gdbmish

GDBMish

Create and read GDBM dump ASCII files.

Citing gdbm:

Gdbm files have never been `portable' between different operating systems, system architectures, or potentially even different compilers. Differences in byte order, the size of file offsets, and even structure packing make gdbm files non-portable.

Therefore, if you intend to send your database to somebody over the wire, please dump it into a portable format using gdbm_dump and send the resulting file instead. The receiving party will be able to recreate the database from the dump using the gdbm_load command.

GDBMish does that by reimplementing the gdbm_dump ASCII format without compiling against gdbm

Installation

Install the gem and add to the application's Gemfile by executing:

bundle add gdbmish

If bundler is not being used to manage dependencies, install the gem by executing:

gem install gdbmish

Usage

require 'gdbmish'

# Create a dump into a StringIO and read it back
io = StringIO.new
dumper = Gdbmish::Dump::Ascii.new(file: "test.db", uid: "1000", user: "ziggy", gid: "1000", group: "staff", mode: 0o640)
dumper.dump(io) do |dump|
    dump.push("some_key", "Some Value")
    dump.push("otherKey", "Other\nValue")
end

io.rewind
reader = Gdbmish::Read::Ascii.new(io, load_meta: :count)
reader.data.to_h  # => {"some_key"=>"Some Value", "otherKey"=>"Other\nValue"}
reader.meta.count # => 2
reader.meta.file  # => "test.db"
reader.meta.uid   # => "1000"

# Dumping a Hash

data = {"key1" => "value", "key2" => "value2"}

# Get dump as String
string = Gdbmish::Dump.ascii(data)

# Write directly into File (or any other IO)
File.open("my_db.dump", "w") do |file|
  Gdbmish::Dump.ascii(data, file)
end

# Provide an original filename
Gdbmish::Dump.ascii(data, file: "my.db")

# Provide an original filename and file permissions
Gdbmish::Dump.ascii(data, file: "my.db", uid: "1000", gid: "1000", mode: 0o600)

# Iterate over a data source and push onto an IO
fileoptions = {file: "my.db", uid: "1000", user: "ziggy", gid: "1000", group: "staff", mode: 0o600}
File.open("my.dump", "w") do |file|
  Gdbmish::Dump::Ascii.new(**fileoptions).dump(io) do |dump|
    MyDataSource.each do |key, value|
      dump.push(key.to_s, value.to_s)
    end
  end
end

# Read from a file

file = File.open("my.dump")
# The file is read lazily, don't close it before you're done reading from it
reader = Gdbmish::Read::Ascii.new(file)

# get meta data
reader.meta.file # => "my.db"

# either iterate over data:
reader.data do |key, value|
  puts "#{key.inspect} => #{value.inspect}"
end

# or use the Iterator to transform into Hash
reader.data.to_h

file.close

Shenanigans

Reading data from a dump file is a lazy one way street. Once data is read, it's read. You can't seek or peak.
However, you can rewind the IO and start over.

File.open("my.dump") do |io|
  reader = Gdbmish::Read::Ascii.new(io)
  reader.data.to_h # => {"key1"=>"value1", "key2"=>"value2"}
  reader.data.to_h # => {}

  io.rewind
  reader.data.to_h # => {"key1"=>"value1", "key2"=>"value2"}

  reader.data.first # => ["key1", "value1"]
  reader.data.first # => ["key2", "value2"]
  io.rewind
  reader.data.first # => ["key1", "value1"]
end

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and the created tag, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/fnordfih/gdbmish.rb. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the code of conduct.

License

The gem is available as open source under the terms of the MIT License.

Code of Conduct

Everyone interacting in the GDBMish project's codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.