func readBits()

in Sources/TSCUtility/Bits.swift [25:48]

• 23 lines of code
• 5 McCabe index (conditional complexity)

  func readBits(atOffset offset: Int, count: Int) -> UInt64 {
    precondition(count >= 0 && count <= 64)
    precondition(offset >= 0)
    precondition(offset &+ count >= offset)
    precondition(offset &+ count <= self.endIndex)

    return buffer.contents.withUnsafeBytes { (bytes: UnsafeRawBufferPointer) in
      let upperBound = offset &+ count
      let topByteIndex = upperBound >> 3
      var result: UInt64 = 0
      if upperBound & 7 != 0 {
        let mask: UInt8 = (1 << UInt8(upperBound & 7)) &- 1
        result = UInt64(bytes[topByteIndex] & mask)
      }
      for i in ((offset >> 3)..<(upperBound >> 3)).reversed() {
        result <<= 8
        result |= UInt64(bytes[i])
      }
      if offset & 7 != 0 {
        result >>= UInt64(offset & 7)
      }
      return result
    }
  }