentSize = maxFragmentSize;
     compressor = new Deflater(compressionLevel, true);
     decompressor = new Inflater(true);
     compressionThreshold = DEFAULT_COMPRESSION_THRESHOLD;
@@ -129,8 +136,8 @@ public int getCompressionLevel() {
     return compressionLevel;
   }
 
-  public int getMaxFrameSize() {
-    return maxFrameSize;
+  public int getMaxFragmentSize() {
+    return maxFragmentSize;
   }
 
   public int getThreshold() {
@@ -257,9 +264,9 @@ private void decompress(ByteBuffer buffer, ByteArrayOutputStream decompressed)
       int length = decompressor.inflate(chunk);
       if (length > 0) {
         decompressed.write(chunk, 0, length);
-        if (maxFrameSize > 0 && maxFrameSize < decompressed.size()) {
+        if (maxFragmentSize > 0 && maxFragmentSize < decompressed.size()) {
           throw new DataFormatException(
-              "Inflated frame size exceeds limit of " + maxFrameSize + " bytes");
+              "Inflated fragment size exceeds limit of " + maxFragmentSize + " bytes");
         }
       } else {
         break;
@@ -550,7 +557,7 @@ public String getProvidedExtensionAsServer() {
   @Override
   public IExtension copyInstance() {
     PerMessageDeflateExtension clone =
-        new PerMessageDeflateExtension(getCompressionLevel(), getMaxFrameSize());
+        new PerMessageDeflateExtension(getCompressionLevel(), getMaxFragmentSize());
     clone.setClientNoContextTakeover(isClientNoContextTakeover());
     clone.setServerNoContextTakeover(isServerNoContextTakeover());
     clone.clientMaxWindowBits = clientMaxWindowBits;