Unzip

Elixir library to stream zip file contents. Works with remote files. Supports Zip64.

Overview

Unzip tries to solve problem of unzipping files from different types of storage (Aws S3, SFTP server, in-memory etc). It separates type of storage from zip implementation. Unzip can stream zip contents from any type of storage which implements Unzip.FileAccess protocol. You can selectively stream files from zip without reading the complete zip. This saves bandwidth and decompression time if you only need few files from the zip. For example, if a zip file contains 100 files and we only want one file then Unzip access only that particular file

Installation

def deps do
  [
    {:unzip, "~> x.x.x"}
  ]
end

Usage

# Unzip.LocalFile implements Unzip.FileAccess
zip_file = Unzip.LocalFile.open("foo/bar.zip")

# `new` reads list of files by reading central directory found at the end of the zip
{:ok, unzip} = Unzip.new(zip_file)

# Alternatively if you have the zip file in memory as binary you can
# directly pass it to `Unzip.new(binary)` to unzip
#
# {:ok, unzip} = Unzip.new(<<binary>>)

# returns list of files along with metadata
file_entries = Unzip.list_entries(unzip)

# returns decompressed file stream
stream = Unzip.file_stream!(unzip, "baz.png")

# if you want to read the whole file as binary
#
# file_content = Enum.into(stream, <<>>, &IO.iodata_to_binary/1)

Supports STORED and DEFLATE compression methods. Supports zip64 specification.

Sample implementations of Unzip.FileAccess protocol

For Aws S3 using ExAws

defmodule Unzip.S3File do
  defstruct [:path, :bucket, :s3_config]
  alias __MODULE__

  def new(path, bucket, s3_config) do
    %S3File{path: path, bucket: bucket, s3_config: s3_config}
  end
end

defimpl Unzip.FileAccess, for: Unzip.S3File do
  alias ExAws.S3

  def size(file) do
    %{headers: headers} = S3.head_object(file.bucket, file.path) |> ExAws.request!(file.s3_config)

    size =
      headers
      |> Enum.find(fn {k, _} -> String.downcase(k) == "content-length" end)
      |> elem(1)
      |> String.to_integer()

    {:ok, size}
  end

  def pread(file, offset, length) do
    {_, chunk} =
      S3.Download.get_chunk(
        %S3.Download{bucket: file.bucket, path: file.path, dest: nil},
        %{start_byte: offset, end_byte: offset + length - 1},
        file.s3_config
      )

    {:ok, chunk}
  end
end


# Using S3File

aws_s3_config = ExAws.Config.new(:s3,
  access_key_id: ["key_id", :instance_role],
  secret_access_key: ["key", :instance_role]
)

file = Unzip.S3File.new("pets.zip", "pics", aws_s3_config)
{:ok, unzip} = Unzip.new(file)
files = Unzip.list_entries(unzip)

Unzip.file_stream!(unzip, "cats/kitty.png")
|> Stream.into(File.stream!("kitty.png"))
|> Stream.run()

For zip file in SFTP server

defmodule Unzip.SftpFile do
  defstruct [:channel_pid, :connection_ref, :handle, :file_path]
  alias __MODULE__

  def new(host, port, sftp_opts, file_path) do
    :ok = :ssh.start()

    {:ok, channel_pid, connection_ref} =
      :ssh_sftp.start_channel(to_charlist(host), port, sftp_opts)

    {:ok, handle} = :ssh_sftp.open(channel_pid, file_path, [:read, :raw, :binary])

    %SftpFile{
      channel_pid: channel_pid,
      connection_ref: connection_ref,
      handle: handle,
      file_path: file_path
    }
  end

  def close(file) do
    :ssh_sftp.close(file.channel_pid, file.handle)
    :ssh_sftp.stop_channel(file.channel_pid)
    :ssh.close(file.connection_ref)
    :ok
  end
end

defimpl Unzip.FileAccess, for: Unzip.SftpFile do
  def size(file) do
    {:ok, file_info} = :ssh_sftp.read_file_info(file.channel_pid, file.file_path)
    {:ok, elem(file_info, 1)}
  end

  def pread(file, offset, length) do
    :ssh_sftp.pread(file.channel_pid, file.handle, offset, length)
  end
end


# Using SftpFile

sftp_opts = [
  user_interaction: false,
  silently_accept_hosts: true,
  rekey_limit: 1_000_000_000_000,
  user: 'user',
  password: 'password'
]

file = Unzip.SftpFile.new('127.0.0.1', 22, sftp_opts, '/home/user/pics.zip')

try do
  {:ok, unzip} = Unzip.new(file)
  files = Unzip.list_entries(unzip)

  Unzip.file_stream!(unzip, "cats/kitty.png")
  |> Stream.into(File.stream!("kitty.png"))
  |> Stream.run()
after
  Unzip.SftpFile.close(file)
end