Database.cc

// Copyright (C) 2013-2014, Gabriel Dos Reis.
// All rights reserved.
// Written by Gabriel Dos Reis.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//     - Redistributions of source code must retain the above copyright
//       notice, this list of conditions and the following disclaimer.
//
//     - Redistributions in binary form must reproduce the above copyright
//       notice, this list of conditions and the following disclaimer in
//       the documentation and/or other materials provided with the
//       distribution.
//
//     - Neither the name of OpenAxiom. nor the names of its contributors
//       may be used to endorse or promote products derived from this
//       software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
// IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
// TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
// PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
// OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
// EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
// PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
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#include <open-axiom/Database>

namespace OpenAxiom {
   namespace VM {
      Database::Database(const std::string& path)
            : file(path), reader{ file.begin(), file.end() }, toc() {
      }

      Value
      Database::find_with(Value key, Lisp::Evaluator& ctx) {
         auto p = dict.find(key);
         if (p != dict.end())
            return p->second;
         if (reader.at_start()) {
            auto x = reader.read();
            auto offset = Lisp::retract_to_fixnum
               (Lisp::retract_to_pair(ctx.make_value(x))->head);
            auto n = FixnumBits(offset);
            reader.position(n);
            toc = Lisp::retract_to_pair(ctx.make_value(reader.read()));
         }
         else {
            auto data = Lisp::assoc(key, toc);
            if (data != Value::nil)
               return dict.insert({ key, data }).first->second;
         }
         return Value::nil;
      }
   }
}