minimal sqlite3 driver

mini-sqlite3.rb

#!/usb/bin/env ruby
require 'fiddle'
require 'fiddle/import'
require 'pp'
 
module Sqlite3
  SQLITE_OK = 0
 
  module Driver
    extend Fiddle::Importer
    dlload 'libsqlite3.dylib'
    extern 'char* sqlite3_errstr(int)'
    extern 'int sqlite3_open(const char *, sqlite3**)'
    extern 'int sqlite3_exec(sqlite3*, const char *, void *, void *, char **)'
    extern 'int sqlite3_close(sqlite3*)'
  end
 
  class Error < StandardError; end
 
  class Connection
    include Fiddle
    
    CALLBACK =[ TYPE_VOIDP, TYPE_INT, TYPE_VOIDP, TYPE_VOIDP ].freeze
 
    def initialize(uri)
      @db = Pointer.malloc(SIZEOF_VOIDP)
      check Driver.sqlite3_open(uri.to_s, @db.ref)
    end
 
    def close
      check Driver.sqlite3_close(@db)
    end
 
    def exec(stmt, &handler)
      @errptr = Pointer.malloc(SIZEOF_VOIDP)
      rownr = 0
      column_cache = {}
      cb = Closure::BlockCaller.new(TYPE_INT, CALLBACK) do |_, argc, argv, columns|
        row = {}
        argc.times do |i|
          column = column_cache[i] || begin
            column_cache[i] = (columns + i * SIZEOF_VOIDP).ptr.to_s
                                                          .downcase.to_sym
          end
          value = (argv + i * SIZEOF_VOIDP).ptr.to_s
          if value =~ /^\d+\.\d+$/
            value = value.to_f
          elsif value =~ /^\d+$/
            value = value.to_i
          end 
          row[column] = value
        end
        handler.call(row, rownr)
        rownr += 1
        0
      end if block_given?
 
      if Driver.sqlite3_exec(@db, stmt, cb, 0, @errptr.ref) != SQLITE_OK
        fail Error, @errptr.to_s
      end
    ensure
      @errptr.free
    end
 
    def check(error_code)
      if error_code != SQLITE_OK
        fail Error, Driver.sqlite3_errstr(error_code).to_s
      end
    end
  end
end
 
connection = Sqlite3::Connection.new(":memory:")
connection.exec "CREATE TABLE COMPANY("  +
                "ID INT PRIMARY KEY     NOT NULL," +
                "NAME           TEXT    NOT NULL," +
                "AGE            INT     NOT NULL," +
                "ADDRESS        CHAR(50)," +
                "SALARY         REAL );"
connection.exec "INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) "  +
                "VALUES (1, 'Paul', 32, 'California', 20000.00 ); " +
                "INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) "  +
                "VALUES (2, 'Allen', 25, 'Texas', 15000.00 ); "     +
                "INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY)" +
                "VALUES (3, 'Teddy', 23, 'Norway', 20000.00 );" +
                "INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY)" +
                "VALUES (4, 'Mark', 25, 'Rich-Mond', 65000.00 );"
connection.exec "SELECT * from COMPANY" do |row, i|
  p [i, row]
end
connection.close