Pretty file size in Ruby?

Question

I\'m trying to make a method that converts an integer that represents bytes to a string with a \'prettied up\' format.

Here\'s my half-working attempt:

Answer 1

This is my solution:

def filesize(size)
  units = ['B', 'KiB', 'MiB', 'GiB', 'TiB', 'Pib', 'EiB']

  return '0.0 B' if size == 0
  exp = (Math.log(size) / Math.log(1024)).to_i
  exp += 1 if (size.to_f / 1024 ** exp >= 1024 - 0.05)
  exp = 6 if exp > 6 

  '%.1f %s' % [size.to_f / 1024 ** exp, units[exp]]
end

Compared to other solutions it's simpler, more efficient, and generates a more proper output.

Format

Both to_filesize and to_human have issues with big numbers. format_mb has a weird case where for example '1 MiB' is considered '1024 KiB' which is something some people might want, but certainly not me.

    origin:       filesize    to_filesize      format_mb       to_human
       0 B:          0.0 B           0.0B            0 b         0.00 B
       1 B:          1.0 B           1.0B            1 b         1.00 B
      10 B:         10.0 B          10.0B           10 b        10.00 B
    1000 B:       1000.0 B        1000.0B         1000 b      1000.00 B
     1 KiB:        1.0 KiB          1.0KB         1024 b        1.00 KB
   1.5 KiB:        1.5 KiB          1.5KB       1536.0 b        1.50 KB
    10 KiB:       10.0 KiB         10.0KB      10.000 kb       10.00 KB
   100 KiB:      100.0 KiB        100.0KB     100.000 kb      100.00 KB
  1000 KiB:     1000.0 KiB       1000.0KB    1000.000 kb     1000.00 KB
     1 MiB:        1.0 MiB          1.0MB    1024.000 kb        1.00 MB
     1 Gib:        1.0 GiB          1.0GB    1024.000 mb        1.00 GB
     1 TiB:        1.0 TiB          1.0TB    1024.000 gb        1.00 TB
     1 PiB:        1.0 Pib          ERROR    1024.000 tb        1.00 PB
     1 EiB:        1.0 EiB          ERROR    1024.000 pb        1.00 EB
     1 ZiB:     1024.0 EiB          ERROR    1024.000 eb          ERROR
     1 YiB:  1048576.0 EiB          ERROR 1048576.000 eb          ERROR

Performance

Also, it has the best performance.

                      user     system      total        real
filesize:         2.740000   0.000000   2.740000 (  2.747873)
to_filesize:      3.560000   0.000000   3.560000 (  3.557808)
format_mb:        2.950000   0.000000   2.950000 (  2.949930)
to_human:         5.770000   0.000000   5.770000 (  5.783925)

I tested each implementation with a realistic random number generator:

def numbers
  Enumerator.new do |enum|
    1000000.times do
      exp = rand(5)
      num = rand(1024 ** exp)
      enum.yield num
    end
  end
end