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//===- DWARFAbbreviationDeclaration.h ---------------------------*- C++ -*-===//

//

// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.

// See https://llvm.org/LICENSE.txt for license information.

// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception

//

//===----------------------------------------------------------------------===//

#ifndef LLVM_DEBUGINFO_DWARF_DWARFABBREVIATIONDECLARATION_H

#define LLVM_DEBUGINFO_DWARF_DWARFABBREVIATIONDECLARATION_H

#include "llvm/ADT/SmallVector.h"

#include "llvm/ADT/iterator_range.h"

#include "llvm/BinaryFormat/Dwarf.h"

#include <cassert>

#include <cstddef>

#include <cstdint>

namespace llvm {

class DataExtractor;

class DWARFFormValue;

class DWARFUnit;

class raw_ostream;

class DWARFAbbreviationDeclaration {

public:

  struct AttributeSpec {

    AttributeSpec(dwarf::Attribute A, dwarf::Form F, int64_t Value)

        : Attr(A), Form(F), Value(Value) {

      assert(isImplicitConst());

    }

    AttributeSpec(dwarf::Attribute A, dwarf::Form F,

                  std::optional<uint8_t> ByteSize)

        : Attr(A), Form(F) {

      assert(!isImplicitConst());

      this->ByteSize.HasByteSize = ByteSize.has_value();

      if (this->ByteSize.HasByteSize)

        this->ByteSize.ByteSize = *ByteSize;

    }

    dwarf::Attribute Attr;

    dwarf::Form Form;

  private:

    /// The following field is used for ByteSize for non-implicit_const

    /// attributes and as value for implicit_const ones, indicated by

    /// Form == DW_FORM_implicit_const.

    /// The following cases are distinguished:

    /// * Form != DW_FORM_implicit_const and HasByteSize is true:

    ///     ByteSize contains the fixed size in bytes for the Form in this

    ///     object.

    /// * Form != DW_FORM_implicit_const and HasByteSize is false:

    ///     byte size of Form either varies according to the DWARFUnit

    ///     that it is contained in or the value size varies and must be

    ///     decoded from the debug information in order to determine its size.

    /// * Form == DW_FORM_implicit_const:

    ///     Value contains value for the implicit_const attribute.

    struct ByteSizeStorage {

      bool HasByteSize;

      uint8_t ByteSize;

    };

    union {

      ByteSizeStorage ByteSize;

      int64_t Value;

    };

  public:

    bool isImplicitConst() const {

      return Form == dwarf::DW_FORM_implicit_const;

    }

    int64_t getImplicitConstValue() const {

      assert(isImplicitConst());

      return Value;

    }

    /// Get the fixed byte size of this Form if possible. This function might

    /// use the DWARFUnit to calculate the size of the Form, like for

    /// DW_AT_address and DW_AT_ref_addr, so this isn't just an accessor for

    /// the ByteSize member.

    std::optional<int64_t> getByteSize(const DWARFUnit &U) const;

  };

  using AttributeSpecVector = SmallVector<AttributeSpec, 8>;

  DWARFAbbreviationDeclaration();

  uint32_t getCode() const { return Code; }

  uint8_t getCodeByteSize() const { return CodeByteSize; }

  dwarf::Tag getTag() const { return Tag; }

  bool hasChildren() const { return HasChildren; }

  using attr_iterator_range =

      iterator_range<AttributeSpecVector::const_iterator>;

  attr_iterator_range attributes() const {

    return attr_iterator_range(AttributeSpecs.begin(), AttributeSpecs.end());

  }

  dwarf::Form getFormByIndex(uint32_t idx) const {

    assert(idx < AttributeSpecs.size());

    return AttributeSpecs[idx].Form;

  }

  size_t getNumAttributes() const {

    return AttributeSpecs.size();

  }

  dwarf::Attribute getAttrByIndex(uint32_t idx) const {

    assert(idx < AttributeSpecs.size());

    return AttributeSpecs[idx].Attr;

  }

  bool getAttrIsImplicitConstByIndex(uint32_t idx) const {

    assert(idx < AttributeSpecs.size());

    return AttributeSpecs[idx].isImplicitConst();

  }

  int64_t getAttrImplicitConstValueByIndex(uint32_t idx) const {

    assert(idx < AttributeSpecs.size());

    return AttributeSpecs[idx].getImplicitConstValue();

  }

  /// Get the index of the specified attribute.

