Add additional fix for not checking scale

The scale of a BigDecimal must also be checked because it must be a
signed octet

(cherry picked from commit ecb31ba)

Author: changlinli

src/main/java/com/rabbitmq/client/impl/ValueWriter.java

@@ -143,6 +143,12 @@ else if(value instanceof Integer) {
         else if(value instanceof BigDecimal) {
             writeOctet('D');
             BigDecimal decimal = (BigDecimal)value;
+            // The scale must be an unsigned octet, therefore its values must
+            // be between 0 and 255
+            if(decimal.scale() > 255 || decimal.scale() < 0)
+                throw new IllegalArgumentException
+                    ("BigDecimal has too large of a scale to be encoded. " +
+                            "The scale was: " + decimal.scale());
             writeOctet(decimal.scale());
             BigInteger unscaled = decimal.unscaledValue();
             // We use 31 instead of 32 because bitLength ignores the sign bit,

src/test/java/com/rabbitmq/client/impl/ValueWriterTest.java

@@ -6,11 +6,13 @@
 import java.io.IOException;
 import java.io.OutputStream;
 import java.math.BigDecimal;
+import java.math.BigInteger;
 import java.util.ArrayDeque;
 import java.util.Queue;
 
 public class ValueWriterTest {
-    @Test(expected = IllegalArgumentException.class) public void writingOverlyLargeBigDecimalShouldFail() throws IOException {
+    @Test(expected = IllegalArgumentException.class) public void writingOverlyLargeBigDecimalShouldFail()
+        throws IOException {
         Queue<Byte> queue = new ArrayDeque<>();
 
         OutputStream outputStream = new OutputStream() {
@@ -27,4 +29,22 @@ public void write(int b) {
         valueWriter.writeFieldValue(new BigDecimal(Integer.MAX_VALUE).add(new BigDecimal(1)));
 
     }
+
+    @Test(expected = IllegalArgumentException.class) public void writingOverlyLargeScaleInBigDecimalShouldFail()
+        throws IOException {
+        Queue<Byte> queue = new ArrayDeque<>();
+
+        OutputStream outputStream = new OutputStream() {
+            @Override
+            public void write(int b) {
+                queue.add((byte) b);
+            }
+        };
+
+        DataOutputStream dataOutputStream = new DataOutputStream(outputStream);
+
+        ValueWriter valueWriter = new ValueWriter(dataOutputStream);
+
+        valueWriter.writeFieldValue(new BigDecimal(BigInteger.ONE, 500));
+    }
 }