text: //===- 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/Optional.h"
  #include "llvm/ADT/SmallVector.h"
  #include "llvm/ADT/iterator_range.h"
  #include "llvm/BinaryFormat/Dwarf.h"
  #include "llvm/Support/DataExtractor.h"
  #include <cassert>
  #include <cstddef>
  #include <cstdint>
  
  namespace llvm {
  
  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, Optional<uint8_t> ByteSize)
          : Attr(A), Form(F) {
        assert(!isImplicitConst());
        this->ByteSize.HasByteSize = ByteSize.hasValue();
        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.
      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, None otherwise.
    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.
    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.
    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.
    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.
    Optional<FixedSizeInfo> FixedAttributeSize;
  };
  
  } // end namespace llvm
  
  #endif // LLVM_DEBUGINFO_DWARF_DWARFABBREVIATIONDECLARATION_H
  