mutating func readBlockInfoBlock()

in Sources/TSCUtility/BitstreamReader.swift [221:276]
50 lines of code
14 McCabe index (conditional complexity)

  mutating func readBlockInfoBlock(abbrevWidth: Int) throws {
    var currentBlockID: UInt64?
    while true {
      switch try cursor.read(abbrevWidth) {
      case Bitstream.AbbreviationID.endBlock.rawValue:
        try cursor.advance(toBitAlignment: 32)
        // FIXME: check expected length
        return

      case Bitstream.AbbreviationID.enterSubblock.rawValue:
        throw Error.nestedBlockInBlockInfo

      case Bitstream.AbbreviationID.defineAbbreviation.rawValue:
        guard let blockID = currentBlockID else {
          throw Error.missingSETBID
        }
        let numOps = Int(try cursor.readVBR(5))
        if globalAbbrevs[blockID] == nil { globalAbbrevs[blockID] = [] }
        globalAbbrevs[blockID]!.append(try readAbbrev(numOps: numOps))

      case Bitstream.AbbreviationID.unabbreviatedRecord.rawValue:
        let code = try cursor.readVBR(6)
        let numOps = try cursor.readVBR(6)
        var operands = [UInt64]()
        for _ in 0..<numOps {
          operands.append(try cursor.readVBR(6))
        }

        switch code {
        case UInt64(Bitstream.BlockInfoCode.setBID.rawValue):
          guard operands.count == 1 else { throw Error.invalidBlockInfoRecord(recordID: code) }
          currentBlockID = operands.first
        case UInt64(Bitstream.BlockInfoCode.blockName.rawValue):
          guard let blockID = currentBlockID else {
            throw Error.missingSETBID
          }
          if blockInfo[blockID] == nil { blockInfo[blockID] = BlockInfo() }
          blockInfo[blockID]!.name = String(bytes: operands.map { UInt8($0) }, encoding: .utf8) ?? "<invalid>"
        case UInt64(Bitstream.BlockInfoCode.setRecordName.rawValue):
          guard let blockID = currentBlockID else {
            throw Error.missingSETBID
          }
          if blockInfo[blockID] == nil { blockInfo[blockID] = BlockInfo() }
          guard let recordID = operands.first else {
            throw Error.invalidBlockInfoRecord(recordID: code)
          }
          blockInfo[blockID]!.recordNames[recordID] = String(bytes: operands.dropFirst().map { UInt8($0) }, encoding: .utf8) ?? "<invalid>"
        default:
          throw Error.invalidBlockInfoRecord(recordID: code)
        }

      case let abbrevID:
        throw Error.noSuchAbbrev(blockID: 0, abbrevID: Int(abbrevID))
      }
    }
  }