lld/lib/Core/NativeWriter.cpp - llvm-project - Git at Google

 //===- Core/NativeWriter.cpp - Creates a native object file ---------------===//
 //
 //                             The LLVM Linker
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//

 #include "lld/Core/NativeWriter.h"
 #include "NativeFileFormat.h"
 #include "lld/Core/File.h"

 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/StringRef.h"

 #include <vector>

 namespace lld {


 ///
 /// Class for writing native object files.
 ///
 class NativeWriter {
 public:
   /// construct writer for an lld::File object
   NativeWriter(const lld::File& file) : _file(file) {
     // reserve first byte for unnamed atoms
     _stringPool.push_back('\0');
     // visit all atoms
     for ( const DefinedAtom *defAtom : file.defined() ) {
       this->addIVarsForDefinedAtom(*defAtom);
     }
     for ( const UndefinedAtom *undefAtom : file.undefined() ) {
       this->addIVarsForUndefinedAtom(*undefAtom);
     }
     for ( const SharedLibraryAtom *shlibAtom : file.sharedLibrary() ) {
       this->addIVarsForSharedLibraryAtom(*shlibAtom);
     }
     for ( const AbsoluteAtom *absAtom : file.absolute() ) {
       this->addIVarsForAbsoluteAtom(*absAtom);
     }


     // construct file header based on atom information accumulated
     makeHeader();
   }

   // write the lld::File in native format to the specified stream
   void write(raw_ostream &out) {
     assert( out.tell() == 0 );
     out.write((char*)_headerBuffer, _headerBufferSize);

     if (!_definedAtomIvars.empty()) {
       assert( out.tell() == findChunk(NCS_DefinedAtomsV1).fileOffset );
       out.write((char*)&_definedAtomIvars[0],
                 _definedAtomIvars.size()*sizeof(NativeDefinedAtomIvarsV1));
     }

     if (!_attributes.empty()) {
       assert( out.tell() == findChunk(NCS_AttributesArrayV1).fileOffset );
       out.write((char*)&_attributes[0],
                 _attributes.size()*sizeof(NativeAtomAttributesV1));
     }

     if ( !_undefinedAtomIvars.empty() ) {
       assert( out.tell() == findChunk(NCS_UndefinedAtomsV1).fileOffset );
       out.write((char*)&_undefinedAtomIvars[0],
               _undefinedAtomIvars.size()*sizeof(NativeUndefinedAtomIvarsV1));
     }

      if ( !_sharedLibraryAtomIvars.empty() ) {
       assert( out.tell() == findChunk(NCS_SharedLibraryAtomsV1).fileOffset );
       out.write((char*)&_sharedLibraryAtomIvars[0],
               _sharedLibraryAtomIvars.size()
               * sizeof(NativeSharedLibraryAtomIvarsV1));
     }

     if ( !_absoluteAtomIvars.empty() ) {
       assert( out.tell() == findChunk(NCS_AbsoluteAtomsV1).fileOffset );
       out.write((char*)&_absoluteAtomIvars[0],
               _absoluteAtomIvars.size()
               * sizeof(NativeAbsoluteAtomIvarsV1));
     }

     if (!_stringPool.empty()) {
       assert( out.tell() == findChunk(NCS_Strings).fileOffset );
       out.write(&_stringPool[0], _stringPool.size());
     }

     if ( !_references.empty() ) {
       assert( out.tell() == findChunk(NCS_ReferencesArrayV1).fileOffset );
       out.write((char*)&_references[0],
               _references.size()*sizeof(NativeReferenceIvarsV1));
     }

     if ( !_targetsTableIndex.empty() ) {
       assert( out.tell() == findChunk(NCS_TargetsTable).fileOffset );
       writeTargetTable(out);
     }

     if ( !_addendsTableIndex.empty() ) {
       assert( out.tell() == findChunk(NCS_AddendsTable).fileOffset );
       writeAddendTable(out);
     }

     if (!_contentPool.empty()) {
       assert( out.tell() == findChunk(NCS_Content).fileOffset );
       out.write((char*)&_contentPool[0], _contentPool.size());
     }
   }

 private:

   void addIVarsForDefinedAtom(const DefinedAtom& atom) {
     _definedAtomIndex[&atom] = _definedAtomIvars.size();
     NativeDefinedAtomIvarsV1 ivar;
     unsigned refsCount;
     ivar.nameOffset = getNameOffset(atom);
     ivar.attributesOffset = getAttributeOffset(atom);
     ivar.referencesStartIndex = getReferencesIndex(atom, refsCount);
     ivar.referencesCount = refsCount;
     ivar.contentOffset = getContentOffset(atom);
     ivar.contentSize = atom.size();
     _definedAtomIvars.push_back(ivar);
   }

   void addIVarsForUndefinedAtom(const UndefinedAtom& atom) {
     _undefinedAtomIndex[&atom] = _undefinedAtomIvars.size();
     NativeUndefinedAtomIvarsV1 ivar;
     ivar.nameOffset = getNameOffset(atom);
     ivar.flags = (atom.canBeNull() & 0x03);
     _undefinedAtomIvars.push_back(ivar);
   }

   void addIVarsForSharedLibraryAtom(const SharedLibraryAtom& atom) {
     _sharedLibraryAtomIndex[&atom] = _sharedLibraryAtomIvars.size();
     NativeSharedLibraryAtomIvarsV1 ivar;
     ivar.nameOffset = getNameOffset(atom);
     ivar.loadNameOffset = getSharedLibraryNameOffset(atom.loadName());
     ivar.flags = atom.canBeNullAtRuntime();
     _sharedLibraryAtomIvars.push_back(ivar);
   }

   void addIVarsForAbsoluteAtom(const AbsoluteAtom& atom) {
     _absoluteAtomIndex[&atom] = _absoluteAtomIvars.size();
     NativeAbsoluteAtomIvarsV1 ivar;
     ivar.nameOffset = getNameOffset(atom);
     ivar.reserved = 0;
     ivar.value = atom.value();
     _absoluteAtomIvars.push_back(ivar);
   }

