About File.rawWrite

[Kai Meyer]

On 11/29/2011 08:00 AM, Denis Shelomovskij wrote:
> 29.11.2011 15:57, bearophile пишет:
>> This D2 program runs in about 5.13 seconds on my PC:
>>
>>
>> import std.stdio;
>> void main() {
>> auto f = File("bytes_test.dat", "wb");
>> ubyte[3] RGB;
>> foreach (_; 0 .. 1_000_000)
>> f.rawWrite(RGB);
>> }
>>
>>
>>
>> While this C program runs in about 0.14 seconds:
>>
>>
>> #include<stdio.h>
>> int main() {
>> FILE *f = fopen("bytes_test.dat", "wb");
>> unsigned char RGB[3] = {0};
>> int i;
>> for (i = 0; i< 1000000; i++)
>> fwrite(RGB, 1, 3, f);
>> return 0;
>> }
>>
>>
>> Is my D2 program wrong, or is File.rawWrite in need of some improvements?
>>
>> (Writing 3 bytes at a time is not efficient, but the C code shows that
>> the runtime is acceptable for me for small files).
>>
>> Bye,
>> bearophile
>
> Your OS is Windows, right? On Windows, rawWrite and rawRead always
> flushes stream, sets binary mode, reads/writes, flushes stream again,
> sets previous mode. This is definitely unnecessary slow - at least it
> should change mode only if needed (the file is opened in a text mode).
> The better solution is to change all other functions so the file mode
> will be changed lazily (for a text file, raw* functions will change file
> mode and leave file in this mode until a call of a function, that really
> needs a file to be in a text mode).
>
> By the way, why this changing mode behaviour is Windows only? Yes, it is
> clearly documented that this is the case, but it isn't documented _why_
> this is the case.
>
> Quick link to the current rawRead implementation (for happy owners of
> Google's Chrome, the fastest beautiful web browser that can BSOD your
> Windows even without administrator rights) (the link isn't for Firefox:
> it will slow down the browser and be displayed incorrectly):
> https://github.com/D-Programming-Language/phobos/blob/master/std/stdio.d#L458
>
My firefox handled the link just fine. Ofcourse my dev machine is an 8 
core i7 with 16 GB of ram.....

-Kai Meyer