bin/zxdb/symbols/lazy_symbol.h

// Copyright 2018 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#pragma once

#include <stdint.h>

#include <memory>

#include "lib/fxl/memory/ref_ptr.h"

namespace zxdb {

class Symbol;
class SymbolFactory;

// Symbols can be complex and in many cases are not required. This class holds
// enough information to construct a type from the symbol file as needed. Once
// constructed, it will cache the type for future use.
class LazySymbol {
 public:
  LazySymbol();  // Creates a !is_valid() one.
  LazySymbol(const LazySymbol& other);
  LazySymbol(LazySymbol&& other);
  LazySymbol(fxl::RefPtr<SymbolFactory> factory, void* factory_data_ptr,
             uint32_t factory_data_offset);
  // Creates a non-lazy one, mostly for tests.
  explicit LazySymbol(fxl::RefPtr<Symbol> symbol);
  explicit LazySymbol(const Symbol* symbol);
  ~LazySymbol();

  LazySymbol& operator=(const LazySymbol& other);
  LazySymbol& operator=(LazySymbol&& other);

  // Validity tests both for the factory and the symbol since non-lazy ones
  // don't need a factory.
  bool is_valid() const { return factory_.get() || symbol_.get(); }
  explicit operator bool() const { return is_valid(); }

  // Returns the type associated with this LazySymbol. If this class is invalid
  // or the symbol fails to resolve this will return an empty one. It will
  // never return null.
  const Symbol* Get() const;

 private:
  // May be null if this contains no type reference.
  fxl::RefPtr<SymbolFactory> factory_;

  // Opaque data passed to the factory to construct a type Symbol for this.
  // In the DWARF factory, this is a DWARFUnit* and unit DIE offset.
  void* factory_data_ptr_ = nullptr;
  uint32_t factory_data_offset_ = 0;

  mutable fxl::RefPtr<Symbol> symbol_;
};

}  // namespace zxdb