//===----------------- MachO.cpp - MachO format utilities -----------------===//
//
// 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
//
//===----------------------------------------------------------------------===//

#include "llvm/ExecutionEngine/Orc/MachO.h"

#include "llvm/BinaryFormat/MachO.h"
#include "llvm/Object/MachOUniversal.h"

#define DEBUG_TYPE "orc"

namespace llvm {
namespace orc {

static std::string objDesc(MemoryBuffer &Obj, const Triple &TT,
                           bool ObjIsSlice) {
  std::string Desc;
  if (ObjIsSlice)
    Desc += (TT.getArchName() + " slice of universal binary").str();
  Desc += Obj.getBufferIdentifier();
  return Desc;
}

template <typename HeaderType>
static Expected<std::unique_ptr<MemoryBuffer>>
checkMachORelocatableObject(std::unique_ptr<MemoryBuffer> Obj,
                            bool SwapEndianness, const Triple &TT,
                            bool ObjIsSlice) {
  StringRef Data = Obj->getBuffer();

  HeaderType Hdr;
  memcpy(&Hdr, Data.data(), sizeof(HeaderType));

  if (SwapEndianness)
    swapStruct(Hdr);

  if (Hdr.filetype != MachO::MH_OBJECT)
    return make_error<StringError>(objDesc(*Obj, TT, ObjIsSlice) +
                                       " is not a MachO relocatable object",
                                   inconvertibleErrorCode());

  auto ObjArch = object::MachOObjectFile::getArch(Hdr.cputype, Hdr.cpusubtype);
  if (ObjArch != TT.getArch())
    return make_error<StringError>(
        objDesc(*Obj, TT, ObjIsSlice) + Triple::getArchTypeName(ObjArch) +
            ", cannot be loaded into " + TT.str() + " process",
        inconvertibleErrorCode());

  return std::move(Obj);
}

Expected<std::unique_ptr<MemoryBuffer>>
checkMachORelocatableObject(std::unique_ptr<MemoryBuffer> Obj, const Triple &TT,
                            bool ObjIsSlice) {
  StringRef Data = Obj->getBuffer();

  if (Data.size() < 4)
    return make_error<StringError>(
        objDesc(*Obj, TT, ObjIsSlice) +
            " is not a valid MachO relocatable object file (truncated header)",
        inconvertibleErrorCode());

  uint32_t Magic;
  memcpy(&Magic, Data.data(), sizeof(uint32_t));

  switch (Magic) {
  case MachO::MH_MAGIC:
  case MachO::MH_CIGAM:
    return checkMachORelocatableObject<MachO::mach_header>(
        std::move(Obj), Magic == MachO::MH_CIGAM, TT, ObjIsSlice);
  case MachO::MH_MAGIC_64:
  case MachO::MH_CIGAM_64:
    return checkMachORelocatableObject<MachO::mach_header_64>(
        std::move(Obj), Magic == MachO::MH_CIGAM_64, TT, ObjIsSlice);
  default:
    return make_error<StringError>(
        objDesc(*Obj, TT, ObjIsSlice) +
            " is not a valid MachO relocatable object (bad magic value)",
        inconvertibleErrorCode());
  }
}

Expected<std::unique_ptr<MemoryBuffer>>
loadMachORelocatableObject(StringRef Path, const Triple &TT) {
  assert((TT.getObjectFormat() == Triple::UnknownObjectFormat ||
          TT.getObjectFormat() == Triple::MachO) &&
         "TT must specify MachO or Unknown object format");

  auto Buf = MemoryBuffer::getFile(Path);
  if (!Buf)
    return createFileError(Path, Buf.getError());

  switch (identify_magic((*Buf)->getBuffer())) {
  case file_magic::macho_object:
    return checkMachORelocatableObject(std::move(*Buf), TT, false);
  case file_magic::macho_universal_binary:
    return loadMachORelocatableObjectFromUniversalBinary(Path, std::move(*Buf),
                                                         TT);
  default:
    return make_error<StringError>(
        Path + " does not contain a relocatable object file compatible with " +
            TT.str(),
        inconvertibleErrorCode());
  }
}

Expected<std::unique_ptr<MemoryBuffer>>
loadMachORelocatableObjectFromUniversalBinary(
    StringRef UBPath, std::unique_ptr<MemoryBuffer> UBBuf, const Triple &TT) {

  auto UniversalBin =
      object::MachOUniversalBinary::create(UBBuf->getMemBufferRef());
  if (!UniversalBin)
    return UniversalBin.takeError();

  auto SliceRange = getMachOSliceRangeForTriple(**UniversalBin, TT);
  if (!SliceRange)
    return SliceRange.takeError();

  auto ObjBuf = errorOrToExpected(MemoryBuffer::getFileSlice(
      UBPath, SliceRange->second, SliceRange->first, false));
  if (!ObjBuf)
    return createFileError(UBPath, ObjBuf.takeError());

  return checkMachORelocatableObject(std::move(*ObjBuf), TT, true);
}

Expected<std::pair<size_t, size_t>>
getMachOSliceRangeForTriple(object::MachOUniversalBinary &UB,
                            const Triple &TT) {

  for (const auto &Obj : UB.objects()) {
    auto ObjTT = Obj.getTriple();
    if (ObjTT.getArch() == TT.getArch() &&
        ObjTT.getSubArch() == TT.getSubArch() &&
        (TT.getVendor() == Triple::UnknownVendor ||
         ObjTT.getVendor() == TT.getVendor())) {
      // We found a match. Return the range for the slice.
      return std::make_pair(Obj.getOffset(), Obj.getSize());
    }
  }

  return make_error<StringError>(Twine("Universal binary ") + UB.getFileName() +
                                     " does not contain a slice for " +
                                     TT.str(),
                                 inconvertibleErrorCode());
}

Expected<std::pair<size_t, size_t>>
getMachOSliceRangeForTriple(MemoryBufferRef UBBuf, const Triple &TT) {

  auto UB = object::MachOUniversalBinary::create(UBBuf);
  if (!UB)
    return UB.takeError();

  return getMachOSliceRangeForTriple(**UB, TT);
}

} // End namespace orc.
} // End namespace llvm.