Efficiency: Let thread do other tasks as long encoder/decoder is busy (#215)

Motivation:

Busy loops are blocking valuable threads, so other tasks are blocked
while the current task spins waiting. This reduces concurrency without a
need, hence makes inefficient use of the existing hardware.

Modification:

Using `Thread.yield()` in all busy waiting loops.

Result:

Other tasks are allowed to run while encode / decoder is busy.

Author: mkarg

brotli4j/src/main/java/com/aayushatharva/brotli4j/decoder/BrotliInputStream.java

@@ -82,6 +82,7 @@ public int read() throws IOException {
             if (decoded != 0) {
                 break;
             }
+            Thread.yield();
         }
 
         if (decoded == -1) {
@@ -105,7 +106,10 @@ public int read(byte[] b, int off, int len) throws IOException {
         }
         int result = 0;
         while (len > 0) {
-            int limit = Math.min(len, decoder.buffer.remaining());
+            int limit;
+            while ((limit = Math.min(len, decoder.buffer.remaining())) == 0) {
+                Thread.yield();
+            }
             decoder.buffer.get(b, off, limit);
             off += limit;
             len -= limit;

brotli4j/src/main/java/com/aayushatharva/brotli4j/encoder/BrotliOutputStream.java

@@ -81,7 +81,7 @@ public void write(int b) throws IOException {
             throw new IOException("write after close");
         }
         while (!encoder.encode(EncoderJNI.Operation.PROCESS)) {
-            // Busy-wait loop.
+            Thread.yield();
         }
         encoder.inputBuffer.put((byte) b);
     }
@@ -98,9 +98,13 @@ public void write(byte[] b, int off, int len) throws IOException {
         }
         while (len > 0) {
             if (!encoder.encode(EncoderJNI.Operation.PROCESS)) {
+                Thread.yield();
                 continue;
             }
-            int limit = Math.min(len, encoder.inputBuffer.remaining());
+            int limit;
+            while ((limit = Math.min(len, encoder.inputBuffer.remaining())) == 0) {
+                Thread.yield();
+            }
             encoder.inputBuffer.put(b, off, limit);
             off += limit;
             len -= limit;