   // fill out native file header and chunk directory
   void makeHeader() {
     const bool hasDefines = !_definedAtomIvars.empty();
     const bool hasUndefines = !_undefinedAtomIvars.empty();
     const bool hasSharedLibraries = !_sharedLibraryAtomIvars.empty();
     const bool hasAbsolutes = !_absoluteAtomIvars.empty();
     const bool hasReferences = !_references.empty();
     const bool hasTargetsTable = !_targetsTableIndex.empty();
     const bool hasAddendTable = !_addendsTableIndex.empty();
     const bool hasContent = !_contentPool.empty();

     int chunkCount = 1; // always have string pool chunk
     if ( hasDefines ) chunkCount += 2;
     if ( hasUndefines ) ++chunkCount;
     if ( hasSharedLibraries ) ++chunkCount;
     if ( hasAbsolutes ) ++chunkCount;
     if ( hasReferences ) ++chunkCount;
     if ( hasTargetsTable ) ++chunkCount;
     if ( hasAddendTable ) ++chunkCount;
     if ( hasContent ) ++chunkCount;

     _headerBufferSize = sizeof(NativeFileHeader)
                          + chunkCount*sizeof(NativeChunk);
     _headerBuffer = reinterpret_cast<NativeFileHeader*>
                                (operator new(_headerBufferSize, std::nothrow));
     NativeChunk *chunks =
       reinterpret_cast<NativeChunk*>(reinterpret_cast<char*>(_headerBuffer)
                                      + sizeof(NativeFileHeader));
     memcpy(_headerBuffer->magic, NATIVE_FILE_HEADER_MAGIC, 16);
     _headerBuffer->endian = NFH_LittleEndian;
     _headerBuffer->architecture = 0;
     _headerBuffer->fileSize = 0;
     _headerBuffer->chunkCount = chunkCount;

     // create chunk for defined atom ivar array
     int nextIndex = 0;
     uint32_t nextFileOffset = _headerBufferSize;
     if ( hasDefines ) {
       NativeChunk& chd = chunks[nextIndex++];
       chd.signature = NCS_DefinedAtomsV1;
       chd.fileOffset = nextFileOffset;
       chd.fileSize = _definedAtomIvars.size()*sizeof(NativeDefinedAtomIvarsV1);
       chd.elementCount = _definedAtomIvars.size();
       nextFileOffset = chd.fileOffset + chd.fileSize;

       // create chunk for attributes
       NativeChunk& cha = chunks[nextIndex++];
       cha.signature = NCS_AttributesArrayV1;
       cha.fileOffset = nextFileOffset;
       cha.fileSize = _attributes.size()*sizeof(NativeAtomAttributesV1);
       cha.elementCount = _attributes.size();
       nextFileOffset = cha.fileOffset + cha.fileSize;
     }

     // create chunk for undefined atom array
     if ( hasUndefines ) {
       NativeChunk& chu = chunks[nextIndex++];
       chu.signature = NCS_UndefinedAtomsV1;
       chu.fileOffset = nextFileOffset;
       chu.fileSize = _undefinedAtomIvars.size() *
                                             sizeof(NativeUndefinedAtomIvarsV1);
       chu.elementCount = _undefinedAtomIvars.size();
       nextFileOffset = chu.fileOffset + chu.fileSize;
     }

     // create chunk for shared library atom array
     if ( hasSharedLibraries ) {
       NativeChunk& chsl = chunks[nextIndex++];
       chsl.signature = NCS_SharedLibraryAtomsV1;
       chsl.fileOffset = nextFileOffset;
       chsl.fileSize = _sharedLibraryAtomIvars.size() *
                                         sizeof(NativeSharedLibraryAtomIvarsV1);
       chsl.elementCount = _sharedLibraryAtomIvars.size();
       nextFileOffset = chsl.fileOffset + chsl.fileSize;
     }

      // create chunk for shared library atom array
     if ( hasAbsolutes ) {
       NativeChunk& chsl = chunks[nextIndex++];
       chsl.signature = NCS_AbsoluteAtomsV1;
       chsl.fileOffset = nextFileOffset;
       chsl.fileSize = _absoluteAtomIvars.size() *
                                         sizeof(NativeAbsoluteAtomIvarsV1);
       chsl.elementCount = _absoluteAtomIvars.size();
       nextFileOffset = chsl.fileOffset + chsl.fileSize;
     }

     // create chunk for symbol strings
     // pad end of string pool to 4-bytes
     while ( (_stringPool.size() % 4) != 0 )
       _stringPool.push_back('\0');
     NativeChunk& chs = chunks[nextIndex++];
     chs.signature = NCS_Strings;
     chs.fileOffset = nextFileOffset;
     chs.fileSize = _stringPool.size();
     chs.elementCount = _stringPool.size();
     nextFileOffset = chs.fileOffset + chs.fileSize;

     // create chunk for references
     if ( hasReferences ) {
       NativeChunk& chr = chunks[nextIndex++];
       chr.signature = NCS_ReferencesArrayV1;
       chr.fileOffset = nextFileOffset;
       chr.fileSize = _references.size() * sizeof(NativeReferenceIvarsV1);
       chr.elementCount = _references.size();
       nextFileOffset = chr.fileOffset + chr.fileSize;
     }

