include/mcld/Target/ELFAttributeData.h

//===- ELFAttributeData.h -------------------------------------------------===//
//
//                     The MCLinker Project
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#ifndef MCLD_TARGET_ELFATTRIBUTEDATA_H_
#define MCLD_TARGET_ELFATTRIBUTEDATA_H_

#include <stdint.h>
#include <string>
#include <utility>

namespace mcld {

class ELFAttributeValue;
class Input;
class LinkerConfig;

/** \class ELFAttributeData
 *  \brief ELFAttributeData handles data in vendor attribute subsection.
 */
class ELFAttributeData {
 public:
  typedef uint32_t TagType;

  // Generic attribute tags shared between all vendors
  enum {
    Tag_NULL = 0,
    Tag_File = 1,
    Tag_Section = 2,
    Tag_Symbol = 3,
  };

 public:
  explicit ELFAttributeData(const char* pVendor) : m_Vendor(pVendor) {}

  virtual ~ELFAttributeData() {}

 public:
  inline const std::string& getVendorName() const { return m_Vendor; }

  /// getAttributeValue - query the data store for the attribute value of the
  /// given tag.
  virtual const ELFAttributeValue* getAttributeValue(TagType pTag) const = 0;

  /// getOrCreateAttributeValue - obtain attribute value for the given tag and
  /// create if it does not exist.
  ///
  /// It returns a pair containing the attribute value instance (guaranteed to
  /// be non-NULL) and a boolean value indicating whether the instance is newly
  /// created (true) or not (false.)
  virtual std::pair<ELFAttributeValue*, bool> getOrCreateAttributeValue(
      TagType pTag) = 0;

  /// preMerge - hooks to call before starting merge the attribute data in an
  /// input.
  virtual bool preMerge(const Input& pInput) { return true; }

  /// merge - implement logics to merge input attribute to the output.
  virtual bool merge(const LinkerConfig& pConfig,
                     const Input& pInput,
                     TagType pTag,
                     const ELFAttributeValue& pInAttr) = 0;

  /// postMerge - hooks to call after finishing merge the attribute data from an
  /// input.
  virtual bool postMerge(const LinkerConfig& pConfig, const Input& pInput) {
    return true;
  }

  /// sizeOutput - obtain number of bytes required to encode the attribute data.
  virtual size_t sizeOutput() const = 0;

  /// emit - write out attribute data to the buffer and return the number of
  /// bytes written
  virtual size_t emit(char* pBuf) const = 0;

 public:
  /// ReadTag - read an attribute tag from input buffer.
  ///
  /// If the read succeeds, pBuf moves to the new position just pass the end of
  /// the tag in the buffer and pBufSize decreases the size of tag in the
  /// buffer. Otherwise, this function will return false and change nothing
  /// except leaving undefined value in pTag.
  static bool ReadTag(TagType& pTag, const char*& pBuf, size_t& pBufSize);

  /// ReadValue - read an attribute value from input buffer
  ///
  /// Similar with ReadTag() while this reads attribute value from the input
  /// buffer. Note that the value type of the attribute must be properly set in
  /// pValue prior the call.
  static bool ReadValue(ELFAttributeValue& pValue,
                        const char*& pBuf,
                        size_t& pBufSize);

  /// WriteAttribute - write an attribute tag plus value to buffer.
  ///
  /// On success, the pBuf moves to the new position just pass the end of the
  /// attribute data just written. Otherwise, it returns false and leaves pBuf
  /// in an undefined position. Note that buffer is guaranteed to be able to
  /// contain the attribute data.
  static bool WriteAttribute(TagType pTag,
                             const ELFAttributeValue& pValue,
                             char*& pBuf);

 private:
  const std::string m_Vendor;
};

}  // namespace mcld

#endif  // MCLD_TARGET_ELFATTRIBUTEDATA_H_