What is the fastest Char-By-Char-Reader in Swift - swift

Question

i have to write a real fast char by char reader in swift. This is my solution so far.
For a 1.4mb file i get it in 0m0.932s. For a 150mb file it took 1m42.931s
Do you know a faster solution?
import Foundation
class CharReader {
let encoding : String.Encoding
let chunkSize : Int
var fileHandle : FileHandle!
let buffer : NSMutableData!
var atEof : Bool = false
var characterPointer: UnsafeMutablePointer<Character>
var startPointer: UnsafeMutablePointer<Character>
var stored_cnt: Int = 0;
var stored_idx: Int = 0;
init?(path: String, encoding: String.Encoding = String.Encoding.utf8, chunkSize : Int = 1024) {
self.chunkSize = chunkSize
self.encoding = encoding
characterPointer = UnsafeMutablePointer<Character>.allocate(capacity: chunkSize)
startPointer = characterPointer
if let fileHandle = FileHandle(forReadingAtPath: path),
let buffer = NSMutableData(capacity: chunkSize){
self.fileHandle = fileHandle
self.buffer = buffer
} else {
self.fileHandle = nil
self.buffer = nil
return nil
}
}
deinit {
self.close()
}
func nextChar() -> Character? {
if atEof {
return nil
}
if stored_cnt > (stored_idx + 1) {
stored_idx += 1
let char = characterPointer.pointee
characterPointer = characterPointer.successor()
return char
}
let tmpData = fileHandle.readData(ofLength: (chunkSize))
if tmpData.count == 0 {
atEof = true
return nil
}
if let s = NSString(data: tmpData, encoding: encoding.rawValue) as String! {
stored_idx = 0
let characters = s.characters
stored_cnt = characters.count
characterPointer = startPointer
characterPointer.initialize(from: characters)
let char = characterPointer.pointee
characterPointer = characterPointer.successor()
return char
}
return nil;
}
/// Close the underlying file. No reading must be done after calling this method.
func close() -> Void {
fileHandle?.closeFile()
fileHandle = nil
}
}
please let me know.
I test the class with this main.swfit:
import Foundation
if CommandLine.arguments.count < 2 {
print("Too less arguments.")
exit(0)
}
let file = CommandLine.arguments[1]
if let aCharReader = CharReader(path: file) {
defer {
aCharReader.close()
}
while let char = aCharReader.nextChar() {
continue
}
}
The Project is on GitHub: https://github.com/petershaw/charsinfile
Thanks a lot,
ps

Answer 1

i updated the repository with both versions in it: https://github.com/petershaw/charsinfile
With help from Martin I fix the mistake in Rob's code.
I tested a bunch of different files and both versions worked fine. Rob Napier's code is more efficient! Thanks a lot, Rob.
Thanks all of you both to help me figuring out the fastest solution. It's gerate to have a so wonderful and polite community for swift and cocoa related stuff here an so.
Have a great week!
ps