     // create chunk for target table
     if ( hasTargetsTable ) {
       NativeChunk& cht = chunks[nextIndex++];
       cht.signature = NCS_TargetsTable;
       cht.fileOffset = nextFileOffset;
       cht.fileSize = _targetsTableIndex.size() * sizeof(uint32_t);
       cht.elementCount = _targetsTableIndex.size();
       nextFileOffset = cht.fileOffset + cht.fileSize;
     }

     // create chunk for addend table
     if ( hasAddendTable ) {
       NativeChunk& chad = chunks[nextIndex++];
       chad.signature = NCS_AddendsTable;
       chad.fileOffset = nextFileOffset;
       chad.fileSize = _addendsTableIndex.size() * sizeof(Reference::Addend);
       chad.elementCount = _addendsTableIndex.size();
       nextFileOffset = chad.fileOffset + chad.fileSize;
     }

     // create chunk for content
     if ( hasContent ) {
       NativeChunk& chc = chunks[nextIndex++];
       chc.signature = NCS_Content;
       chc.fileOffset = nextFileOffset;
       chc.fileSize = _contentPool.size();
       chc.elementCount = _contentPool.size();
       nextFileOffset = chc.fileOffset + chc.fileSize;
     }

     _headerBuffer->fileSize = nextFileOffset;
   }

   // scan header to find particular chunk
   NativeChunk& findChunk(uint32_t signature) {
     const uint32_t chunkCount = _headerBuffer->chunkCount;
     NativeChunk* chunks =
       reinterpret_cast<NativeChunk*>(reinterpret_cast<char*>(_headerBuffer)
                                      + sizeof(NativeFileHeader));
     for (uint32_t i=0; i < chunkCount; ++i) {
       if ( chunks[i].signature == signature )
         return chunks[i];
     }
     assert(0 && "findChunk() signature not found");
     static NativeChunk x; return x; // suppress warning
   }

   // append atom name to string pool and return offset
   uint32_t getNameOffset(const Atom& atom) {
     return this->getNameOffset(atom.name());
   }

   // check if name is already in pool or append and return offset
   uint32_t getSharedLibraryNameOffset(StringRef name) {
     assert( ! name.empty() );
     // look to see if this library name was used by another atom
     for(NameToOffsetVector::iterator it = _sharedLibraryNames.begin();
                                     it != _sharedLibraryNames.end(); ++it) {
       if ( name.equals(it->first) )
         return it->second;
     }
     // first use of this library name
     uint32_t result = this->getNameOffset(name);
     _sharedLibraryNames.push_back(std::make_pair(name, result));
     return result;
   }

   // append atom name to string pool and return offset
   uint32_t getNameOffset(StringRef name) {
     if ( name.empty() )
       return 0;
     uint32_t result = _stringPool.size();
     _stringPool.insert(_stringPool.end(), name.begin(), name.end());
     _stringPool.push_back(0);
     return result;
   }

   // append atom cotent to content pool and return offset
   uint32_t getContentOffset(const class DefinedAtom& atom) {
     if ( atom.contentType() == DefinedAtom::typeZeroFill )
       return 0;
     uint32_t result = _contentPool.size();
     ArrayRef<uint8_t> cont = atom.rawContent();
     _contentPool.insert(_contentPool.end(), cont.begin(), cont.end());
     return result;
   }

   // reuse existing attributes entry or create a new one and return offet
   uint32_t getAttributeOffset(const class DefinedAtom& atom) {
     NativeAtomAttributesV1 attrs;
     computeAttributesV1(atom, attrs);
     for(unsigned int i=0; i < _attributes.size(); ++i) {
       if ( !memcmp(&_attributes[i], &attrs, sizeof(NativeAtomAttributesV1)) ) {
         // found that this set of attributes already used, so re-use
         return i * sizeof(NativeAtomAttributesV1);
       }
     }
     // append new attribute set to end
     uint32_t result = _attributes.size() * sizeof(NativeAtomAttributesV1);
     _attributes.push_back(attrs);
     return result;
   }

   uint32_t sectionNameOffset(const class DefinedAtom& atom) {
     // if section based on content, then no custom section name available
     if ( atom.sectionChoice() == DefinedAtom::sectionBasedOnContent )
       return 0;
     StringRef name = atom.customSectionName();
     assert( ! name.empty() );
     // look to see if this section name was used by another atom
     for(NameToOffsetVector::iterator it=_sectionNames.begin();
                                             it != _sectionNames.end(); ++it) {
       if ( name.equals(it->first) )
         return it->second;
     }
     // first use of this section name
     uint32_t result = this->getNameOffset(name);
     _sectionNames.push_back(std::make_pair(name, result));
     return result;
   }

   void computeAttributesV1(const class DefinedAtom& atom,
                                                 NativeAtomAttributesV1& attrs) {
     attrs.sectionNameOffset = sectionNameOffset(atom);
     attrs.align2            = atom.alignment().powerOf2;
     attrs.alignModulus      = atom.alignment().modulus;
     attrs.scope             = atom.scope();
     attrs.interposable      = atom.interposable();
     attrs.merge             = atom.merge();
     attrs.contentType       = atom.contentType();
     attrs.sectionChoice     = atom.sectionChoice();
     attrs.deadStrip         = atom.deadStrip();
     attrs.permissions       = atom.permissions();
     //attrs.thumb             = atom.isThumb();
     attrs.alias             = atom.isAlias();
   }

