#853 Fix IBM single precision floating point (COMP-1) decoder to produce correct results.

cobol-parser/src/main/scala/za/co/absa/cobrix/cobol/parser/decoders/FloatingPointDecoders.scala

@@ -128,7 +128,7 @@ object FloatingPointDecoders {
   def decodeIbmSingleBigEndian(bytes: Array[Byte]): java.lang.Float = {
     try {
       val IBM32_SIGN_MASK = 0x80000000
-      val IBM32_EXPONENT_MASK = 0x80000000
+      val IBM32_EXPONENT_MASK = 0x7F000000
       val IBM32_FRACTURE_MASK = 0x00FFFFFF
       val IBM32_MS_NIBBLE = 0x00F00000
 
@@ -148,7 +148,7 @@ object FloatingPointDecoders {
         }
         val leadingZeros = ((BIT_COUNT_MAGIC >> (topNibble >> 19)) & 3).toInt
         fracture <<= leadingZeros
-        val convertedExp = exponent + 131 - leadingZeros
+        val convertedExp = exponent - 131 - leadingZeros
 
         if (convertedExp >=0 && convertedExp < 254) {
           val ieee754Int = sign + (convertedExp << 23) + fracture

cobol-parser/src/test/scala/za/co/absa/cobrix/cobol/parser/decoders/FloatingPointDecodersSpec.scala

@@ -29,10 +29,52 @@ class FloatingPointDecodersSpec extends AnyWordSpec {
   }
 
   "decodeIbmSingleBigEndian()" should {
-    "decode IBM single precision / big-endian FP numbers" in {
+    "decode IBM single precision / big-endian FP number 1.0" in {
       val bytes = Array[Byte](
-        0x43.toByte, 0x14.toByte, 0x2E.toByte, 0xFC.toByte)
-      assertFloatEqual(FloatingPointDecoders.decodeIbmSingleBigEndian(bytes), 5.045883f)
+        0x41.toByte, 0x10.toByte, 0x00.toByte, 0x00.toByte)
+      assertFloatEqual(FloatingPointDecoders.decodeIbmSingleBigEndian(bytes), 1.0f)
+    }
+
+    "decode IBM single precision / big-endian FP number 1234.0" in {
+      val bytes = Array[Byte](
+        0x43.toByte, 0x4D.toByte, 0x20.toByte, 0x00.toByte)
+      assertFloatEqual(FloatingPointDecoders.decodeIbmSingleBigEndian(bytes), 1234.0f)
+    }
+
+    "decode IBM single precision / big-endian FP number -1234.0" in {
+      val bytes = Array[Byte](
+        0xC3.toByte, 0x4D.toByte, 0x20.toByte, 0x00.toByte)
+      assertFloatEqual(FloatingPointDecoders.decodeIbmSingleBigEndian(bytes), -1234.0f)
+    }
+
+    "decode IBM single precision / big-endian FP number 4.5" in {
+      val bytes = Array[Byte](
+        0x41.toByte, 0x48.toByte, 0x00.toByte, 0x00.toByte)
+      assertFloatEqual(FloatingPointDecoders.decodeIbmSingleBigEndian(bytes), 4.5f)
+    }
+
+    "decode IBM single precision / big-endian FP number -3.75" in {
+      val bytes = Array[Byte](
+        0xC1.toByte, 0x3C.toByte, 0x00.toByte, 0x00.toByte)
+      assertFloatEqual(FloatingPointDecoders.decodeIbmSingleBigEndian(bytes), -3.75f)
+    }
+
+    "decode IBM single precision / big-endian FP number 2.5" in {
+      val bytes = Array[Byte](
+        0x41.toByte, 0x28.toByte, 0x00.toByte, 0x00.toByte)
+      assertFloatEqual(FloatingPointDecoders.decodeIbmSingleBigEndian(bytes), 2.5f)
+    }
+
+    "decode IBM single precision / big-endian FP number 0" in {
+      val bytes = Array[Byte](
+        0x00.toByte, 0x00.toByte, 0x00.toByte, 0x00.toByte)
+      assertFloatEqual(FloatingPointDecoders.decodeIbmSingleBigEndian(bytes), 0f)
+    }
+
+    "decode IBM single precision / big-endian FP number infinity" in {
+      val bytes = Array[Byte](
+        0x7F.toByte, 0xFF.toByte, 0xFF.toByte, 0xFF.toByte)
+      assert(FloatingPointDecoders.decodeIbmSingleBigEndian(bytes).isInfinite)
     }
   }
 
