Re: [swift-users] proper syntax for inout array handling?

2016-06-10 Thread Ken Burgett via swift-users 

On 2016-06-09 21:37, Joe Groff wrote:
On Jun 9, 2016, at 8:39 PM, Saagar Jha via swift-users 
 wrote:


Nevermind, I lied. Swift does allow direct pointer arithmetic:

import Foundation

var source = [UInt8](repeating: 0x1f, count: 32)
var destination = [UInt8](repeating: 0, count: 64)

memcpy(, source, 32) // the C function

memcpy( + 3, source, 13) // the + operator works to offset


Arrays can indeed be used as pointer parameters, but the second one
only works by accident. The pointer bridging has the same semantics as
an 'inout' parameter, so the pointer is only valid for the duration of
the immediate call, and since operators in Swift are also function
calls, the pointer expires after the '+' operation. If you're doing
anything with an array other than passing it off to a single C
function, you should use withUnsafeMutableBufferPointer instead:

destination.withUnsafeMutableBufferPointer { p in
  memcpy(p.baseAddress, source, 32)
  memcpy(p.baseAddress + 3, source, 13)
}

In addition to not having undefined behavior, this will also probably
be faster, since it'll only need to pin the array for pointer access
once instead of twice.

-Joe


Thanks for the good answers, both Saager and Joe.  I like the way you 
both developed solutions and then improved them, and for good reasons.


I do have a situation in the ugly C code I am porting to Swift where a 
pointer gets passed down to a second function, so Joe's solution looks 
like the right approach.


Thanks again.
--
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Principal Software Engineer
Email: k...@iotone.io
Office: 530.693.4449
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[swift-users] Looking for a Swift3 JSON parser

2016-06-08 Thread Ken Burgett via swift-users 
I am looking for a parser for JSON is compatible with Swift 3 on Linux.  
SwiftyJSON looks interesting, but it is Swift 2.2 compatible, AFAIK.  
Any URL will be appreciated, and a Swift3 package would bring joy.


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Re: [swift-users] Simple text file I/O with Swift 3 (Quinn "The Eskimo!")

2016-05-30 Thread Ken Burgett via swift-users 

On 2016-05-30 10:00, swift-users-requ...@swift.org wrote:

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Today's Topics:

   1. Re: Simple text file I/O with Swift 3 (Quinn "The Eskimo!")


--

Message: 1
Date: Mon, 30 May 2016 09:11:41 +0100
From: "Quinn \"The Eskimo!\"" <eski...@apple.com>
To: Swift Users List <swift-users@swift.org>
Subject: Re: [swift-users] Simple text file I/O with Swift 3
Message-ID: <d94a5001-be92-44fb-adb8-ce0d68e62...@apple.com>
Content-Type: text/plain; charset=us-ascii


On 28 May 2016, at 19:05, Ken Burgett via swift-users
<swift-users@swift.org> wrote:


print(buf)



The trick here is to replace the above line with:

print(String(validatingUTF8: buf))

`fgets` sets up `buf` to hold a C string, so you have to convert it to
a Swift string.  How do you do this depends on the encoding of the
bytes.  If you expect the C string to be UTF-8, then
`String(validatingUTF8:)` is the way to go.

IMPORTANT: This conversion can fail, which is why the above will print
a bunch of optional strings, and you will have to decide what to your
program should do when it does.

   *   *   *

btw This question came up recently.  See the thread for other
suggestions about how to handle it.

<http://article.gmane.org/gmane.comp.lang.swift.user/1943>

Share and Enjoy
--
Quinn "The Eskimo!"
<http://www.apple.com/developer/>
Apple Developer Relations, Developer Technical Support, Core 
OS/Hardware





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End of swift-users Digest, Vol 6, Issue 28
**



Hi Quinn,

The link you referenced above 
<http://article.gmane.org/gmane.comp.lang.swift.user/1943> is all about 
Swift 2.2.  I had already found that one on StackOverflow and gave it a 
try, which caused me to generate the string of queries, when it all fell 
apart under Swift 3.


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Principal Software Engineer
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Re: [swift-users] swift-users Digest, Vol 6, Issue 28

2016-05-30 Thread Ken Burgett via swift-users 

On 2016-05-30 10:00, swift-users-requ...@swift.org wrote:

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You can reach the person managing the list at
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When replying, please edit your Subject line so it is more specific
than "Re: Contents of swift-users digest..."


Today's Topics:

   1. Re: Simple text file I/O with Swift 3 (Quinn "The Eskimo!")


--

Message: 1
Date: Mon, 30 May 2016 09:11:41 +0100
From: "Quinn \"The Eskimo!\"" <eski...@apple.com>
To: Swift Users List <swift-users@swift.org>
Subject: Re: [swift-users] Simple text file I/O with Swift 3
Message-ID: <d94a5001-be92-44fb-adb8-ce0d68e62...@apple.com>
Content-Type: text/plain; charset=us-ascii


On 28 May 2016, at 19:05, Ken Burgett via swift-users
<swift-users@swift.org> wrote:


print(buf)



The trick here is to replace the above line with:

print(String(validatingUTF8: buf))

`fgets` sets up `buf` to hold a C string, so you have to convert it to
a Swift string.  How do you do this depends on the encoding of the
bytes.  If you expect the C string to be UTF-8, then
`String(validatingUTF8:)` is the way to go.

IMPORTANT: This conversion can fail, which is why the above will print
a bunch of optional strings, and you will have to decide what to your
program should do when it does.

