[SR-3901] seemingly inconsistent File IO

[swift-ci]

Previous ID	SR-3901
Radar	None
Original Reporter	kelko (JIRA User)
Type	Improvement

Attachment: Download

Additional Detail from JIRA

Votes	1
Component/s	Foundation, Standard Library
Labels	Improvement, LanguageFeatureRequest
Assignee	None
Priority	Medium

md5: d78492d6b6817bd309d8e3ab74f9e649

Issue Description:

For me it seems, that the classes for handling IO in/from files are inconsistent to each other.

On the one hand there is InputStream, subclassing Stream, and main API like:

func read(_ buffer: UnsafeMutablePointer<UInt8>, maxLength len: Int) -> Int
func getBuffer(_ buffer: UnsafeMutablePointer<UnsafeMutablePointer<UInt8>?>, length len: UnsafeMutablePointer<Int>) -> Bool
var hasBytesAvailable: Bool { get }

On the other hand there is FileHandle with an API for reading like

var availableData: Data { get }
func readDataToEndOfFile() -> Data
func readData(ofLength length: Int) -> Data

For writing there is same FileHandle with writeData, but also OutputStream. To add to the confusion there is also TextOutputStream which does not seem to be an extension of OutputStream - although the name might suggest otherwise.
And why is there no TextInputStream?

It really makes it hard to unify handling of different input types (FileHandle has built-in support for Console, InputStream can be used to read from an URL or an Data object., Why is there no TextInputStream to read from a String?) and output types.

No matter which class I end up using it always feels like I might be making the wrong choice and cut myself off of yet unseen new features.

[swift-ci]

Comment by Gregor Karzelek (JIRA)

Also what I don't understand, taking a look at the evolution of swifts String, is why there is only byte-array reading and no Character based reading from files. Byte-based reading is error-prone as you can't be sure you don't just cut an combined character like emojis into half.

guard let inputHandle = FileHandle(forReadingAtPath: "input.txt") else {
    exit(EXIT_FAILURE)
}


var atEOF = false

while(!atEOF) {
    
    let readInput = inputHandle.readData(ofLength: 4)
    if readInput.count > 0 {
        puts(String(data: readInput, encoding: .utf8))
        
    } else {
        atEOF = true
    }
}

Input:

Hello World! :smilingemoji:

(Of course ":smilingemoj: was the real smiling emoji. But with that in place I could not send this comment, jira was unable to process it)

Output on the console:

Hell
o Wo
rld!
(null)
(null)

[swift-ci]

Comment by Gregor Karzelek (JIRA)

I thought about what kind of API I would love to see in Swift for this topic. See attached ZIP with proposal.