Change # of bits ValueWriter checks for BigDecimal

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

@@ -143,9 +143,17 @@ 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();
-            if(unscaled.bitLength() > 32) /*Integer.SIZE in Java 1.5*/
+            // We use 31 instead of 32 because bitLength ignores the sign bit,
+            // so e.g. new BigDecimal(Integer.MAX_VALUE) comes out to 31 bits.
+            if(unscaled.bitLength() > 31) /*Integer.SIZE in Java 1.5*/
                 throw new IllegalArgumentException
                     ("BigDecimal too large to be encoded");
             writeLong(decimal.unscaledValue().intValue());

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

@@ -0,0 +1,44 @@
+package com.rabbitmq.client.impl;
+
+import org.junit.Test;
+
+import java.io.DataOutputStream;
+import java.io.IOException;
+import java.io.OutputStream;
+import java.math.BigDecimal;
+import java.math.BigInteger;
+
+public class ValueWriterTest {
+    @Test(expected = IllegalArgumentException.class) public void writingOverlyLargeBigDecimalShouldFail()
+        throws IOException {
+
+        OutputStream outputStream = new OutputStream() {
+            @Override
+            public void write(int b) {
+            }
+        };
+
+        DataOutputStream dataOutputStream = new DataOutputStream(outputStream);
+
+        ValueWriter valueWriter = new ValueWriter(dataOutputStream);
+
+        valueWriter.writeFieldValue(new BigDecimal(Integer.MAX_VALUE).add(new BigDecimal(1)));
+
+    }
+
+    @Test(expected = IllegalArgumentException.class) public void writingOverlyLargeScaleInBigDecimalShouldFail()
+        throws IOException {
+
+        OutputStream outputStream = new OutputStream() {
+            @Override
+            public void write(int b) {
+            }
+        };
+
+        DataOutputStream dataOutputStream = new DataOutputStream(outputStream);
+
+        ValueWriter valueWriter = new ValueWriter(dataOutputStream);
+
+        valueWriter.writeFieldValue(new BigDecimal(BigInteger.ONE, 500));
+    }
+}