Ruby FFI is a cross-VM library for calling foreign functions (i.e. C or C++). It isn’t obvious from the introductory blog posts how you specify which library to use, but the answer isn’t hard to find in the source.
Examples speak louder than words:
extend FFI::Library
# The lib name gets spackled with platform-specific
# prefix and suffix. On Mac OS X, e.g., the ffi_lib
# name turns into 'libmdb.dylib'
ffi_lib 'mdb'
# Who needs enum, anyway?
NOFLAGS = 0
MDB_TABLE = 1
attach_function :mdb_init, [], :void
attach_function :mdb_exit, [], :void
# In the libmdb headers, you'll find that this function
# actually returns a pointer to an MDBHandle struct.
# FFI::Struct would likely help out here, but just
# calling the return result a :pointer works for now.
attach_function :mdb_open, [ :string, :int], :pointer
attach_function :mdb_close, [ :pointer], :void
MDB.mdb_init
db = MDB.mdb_open( path, MDB::NOFLAGS)
yield db
MDB.mdb_close(db)
MDB.mdb_exit
end
attach_function :mdb_dump_catalog, [:pointer, :int], :pointer
end
MDB.open('mdb_files/sample.mdb') do |db|
MDB.mdb_dump_catalog(db, MDB::MDB_TABLE)
end