Xcode 6.1 version of source for this SO answer http://stackoverflow.com/a/24648951/292145

StreamReader.swift

import Foundation

class StreamReader  {

	let encoding : UInt
	let chunkSize : Int
	var atEof : Bool = false

	var fileHandle : NSFileHandle!
	let buffer : NSMutableData!
	let delimData : NSData!

	init?(path: String, delimiter: String = "\n", encoding: UInt = NSUTF8StringEncoding, chunkSize : Int = 4096) {
		self.chunkSize = chunkSize
		self.encoding = encoding

		self.fileHandle = NSFileHandle(forReadingFromURL: NSURL(fileURLWithPath: path)!, error: nil)

		if self.fileHandle == nil {
			return nil
		}

		self.buffer = NSMutableData(capacity: chunkSize)!

		// Create NSData object containing the line delimiter:
		delimData = delimiter.dataUsingEncoding(NSUTF8StringEncoding)!
	}

	deinit {
		self.close()
	}

	/// Return next line, or nil on EOF.
	func nextLine() -> String? {

		if atEof {
			return nil
		}

		// Read data chunks from file until a line delimiter is found:
		var range = buffer.rangeOfData(delimData, options: NSDataSearchOptions(0), range: NSMakeRange(0, buffer.length))
		while range.location == NSNotFound {
			var tmpData = fileHandle.readDataOfLength(chunkSize)
			if tmpData.length == 0 {
				// EOF or read error.
				atEof = true
				if buffer.length > 0 {
					// Buffer contains last line in file (not terminated by delimiter).
					let line = NSString(data: buffer, encoding: encoding);
					buffer.length = 0
					return line
				}
				// No more lines.
				return nil
			}
			buffer.appendData(tmpData)
			range = buffer.rangeOfData(delimData, options: NSDataSearchOptions(0), range: NSMakeRange(0, buffer.length))
		}

		// Convert complete line (excluding the delimiter) to a string:
		let line = NSString(data: buffer.subdataWithRange(NSMakeRange(0, range.location)),
			encoding: encoding)
		// Remove line (and the delimiter) from the buffer:
		buffer.replaceBytesInRange(NSMakeRange(0, range.location + range.length), withBytes: nil, length: 0)

		return line
	}

	/// Start reading from the beginning of file.
	func rewind() -> Void {
		fileHandle.seekToFileOffset(0)
		buffer.length = 0
		atEof = false
	}

	/// Close the underlying file. No reading must be done after calling this method.
	func close() -> Void {
		if fileHandle != nil {
			fileHandle.closeFile()
			fileHandle = nil
		}
	}
}

extension StreamReader : SequenceType {
	func generate() -> GeneratorOf<String> {
		return GeneratorOf<String> {
			return self.nextLine()
		}
	}
}

Cool. Thanks a lot for the code. Is it possible to get a nextChar() function, too. How to implement a method that just returns one character?

use this - https://github.com/hectr/swift-stream-reader