async file reader

NOTICE.txt

@@ -0,0 +1,13 @@
+The work in org.xbib.event.async is based upon the work in
+
+https://github.com/javasync/RxIo
+
+and org.xbib.event.yield is based upon the work in
+
+https://github.com/tinyield/jayield
+
+by Fernando Miguel Gamboa de Carvalho (fmcarvalho)
+
+branched as of 23 December, 2021
+
+License: Apache 2.0

src/main/java/org/xbib/event/async/AbstractAsyncFileReaderLines.java

@@ -16,46 +16,16 @@ import static java.nio.channels.AsynchronousFileChannel.open;
  * Asynchronous non-blocking read operations that use an underlying AsynchronousFileChannel.
  */
 public abstract class AbstractAsyncFileReaderLines {
-    static final int BUFFER_SIZE = 4096 * 8; // the transfer buffer size
+
+    static final int BUFFER_SIZE = 8192;
+
     private static final int MAX_LINE_SIZE = 4096;
+
     private static final int LF = '\n';
-    private static final int CR = '\r';
-    //
-    // This flag will track whether this `Subscription` is to be considered cancelled or not.
-    private boolean cancelled = false;
 
-    /**
-     * Asynchronous read chunk operation, callback based.
-     */
-    private static void readBytes(
-            AsynchronousFileChannel asyncFile,
-            long position, // current read or write position in file
-            byte[] data,   // buffer for current producing line
-            int size,
-            ObjIntConsumer<Throwable> completed) {
-        if (completed == null)
-            throw new InvalidParameterException("callback can't be null!");
-        if (size > data.length)
-            size = data.length;
-        if (size == 0) {
-            completed.accept(null, 0);
-            return;
-        }
-        ByteBuffer buf = ByteBuffer.wrap(data, 0, size);
-        CompletionHandler<Integer, Object> readCompleted =
-                new CompletionHandler<>() {
-                    @Override
-                    public void completed(Integer result, Object attachment) {
-                        completed.accept(null, result);
-                    }
+    private static final int CR = '\r';
 
-                    @Override
-                    public void failed(Throwable exc, Object attachment) {
-                        completed.accept(exc, 0);
-                    }
-                };
-        asyncFile.read(buf, position, null, readCompleted);
-    }
+    private boolean cancelled = false;
 
     protected abstract void onError(Throwable error);
 
@@ -81,11 +51,9 @@ public abstract class AbstractAsyncFileReaderLines {
      * The resulting characters are parsed by line and passed to the destination buffer.
      *
      * @param asyncFile  the nio associated file channel.
-     * @param bufferSize
+     * @param bufferSize buffer size
      */
-    final void readLines(
-            AsynchronousFileChannel asyncFile,
-            int bufferSize) {
+    final void readLines(AsynchronousFileChannel asyncFile, int bufferSize) {
         readLines(asyncFile, 0, 0, 0, new byte[bufferSize], new byte[MAX_LINE_SIZE], 0);
     }
 
@@ -102,14 +70,8 @@ public abstract class AbstractAsyncFileReaderLines {
      * @param auxline   the transfer buffer.
      * @param linepos   current position in producing line.
      */
-    private void readLines(
-            AsynchronousFileChannel asyncFile,
-            long position,  // current read or write position in file
-            int bufpos,     // read position in buffer
-            int bufsize,    // total bytes in buffer
-            byte[] buffer,  // buffer for current producing line
-            byte[] auxline, // the transfer buffer
-            int linepos)    // current position in producing line
+    private void readLines(AsynchronousFileChannel asyncFile, long position, int bufpos,
+            int bufsize, byte[] buffer, byte[] auxline, int linepos)
     {
         while (bufpos < bufsize) {
             if (buffer[bufpos] == LF) {
@@ -122,7 +84,7 @@ public abstract class AbstractAsyncFileReaderLines {
                 linepos = 0;
             } else auxline[linepos++] = buffer[bufpos++];
         }
-        int lastLinePos = linepos; // we need a final variable captured in the next lambda
+        int lastLinePos = linepos;
         if (!isCancelled()) readBytes(asyncFile, position, buffer, buffer.length, (err, res) -> {
             if (isCancelled())
                 return;
@@ -132,11 +94,9 @@ public abstract class AbstractAsyncFileReaderLines {
                 return;
             }
             if (res <= 0) {
-                // needed for last line that doesn't end with LF
                 if (lastLinePos > 0) {
                     produceLine(auxline, lastLinePos);
                 }
-                // Following it will invoke onComplete()
                 close(asyncFile);
             } else {
                 readLines(asyncFile, position + res, 0, res, buffer, auxline, lastLinePos);
@@ -144,17 +104,11 @@ public abstract class AbstractAsyncFileReaderLines {
         });
     }
 
-    /**
-     * Performed from the IO background thread when it reached the end of the file.
-     *
-     * @param asyncFile
-     */
     private void close(AsynchronousFileChannel asyncFile) {
         try {
             asyncFile.close();
         } catch (IOException e) {
-            onError(e); // Failed terminal state.
-            // Emission has finished. Does not propagate error on CompletableFuture.
+            onError(e);
         } finally {
             onComplete();
         }
@@ -170,4 +124,34 @@ public abstract class AbstractAsyncFileReaderLines {
         String line = new String(auxline, 0, linepos, StandardCharsets.UTF_8);
         onProduceLine(line);
     }
+
+    /**
+     * Asynchronous read chunk operation, callback based.
+     */
+    private static void readBytes(AsynchronousFileChannel asyncFile,
+            long position, byte[] data, int size, ObjIntConsumer<Throwable> completed) {
+        if (completed == null) {
+            throw new InvalidParameterException("callback can't be null!");
+        }
+        if (size > data.length) {
+            size = data.length;
+        }
+        if (size == 0) {
+            completed.accept(null, 0);
+            return;
+        }
+        ByteBuffer buf = ByteBuffer.wrap(data, 0, size);
+        CompletionHandler<Integer, Object> readCompleted = new CompletionHandler<>() {
+                    @Override
+                    public void completed(Integer result, Object attachment) {
+                        completed.accept(null, result);
+                    }
+
+                    @Override
+                    public void failed(Throwable exc, Object attachment) {
+                        completed.accept(exc, 0);
+                    }
+                };
+        asyncFile.read(buf, position, null, readCompleted);
+    }
 }

src/main/java/org/xbib/event/async/AsyncFileReaderBytes.java

@@ -21,8 +21,7 @@ public class AsyncFileReaderBytes {
             int position,
             ByteArrayOutputStream out) {
         return readToByteArrayStream(asyncFile, buffer, position, out)
-                .thenCompose(index ->
-                        index < 0
+                .thenCompose(index -> index < 0
                                 ? completedFuture(position)
                                 : readAllBytes(asyncFile, buffer.clear(), position + index, out));
 
@@ -34,12 +33,12 @@ public class AsyncFileReaderBytes {
             int position,
             ByteArrayOutputStream out) {
         CompletableFuture<Integer> promise = new CompletableFuture<>();
-        asyncFile.read(buffer, position, buffer, new CompletionHandler<Integer, ByteBuffer>() {
+        asyncFile.read(buffer, position, buffer, new CompletionHandler<>() {
             @Override
             public void completed(Integer result, ByteBuffer attachment) {
                 if (result > 0) {
                     attachment.flip();
-                    byte[] data = new byte[attachment.limit()]; // limit = result
+                    byte[] data = new byte[attachment.limit()];
                     attachment.get(data);
                     write(out, data);
                 }