   // add references for this atom in a contiguous block in NCS_ReferencesArrayV1
   uint32_t getReferencesIndex(const DefinedAtom& atom, unsigned& count) {
     count = 0;
     size_t startRefSize = _references.size();
     uint32_t result = startRefSize;
     for (const Reference *ref : atom) {
       NativeReferenceIvarsV1 nref;
       nref.offsetInAtom = ref->offsetInAtom();
       nref.kind = ref->kind();
       nref.targetIndex = this->getTargetIndex(ref->target());
       nref.addendIndex = this->getAddendIndex(ref->addend());
       _references.push_back(nref);
     }
     count = _references.size() - startRefSize;
     if ( count == 0 )
       return 0;
     else
       return result;
   }

   uint32_t getTargetIndex(const Atom* target) {
     if ( target == nullptr )
       return NativeReferenceIvarsV1::noTarget;
     TargetToIndex::const_iterator pos = _targetsTableIndex.find(target);
     if ( pos != _targetsTableIndex.end() ) {
       return pos->second;
     }
     uint32_t result = _targetsTableIndex.size();
     _targetsTableIndex[target] = result;
     return result;
   }

   void writeTargetTable(raw_ostream &out) {
     // Build table of target indexes
     uint32_t maxTargetIndex = _targetsTableIndex.size();
     assert(maxTargetIndex > 0);
     std::vector<uint32_t> targetIndexes(maxTargetIndex);
     for (TargetToIndex::iterator it = _targetsTableIndex.begin();
                                  it != _targetsTableIndex.end(); ++it) {
       const Atom* atom = it->first;
       uint32_t targetIndex = it->second;
       assert(targetIndex < maxTargetIndex);
       uint32_t atomIndex = 0;
       TargetToIndex::iterator pos = _definedAtomIndex.find(atom);
       if ( pos != _definedAtomIndex.end() ) {
         atomIndex = pos->second;
       }
       else {
         pos = _undefinedAtomIndex.find(atom);
         if ( pos != _undefinedAtomIndex.end() ) {
           atomIndex = pos->second + _definedAtomIvars.size();
         }
         else {
           pos = _sharedLibraryAtomIndex.find(atom);
           if ( pos != _sharedLibraryAtomIndex.end() ) {
             assert(pos != _sharedLibraryAtomIndex.end());
             atomIndex = pos->second
                       + _definedAtomIvars.size()
                       + _undefinedAtomIndex.size();
           }
           else {
             pos = _absoluteAtomIndex.find(atom);
             assert(pos != _absoluteAtomIndex.end());
             atomIndex = pos->second
                       + _definedAtomIvars.size()
                       + _undefinedAtomIndex.size()
                       + _sharedLibraryAtomIndex.size();
          }
         }
       }
       targetIndexes[targetIndex] = atomIndex;
     }
     // write table
     out.write((char*)&targetIndexes[0], maxTargetIndex*sizeof(uint32_t));
   }

   uint32_t getAddendIndex(Reference::Addend addend) {
     if ( addend == 0 )
       return 0; // addend index zero is used to mean "no addend"
     AddendToIndex::const_iterator pos = _addendsTableIndex.find(addend);
     if ( pos != _addendsTableIndex.end() ) {
       return pos->second;
     }
     uint32_t result = _addendsTableIndex.size() + 1; // one-based index
     _addendsTableIndex[addend] = result;
     return result;
   }

   void writeAddendTable(raw_ostream &out) {
     // Build table of addends
     uint32_t maxAddendIndex = _addendsTableIndex.size();
     std::vector<Reference::Addend> addends(maxAddendIndex);
     for (AddendToIndex::iterator it = _addendsTableIndex.begin();
                                  it != _addendsTableIndex.end(); ++it) {
       Reference::Addend addend = it->first;
       uint32_t index = it->second;
       assert(index <= maxAddendIndex);
       addends[index-1] = addend;
     }
     // write table
     out.write((char*)&addends[0], maxAddendIndex*sizeof(Reference::Addend));
   }

   typedef std::vector<std::pair<StringRef, uint32_t> > NameToOffsetVector;

   typedef llvm::DenseMap<const Atom*, uint32_t> TargetToIndex;
   typedef llvm::DenseMap<Reference::Addend, uint32_t> AddendToIndex;

   const lld::File&                        _file;
   NativeFileHeader*                       _headerBuffer;
   size_t                                  _headerBufferSize;
   std::vector<char>                       _stringPool;
   std::vector<uint8_t>                    _contentPool;
   std::vector<NativeDefinedAtomIvarsV1>   _definedAtomIvars;
   std::vector<NativeAtomAttributesV1>     _attributes;
   std::vector<NativeUndefinedAtomIvarsV1> _undefinedAtomIvars;
   std::vector<NativeSharedLibraryAtomIvarsV1> _sharedLibraryAtomIvars;
   std::vector<NativeAbsoluteAtomIvarsV1>  _absoluteAtomIvars;
   std::vector<NativeReferenceIvarsV1>     _references;
   TargetToIndex                           _targetsTableIndex;
   TargetToIndex                           _definedAtomIndex;
   TargetToIndex                           _undefinedAtomIndex;
   TargetToIndex                           _sharedLibraryAtomIndex;
   TargetToIndex                           _absoluteAtomIndex;
   AddendToIndex                           _addendsTableIndex;
   NameToOffsetVector                      _sectionNames;
   NameToOffsetVector                      _sharedLibraryNames;
 };


 /// writeNativeObjectFile - writes the lld::File object in native object
 /// file format to the specified stream.
 int writeNativeObjectFile(const File &file, raw_ostream &out) {
   NativeWriter writer(file);
   writer.write(out);
   return 0;
 }

 /// writeNativeObjectFile - writes the lld::File object in native object
 /// file format to the specified file path.
 int writeNativeObjectFile(const File &file, StringRef path) {
   std::string errorInfo;
   llvm::raw_fd_ostream out( path.data()
                           , errorInfo
                           , llvm::raw_fd_ostream::F_Binary);
   if (!errorInfo.empty())
     return -1;
   return writeNativeObjectFile(file, out);
 }

