Hi,

I read several posts about reading in files, but I can't find the "best" way for my purpose. I am using std.file in the examples bellow.

1.) I'm trying to read an OpenGL Vertex and Fragment Shader. The wired thing on my approach is that it works ... sometimes, but sometimes the Shaders cannot be compiled.
So how should I read a file as one complete char[] in a safe way ? This is my way:
  auto fileFrag = cast( GLchar[] )readText( "Shader/Shader_01.frag" ) ;
  const GLchar * fragSource = cast( GLchar * )fileFrag ;

2.) I am reading in Vertex Data from a file. It holds only floats, e.g.:
-38.3887 97.7612 -10.5231
-38.3572 98.8543 -10.5064
...
There is no metadata in the file giving information about the count of values. I use a dynamic array, and append each line to my array, which I think is not the most clever or efficient approach:
  vertices = new GLfloat[0] ;
  auto file = File( "Data/Vertices_01.txt" ) ;
  foreach( line ; file.byLine() )
    vertices ~= to!( GLfloat[] )( line.split ) ;
  file.close() ;

Can I get all floats ( words as float ) from a file at once without using file.byLine into a Dynamic array ( or fixed array, I know the word count ) ? If not, what would be the most efficient approach for these kind of files ( they might get huge ) ?

3.) When reading a file line by line it would be nice to have the count of Lines of the file ( numLines ) and the line number in a variable, so I could random access a fixed size array with this line number. I tried this code, which works for arrays, but unfortunately not for lines ( for me ).
  GLfloat arrVertex[ numLines ][ 3 ] ;
  foreach( i , line ; file.byLine() )
    arrVertex[ i ] = to!( GLfloat[3] )( line.split ) ;

How can I get the Line count from a file, and how can I get the line numbers without initializing a counter in front of the foreach loop and increase it manually inside the loop ?

Thank you for any advice,

Cheers, ParticlePeter !

I have a funky feeling you're reading NeHe? Try this:

https://github.com/AndrejMitrovic/DNeonHelium/blob/master/Samples/win32/lesson25.d#L87

Andrej Mitrovic Wrote:

> I have a funky feeling you're reading NeHe? Try this:

THX, that's very cool, will definitly look deeper into these samples. I know NeHe, but am following The OpenGL Book, and using DerelictSDL. This shows me how you do it, but does not answer my questions, my Shader Issue in particular.
I need to add that when I use the Shaders from within my code, defined as a String, the Shader Program compiles and links always, but when I read the same Shaders from a file with my method they compile and link randomly. How do you read in Shaders ?

Cheers, ParticlePeter !

ParticlePeter:

>   auto fileFrag = cast( GLchar[] )readText( "Shader/Shader_01.frag" ) ;
>   const GLchar * fragSource = cast( GLchar * )fileFrag ;

Avoid raw casts every time it is possible. The second cast is not necessary, using the ".ptr".


> I use a dynamic array, and append each line to my array, which I think is not the most clever or efficient approach:

Try std.array.appender.


> 3.) When reading a file line by line it would be nice to have the count of Lines of the file ( numLines ) and the line number in a variable, so I could random access a fixed size array with this line number.

Fixed-sized arrays are often not good if you need to put lot of data inside them, because the stack has limited space (unless you allocate the fixed sized array on the heap).


> Can I get all floats ( words as float ) from a file at once without using file.byLine into a Dynamic array ( or fixed array, I know the word count ) ?

In theory std.conv.parse is useful for this:

import std.stdio, std.conv;
void main() {
    string s = "[[1,2],[3,4]]";
    auto p = parse!(double[][])(s);
    writeln(p);
}

In practice the signature of one parse overload is:
Target parse(Target, Source)(ref Source s, dchar lbracket = '[', dchar rbracket = ']', dchar comma = ',');

lbracket is a char instead of being a string, so I don't know how to parse a row that lacks commas and brackets. This seems an enhancement request.


> How can I get the Line count from a file,

You probably need to just iterate the file lines, and count them.


> and how can I get the line numbers without initializing a counter in front of the foreach loop and increase it manually inside the loop ?

With walkLength:


import std.stdio, std.range;
void main() {
    immutable size_t nLines = walkLength(File("data.txt").byLine());
    writeln(nLines);
}

Bye,
bearophile

> 2.) I am reading in Vertex Data from a file. It holds only floats, e.g.:
> -38.3887 97.7612 -10.5231 -38.3572 98.8543 -10.5064 ...
> There is no metadata in the file giving information about the count of values.
> 3.) When reading a file line by line it would be nice to have the count of Lines of the file ( numLines )

If each line takes at least 25 bytes, you can divide file size by 25 - this will be an estimation of number of lines.

On 12/12/2011 09:31, ParticlePeter wrote:
> Hi,
>
> I read several posts about reading in files, but I can't find the "best" way for my purpose. I am using std.file in the examples bellow.
>
> 1.) I'm trying to read an OpenGL Vertex and Fragment Shader. The wired thing on my approach is that it works ... sometimes, but sometimes the Shaders cannot be compiled.
> So how should I read a file as one complete char[] in a safe way ? This is my way:
>    auto fileFrag = cast( GLchar[] )readText( "Shader/Shader_01.frag" ) ;
>    const GLchar * fragSource = cast( GLchar * )fileFrag ;

string literals are zero terminated, but strings returned by library functions may not be.

Try appending a zero to the read string:

string fragString = readText( "Shader.vert" ) ~ "\0";

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