MemoryBuffer.cpp

//===--- MemoryBuffer.cpp - Memory Buffer implementation ------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
//  This file implements the MemoryBuffer interface.
//
//===----------------------------------------------------------------------===//

#include "llvm/Support/MemoryBuffer.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/Config/config.h"
#include "llvm/Support/Errc.h"
#include "llvm/Support/Errno.h"
#include "llvm/Support/FileSystem.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/Path.h"
#include "llvm/Support/Process.h"
#include "llvm/Support/Program.h"
#include "llvm/Support/SmallVectorMemoryBuffer.h"
#include <cassert>
#include <cerrno>
#include <cstring>
#include <new>
#include <sys/types.h>
#include <system_error>
#if !defined(_MSC_VER) && !defined(__MINGW32__)
#include <unistd.h>
#else
#include <io.h>
#endif
using namespace llvm;

//===----------------------------------------------------------------------===//
// MemoryBuffer implementation itself.
//===----------------------------------------------------------------------===//

MemoryBuffer::~MemoryBuffer() { }

/// init - Initialize this MemoryBuffer as a reference to externally allocated
/// memory, memory that we know is already null terminated.
void MemoryBuffer::init(const char *BufStart, const char *BufEnd,
                        bool RequiresNullTerminator) {
  assert((!RequiresNullTerminator || BufEnd[0] == 0) &&
         "Buffer is not null terminated!");
  BufferStart = BufStart;
  BufferEnd = BufEnd;
}

//===----------------------------------------------------------------------===//
// MemoryBufferMem implementation.
//===----------------------------------------------------------------------===//

/// CopyStringRef - Copies contents of a StringRef into a block of memory and
/// null-terminates it.
static void CopyStringRef(char *Memory, StringRef Data) {
  if (!Data.empty())
    memcpy(Memory, Data.data(), Data.size());
  Memory[Data.size()] = 0; // Null terminate string.
}

namespace {
struct NamedBufferAlloc {
  const Twine &Name;
  NamedBufferAlloc(const Twine &Name) : Name(Name) {}
};
}

void *operator new(size_t N, const NamedBufferAlloc &Alloc) {
  SmallString<256> NameBuf;
  StringRef NameRef = Alloc.Name.toStringRef(NameBuf);

  char *Mem = static_cast<char *>(operator new(N + NameRef.size() + 1));
  CopyStringRef(Mem + N, NameRef);
  return Mem;
}

namespace {
/// MemoryBufferMem - Named MemoryBuffer pointing to a block of memory.
template<typename MB>
class MemoryBufferMem : public MB {
public:
  MemoryBufferMem(StringRef InputData, bool RequiresNullTerminator) {
    MemoryBuffer::init(InputData.begin(), InputData.end(),
                       RequiresNullTerminator);
  }

  /// Disable sized deallocation for MemoryBufferMem, because it has
  /// tail-allocated data.
  void operator delete(void *p) { ::operator delete(p); }

  StringRef getBufferIdentifier() const override {
    // The name is stored after the class itself.
    return StringRef(reinterpret_cast<const char *>(this + 1));
  }

  MemoryBuffer::BufferKind getBufferKind() const override {
    return MemoryBuffer::MemoryBuffer_Malloc;
  }
};
}

template <typename MB>
static ErrorOr<std::unique_ptr<MB>>
getFileAux(const Twine &Filename, int64_t FileSize, uint64_t MapSize,
           uint64_t Offset, bool RequiresNullTerminator, bool IsVolatile);

std::unique_ptr<MemoryBuffer>
MemoryBuffer::getMemBuffer(StringRef InputData, StringRef BufferName,
                           bool RequiresNullTerminator) {
  auto *Ret = new (NamedBufferAlloc(BufferName))
      MemoryBufferMem<MemoryBuffer>(InputData, RequiresNullTerminator);
  return std::unique_ptr<MemoryBuffer>(Ret);
}

std::unique_ptr<MemoryBuffer>
MemoryBuffer::getMemBuffer(MemoryBufferRef Ref, bool RequiresNullTerminator) {
  return std::unique_ptr<MemoryBuffer>(getMemBuffer(
      Ref.getBuffer(), Ref.getBufferIdentifier(), RequiresNullTerminator));
}

