GDBMish

Convert crystal data structures into a gdbm_dump ASCII format.

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

1. Add the dependency to your shard.yml:

   dependencies:
     gdbmish:
       github: fnordfish/gdbmish

2. Run shards install

Usage

Create a GDBM Dump:

require "gdbmish"

# Get dump as String
string = Gdbmish::Dump.ascii({"key1" => "value", "key2" => "value2"})

# Write directly into File (or any other IO)
File.open("my_db.dump", "w") do |file|
  Gdbmish::Dump.ascii({"key1" => "value", "key2" => "value2"}, 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 |appender|
    MyDataSource.each do |key, value|
      appender << {key.to_s, value.to_s}
    end
  end
end

On the target host, use a tool like gdbm_load to convert the dump into a db that works with that hosts gdbm.

Read a GDBM Dump:

reader = Gdbmish::Read::Ascii.new(File.open("my.dump"))

# 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

Development

• Run specs using crystal spec
• Format files using crystal tool format

Limitations

• Currently only supports the ASCII format and not the Binary format

Contributing

1. Fork it (https://github.com/fnordfish/gdbmish/fork)
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create a new Pull Request

Contributors

• Robert Schulze - creator and maintainer