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digitalmars.D.learn - convert string to ubyte[]

reply aki <aki google.com> writes:
Hello,

This will be trivial question but I cannot figure out
what's wrong. I want to convert string to an array of ubyte.

import std.conv;
void main() {
         auto s = "hello";
         ubyte[] b = to!(ubyte[])(s);
}

It compiles but cause run time error:

std.conv.ConvException C:\APP\D\dmd2\windows\bin\..\..\src\phob
s\std\conv.d(3530): Can't parse string: "[" is missing

I cannot understand the meaning of this message.
Replacing s with s.dup to remove immutable doesn't help.
Do I need to use cast?

Regards,
Aki
Nov 11 2017
next sibling parent Guillaume Piolat <contact spam.com> writes:
On Saturday, 11 November 2017 at 15:38:18 UTC, aki wrote:

 Hello,

 This will be trivial question but I cannot figure out
 what's wrong. I want to convert string to an array of ubyte.

 import std.conv;
 void main() {
         auto s = "hello";
         ubyte[] b = to!(ubyte[])(s);
 }

 It compiles but cause run time error:

 std.conv.ConvException C:\APP\D\dmd2\windows\bin\..\..\src\phob
s\std\conv.d(3530): Can't parse string: "[" is missing

 I cannot understand the meaning of this message.
 Replacing s with s.dup to remove immutable doesn't help.
 Do I need to use cast?

 Regards,
 Aki


to!(ubyte[]) is a semantic transformation that tries to parse an 
array literal it seems.

You can use slice casting instead:

      import std.conv;
      void main() {
           auto s = "hello";
           ubyte[] b = cast(ubyte[])(s.dup);
      }
Nov 11 2017
prev sibling parent reply Mike Parker <aldacron gmail.com> writes:
On Saturday, 11 November 2017 at 15:38:18 UTC, aki wrote:

 Hello,

 This will be trivial question but I cannot figure out
 what's wrong. I want to convert string to an array of ubyte.

 import std.conv;
 void main() {
         auto s = "hello";
         ubyte[] b = to!(ubyte[])(s);
 }

 It compiles but cause run time error:

 std.conv.ConvException C:\APP\D\dmd2\windows\bin\..\..\src\phob
s\std\conv.d(3530): Can't parse string: "[" is missing

 I cannot understand the meaning of this message.
 Replacing s with s.dup to remove immutable doesn't help.
 Do I need to use cast?

 Regards,
 Aki


I don't know about the error you're seeing, but the generic way 
to get an array of the underlying data type of a string is via 
std.string.representation.

import std.string;
auto s = "hello";
auto bytes = s.representation;

https://dlang.org/phobos/std_string.html#.representation

You can also simply cast to the appropriate type if you already 
know what type of string you have.

auto bytes = cast(immutable(ubyte)[])s;

Of course, if you need a mutable array you should dup:

auto bytes = cast(ubyte[])s.dup;
Nov 11 2017
next sibling parent user1234 <user1234 12.nl> writes:
On Saturday, 11 November 2017 at 15:48:59 UTC, Mike Parker wrote:

 On Saturday, 11 November 2017 at 15:38:18 UTC, aki wrote:
 auto bytes = cast(immutable(ubyte)[])s;

 Of course, if you need a mutable array you should dup:

 auto bytes = cast(ubyte[])s.dup;


Not only "should" but he "must" otherwise with string literals 
he'll get a violation access error.
Nov 11 2017
prev sibling next sibling parent bauss <jj_1337 live.dk> writes:
On Saturday, 11 November 2017 at 15:48:59 UTC, Mike Parker wrote:

 On Saturday, 11 November 2017 at 15:38:18 UTC, aki wrote:

 [...]


 I don't know about the error you're seeing, but the generic way 
 to get an array of the underlying data type of a string is via 
 std.string.representation.

 import std.string;
 auto s = "hello";
 auto bytes = s.representation;

 https://dlang.org/phobos/std_string.html#.representation

 You can also simply cast to the appropriate type if you already 
 know what type of string you have.

 auto bytes = cast(immutable(ubyte)[])s;

 Of course, if you need a mutable array you should dup:

 auto bytes = cast(ubyte[])s.dup;


That function needs to be highlighted more through documentation. 
I've always implemented my own versions to achieve the same as 
representation. I had no idea that function existed.

If just I knew.
Nov 11 2017
prev sibling parent aki <aki google.com> writes:
On Saturday, 11 November 2017 at 15:48:59 UTC, Mike Parker wrote:

 auto s = "hello";
 auto bytes = s.representation;

 https://dlang.org/phobos/std_string.html#.representation


Thank you for the replay.
Now I know.

aki
Nov 11 2017