mbeckerle commented on a change in pull request #77: Modifications to IO layer
to support streaming input data
URL: https://github.com/apache/incubator-daffodil/pull/77#discussion_r201029459
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File path: daffodil-lib/src/main/scala/org/apache/daffodil/util/BitOrder.scala
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@@ -213,4 +213,60 @@ object Bits {
String.format("%8s", unsignedByte.toBinaryString).replace(' ', '0')
}
+ def signExtend(l: Long, bitLength: Int): Long = {
+ Assert.usage(bitLength > 0 && bitLength <= 64)
+ if (bitLength == 1) return l // a single bit has no sign to extend
+ val shift = 64 - bitLength
+ val res = ((l << shift) >> shift) // arithmetic shift right extends sign.
+ res
+ }
+
+ def unSignExtend(l: Long, bitLength: Int): Long = {
+ Assert.usage(bitLength > 0 && bitLength <= 64)
+ val mask = if (bitLength == 64) -1L else (1L << bitLength) - 1
+ l & mask
+ }
+
+ /**
+ * Round up the bitPosition to the nearest byte position.
+ *
+ * For example, say we want to read up to a bit position that is not a full
+ * byte. That will require reading the full byte, leaving the bytePosition
+ * past our bit position. This function can be used to determine where that
+ * byte position will be. Essentially, if bitPos0b is not a multiple of 8, we
+ * round up one byte.
+ */
+ def roundUpToByte(bitPos0b: Long): Long = {
Review comment:
I know it's very verbose, but I recommend naming this to
"alignToNextBytePosition" or "roundBitPositionUpToBytePosition".
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