[swift-server-dev] Convert HTTPVersion to struct

[Rien]

> On 14 Jun 2017, at 09:12, Michael Chiu <hatsuneyuji at icloud.com> wrote:
> 
> I think currently the http version is come from the http_parser which has parsed the version string to number anyway. hence the performance should be similar.

That is likely, but imo the HTTP API should be judged on its own merits.


> 
> I do see some advantage to use struct tho, for example comparing only major version.


That is where I don’t see a real world advantage. Theoretically you are correct, but in a real world example?, do you have an example where this is indeed useful?
Given the limited range of useful versions numbers (only 3!) I just don’t see it.

I realize that this reaches into preferred programming techniques, but I like to use capability test on the type.
I.e. I would write

enum HttpVersion { case http1_0, http1_1, http2_0 }

extension HttpVersion {
	var isMultipleDomainCapable: Bool {
		switch self {
		case .http1_0: return false
		case .http1_1: return true
		case .http2_0: return true
		}
	}
}

if version.isMultipleDomainCapable {	}

instead of:

struct HttpVersion {
	let major: Int
	let minor: Int

	static func == ...
}

if (version == HttpVersion(1, 1) || (version == HttpVersion(2, 0)) {
	// supports multiple domains
}

Regards,
Rien

Site: http://balancingrock.nl
Blog: http://swiftrien.blogspot.com
Github: http://github.com/Balancingrock
Project: http://swiftfire.nl - An HTTP(S) web server framework in Swift

> 
> Michael
> 
>> On Jun 13, 2017, at 11:41 PM, Rien via swift-server-dev <swift-server-dev at swift.org> wrote:
>> 
>> The choices seem to be:
>> 
>> 1) String
>> 2) Enum
>> 3) Tuple
>> 4) Struct
>> 5) Class
>> 
>> 1) String
>> Advantage: it is in fact an utf-8 string. No conversions needed.
>> Disadvantage: It is mostly thought of as a number, thus the abstraction does not match the type, very minor performance penalty in comparing. Illogical to add HTTP-version extensions to the type.
>> 
>> 2) Enum
>> Advantage: shortest possible representation (?), fastest compare (?), easy to use.
>> Disadvantage: Needs converting to and from.
>> 
>> 3) Tuple
>> Advantage: Matches fairly wel with the abstraction.
>> Disadvantage: Fairly complex conversion, adding members/operations is non-intuitive, not very easy to use.
>> 
>> 4) Struct
>> Advantage: Matches fairly wel with the abstraction.
>> Disadvantage: Fairly complex conversion. Not very easy to use without adding members/operations.
>> 
>> 5) This was for completeness only, I would be very surprised if anybody would actually propose this… ;-)
>> 
>> 
>> To me that leaves option 2 and 4.
>> Advantage of 2 over 4:
>> 
>> - I find the abstraction a better match. The difference between 1, 1.1 and 2 is such that it makes little sense to be to differentiate based on the numerical values. It makes much more sense to differentiate based on the “whole number”. AFAIIC they could just as easily have named the versions A, B, C etc. The numbers do not convey any information as such.
>> - Switch is easier and more intuitive to use.
>> - Enums can have additional properties and operations similar to struct.
>> 
>> Advantage of 4 over 2:
>> I don’t see any.
>> 
>> Regards,
>> Rien
>> 
>> Site: http://balancingrock.nl
>> Blog: http://swiftrien.blogspot.com
>> Github: http://github.com/Balancingrock
>> Project: http://swiftfire.nl - An HTTP(S) web server framework in Swift
>> 
>> 
>> 
>>> On 13 Jun 2017, at 22:44, Chris Bailey via swift-server-dev <swift-server-dev at swift.org> wrote:
>>> 
>>> Based on our discussed approach of reviewing each of the types in the HTTP project, I've raised the following PR to convert HTTPVersion from (Int, Int) to a struct based on Paulo's proposal: 
>>>      https://github.com/swift-server/http/pull/6 
>>> 
>>> I've not yet added Hashable, Equatable and CustomStringConvertible protocols - we can do that if we're happy with the change. 
>>> 
>>> Chris
>>> Unless stated otherwise above:
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>> 
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> 

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