This code is a private function that takes in an...

March 29, 2023 at 08:59 AM

private func parseDate(_ buffer: UnsafeRawBufferPointer, separator: UInt8, at: Int) -> Double {
  let dateString = buffer.split(separator: separator, maxSplits: at + 1, omittingEmptySubsequences: false)[at]
  let date = dateString.split(maxSplits: 6, omittingEmptySubsequences: false, whereSeparator: { $0 < UInt8(ascii: "0") || $0 > UInt8(ascii: "9")})
  let values = date.prefix(6).map { c -> Int32 in
    c.map { Int32($0) - 48 }.reduce(into: 0, { $0 = $0 * 10 + $1 })
  }
  var t = time_t()
  time(&t)
  #if os(Windows)
  var info = tm()
  localtime_s(&info, &t)
  #else
  var info = localtime(&t)!.pointee
  #endif
  info.tm_year = values[0] - 1900
  info.tm_mon = values[1] - 1
  info.tm_mday = values[2]
  if values.count > 4 {
    info.tm_hour = values[3]
    info.tm_min = values[4]
  }
  if values.count > 5 {
    info.tm_sec = values[5]
  }
  return Double(mktime(&info))
}

This code is a private function that takes in an UnsafeRawBufferPointer, a separator character, and an integer at. It returns a Double value by parsing the dateString from the buffer, separating it into its constituent parts, and then converting this to a time value using the standard C library function mktime.

The function first splits the buffer into substrings separated by the given separator and selects the substring at index at. It then splits this selected substring into six parts based on non-numeric characters and creates an array of integers from these parts.

Finally, it uses the standard C library function time to get the current time as a time_t value, and then populates a tm struct with the parsed date values. The tm struct represents a calendar time broken down into its components (year, month, day, hour, minute, second). Finally, it converts this tm struct into a time value using the standard C library function mktime, which returns seconds elapsed since January 1, 1970.

Note: There is some platform-specific code to handle differences between Windows and other operating systems in the way they handle time information.

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