daffodil-core/src/main/scala/edu/illinois/ncsa/daffodil/grammar/AlignedMixin.scala

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package edu.illinois.ncsa.daffodil.grammar

import edu.illinois.ncsa.daffodil.dsom.Term

trait AlignedMixin extends GrammarMixin { self: Term =>

  /**
   * true if we can statically determine that the start of this
   * will be properly aligned by where the prior thing left us positioned.
   * Hence we are guaranteed to be properly aligned.
   */
  // TODO: make this actually do the position analysis - that however, requires computing
  // known alignment information based on the starting known alignment and known length
  // of prior things (recursively). I.e., it's a bit tricky.
  //  private lazy val isKnownPreAligned = {
  //    val res = self.isScannable || // if we are scannable, then mandatory text alignment takes care of this alignment.
  //      (alignment == 1 && alignmentUnits == AlignmentUnits.Bits) // if we are 1-bit alignment, we're always aligned.
  //    // useful place for a breakpoint to watch this optimization
  //    res
  //  }

  final def isKnownToBeAligned: Boolean = LV('isKnownToBeAligned) {
    if (alignmentValueInBits == 1) true
    else if (alignmentValueInBits == 8)
      isKnownToBePrecededByAllByteLengthItems
    else false
  }.value

  final lazy val isKnownToBeTextAligned: Boolean = {
    if (self.encodingInfo.isKnownEncoding &&
      self.encodingInfo.knownEncodingAlignmentInBits == 1)
      true
    else if (isKnownToBePrecededByAllByteLengthItems)
      true
    else if (this.rootElement.get.isScannable)
      true
    else
      false
  }

  // TODO: deal with case of a bit field that is not a multiple of bytes wide
  // but has a terminator which is text and so has mandatory alignment.
  //  /**
  //   * Region of up to 7 bits to get us to a byte boundary for text.
  //   */
  //  lazy val initiatorAlign = Prod("initiatorAlign", this, !isInitiatorPreAligned, TextAlign(mandatoryAlignment))
  //  lazy val terminatorAlign = Prod("terminatorAlign", this, !isTerminatorPreAligned, TextAlign(mandatoryAlignment))
  //  lazy val separatorAlign = Prod("separatorAlign", this, !isSeparatorPreAligned, TextAlign(mandatoryAlignment))
  //
  //  lazy val isInitiatorPreAligned = {
  //    if (!hasInitiator) true
  //    else {
  //      alignmentCompatible(precedingTermAlignment, mandatoryAlignment)
  //    }
  //  }

  final lazy val hasNoSkipRegions = leadingSkip == 0 && trailingSkip == 0

}