Fix NumericDecodeUtils.decodeBinary(byteBuf) decoding.

Previously, decodeBinary returned a wrong result for BigDecimal between 1 and -1. Now the decoding is implemented as per the Postgres spec.

[#558][resolves #556]

src/main/java/io/r2dbc/postgresql/codec/NumericDecodeUtils.java

@@ -23,6 +23,7 @@
 import reactor.util.annotation.Nullable;
 
 import java.math.BigDecimal;
+import java.math.RoundingMode;
 
 import static io.r2dbc.postgresql.message.Format.FORMAT_BINARY;
 
@@ -110,40 +111,18 @@ public static BigDecimal decodeBinary(ByteBuf byteBuf) {
             digits[i] = byteBuf.readShort();
         }
 
-        StringBuilder builder = new StringBuilder();
-        // whole part
-        builder.append(digits[0]);
-        for (short i = 0; i < weight * 4; i++) {
-            builder.append(0);
+        StringBuilder sb = new StringBuilder();
+        if (sign != 0) {
+            sb.append("-");
         }
-        // decimal part
-        if (scale > 0) {
-            builder.append('.');
-            for (short i = 0; i < scale; i++) {
-                builder.append(0);
-            }
+        sb.append("0.");
+        for (short digit : digits) {
+            sb.append(String.format("%04d", digit));
         }
 
-        int expectedLength = builder.length();
-        int baseOffset = Short.toString(digits[0]).length();
-
-        for (short i = 1; i < numOfDigits; i++) {
-            weight--;
-            String temp = Short.toString(digits[i]);
-            int offset = baseOffset + 4 * i - temp.length();
-            if (weight < 0) {
-                offset++; // dot between whole and decimal parts
-            }
-            builder.replace(offset, offset + temp.length(), temp);
-        }
-
-        builder.setLength(expectedLength); // remove zeros from the end
-
-        if (sign == 0) {
-            return new BigDecimal(builder.toString());
-        } else {
-            return new BigDecimal("-" + builder.toString());
-        }
+        return new BigDecimal(sb.toString())
+            .movePointRight((weight + 1) * 4)
+            .setScale(scale, RoundingMode.DOWN);
     }
 
 }

src/test/java/io/r2dbc/postgresql/codec/NumericDecodeUtilsTest.java

@@ -0,0 +1,87 @@
+package io.r2dbc.postgresql.codec;
+
+import io.netty.buffer.ByteBuf;
+import io.r2dbc.postgresql.util.TestByteBufAllocator;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.MethodSource;
+import org.postgresql.util.ByteConverter;
+
+import java.math.BigDecimal;
+import java.math.BigInteger;
+import java.math.RoundingMode;
+import java.util.stream.Stream;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class NumericDecodeUtilsTest {
+
+    static Stream<Object[]> bigDecimalValues() {
+        return Stream.of(
+            new Object[]{new BigDecimal("0.1")},
+            new Object[]{new BigDecimal("0.10")},
+            new Object[]{new BigDecimal("0.01")},
+            new Object[]{new BigDecimal("0.001")},
+            new Object[]{new BigDecimal("0.0001")},
+            new Object[]{new BigDecimal("0.00001")},
+            new Object[]{new BigDecimal("-0.1")},
+            new Object[]{new BigDecimal("-0.10")},
+            new Object[]{new BigDecimal("-0.01")},
+            new Object[]{new BigDecimal("-0.002")},
+            new Object[]{new BigDecimal("-0.0033")},
+            new Object[]{new BigDecimal("-0.004343")},
+            new Object[]{new BigDecimal("1.0")},
+            new Object[]{new BigDecimal("0.000000000000000000000000000000000000000000000000000")},
+            new Object[]{new BigDecimal("0.100000000000000000000000000000000000000000000009900")},
+            new Object[]{new BigDecimal("-1.0")},
+            new Object[]{new BigDecimal("-1")},
+            new Object[]{new BigDecimal("1.2")},
+            new Object[]{new BigDecimal("-2.05")},
+            new Object[]{new BigDecimal("0.000000000000000000000000000990")},
+            new Object[]{new BigDecimal("-0.000000000000000000000000000990")},
+            new Object[]{new BigDecimal("10.0000000000099")},
+            new Object[]{new BigDecimal(".10000000000000")},
+            new Object[]{new BigDecimal("1.10000000000000")},
+            new Object[]{new BigDecimal("99999.2")},
+            new Object[]{new BigDecimal("99999")},
+            new Object[]{new BigDecimal("-99999.2")},
+            new Object[]{new BigDecimal("-99999")},
+            new Object[]{new BigDecimal("2147483647")},
+            new Object[]{new BigDecimal("-2147483648")},
+            new Object[]{new BigDecimal("2147483648")},
+            new Object[]{new BigDecimal("-2147483649")},
+            new Object[]{new BigDecimal("9223372036854775807")},
+            new Object[]{new BigDecimal("-9223372036854775808")},
+            new Object[]{new BigDecimal("9223372036854775808")},
+            new Object[]{new BigDecimal("-9223372036854775809")},
+            new Object[]{new BigDecimal("10223372036850000000")},
+            new Object[]{new BigDecimal("19223372036854775807")},
+            new Object[]{new BigDecimal("19223372036854775807.300")},
+            new Object[]{new BigDecimal("-19223372036854775807.300")},
+            new Object[]{new BigDecimal(BigInteger.valueOf(1234567890987654321L), -1)},
+            new Object[]{new BigDecimal(BigInteger.valueOf(1234567890987654321L), -5)},
+            new Object[]{new BigDecimal(BigInteger.valueOf(-1234567890987654321L), -3)},
+            new Object[]{new BigDecimal(BigInteger.valueOf(6), -8)},
+            new Object[]{new BigDecimal("30000")},
+            new Object[]{new BigDecimal("40000").setScale(15, RoundingMode.UNNECESSARY)},
+            new Object[]{new BigDecimal("20000.000000000000000000")},
+            new Object[]{new BigDecimal("9990000").setScale(8, RoundingMode.UNNECESSARY)},
+            new Object[]{new BigDecimal("1000000").setScale(31, RoundingMode.UNNECESSARY)},
+            new Object[]{new BigDecimal("10000000000000000000000000000000000000").setScale(14, RoundingMode.UNNECESSARY)},
+            new Object[]{new BigDecimal("90000000000000000000000000000000000000")},
+            new Object[]{new BigDecimal("1234567890.12")},
+            new Object[]{new BigDecimal("-3.141592653590")},
+            new Object[]{new BigDecimal("3.141592653590")},
+            new Object[]{new BigDecimal("-0.141592653590")},
+            new Object[]{new BigDecimal("0.141592653590")}
+        );
+    }
+
+    @MethodSource("bigDecimalValues")
+    @ParameterizedTest
+    void decodeBinary2(BigDecimal value) {
+        ByteBuf byteBuf = TestByteBufAllocator.TEST.buffer();
+        byteBuf.writeBytes(ByteConverter.numeric(value));
+        assertThat(NumericDecodeUtils.decodeBinary(byteBuf)).isEqualByComparingTo(value);
+    }
+
+}