jadams-tresys commented on a change in pull request #16: Implemented packed 
binary formats
URL: https://github.com/apache/incubator-daffodil/pull/16#discussion_r162089955
 
 

 ##########
 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:
   Ok, I understand what you are gettting at now.  Currently what I am doing is 
not converting the BigDecimal to a BigInteger, instead I am just calling 
bigDec.toPlainString and doing fromBigInteger on that string, and then in 
FromBigInteger I am removing the decimal point character from the string.
   
   What you are suggesting would probably be clearer in the code and removes 
the need for me to run a regex on the input string in FromBigInteger.  I hadn't 
really considered a malformed infoset when unparsing.  I'll start working on 
these changes.

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