 } // namespace lld
	//===- Core/NativeWriter.cpp - Creates a native object file ---------------===//
	//
	// The LLVM Linker
	//
	// This file is distributed under the University of Illinois Open Source
	// License. See LICENSE.TXT for details.
	//
	//===----------------------------------------------------------------------===//

	#include "lld/Core/NativeWriter.h"
	#include "NativeFileFormat.h"
	#include "lld/Core/File.h"

	#include "llvm/ADT/ArrayRef.h"
	#include "llvm/ADT/DenseMap.h"
	#include "llvm/ADT/StringRef.h"

	#include <vector>

	namespace lld {


	///
	/// Class for writing native object files.
	///
	class NativeWriter {
	public:
	/// construct writer for an lld::File object
	NativeWriter(const lld::File& file) : _file(file) {
	// reserve first byte for unnamed atoms
	_stringPool.push_back('\0');
	// visit all atoms
	for ( const DefinedAtom *defAtom : file.defined() ) {
	this->addIVarsForDefinedAtom(*defAtom);
	}
	for ( const UndefinedAtom *undefAtom : file.undefined() ) {
	this->addIVarsForUndefinedAtom(*undefAtom);
	}
	for ( const SharedLibraryAtom *shlibAtom : file.sharedLibrary() ) {
	this->addIVarsForSharedLibraryAtom(*shlibAtom);
	}
	for ( const AbsoluteAtom *absAtom : file.absolute() ) {
	this->addIVarsForAbsoluteAtom(*absAtom);
	}



	// construct file header based on atom information accumulated
	makeHeader();
	}

	// write the lld::File in native format to the specified stream
	void write(raw_ostream &out) {
	assert( out.tell() == 0 );
	out.write((char*)_headerBuffer, _headerBufferSize);

	if (!_definedAtomIvars.empty()) {
	assert( out.tell() == findChunk(NCS_DefinedAtomsV1).fileOffset );
	out.write((char*)&_definedAtomIvars[0],
	_definedAtomIvars.size()*sizeof(NativeDefinedAtomIvarsV1));
	}

	if (!_attributes.empty()) {
	assert( out.tell() == findChunk(NCS_AttributesArrayV1).fileOffset );
	out.write((char*)&_attributes[0],
	_attributes.size()*sizeof(NativeAtomAttributesV1));
	}

	if ( !_undefinedAtomIvars.empty() ) {
	assert( out.tell() == findChunk(NCS_UndefinedAtomsV1).fileOffset );
	out.write((char*)&_undefinedAtomIvars[0],
	_undefinedAtomIvars.size()*sizeof(NativeUndefinedAtomIvarsV1));
	}

	if ( !_sharedLibraryAtomIvars.empty() ) {
	assert( out.tell() == findChunk(NCS_SharedLibraryAtomsV1).fileOffset );
	out.write((char*)&_sharedLibraryAtomIvars[0],
	_sharedLibraryAtomIvars.size()
	* sizeof(NativeSharedLibraryAtomIvarsV1));
	}

	if ( !_absoluteAtomIvars.empty() ) {
	assert( out.tell() == findChunk(NCS_AbsoluteAtomsV1).fileOffset );
	out.write((char*)&_absoluteAtomIvars[0],
	_absoluteAtomIvars.size()
	* sizeof(NativeAbsoluteAtomIvarsV1));
	}

	if (!_stringPool.empty()) {
	assert( out.tell() == findChunk(NCS_Strings).fileOffset );
	out.write(&_stringPool[0], _stringPool.size());
	}

	if ( !_references.empty() ) {
	assert( out.tell() == findChunk(NCS_ReferencesArrayV1).fileOffset );
	out.write((char*)&_references[0],
	_references.size()*sizeof(NativeReferenceIvarsV1));
	}

	if ( !_targetsTableIndex.empty() ) {
	assert( out.tell() == findChunk(NCS_TargetsTable).fileOffset );
	writeTargetTable(out);
	}

	if ( !_addendsTableIndex.empty() ) {
	assert( out.tell() == findChunk(NCS_AddendsTable).fileOffset );
	writeAddendTable(out);
	}

	if (!_contentPool.empty()) {
	assert( out.tell() == findChunk(NCS_Content).fileOffset );
	out.write((char*)&_contentPool[0], _contentPool.size());
	}
	}

	private:

	void addIVarsForDefinedAtom(const DefinedAtom& atom) {
	_definedAtomIndex[&atom] = _definedAtomIvars.size();
	NativeDefinedAtomIvarsV1 ivar;
	unsigned refsCount;
	ivar.nameOffset = getNameOffset(atom);
	ivar.attributesOffset = getAttributeOffset(atom);
	ivar.referencesStartIndex = getReferencesIndex(atom, refsCount);
	ivar.referencesCount = refsCount;
	ivar.contentOffset = getContentOffset(atom);
	ivar.contentSize = atom.size();
	_definedAtomIvars.push_back(ivar);
	}

	void addIVarsForUndefinedAtom(const UndefinedAtom& atom) {
	_undefinedAtomIndex[&atom] = _undefinedAtomIvars.size();
	NativeUndefinedAtomIvarsV1 ivar;
	ivar.nameOffset = getNameOffset(atom);
	ivar.flags = (atom.canBeNull() & 0x03);
	_undefinedAtomIvars.push_back(ivar);
	}

	void addIVarsForSharedLibraryAtom(const SharedLibraryAtom& atom) {
	_sharedLibraryAtomIndex[&atom] = _sharedLibraryAtomIvars.size();
	NativeSharedLibraryAtomIvarsV1 ivar;
	ivar.nameOffset = getNameOffset(atom);
	ivar.loadNameOffset = getSharedLibraryNameOffset(atom.loadName());
	ivar.flags = atom.canBeNullAtRuntime();
	_sharedLibraryAtomIvars.push_back(ivar);
	}

	void addIVarsForAbsoluteAtom(const AbsoluteAtom& atom) {
	_absoluteAtomIndex[&atom] = _absoluteAtomIvars.size();
	NativeAbsoluteAtomIvarsV1 ivar;
	ivar.nameOffset = getNameOffset(atom);
	ivar.reserved = 0;
	ivar.value = atom.value();
	_absoluteAtomIvars.push_back(ivar);
	}

