Fixed #105 - bug in sliceToByte

scodec · Jan 17, 2019 · 4a467cf · 4a467cf
1 parent 21e1208
commit 4a467cf
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Showing 2 changed files with 10 additions and 2 deletions.
diff --git a/core/shared/src/main/scala/scodec/bits/BitVector.scala b/core/shared/src/main/scala/scodec/bits/BitVector.scala
@@ -770,13 +770,13 @@ sealed abstract class BitVector extends BitwiseOperations[BitVector, Long] with
    */
   final def sliceToByte(start: Long, bits: Int, signed: Boolean = true): Byte = {
     if (start % 8 != 0) drop(start).sliceToByte(0, bits, signed)
-    else if (isEmpty) 0.toByte
+    else if (isEmpty || bits == 0) 0.toByte
     else getByte(start, bits, signed)
   }
 
   private def getByte(start: Long, bits: Int, signed: Boolean): Byte = {
     require(sizeGreaterThanOrEqual(start + bits) && bits >= 0 && bits <= 8)
-    var result = 0x0ff & getByte(0)
+    var result = 0x0ff & getByte(start / 8)
     if (bits != 0) result = result >>> (8 - bits)
     // Sign extend if necessary
     if (signed && bits != 8 && ((1 << (bits - 1)) & result) != 0) {

diff --git a/core/shared/src/test/scala/scodec/bits/BitVectorTest.scala b/core/shared/src/test/scala/scodec/bits/BitVectorTest.scala
@@ -576,6 +576,14 @@ class BitVectorTest extends BitsSuite {
     hex"001122334455".bits.slice(-21, -5) shouldBe hex"".bits
   }
 
+  test("sliceToByte") {
+    forAll { (x: BitVector, offset0: Long, sliceSize0: Int) =>
+      val offset = if (x.nonEmpty) (offset0 % x.size).abs else 0
+      val sliceSize = (sliceSize0 % 9).abs.min((x.size - offset).toInt)
+      x.sliceToByte(offset, sliceSize).toInt shouldBe x.drop(offset).take(sliceSize.toLong).toInt()
+    }
+  }
+
   test("highByte") {
     BitVector.highByte.toBin shouldBe "11111111"
   }