Hello D community!

I'm developing an application that must work on audio especially playback Ogg files. So I took library DerelictVorbis [0] testing basic functions like `ov_fopen`. The tests were successful so I decided to implement core components of the application using D and Derelict libraries.

Today I encountered a problem, the `ov_fopen` returns -1 instead of 0. It means that something goes wrong and the file that is pointed by a string is not opened. I figured out it so there is the error is not occurred when a file path is pointed by a string variable from CLI input arguments but it is occurred when the path is pointed by a string variable filled dynamically (for example file path is read from another file).

Here code goes

public import derelict.vorbis;
public import derelict.vorbis.file;

void main(string[] args) {
	DerelictVorbis.load();
	DerelictVorbisFile.load();
	OggVorbis_File _ovFile;

	immutable filepath = args[1];
	

	import std.file;
	import std.string;
	string filepath2 = "./name.txt".readText.strip;
	assert(filepath2 == filepath);
	int res = ov_fopen(filepath2.ptr, &_ovFile); // res == -1
	// int res = ov_fopen(filepath.ptr, &_ovFile); // res == 0
	assert(res == 0, "ov_fopen returns %d".format(res));
}

Actually I get it worked replacing `string filepath2` by `char[] filepath2` but filepath is string still and it works correctly.

So what detail The devil is in? Is there an issue in DerelictVorbis or in compiler. Don't I know something about implementation of strings or pointers in D?

Thanks in advance!

DMD 2.080
DerelictVorbis 2.0.0-beta.2

[0] https://github.com/DerelictOrg/DerelictVorbis

On Sunday, 24 June 2018 at 01:26:48 UTC, ANtlord wrote:
>
> Actually I get it worked replacing `string filepath2` by `char[] filepath2` but filepath is string still and it works correctly.

It doesn't work

On Sunday, 24 June 2018 at 01:43:41 UTC, ANtlord wrote:
> On Sunday, 24 June 2018 at 01:26:48 UTC, ANtlord wrote:
>>
>> Actually I get it worked replacing `string filepath2` by `char[] filepath2` but filepath is string still and it works correctly.
>
> It doesn't work

Vorbis is a C library, so you need to null terminate your string using toStringz. The reason why the one from the command line works is because it is already null terminate.

On 24/06/2018 1:26 PM, ANtlord wrote:
> Hello D community!
> 
> I'm developing an application that must work on audio especially playback Ogg files. So I took library DerelictVorbis [0] testing basic functions like `ov_fopen`. The tests were successful so I decided to implement core components of the application using D and Derelict libraries.
> 
> Today I encountered a problem, the `ov_fopen` returns -1 instead of 0. It means that something goes wrong and the file that is pointed by a string is not opened. I figured out it so there is the error is not occurred when a file path is pointed by a string variable from CLI input arguments but it is occurred when the path is pointed by a string variable filled dynamically (for example file path is read from another file).
> 
> Here code goes
> 
> public import derelict.vorbis;
> public import derelict.vorbis.file;
> 
> void main(string[] args) {
>      DerelictVorbis.load();
>      DerelictVorbisFile.load();
>      OggVorbis_File _ovFile;
> 
>      immutable filepath = args[1];
> 
> 
>      import std.file;
>      import std.string;
>      string filepath2 = "./name.txt".readText.strip;
>      assert(filepath2 == filepath);
>      int res = ov_fopen(filepath2.ptr, &_ovFile); // res == -1
>      // int res = ov_fopen(filepath.ptr, &_ovFile); // res == 0
>      assert(res == 0, "ov_fopen returns %d".format(res));
> }
> 
> Actually I get it worked replacing `string filepath2` by `char[] filepath2` but filepath is string still and it works correctly.
> 
> So what detail The devil is in? Is there an issue in DerelictVorbis or in compiler. Don't I know something about implementation of strings or pointers in D?
> 
> Thanks in advance!
> 
> DMD 2.080
> DerelictVorbis 2.0.0-beta.2
> 
> [0] https://github.com/DerelictOrg/DerelictVorbis

So where exactly is the null byte for the C string?

On Sunday, 24 June 2018 at 01:54:52 UTC, Nicholas Wilson wrote:
> On Sunday, 24 June 2018 at 01:43:41 UTC, ANtlord wrote:
>> On Sunday, 24 June 2018 at 01:26:48 UTC, ANtlord wrote:
>>>
>>> Actually I get it worked replacing `string filepath2` by `char[] filepath2` but filepath is string still and it works correctly.
>>
>> It doesn't work
>
> Vorbis is a C library, so you need to null terminate your string using toStringz. The reason why the one from the command line works is because it is already null terminate.

It works! Thank you!