   *   *   *

btw This question came up recently.  See the thread for other
suggestions about how to handle it.

<http://article.gmane.org/gmane.comp.lang.swift.user/1943>

Share and Enjoy
--
Quinn "The Eskimo!"
<http://www.apple.com/developer/>
Apple Developer Relations, Developer Technical Support, Core 
OS/Hardware





--

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End of swift-users Digest, Vol 6, Issue 28
**

Hi Quinn,

Thanks for the tip on  print(String(validatingUTF8: buf)), that does 
reproduce my input text, line for line, EXCEPT for wrapping every line 
in "Optional(line-of-text-with-terminator)", for example 
"Optional("import Glibc\n")".


So, how does wrapping a line of UTF8 text in another character string 
"Optional()" help me print the text?  Is Optional() some kind of 
function?  If so, how is it intended to be used?


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Principal Software Engineer
Email: k...@iotone.io
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Mobile: 831.332.6846
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[swift-users] Simple text file I/O with Swift 3

2016-05-28 Thread Ken Burgett via swift-users 

Hi all,

I am trying to understand how Swift 3 File I/O works in a linux 
environment.  I put together a trivial test program using what I

can glean from the few examples I can find.  See below.

===
import Glibc
import Foundation

let filename = Process.arguments[1]
let file_handle = fopen (filename, "r")
let BUFSIZE = 1024
var buf = [CChar](repeating:CChar(0), count:BUFSIZE)
while fgets(, Int32(BUFSIZE), file_handle) != nil
{
  print(buf)
}
exit(0)
===

The program runs, but produces a stream of integer arrays, each of 1024 
bytes.  I can see what appears to be ASCII character values in the 
sample text, plus a lot of trailing zeros.  I suspect I haven't mapped 
the bytes in buf to Strings, so how should that be done?

--
Ken Burgett
Principal Software Engineer
Email: k...@iotone.io
Office: 530.693.4449
Mobile: 831.332.6846
URL: www.iotone.coimport Glibc
import Foundation
//
// 'main program'
//
// command: "blake2b filename [key]", 
//
guard Process.arguments.count == 2 else 
{
  print("Usage:  blake2b FILENAME")
  exit(-1)
}

let filename = Process.arguments[1]

let file_handle = fopen (filename, "r")

let BUFSIZE = 1024

var buf = [CChar](repeating:CChar(0), count:BUFSIZE)

while fgets(, Int32(BUFSIZE), file_handle) != nil {
  print(buf)
}

exit(0)
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Re: [swift-users] Printing large hexadecimal values

2016-05-25 Thread Ken Burgett via swift-users 

On 2016-05-25 12:00, Jens Alfke wrote:

On May 25, 2016, at 11:11 AM, Ken Burgett  wrote:

the "%llx" field is not getting interpreted...


You have to import Foundation to bring in the String.init(format:…)
method, which is bridged from Foundation's NSString class.
(This is a temporary inconvenience until the Swift standard library is
complete.)

—Jens

Hi Jens,

You are correct, the "%llx" works for UInt64, while "%16x" does not. 
"%llX" also works, producing an uppercase string.


Should this be reported as a bug?
--
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Principal Software Engineer
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[swift-users] Printing large hexadecimal values

2016-05-25 Thread Ken Burgett via swift-users 
I really shouldn't have to ask this question for a variety of other 
languages, but print format conversion in Swift a black box to me.


I wish to print a 64-bit unsigned integer as 8 hexadecimal digits, and I 
can't find any documentation on this.  Please advise.


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[swift-users] error: NoSources("/home/kenb/.../Cpp_Swift/Sources/cwrapper")

2016-05-24 Thread Ken Burgett via swift-users 
I tried build a system module, following the cpp and swift variant 
mentioned here 
(http://ankit.im/swift/2016/05/21/creating-objc-cpp-packages-with-swift-package-manager/). 
 I hope the author will answer in detail, but I would like to know what 
produces the 'error: NoSources(..)' error message?


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[swift-users] Need documentation on how to import C header into Swift 3.0

2016-05-21 Thread Ken Burgett via swift-users 

Hi Joe,

Can you point me to a good example of how to build a Swift 3.0 module 
that wraps some C code?  I have searched, but keep finding Swift 2.2 
documentation and it all seems to involve connecting to Objective-C, 
while my interests are accessing C code on a Linux platform, using the 
latest Ubuntu Linux 14.04 version of the Swift 3.0 toolchain.


Thanks in advance for your help.

--
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Principal Software Engineer
Email: k...@iotone.io
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Re: [swift-users] Mapping C semantics to Swift

2016-05-20 Thread Ken Burgett via swift-users 

On 2016-05-20 08:55, Jens Alfke wrote:

On May 20, 2016, at 7:33 AM, Ken Burgett via swift-users
<swift-users@swift.org> wrote:

the required C struct morphs into a Swift class, with a member
function 'as_C_byte_array' which answers an array of the required
form. Internally, this function will shift and mask class attributes
in order to build the necessary result.


It would be nice to see Swift acquire structured-data I/O APIs as
found in languages like Ruby and Python — these take a printf-like
format string and parameters, but read and write values in binary. The
format syntax offers modifiers to specify things like byte order,
string encoding, etc. This is so much more reliable and readable than
doing the encoding by hand.

—Jens

Hi Jens,

I understand the value of strong typing from a runtime point of view, 
but I really miss the quickness and simplicity of writing a class in 
Ruby, where duck-typing is king.

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