jadams-tresys commented on a change in pull request #16: Implemented packed 
binary formats
URL: https://github.com/apache/incubator-daffodil/pull/16#discussion_r162072337
 
 

 ##########
 File path: 
daffodil-lib/src/main/scala/edu/illinois/ncsa/daffodil/util/DecimalUtils.scala
 ##########
 @@ -0,0 +1,342 @@
+/*
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package edu.illinois.ncsa.daffodil.util
+
+import 
edu.illinois.ncsa.daffodil.schema.annotation.props.gen.BinaryNumberCheckPolicy
+
+import java.math.{ BigInteger => JBigInteger, BigDecimal => JBigDecimal }
+
+object DecimalUtils {
+
+  def signCodesToHex(signCodes: String, policy: BinaryNumberCheckPolicy): 
Map[String, List[Int]] = {
+    // remove all spaces from the string
+    val str: String = signCodes.replaceAll("\\s", "")
+    val chars: Array[Char] = str.toCharArray()
+
+    val valid_positives: List[Int] = List(
+      Integer.parseInt(String.valueOf('A'), 16),
+      Integer.parseInt(String.valueOf('C'), 16),
+      Integer.parseInt(String.valueOf('E'), 16),
+      Integer.parseInt(String.valueOf('F'), 16))
+    val valid_negatives: List[Int] = List(
+      Integer.parseInt(String.valueOf('B'), 16),
+      Integer.parseInt(String.valueOf('D'), 16))
+    val valid_unsigneds: List[Int] = List(
+      Integer.parseInt(String.valueOf('F'), 16))
+    val valid_zero_signs: List[Int] = List(
+      Integer.parseInt(String.valueOf('A'), 16),
+      Integer.parseInt(String.valueOf('C'), 16),
+      Integer.parseInt(String.valueOf('E'), 16),
+      Integer.parseInt(String.valueOf('F'), 16),
+      Integer.parseInt(String.valueOf('0'), 16))
+
+    val positives: List[Int] = List(Integer.parseInt(String.valueOf(chars(0)), 
16))
+    val negatives: List[Int] = List(Integer.parseInt(String.valueOf(chars(1)), 
16))
+    val unsigneds: List[Int] = List(Integer.parseInt(String.valueOf(chars(2)), 
16))
+    val zero_signs: List[Int] = 
List(Integer.parseInt(String.valueOf(chars(3)), 16))
+
+    val hexCodes = policy match {
+      case BinaryNumberCheckPolicy.Strict => Map("positive" -> positives, 
"negative" -> negatives, "unsigned" -> unsigneds, "zero_sign" -> zero_signs)
+      case BinaryNumberCheckPolicy.Lax => Map("positive" -> valid_positives, 
"negative" -> valid_negatives, "unsigned" -> valid_unsigneds, "zero_sign" -> 
valid_zero_signs)
+    }
+
+    hexCodes
+  }
+
+  def packedToBigInteger(num: Array[Byte], signCodes: String, policy: 
BinaryNumberCheckPolicy): JBigInteger = {
+    val hexCodes: Map[String, List[Int]] = signCodesToHex(signCodes, policy)
+    val numDigits: Int = num.size * 2  // 2 digits stored per byte
+    val outputData: Array[Char] = new Array[Char](numDigits-1)
+    var outputPos: Int = 0
+    var offset: Int = 0
+    var nibble: Int = 0
+    var negative: Boolean = false
+
+    // Parse and validate the last (sign) bit
+    nibble = (num(offset +  num.size - 1) & 0x0F)
+    if (hexCodes("negative").contains(nibble)) {
+      negative = true
+    } else if (!hexCodes("positive").contains(nibble)) {
+      throw new NumberFormatException("Invalid low nibble")
+    }
+
+    while (outputPos < outputData.size - 1) {
+      // Parse high nibble
+      nibble = (num(offset) & 0xFF) >>> 4
+      if (nibble > 0x09) {
+        throw new NumberFormatException("Invalid high nibble")
+      }
+
+      outputData(outputPos) = (nibble | 0x0030).toChar
+      outputPos = outputPos + 1
+
+      // Parse low nibble
+      nibble = (num(offset) & 0x0F)
+      offset = offset + 1
+      if (nibble > 0x09) {
+        throw new NumberFormatException("Invalid low nibble")
+      }
+
+      outputData(outputPos) = (nibble | 0x0030).toChar
+      outputPos = outputPos + 1
+    }
+
+    // Parse last digit
+    nibble = (num(offset) & 0xFF) >>> 4
+    if (nibble > 0x09) {
+      throw new NumberFormatException("Invalid high nibble")
+    }
+
+    outputData(outputPos) = (nibble | 0x0030).toChar
+
+    if (negative)
+      new JBigInteger(new String(outputData)).negate()
+    else
+      new JBigInteger(new String(outputData))
+
+  }
+
+  def packedToBigDecimal(num: Array[Byte], scale: Int, signCodes: String, 
policy: BinaryNumberCheckPolicy): JBigDecimal = {
+    return new JBigDecimal(packedToBigInteger(num, signCodes, policy), scale)
+  }
+
+  def packedFromBigInteger(num: String, nBits: Int, signCodes:String, policy: 
BinaryNumberCheckPolicy): Array[Byte] = {
+    val negative: Boolean = (num.charAt(0) == '-')
+    // Discard any sign symbols or decimal points from the string (decimal 
point will be maintained in binaryVirtualDecimalPoint)
 
 Review comment:
   It might make the most sense to just remove the part about 
binaryVirtualDecimalPoint from the comment.  I was trying to convey that when 
we are creating the packed/bcd/ibm4690 from the BigInteger string that we do 
not need to keep track of the decimal point as the unparser already has the 
information on where the decimal point is supposed to go in the 
binaryVirtualDecimalPoint property.
   
   I think I'll go ahead and change the function name to _FromBigNumber as this 
function works on both BigInteger numbers and BigDecimal numbers that have been 
converted to string.

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