From: William James <w_a_x_man@...>
Date: 2007-09-25T20:25:04+09:00
Subject: Re: I am new to Ruby and I could use some expert advice as to how I can make this code run faster.

On Sep 24, 6:50 pm, "Ilmari Heikkinen" <ilmari.heikki...@gmail.com>
wrote:
> On 9/24/07, Ilmari Heikkinen <ilmari.heikki...@gmail.com> wrote:
>
> > On 9/24/07, Joel VanderWerf <vj...@path.berkeley.edu> wrote:
> > > On 9/24/07, Ilmari Heikkinen <ilmari.heikki...@gmail.com> wrote:
> > > ...
> > >  > And here's a C version:
>
> > > To give C its fair due, you might try with
>
> > >     unsigned long *buf;
>
> > > and
>
> > >         buf[i] |= 0x80808080;
>
> > > (and the other necessary changes, of course).
>
> > And a version with 64-bit ints was even faster. But it had a bug too.
>
> > Anyone wish to contribute working versions :)?
>
> Guess not, so here's one:
>
> $ time ./scramble64 trace trace.scramblec
>
> real    0m0.022s
> user    0m0.004s
> sys     0m0.020s
>
> $ export RUBYOPT=  # -rubygems takes ~40ms
> $ time ruby -rscramble -e 'scramble_nobu("trace")'
>
> real    0m0.049s
> user    0m0.016s
> sys     0m0.032s
>
> $ diff trace.scramble*
> $
>
> $ cat scramble64.c
>
> #include <stdlib.h>
> #include <stdio.h>
> #include <sys/types.h>
> #include <sys/stat.h>
> #include <unistd.h>
>
> #define BUF_SIZE 4096
>
> int main(int argc, char** argv) {
>  int i, j, k, rsz, wsz;
>  FILE *in_f, *out_f;
>  unsigned long long isz;
>  struct stat st;
>  long long buf[BUF_SIZE];
>
>  if (argc != 3) {
>    printf("USAGE: %s INFILE OUTFILE\n", argv[0]);
>    return 1;
>  }
>
>  isz = sizeof(long long);
>
>  in_f = fopen(argv[1], "r");
>  if (NULL == in_f) {
>    printf("Failed to open input file %s\n", argv[0]);
>    return 2;
>  }
>
>  out_f = fopen(argv[2], "w");
>  if (NULL == out_f) {
>    printf("Failed to open output file %s\n", argv[1]);
>    fclose(in_f);
>    return 4;
>  }
>
>  fstat(fileno(in_f), &st);
>  for(i=0,j = st.st_size / (isz*BUF_SIZE); i<j; i++) {
>    rsz = fread(buf, isz, BUF_SIZE, in_f);
>    for(k=0; k<rsz; k++)
>      buf[k] |= 0x8080808080808080;
>    wsz = fwrite(buf, isz, rsz, out_f);
>    if (wsz != rsz) {
>      printf("Failed to write to output file\n");
>      break;
>    }
>  }
>  rsz = fread(buf, 1, isz*BUF_SIZE, in_f);
>  for(k=0; k<rsz; k++)
>    ((char*)buf)[k] |= 0x80;
>  wsz = fwrite(buf, 1, rsz, out_f);
>  if (wsz != rsz) {
>    printf("Failed to write to output file\n");
>  }
>
>  fclose(in_f);
>  fclose(out_f);
>  return 0;}

Here's my version in FreeBasic.


#define BUF_SIZE 4096

function scramble( filename as string ) as double
  dim outname as string
  dim as integer  in_handle, out_handle, i, size
  dim buffer( 0 to BUF_SIZE - 1 ) as byte
  dim p as longint ptr

  outname = filename & ".scrambled"
  in_handle = freefile
  if open( filename, for binary  access read,  as in_handle) then
    ? "Can't read "; filename
    end 2
  end if
  out_handle = freefile
  if open( outname, for binary access write as out_handle) then
    ? "Can't write to "; outname
    close in_handle
    end 4
  end if
  while not eof( in_handle )
    size = seek( in_handle )
    get #in_handle, , buffer()
    size = seek( in_handle ) - size
    p = @buffer(0)
    while p < @buffer( BUF_SIZE )
      *p = *p or &h8080808080808080
      p += 1
    wend
    if put( #out_handle, , buffer(0), size ) then
      ? "Failed while writing to "; outname
      exit while
    end if
  wend
  close  '-- Caution.  Closes all open files.
  return 0.0
end function


if command(1) = "" then
  ? "Give me a filename next time."
  end 1
end if
print -timer + scramble( command(1) ) + timer