show hdisk gpt part info

showgpt.rb

require 'zlib'

def show_lba0(rawdata)
  puts "LBA0 ( MBR  or  PMBR )"
  mbr = rawdata[446...512]
  if mbr.size!=66 ||  mbr[-2..-1].unpack('CC') != [0x55, 0xaa]
    puts "Not valid MRB part data"
    puts
    return
  end
  pss = []
  4.times do |n|
    dx = mbr[n*16,16]
    i=0
    x1 = dx[i...i+=1].unpack('C')[0] #part state (00-> not active, 80-> active)
  
    x2 = dx[i...i+=1].unpack('C')[0] # begin disk head
  
    v1 = dx[i...i+=1].unpack('C')[0] 
    x3 = v1&0b111111 # begin sector
    x4 = ((v1&0b11000000)<<2) + dx[i...i+=1].unpack('C')[0] # begin cylinder
  
    x5 = dx[i...i+=1].unpack('C')[0] #filesystem flag
  
    x6 = dx[i...i+=1].unpack('C')[0] # end disk head
    v1 = dx[i...i+=1].unpack('C')[0] 
    x7 = v1&0b111111 # end sector
    x8 = ((v1&0b11000000)<<2) + dx[i...i+=1].unpack('C')[0] # end cylinder
  
    x9 = dx[i...i+=4].unpack('I')[0] # begin sector(obs)
    x10 = dx[i...i+=4].unpack('I')[0] * 512 # part size, sector number
    pss << [x1, x2, x3, x4, x5, x6, x7, x8, x9, x10]
  end

  puts "partstate | begin head | sector | cylinder | fs flag | end head | sector | cylinder | obs pos(sector) | part size(byte)"
  pss.each do |x|
    p x
  end
  puts
end

def show_lba1(rawdata)
  puts "LBA1 ( GPT info table )"
  dx = rawdata[512, 512]
  dx2 = dx.clone[0..91]
  dx2[16, 4]="\x00\x00\x00\x00"
  if (a=Zlib.crc32(dx2).to_s(16)) != (b=dx[16, 4].unpack('L')[0].to_s(16))
    puts "crc check error #{a}  #{b} #{dx[16, 4].bytes}"
    puts
    return
  end

  i = 0
  p dx[i...i+=8].unpack('a*')[0] # 'EFI PART'
  p dx[i...i+=4].unpack('cccc') #[0,0,1,0]
  p dx[i...i+=4].unpack('I')[0] #92 if version==1.0
  p dx[i...i+=4].unpack('L')[0].to_s(16) #set to 0, this 92 bytes crc32
  p dx[i...i+=4].unpack('cccc') #[0,0,0,0]
  p dx[i...i+=8].unpack('q')[0] #this lba position
  p dx[i...i+=8].unpack('q')[0] #backup lba position
  p dx[i...i+=8].unpack('q')[0] #first part lba
  p dx[i...i+=8].unpack('q')[0] #last part lba
  p dx[i...i+=16].unpack('C*').map { |e| "%02X"%e }.join # harddisk UUID
  p dx[i...i+=8].unpack('q')[0] #partitem begin lba , 2 if master
  p dx[i...i+=4].unpack('I')[0] #partitem, default 128 
  p dx[i...i+=4].unpack('I')[0] #partitem size, default 128
  p dx[i...i+=4].unpack('I')[0].to_s(16) #crc32
  puts
end

def show_lbax(rawdata)
  puts "LBA2..33 ( GPT partitem infos )"
  ps = rawdata[1024, 128*128]
  pss = []
  128.times do |n|
    dx = ps[n*128, 128]
    break if dx.empty?
    next if dx == "\x00" * 128
    i = 0
    x1 = dx[i...i+=16].unpack('C*').map { |e| "%02X"%e }.join # part type UUID
    x2 = dx[i...i+=16].unpack('C*').map { |e| "%02X"%e }.join # part UUID
    x3 = bb = dx[i...i+=8].unpack('q')[0] #begin lba
    x4 = ee = dx[i...i+=8].unpack('q')[0] #end lba
    x5 = dx[i...i+=8].unpack('q')[0] #attrib
    x6 = dx[i...i+=72].unpack('S') # 32's UTF-16
    x7 = (ee-bb+1)*512
    pss << [x1, x2, x3, x4, x5, x6, x7]
  end

  puts "part type UUID    | part UUID | begin lba | end lba | attrib | 32's UTF-16  |  part size (byte)"
  pss.each do |x|
    p x
  end
  puts
end



if __FILE__ == $0
  if ARGV.size != 1
    abort %Q{syntax:
    dd if=/dev/sda of=sda.img bs=512 count=35
    ruby showgpt.rb sda.img}
  end
  rawdata = File.binread(ARGV[0])
  show_lba0(rawdata)
  show_lba1(rawdata)
  show_lbax(rawdata)
end