Merge pull request #27 from Christewart/master

Adding utility function to convert a byte to a bit vector and vice versa

src/main/scala/org/bitcoins/core/util/BitcoinSUtil.scala

@@ -89,6 +89,31 @@ trait BitcoinSUtil {
     val paddedHex = padding.mkString + hex
     paddedHex
   }
+
+  /** Converts a sequence of bytes to a sequence of bit vectors - assumes the sequence of bytes are big endian */
+  def bytesToBitVectors(bytes: Seq[Byte]): Seq[Seq[Boolean]] = bytes.map(byteToBitVector)
+
+  /** Converts a byte to a bit vector representing that byte - the bit vector is big endian */
+  def byteToBitVector(byte: Byte): Seq[Boolean] = {
+    (0 to 7).map(index => isBitSet(byte,7 - index))
+  }
+
+  /** Checks if the bit at the given index is set */
+  def isBitSet(byte: Byte, index: Int): Boolean = ((byte >> index) & 1) == 1
+
+  /** Converts a bit vector to a single byte -- assumes the bits are big endian */
+  def bitVectorToByte(bits: Seq[Boolean]): Byte = {
+    require(bits.size <= 8, "Cannot convert a bit vector to a byte when the size of the bit vector is larger than 8, got: " + bits)
+    val b = bits.reverse
+    val result: Seq[Int] = b.zipWithIndex.map { case (b, index) =>
+        if (b) NumberUtil.pow2(index).toInt else 0
+    }
+    result.sum.toByte
+  }
+
+  /** Converts a sequence of bit vectors to a sequence of bytes */
+  def bitVectorsToBytes(bits: Seq[Seq[Boolean]]): Seq[Byte] = bits.map(bitVectorToByte)
+
 }
 
 object BitcoinSUtil extends BitcoinSUtil

src/test/scala/org/bitcoins/core/util/BitcoinSUtilSpec.scala

@@ -1,6 +1,6 @@
 package org.bitcoins.core.util
 
-import org.bitcoins.core.gen.StringGenerators
+import org.bitcoins.core.gen.{CryptoGenerators, NumberGenerator, StringGenerators}
 import org.scalacheck.{Gen, Prop, Properties}
 /**
   * Created by chris on 6/20/16.
@@ -16,4 +16,15 @@ class BitcoinSUtilSpec extends Properties("BitcoinSUtilSpec") with BitcoinSLogge
     Prop.forAll(StringGenerators.hexString) { hex : String =>
       BitcoinSUtil.flipEndianess(BitcoinSUtil.flipEndianess(hex)) == hex
     }
+
+  property("Convert a byte to a bit vector, convert it back to the original byte") =
+    Prop.forAll { byte: Byte =>
+      BitcoinSUtil.bitVectorToByte(BitcoinSUtil.byteToBitVector(byte)) == byte
+    }
+
+  property("Convert a sequence of bit vectors to a sequence of bytes") =
+    Prop.forAll(NumberGenerator.bitVectors) { bitVectors: Seq[Seq[Boolean]] =>
+      BitcoinSUtil.bytesToBitVectors(BitcoinSUtil.bitVectorsToBytes(bitVectors)) == bitVectors
+
+    }
 }

src/test/scala/org/bitcoins/core/util/BitcoinSUtilTest.scala

@@ -21,4 +21,36 @@ class BitcoinSUtilTest extends FlatSpec with MustMatchers {
     //fail to parse a hex string that is uneven
     BitcoinSUtil.isHex("123") must be (false)
   }
+
+  it must "convert a byte to a bit vector" in {
+    val byte = 0.toByte
+    BitcoinSUtil.byteToBitVector(byte) must be (Seq(false,false,false,false,false,false,false,false))
+
+    val byte1 = 1.toByte
+    BitcoinSUtil.byteToBitVector(byte1) must be (Seq(false,false,false,false,false,false,false,true))
+
+    val byte2 = 2.toByte
+    BitcoinSUtil.byteToBitVector(byte2) must be (Seq(false,false,false,false,false,false,true,false))
+
+    val byte3 = 3.toByte
+    BitcoinSUtil.byteToBitVector(byte3) must be (Seq(false,false,false,false,false,false,true,true))
+
+    val maxByte = 0xff.toByte
+    BitcoinSUtil.byteToBitVector(maxByte) must be (Seq(true,true,true,true,true,true,true,true))
+  }
+
+  it must "convert a bit vector to a byte" in {
+    val bitVector0 = Seq(false,false,false,false,false,false,false,false)
+    BitcoinSUtil.bitVectorToByte(bitVector0) must be (0.toByte)
+
+    val bitVector1 = Seq(false,false,false,false,false,false,false,true)
+    BitcoinSUtil.bitVectorToByte(bitVector1) must be (1.toByte)
+
+    val bitVector2 = Seq(false,false,false,false,false,false,true,false)
+    BitcoinSUtil.bitVectorToByte(bitVector2) must be (2.toByte)
+
+    val bitVectorMax = Seq(true,true,true,true,true,true,true,true)
+    BitcoinSUtil.bitVectorToByte(bitVectorMax) must be (0xff.toByte)
+
+  }
 }