  ///

  /// Searches the this abbreviation declaration for the index of the specified

  /// attribute.

  ///

  /// \param attr DWARF attribute to search for.

  /// \returns Optional index of the attribute if found, std::nullopt otherwise.

  std::optional<uint32_t> findAttributeIndex(dwarf::Attribute attr) const;

  /// Extract a DWARF form value from a DIE specified by DIE offset.

  ///

  /// Extract an attribute value for a DWARFUnit given the DIE offset and the

  /// attribute.

  ///

  /// \param DIEOffset the DIE offset that points to the ULEB128 abbreviation

  /// code in the .debug_info data.

  /// \param Attr DWARF attribute to search for.

  /// \param U the DWARFUnit the contains the DIE.

  /// \returns Optional DWARF form value if the attribute was extracted.

  std::optional<DWARFFormValue> getAttributeValue(const uint64_t DIEOffset,

                                                  const dwarf::Attribute Attr,

                                                  const DWARFUnit &U) const;

  /// Compute an offset from a DIE specified by DIE offset and attribute index.

  ///

  /// \param AttrIndex an index of DWARF attribute.

  /// \param DIEOffset the DIE offset that points to the ULEB128 abbreviation

  /// code in the .debug_info data.

  /// \param U the DWARFUnit the contains the DIE.

  /// \returns an offset of the attribute.

  uint64_t getAttributeOffsetFromIndex(uint32_t AttrIndex, uint64_t DIEOffset,

                                       const DWARFUnit &U) const;

  /// Extract a DWARF form value from a DIE speccified by attribute index and

  /// its offset.

  ///

  /// \param AttrIndex an index of DWARF attribute.

  /// \param Offset offset of the attribute.

  /// \param U the DWARFUnit the contains the DIE.

  /// \returns Optional DWARF form value if the attribute was extracted.

  std::optional<DWARFFormValue>

  getAttributeValueFromOffset(uint32_t AttrIndex, uint64_t Offset,

                              const DWARFUnit &U) const;

  bool extract(DataExtractor Data, uint64_t* OffsetPtr);

  void dump(raw_ostream &OS) const;

  // Return an optional byte size of all attribute data in this abbreviation

  // if a constant byte size can be calculated given a DWARFUnit. This allows

  // DWARF parsing to be faster as many DWARF DIEs have a fixed byte size.

  std::optional<size_t> getFixedAttributesByteSize(const DWARFUnit &U) const;

private:

  void clear();

  /// A helper structure that can quickly determine the size in bytes of an

  /// abbreviation declaration.

  struct FixedSizeInfo {

    /// The fixed byte size for fixed size forms.

    uint16_t NumBytes = 0;

    /// Number of DW_FORM_address forms in this abbrevation declaration.

    uint8_t NumAddrs = 0;

    /// Number of DW_FORM_ref_addr forms in this abbrevation declaration.

    uint8_t NumRefAddrs = 0;

    /// Number of 4 byte in DWARF32 and 8 byte in DWARF64 forms.

    uint8_t NumDwarfOffsets = 0;

    FixedSizeInfo() = default;

    /// Calculate the fixed size in bytes given a DWARFUnit.

    ///

    /// \param U the DWARFUnit to use when determing the byte size.

    /// \returns the size in bytes for all attribute data in this abbreviation.

    /// The returned size does not include bytes for the  ULEB128 abbreviation

    /// code

    size_t getByteSize(const DWARFUnit &U) const;

  };

  uint32_t Code;

  dwarf::Tag Tag;

  uint8_t CodeByteSize;

  bool HasChildren;

  AttributeSpecVector AttributeSpecs;

  /// If this abbreviation has a fixed byte size then FixedAttributeSize member

  /// variable below will have a value.

  std::optional<FixedSizeInfo> FixedAttributeSize;

};

} // end namespace llvm

#endif // LLVM_DEBUGINFO_DWARF_DWARFABBREVIATIONDECLARATION_H