	// fill out native file header and chunk directory
	void makeHeader() {
	const bool hasDefines = !_definedAtomIvars.empty();
	const bool hasUndefines = !_undefinedAtomIvars.empty();
	const bool hasSharedLibraries = !_sharedLibraryAtomIvars.empty();
	const bool hasAbsolutes = !_absoluteAtomIvars.empty();
	const bool hasReferences = !_references.empty();
	const bool hasTargetsTable = !_targetsTableIndex.empty();
	const bool hasAddendTable = !_addendsTableIndex.empty();
	const bool hasContent = !_contentPool.empty();

	int chunkCount = 1; // always have string pool chunk
	if ( hasDefines ) chunkCount += 2;
	if ( hasUndefines ) ++chunkCount;
	if ( hasSharedLibraries ) ++chunkCount;
	if ( hasAbsolutes ) ++chunkCount;
	if ( hasReferences ) ++chunkCount;
	if ( hasTargetsTable ) ++chunkCount;
	if ( hasAddendTable ) ++chunkCount;
	if ( hasContent ) ++chunkCount;

	_headerBufferSize = sizeof(NativeFileHeader)
	+ chunkCount*sizeof(NativeChunk);
	_headerBuffer = reinterpret_cast<NativeFileHeader*>
	(operator new(_headerBufferSize, std::nothrow));
	NativeChunk *chunks =
	reinterpret_cast<NativeChunk>(reinterpret_cast<char>(_headerBuffer)
	+ sizeof(NativeFileHeader));
	memcpy(_headerBuffer->magic, NATIVE_FILE_HEADER_MAGIC, 16);
	_headerBuffer->endian = NFH_LittleEndian;
	_headerBuffer->architecture = 0;
	_headerBuffer->fileSize = 0;
	_headerBuffer->chunkCount = chunkCount;

	// create chunk for defined atom ivar array
	int nextIndex = 0;
	uint32_t nextFileOffset = _headerBufferSize;
	if ( hasDefines ) {
	NativeChunk& chd = chunks[nextIndex++];
	chd.signature = NCS_DefinedAtomsV1;
	chd.fileOffset = nextFileOffset;
	chd.fileSize = _definedAtomIvars.size()*sizeof(NativeDefinedAtomIvarsV1);
	chd.elementCount = _definedAtomIvars.size();
	nextFileOffset = chd.fileOffset + chd.fileSize;

	// create chunk for attributes
	NativeChunk& cha = chunks[nextIndex++];
	cha.signature = NCS_AttributesArrayV1;
	cha.fileOffset = nextFileOffset;
	cha.fileSize = _attributes.size()*sizeof(NativeAtomAttributesV1);
	cha.elementCount = _attributes.size();
	nextFileOffset = cha.fileOffset + cha.fileSize;
	}

	// create chunk for undefined atom array
	if ( hasUndefines ) {
	NativeChunk& chu = chunks[nextIndex++];
	chu.signature = NCS_UndefinedAtomsV1;
	chu.fileOffset = nextFileOffset;
	chu.fileSize = _undefinedAtomIvars.size() *
	sizeof(NativeUndefinedAtomIvarsV1);
	chu.elementCount = _undefinedAtomIvars.size();
	nextFileOffset = chu.fileOffset + chu.fileSize;
	}

	// create chunk for shared library atom array
	if ( hasSharedLibraries ) {
	NativeChunk& chsl = chunks[nextIndex++];
	chsl.signature = NCS_SharedLibraryAtomsV1;
	chsl.fileOffset = nextFileOffset;
	chsl.fileSize = _sharedLibraryAtomIvars.size() *
	sizeof(NativeSharedLibraryAtomIvarsV1);
	chsl.elementCount = _sharedLibraryAtomIvars.size();
	nextFileOffset = chsl.fileOffset + chsl.fileSize;
	}

	// create chunk for shared library atom array
	if ( hasAbsolutes ) {
	NativeChunk& chsl = chunks[nextIndex++];
	chsl.signature = NCS_AbsoluteAtomsV1;
	chsl.fileOffset = nextFileOffset;
	chsl.fileSize = _absoluteAtomIvars.size() *
	sizeof(NativeAbsoluteAtomIvarsV1);
	chsl.elementCount = _absoluteAtomIvars.size();
	nextFileOffset = chsl.fileOffset + chsl.fileSize;
	}

	// create chunk for symbol strings
	// pad end of string pool to 4-bytes
	while ( (_stringPool.size() % 4) != 0 )
	_stringPool.push_back('\0');
	NativeChunk& chs = chunks[nextIndex++];
	chs.signature = NCS_Strings;
	chs.fileOffset = nextFileOffset;
	chs.fileSize = _stringPool.size();
	chs.elementCount = _stringPool.size();
	nextFileOffset = chs.fileOffset + chs.fileSize;

	// create chunk for references
	if ( hasReferences ) {
	NativeChunk& chr = chunks[nextIndex++];
	chr.signature = NCS_ReferencesArrayV1;
	chr.fileOffset = nextFileOffset;
	chr.fileSize = _references.size() * sizeof(NativeReferenceIvarsV1);
	chr.elementCount = _references.size();
	nextFileOffset = chr.fileOffset + chr.fileSize;
	}

