[swift-users] changes to pointer data types in Xcode 8 beta 6

[davelist at mac.com]

Zach,

Thanks for the fix!

Ah, I think I now see the difference between a UnsafeBufferPointer (it essentially holds the address an array of data) vs. a UnsafePointer (it holds the address where one piece of data is stored), but I'll still need to read the final documentation when it's done.

Dave

> On Aug 15, 2016, at 9:15 PM, Zach Waldowski via swift-users <swift-users at swift.org> wrote:
> 
> Nerd here!
> 
> That part of the code ends up not needing to go through the
> UnsafeRawPointer API, as it's processing UTF-8 bytes, see also:
> <https://github.com/bignerdranch/Freddy/pull/191>.
> 
> That being said, good resources for reading about the new pointer system
> are:
> - [SE-0107]:
> <https://github.com/apple/swift-evolution/blob/master/proposals/0107-unsaferawpointer.md>
> - [The Apple API reference], once it's updated:
> <https://developer.apple.com/reference/swift>
> 
> You can also look up the documentation using the "Documentation and API
> Reference" menu in Xcode 8 Beta 6, as it's currently updated.
> 
> Sincerely,
>   Zachary Waldowski
>   zachary at bignerdranch.com
> 
> On Mon, Aug 15, 2016, at 03:05 PM, Dave Reed via swift-users wrote:
>> I'm trying to convert the following code (from the Big Nerd Ranch's
>> Freddy JSON parser) that works in Xcode 8 beta 5 and convert it to work
>> with beta 6. Essentially it appears it needs to take a Data object and
>> convert it to a UnsafeBufferPointer<UInt8> if I understand it correctly.
>> 
>> 
>>    /// Creates a `JSONParser` ready to parse UTF-8 encoded `NSData`.
>>    ///
>>    /// If the data is mutable, it is copied before parsing. The data's
>>    lifetime
>>    /// is extended for the duration of parsing.
>>    init(utf8Data inData: Data) {
>>        let data = (inData as NSData).copy() as! Data
>>        let buffer = UnsafeBufferPointer(start:
>>        UnsafePointer<UInt8>((data as NSData).bytes), count: data.count)
>>        self.init(buffer: buffer, owner: data)
>>    }
>> 
>> And this case appears to be going from a String to
>> UnsafeBufferPointer<Uint8>
>> 
>> 
>>    /// Creates a `JSONParser` from the code units represented by the
>>    `string`.
>>    ///
>>    /// The synthesized string is lifetime-extended for the duration of
>>    parsing.
>>    init(string: String) {
>>        let codePoints = string.nulTerminatedUTF8
>>        let buffer = codePoints.withUnsafeBufferPointer {
>>        nulTerminatedBuffer in
>>            // don't want to include the nul termination in the buffer -
>>            trim it off
>>            UnsafeBufferPointer(start: nulTerminatedBuffer.baseAddress,
>>            count: nulTerminatedBuffer.count - 1)
>>        }
>>        self.init(buffer: buffer, owner: codePoints)
>>    }
>> 
>> }
>> 
>> 
>> I understand pointers from my C/C++/Objective-C days but I don't yet
>> understand the various Swift pointer types. Any help is appreciated.
>> 
>> Note: I don't work for Big Nerd Ranch. I'm just trying to use the code
>> and better understand the various Swift pointer types.
>> 
>> Thanks,
>> Dave Reed
>> 
>> 
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