[3/3] msvcrt: Implement 4k block flushing behavior.

[Piotr Caban]

On 05/31/14 01:00, Grazvydas Ignotas wrote:
> +        } else if(wrcnt >= MSVCRT_WRITE_BLOCK_SIZE) {
> +            if(msvcrt_set_write_direction(file) != 0)
> +                break;
> +
> +            if(file->_bufsiz && file->_ptr != file->_base)
> +                if(msvcrt_flush_buffer(file) == MSVCRT_EOF)
> +                    break;
> +
> +            if(MSVCRT__write(file->_file, ptr, MSVCRT_WRITE_BLOCK_SIZE) <= 0) {
> +                file->_flag |= MSVCRT__IOERR;
> +                break;
> +            }
> +            written += MSVCRT_WRITE_BLOCK_SIZE;
> +            wrcnt -= MSVCRT_WRITE_BLOCK_SIZE;
> +            ptr = (const char*)ptr + MSVCRT_WRITE_BLOCK_SIZE;
This doesn't look right for me. It doesn't make sense to have some 
special size blocks written in different way.

I think this is caused by 2 differences in native and wine's 
implementation of fwrite:
  - if you check file->_bufsiz value on windows it's set to 4096 (on 
wine it's 512), this is probably causing the flash to be done when 4096 
bytes are written
  - probably there's some kind of optimization that writes integral 
number of buffers directly to file
  - I was not checking it but maybe native flushes the output when 
buffer is full, wine will exit fwrite with full buffer in this case

I've also seen that _bufsiz is set to 0 on wine if buffer was not yet 
allocated. On windows it's value is 4096 just after opening the file.

Cheers,
Piotr