	// create chunk for target table
	if ( hasTargetsTable ) {
	NativeChunk& cht = chunks[nextIndex++];
	cht.signature = NCS_TargetsTable;
	cht.fileOffset = nextFileOffset;
	cht.fileSize = _targetsTableIndex.size() * sizeof(uint32_t);
	cht.elementCount = _targetsTableIndex.size();
	nextFileOffset = cht.fileOffset + cht.fileSize;
	}

	// create chunk for addend table
	if ( hasAddendTable ) {
	NativeChunk& chad = chunks[nextIndex++];
	chad.signature = NCS_AddendsTable;
	chad.fileOffset = nextFileOffset;
	chad.fileSize = _addendsTableIndex.size() * sizeof(Reference::Addend);
	chad.elementCount = _addendsTableIndex.size();
	nextFileOffset = chad.fileOffset + chad.fileSize;
	}

	// create chunk for content
	if ( hasContent ) {
	NativeChunk& chc = chunks[nextIndex++];
	chc.signature = NCS_Content;
	chc.fileOffset = nextFileOffset;
	chc.fileSize = _contentPool.size();
	chc.elementCount = _contentPool.size();
	nextFileOffset = chc.fileOffset + chc.fileSize;
	}

	_headerBuffer->fileSize = nextFileOffset;
	}

	// scan header to find particular chunk
	NativeChunk& findChunk(uint32_t signature) {
	const uint32_t chunkCount = _headerBuffer->chunkCount;
	NativeChunk* chunks =
	reinterpret_cast<NativeChunk>(reinterpret_cast<char>(_headerBuffer)
	+ sizeof(NativeFileHeader));
	for (uint32_t i=0; i < chunkCount; ++i) {
	if ( chunks[i].signature == signature )
	return chunks[i];
	}
	assert(0 && "findChunk() signature not found");
	static NativeChunk x; return x; // suppress warning
	}

	// append atom name to string pool and return offset
	uint32_t getNameOffset(const Atom& atom) {
	return this->getNameOffset(atom.name());
	}

	// check if name is already in pool or append and return offset
	uint32_t getSharedLibraryNameOffset(StringRef name) {
	assert( ! name.empty() );
	// look to see if this library name was used by another atom
	for(NameToOffsetVector::iterator it = _sharedLibraryNames.begin();
	it != _sharedLibraryNames.end(); ++it) {
	if ( name.equals(it->first) )
	return it->second;
	}
	// first use of this library name
	uint32_t result = this->getNameOffset(name);
	_sharedLibraryNames.push_back(std::make_pair(name, result));
	return result;
	}

	// append atom name to string pool and return offset
	uint32_t getNameOffset(StringRef name) {
	if ( name.empty() )
	return 0;
	uint32_t result = _stringPool.size();
	_stringPool.insert(_stringPool.end(), name.begin(), name.end());
	_stringPool.push_back(0);
	return result;
	}

	// append atom cotent to content pool and return offset
	uint32_t getContentOffset(const class DefinedAtom& atom) {
	if ( atom.contentType() == DefinedAtom::typeZeroFill )
	return 0;
	uint32_t result = _contentPool.size();
	ArrayRef<uint8_t> cont = atom.rawContent();
	_contentPool.insert(_contentPool.end(), cont.begin(), cont.end());
	return result;
	}

	// reuse existing attributes entry or create a new one and return offet
	uint32_t getAttributeOffset(const class DefinedAtom& atom) {
	NativeAtomAttributesV1 attrs;
	computeAttributesV1(atom, attrs);
	for(unsigned int i=0; i < _attributes.size(); ++i) {
	if ( !memcmp(&_attributes[i], &attrs, sizeof(NativeAtomAttributesV1)) ) {
	// found that this set of attributes already used, so re-use
	return i * sizeof(NativeAtomAttributesV1);
	}
	}
	// append new attribute set to end
	uint32_t result = _attributes.size() * sizeof(NativeAtomAttributesV1);
	_attributes.push_back(attrs);
	return result;
	}

	uint32_t sectionNameOffset(const class DefinedAtom& atom) {
	// if section based on content, then no custom section name available
	if ( atom.sectionChoice() == DefinedAtom::sectionBasedOnContent )
	return 0;
	StringRef name = atom.customSectionName();
	assert( ! name.empty() );
	// look to see if this section name was used by another atom
	for(NameToOffsetVector::iterator it=_sectionNames.begin();
	it != _sectionNames.end(); ++it) {
	if ( name.equals(it->first) )
	return it->second;
	}
	// first use of this section name
	uint32_t result = this->getNameOffset(name);
	_sectionNames.push_back(std::make_pair(name, result));
	return result;
	}

	void computeAttributesV1(const class DefinedAtom& atom,
	NativeAtomAttributesV1& attrs) {
	attrs.sectionNameOffset = sectionNameOffset(atom);
	attrs.align2 = atom.alignment().powerOf2;
	attrs.alignModulus = atom.alignment().modulus;
	attrs.scope = atom.scope();
	attrs.interposable = atom.interposable();
	attrs.merge = atom.merge();
	attrs.contentType = atom.contentType();
	attrs.sectionChoice = atom.sectionChoice();
	attrs.deadStrip = atom.deadStrip();
	attrs.permissions = atom.permissions();
	//attrs.thumb = atom.isThumb();
	attrs.alias = atom.isAlias();
	}

