include/mcld/Target/ELFAttribute.h

//===- ELFAttribute.h -----------------------------------------------------===//
//
//                     The MCLinker Project
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#ifndef MCLD_TARGET_ELFATTRIBUTE_H
#define MCLD_TARGET_ELFATTRIBUTE_H
#ifdef ENABLE_UNITTEST
#include <gtest.h>
#endif

#include <mcld/Support/MemoryRegion.h>
#include <mcld/Target/ELFAttributeData.h>

#include <llvm/ADT/SmallVector.h>
#include <llvm/ADT/StringRef.h>

namespace mcld {

class ELFAttributeData;
class GNULDBackend;
class Input;
class LDSection;
class LinkerConfig;

/** \class ELFAttribute
 *  \brief ELFAttribute is the attribute section in an ELF file.
 */
class ELFAttribute
{
public:
  // ARM [ABI-addenda], 2.2.3.
  static const char   FormatVersion = 'A';
  static const size_t FormatVersionFieldSize = sizeof(FormatVersion); // a byte
  static const size_t SubsectionLengthFieldSize = 4; // a 4-byte integer

  // MinimalELFAttributeSubsectionSize is the minimal number of bytes a valid
  // subsection in ELF attribute section should have.
  static const size_t MinimalELFAttributeSubsectionSize
      = 1 /* Tag_File, see ARM [ABI-addenda], 2.2.4 */ +
        4 /* byte-size, see ARM [ABI-addenda], 2.2.4 */;

  // MinimalELFAttributeSectionSize is the minimal number of bytes a valid ELF
  // attribute section should have.
  static const size_t MinimalELFAttributeSectionSize
      = FormatVersionFieldSize + SubsectionLengthFieldSize +
        2 /* vendor-name, a char plus '\0', see ARM [ABI-addenda], 2.2.3 */ +
        1 * MinimalELFAttributeSubsectionSize;

public:
  ELFAttribute(const GNULDBackend &pBackend, const LinkerConfig& pConfig)
    : m_Backend(pBackend), m_Config(pConfig) { }

  ~ELFAttribute();

public:
  /// merge - merge attributes from input (attribute) section
  bool merge(const Input &pInput, LDSection &pInputAttrSectHdr);

  /// sizeOutput - calculate the number of bytes required to encode this
  /// attribute data section
  size_t sizeOutput() const;

  /// emit - encode and write out this attribute section
  size_t emit(MemoryRegion &pRegion) const;

  inline const GNULDBackend &backend() const { return m_Backend; }

  inline const LinkerConfig &config() const { return m_Config; }

  // Place vendor's attribute data under the management.
  void registerAttributeData(ELFAttributeData& pAttrData);

private:
  /** \class Subsection
   *  \brief A helper class to wrap ELFAttributeData and to provide general
   *  interfaces for ELFAttribute to operate on
   */
  class Subsection {
  public:
    Subsection(ELFAttribute &pParent, ELFAttributeData &pAttrData)
      : m_Parent(pParent), m_AttrData(pAttrData) { }

  public:
    bool isMyAttribute(llvm::StringRef pVendorName) const
    {
      return (m_AttrData.getVendorName() == pVendorName);
    }

    /// merge -  Merge the attributes from the section in the input data.
    bool merge(const Input &pInput, ConstAddress pData, size_t pSize);

    /// sizeOutput - calculate the number of bytes required to encode this
    /// subsection
    size_t sizeOutput() const;

    /// emit - write out this attribute subsection to the buffer.
    size_t emit(char *pBuf) const;

  private:
    // The attribute section this subsection belongs to
    ELFAttribute &m_Parent;

    // The attribute data containing in this subsection
    ELFAttributeData &m_AttrData;
  };

  // Obtain the corresponding subsection of the specified vendor
  Subsection *getSubsection(llvm::StringRef pVendorName) const;

private:
  const GNULDBackend &m_Backend;

  const LinkerConfig &m_Config;

  // There is at most two subsections ("aeabi" and "gnu") in most cases.
  llvm::SmallVector<Subsection*, 2> m_Subsections;
};

} // namespace of mcld

#endif