static ErrorOr<std::unique_ptr<WritableMemoryBuffer>>
getMemBufferCopyImpl(StringRef InputData, const Twine &BufferName) {
  auto Buf = WritableMemoryBuffer::getNewUninitMemBuffer(InputData.size(), BufferName);
  if (!Buf)
    return make_error_code(errc::not_enough_memory);
  memcpy(Buf->getBufferStart(), InputData.data(), InputData.size());
  return std::move(Buf);
}

std::unique_ptr<MemoryBuffer>
MemoryBuffer::getMemBufferCopy(StringRef InputData, const Twine &BufferName) {
  auto Buf = getMemBufferCopyImpl(InputData, BufferName);
  if (Buf)
    return std::move(*Buf);
  return nullptr;
}

ErrorOr<std::unique_ptr<MemoryBuffer>>
MemoryBuffer::getFileOrSTDIN(const Twine &Filename, int64_t FileSize,
                             bool RequiresNullTerminator) {
  SmallString<256> NameBuf;
  StringRef NameRef = Filename.toStringRef(NameBuf);

  if (NameRef == "-")
    return getSTDIN();
  return getFile(Filename, FileSize, RequiresNullTerminator);
}

ErrorOr<std::unique_ptr<MemoryBuffer>>
MemoryBuffer::getFileSlice(const Twine &FilePath, uint64_t MapSize,
                           uint64_t Offset, bool IsVolatile) {
  return getFileAux<MemoryBuffer>(FilePath, -1, MapSize, Offset, false,
                                  IsVolatile);
}

//===----------------------------------------------------------------------===//
// MemoryBuffer::getFile implementation.
//===----------------------------------------------------------------------===//

#if 0 // XXX BINARYEN
namespace {
/// Memory maps a file descriptor using sys::fs::mapped_file_region.
///
/// This handles converting the offset into a legal offset on the platform.
template<typename MB>
class MemoryBufferMMapFile : public MB {
  sys::fs::mapped_file_region MFR;

  static uint64_t getLegalMapOffset(uint64_t Offset) {
    return Offset & ~(sys::fs::mapped_file_region::alignment() - 1);
  }

  static uint64_t getLegalMapSize(uint64_t Len, uint64_t Offset) {
    return Len + (Offset - getLegalMapOffset(Offset));
  }

  const char *getStart(uint64_t Len, uint64_t Offset) {
    return MFR.const_data() + (Offset - getLegalMapOffset(Offset));
  }

public:
  MemoryBufferMMapFile(bool RequiresNullTerminator, sys::fs::file_t FD, uint64_t Len,
                       uint64_t Offset, std::error_code &EC)
      : MFR(FD, MB::Mapmode, getLegalMapSize(Len, Offset),
            getLegalMapOffset(Offset), EC) {
    if (!EC) {
      const char *Start = getStart(Len, Offset);
      MemoryBuffer::init(Start, Start + Len, RequiresNullTerminator);
    }
  }

  /// Disable sized deallocation for MemoryBufferMMapFile, because it has
  /// tail-allocated data.
  void operator delete(void *p) { ::operator delete(p); }

  StringRef getBufferIdentifier() const override {
    // The name is stored after the class itself.
    return StringRef(reinterpret_cast<const char *>(this + 1));
  }

  MemoryBuffer::BufferKind getBufferKind() const override {
    return MemoryBuffer::MemoryBuffer_MMap;
  }
};
}
#endif

static ErrorOr<std::unique_ptr<WritableMemoryBuffer>>
getMemoryBufferForStream(sys::fs::file_t FD, const Twine &BufferName) {
  llvm_unreachable("getMemoryBufferForStream");
}


ErrorOr<std::unique_ptr<MemoryBuffer>>
MemoryBuffer::getFile(const Twine &Filename, int64_t FileSize,
                      bool RequiresNullTerminator, bool IsVolatile) {
  return getFileAux<MemoryBuffer>(Filename, FileSize, FileSize, 0,
                                  RequiresNullTerminator, IsVolatile);
}

template <typename MB>
static ErrorOr<std::unique_ptr<MB>>
getOpenFileImpl(sys::fs::file_t FD, const Twine &Filename, uint64_t FileSize,
                uint64_t MapSize, int64_t Offset, bool RequiresNullTerminator,
                bool IsVolatile);

template <typename MB>
static ErrorOr<std::unique_ptr<MB>>
getFileAux(const Twine &Filename, int64_t FileSize, uint64_t MapSize,
           uint64_t Offset, bool RequiresNullTerminator, bool IsVolatile) {
  llvm_unreachable("getFileAux");
}