	// add references for this atom in a contiguous block in NCS_ReferencesArrayV1
	uint32_t getReferencesIndex(const DefinedAtom& atom, unsigned& count) {
	count = 0;
	size_t startRefSize = _references.size();
	uint32_t result = startRefSize;
	for (const Reference *ref : atom) {
	NativeReferenceIvarsV1 nref;
	nref.offsetInAtom = ref->offsetInAtom();
	nref.kind = ref->kind();
	nref.targetIndex = this->getTargetIndex(ref->target());
	nref.addendIndex = this->getAddendIndex(ref->addend());
	_references.push_back(nref);
	}
	count = _references.size() - startRefSize;
	if ( count == 0 )
	return 0;
	else
	return result;
	}

	uint32_t getTargetIndex(const Atom* target) {
	if ( target == nullptr )
	return NativeReferenceIvarsV1::noTarget;
	TargetToIndex::const_iterator pos = _targetsTableIndex.find(target);
	if ( pos != _targetsTableIndex.end() ) {
	return pos->second;
	}
	uint32_t result = _targetsTableIndex.size();
	_targetsTableIndex[target] = result;
	return result;
	}

	void writeTargetTable(raw_ostream &out) {
	// Build table of target indexes
	uint32_t maxTargetIndex = _targetsTableIndex.size();
	assert(maxTargetIndex > 0);
	std::vector<uint32_t> targetIndexes(maxTargetIndex);
	for (TargetToIndex::iterator it = _targetsTableIndex.begin();
	it != _targetsTableIndex.end(); ++it) {
	const Atom* atom = it->first;
	uint32_t targetIndex = it->second;
	assert(targetIndex < maxTargetIndex);
	uint32_t atomIndex = 0;
	TargetToIndex::iterator pos = _definedAtomIndex.find(atom);
	if ( pos != _definedAtomIndex.end() ) {
	atomIndex = pos->second;
	}
	else {
	pos = _undefinedAtomIndex.find(atom);
	if ( pos != _undefinedAtomIndex.end() ) {
	atomIndex = pos->second + _definedAtomIvars.size();
	}
	else {
	pos = _sharedLibraryAtomIndex.find(atom);
	if ( pos != _sharedLibraryAtomIndex.end() ) {
	assert(pos != _sharedLibraryAtomIndex.end());
	atomIndex = pos->second
	+ _definedAtomIvars.size()
	+ _undefinedAtomIndex.size();
	}
	else {
	pos = _absoluteAtomIndex.find(atom);
	assert(pos != _absoluteAtomIndex.end());
	atomIndex = pos->second
	+ _definedAtomIvars.size()
	+ _undefinedAtomIndex.size()
	+ _sharedLibraryAtomIndex.size();
	}
	}
	}
	targetIndexes[targetIndex] = atomIndex;
	}
	// write table
	out.write((char)&targetIndexes[0], maxTargetIndexsizeof(uint32_t));
	}

	uint32_t getAddendIndex(Reference::Addend addend) {
	if ( addend == 0 )
	return 0; // addend index zero is used to mean "no addend"
	AddendToIndex::const_iterator pos = _addendsTableIndex.find(addend);
	if ( pos != _addendsTableIndex.end() ) {
	return pos->second;
	}
	uint32_t result = _addendsTableIndex.size() + 1; // one-based index
	_addendsTableIndex[addend] = result;
	return result;
	}

	void writeAddendTable(raw_ostream &out) {
	// Build table of addends
	uint32_t maxAddendIndex = _addendsTableIndex.size();
	std::vector<Reference::Addend> addends(maxAddendIndex);
	for (AddendToIndex::iterator it = _addendsTableIndex.begin();
	it != _addendsTableIndex.end(); ++it) {
	Reference::Addend addend = it->first;
	uint32_t index = it->second;
	assert(index <= maxAddendIndex);
	addends[index-1] = addend;
	}
	// write table
	out.write((char)&addends[0], maxAddendIndexsizeof(Reference::Addend));
	}

	typedef std::vector<std::pair<StringRef, uint32_t> > NameToOffsetVector;

	typedef llvm::DenseMap<const Atom*, uint32_t> TargetToIndex;
	typedef llvm::DenseMap<Reference::Addend, uint32_t> AddendToIndex;

	const lld::File& _file;
	NativeFileHeader* _headerBuffer;
	size_t _headerBufferSize;
	std::vector<char> _stringPool;
	std::vector<uint8_t> _contentPool;
	std::vector<NativeDefinedAtomIvarsV1> _definedAtomIvars;
	std::vector<NativeAtomAttributesV1> _attributes;
	std::vector<NativeUndefinedAtomIvarsV1> _undefinedAtomIvars;
	std::vector<NativeSharedLibraryAtomIvarsV1> _sharedLibraryAtomIvars;
	std::vector<NativeAbsoluteAtomIvarsV1> _absoluteAtomIvars;
	std::vector<NativeReferenceIvarsV1> _references;
	TargetToIndex _targetsTableIndex;
	TargetToIndex _definedAtomIndex;
	TargetToIndex _undefinedAtomIndex;
	TargetToIndex _sharedLibraryAtomIndex;
	TargetToIndex _absoluteAtomIndex;
	AddendToIndex _addendsTableIndex;
	NameToOffsetVector _sectionNames;
	NameToOffsetVector _sharedLibraryNames;
	};





	/// writeNativeObjectFile - writes the lld::File object in native object
	/// file format to the specified stream.
	int writeNativeObjectFile(const File &file, raw_ostream &out) {
	NativeWriter writer(file);
	writer.write(out);
	return 0;
	}

	/// writeNativeObjectFile - writes the lld::File object in native object
	/// file format to the specified file path.
	int writeNativeObjectFile(const File &file, StringRef path) {
	std::string errorInfo;
	llvm::raw_fd_ostream out( path.data()
	, errorInfo
	, llvm::raw_fd_ostream::F_Binary);
	if (!errorInfo.empty())
	return -1;
	return writeNativeObjectFile(file, out);
	}

	} // namespace lld