@@ -53,10 +95,40 @@ class FloatingPointDecodersSpec extends AnyWordSpec {
   }
 
   "decodeIbmSingleLittleEndian()" should {
-    "decode IBM single precision / little-endian FP numbers" in {
+    "decode IBM single precision / little-endian FP number 1.0" in {
       val bytes = Array[Byte](
-        0xFC.toByte, 0x2E.toByte, 0x14.toByte, 0x43.toByte)
-      assertFloatEqual(FloatingPointDecoders.decodeIbmSingleLittleEndian(bytes), 5.045883f)
+        0x00.toByte, 0x00.toByte, 0x10.toByte, 0x41.toByte)
+      assertFloatEqual(FloatingPointDecoders.decodeIbmSingleLittleEndian(bytes), 1.0f)
+    }
+
+    "decode IBM single precision / little-endian FP number 1234.0" in {
+      val bytes = Array[Byte](
+        0x00.toByte, 0x20.toByte, 0x4D.toByte, 0x43.toByte)
+      assertFloatEqual(FloatingPointDecoders.decodeIbmSingleLittleEndian(bytes), 1234.0f)
+    }
+
+    "decode IBM single precision / little-endian FP number -1234.0" in {
+      val bytes = Array[Byte](
+        0x00.toByte, 0x20.toByte, 0x4D.toByte, 0xC3.toByte)
+      assertFloatEqual(FloatingPointDecoders.decodeIbmSingleLittleEndian(bytes), -1234.0f)
+    }
+
+    "decode IBM single precision / little-endian FP number 4.5" in {
+      val bytes = Array[Byte](
+        0x00.toByte, 0x00.toByte, 0x48.toByte, 0x41.toByte)
+      assertFloatEqual(FloatingPointDecoders.decodeIbmSingleLittleEndian(bytes), 4.5f)
+    }
+
+    "decode IBM single precision / little-endian FP number -3.75" in {
+      val bytes = Array[Byte](
+        0x00.toByte, 0x00.toByte, 0x3C.toByte, 0xC1.toByte)
+      assertFloatEqual(FloatingPointDecoders.decodeIbmSingleLittleEndian(bytes), -3.75f)
+    }
+
+    "decode IBM single precision / little-endian FP number infinity" in {
+      val bytes = Array[Byte](
+        0xFF.toByte, 0xFF.toByte, 0xFF.toByte, 0x7F.toByte)
+      assert(FloatingPointDecoders.decodeIbmSingleLittleEndian(bytes).isInfinite)
     }
   }
 

spark-cobol/src/test/scala/za/co/absa/cobrix/spark/cobol/source/regression/Test03IbmFloats.scala

@@ -114,7 +114,7 @@ class Test03IbmFloats extends AnyFunSuite with BeforeAndAfterAll with SparkTestB
     val f = df.select(col("F")).take(1)(0)(0).asInstanceOf[Float]
     val d = df.select(col("D")).take(1)(0)(0).asInstanceOf[Double]
 
-    assertFloatEqual(f, 5.045883f)
+    assertFloatEqual(f, 322.93652f)
     assertDoubleEqual(d, 322.936717)
   }
 
@@ -132,7 +132,7 @@ class Test03IbmFloats extends AnyFunSuite with BeforeAndAfterAll with SparkTestB
     val f = df.select(col("F")).take(1)(0)(0).asInstanceOf[Float]
     val d = df.select(col("D")).take(1)(0)(0).asInstanceOf[Double]
 
-    assertFloatEqual(f, 5.045883f)
+    assertFloatEqual(f, 322.93652f)
     assertDoubleEqual(d, 322.936717)
   }