Here is the algorithm in ruby...

require 'digest'

# PART_SIZE should match the chosen part size of the multipart upload
# Set here as 10MB
PART_SIZE = 1024*1024*10 

class File
  def each_part(part_size = PART_SIZE)
    yield read(part_size) until eof?
  end
end

file = File.new('<path_to_file>')

hashes = []

file.each_part do |part|
  hashes << Digest::MD5.hexdigest(part)
end

multipart_hash = Digest::MD5.hexdigest([hashes.join].pack('H*'))
multipart_etag = "#{multi_part_hash}-#{hashes.count}"

Thanks to Shortest Hex2Bin in Ruby and Multipart Uploads to S3 ...

Here is the algorithm in ruby...

require 'digest'

# PART_SIZE should match the chosen part size of the multipart upload
# Set here as 10MB
PART_SIZE = 1024*1024*10 

class File
  def each_part(part_size = PART_SIZE)
    yield read(part_size) until eof?
  end
end

file = File.new('<path_to_file>')

hashes = []

file.each_part do |part|
  hashes << Digest::MD5.hexdigest(part)
end

multipart_hash = Digest::MD5.hexdigest([hashes.join].pack('H*'))
multipart_etag = "#{multipart_hash}-#{hashes.count}"

Thanks to Shortest Hex2Bin in Ruby and Multipart Uploads to S3 ...

Here is the algorithm in ruby...

require 'digest'

# PART_SIZE should match the chosen part size of the multipart upload
# Set here as 10MB
PART_SIZE = 1024*1024*10 

class File
  def each_part(part_size = PART_SIZE)
    yield read(part_size) until eof?
  end
end

file = File.new('<path_to_file>')

hashes = []

file.each_part do |part|
  hashes << Digest::MD5.hexdigest(part)
end

multipart_hash = Digest::MD5.hexdigest([hashes.join].pack('H*'))
multipart_etag = "#{multi_part_hash}-#{hashes.count}"

Thanks to Shortest Hex2Bin in Ruby and Multipart Uploads to S3 ...

Here is the algorithm in ruby...

require 'digest'

# PART_SIZE should match the chosen part size of the multipart upload
# Set here as 10MB
PART_SIZE = 1024*1024*10 

class File
  def each_part(part_size = PART_SIZE)
    yield read(part_size) until eof?
  end
end

file = File.new('<path_to_file>')

hashes = []

file.each_part do |part|
  hashes << Digest::MD5.hexdigest(part)
end

multipart_hash = Digest::MD5.hexdigest([hashes.join].pack('H*'))
multipart_etag = "#{multi_part_hash}-#{hashes.count}"

Thanks to Shortest Hex2Bin in Ruby and Multipart Uploads to S3 ...