ErrorOr<std::unique_ptr<WritableMemoryBuffer>>
WritableMemoryBuffer::getFile(const Twine &Filename, int64_t FileSize,
                              bool IsVolatile) {
  return getFileAux<WritableMemoryBuffer>(Filename, FileSize, FileSize, 0,
                                          /*RequiresNullTerminator*/ false,
                                          IsVolatile);
}

ErrorOr<std::unique_ptr<WritableMemoryBuffer>>
WritableMemoryBuffer::getFileSlice(const Twine &Filename, uint64_t MapSize,
                                   uint64_t Offset, bool IsVolatile) {
  return getFileAux<WritableMemoryBuffer>(Filename, -1, MapSize, Offset, false,
                                          IsVolatile);
}

std::unique_ptr<WritableMemoryBuffer>
WritableMemoryBuffer::getNewUninitMemBuffer(size_t Size, const Twine &BufferName) {
  using MemBuffer = MemoryBufferMem<WritableMemoryBuffer>;
  // Allocate space for the MemoryBuffer, the data and the name. It is important
  // that MemoryBuffer and data are aligned so PointerIntPair works with them.
  // TODO: Is 16-byte alignment enough?  We copy small object files with large
  // alignment expectations into this buffer.
  SmallString<256> NameBuf;
  StringRef NameRef = BufferName.toStringRef(NameBuf);
  size_t AlignedStringLen = alignTo(sizeof(MemBuffer) + NameRef.size() + 1, 16);
  size_t RealLen = AlignedStringLen + Size + 1;
  char *Mem = static_cast<char*>(operator new(RealLen, std::nothrow));
  if (!Mem)
    return nullptr;

  // The name is stored after the class itself.
  CopyStringRef(Mem + sizeof(MemBuffer), NameRef);

  // The buffer begins after the name and must be aligned.
  char *Buf = Mem + AlignedStringLen;
  Buf[Size] = 0; // Null terminate buffer.

  auto *Ret = new (Mem) MemBuffer(StringRef(Buf, Size), true);
  return std::unique_ptr<WritableMemoryBuffer>(Ret);
}

std::unique_ptr<WritableMemoryBuffer>
WritableMemoryBuffer::getNewMemBuffer(size_t Size, const Twine &BufferName) {
  auto SB = WritableMemoryBuffer::getNewUninitMemBuffer(Size, BufferName);
  if (!SB)
    return nullptr;
  memset(SB->getBufferStart(), 0, Size);
  return SB;
}

static bool shouldUseMmap(sys::fs::file_t FD,
                          size_t FileSize,
                          size_t MapSize,
                          off_t Offset,
                          bool RequiresNullTerminator,
                          int PageSize,
                          bool IsVolatile) {
  // XXX BINARYEn
  return false;
}

static ErrorOr<std::unique_ptr<WriteThroughMemoryBuffer>>
getReadWriteFile(const Twine &Filename, uint64_t FileSize, uint64_t MapSize,
                 uint64_t Offset) {
  llvm_unreachable("getReadWriteFile");
}

ErrorOr<std::unique_ptr<WriteThroughMemoryBuffer>>
WriteThroughMemoryBuffer::getFile(const Twine &Filename, int64_t FileSize) {
  return getReadWriteFile(Filename, FileSize, FileSize, 0);
}

/// Map a subrange of the specified file as a WritableMemoryBuffer.
ErrorOr<std::unique_ptr<WriteThroughMemoryBuffer>>
WriteThroughMemoryBuffer::getFileSlice(const Twine &Filename, uint64_t MapSize,
                                       uint64_t Offset) {
  return getReadWriteFile(Filename, -1, MapSize, Offset);
}

template <typename MB>
static ErrorOr<std::unique_ptr<MB>>
getOpenFileImpl(sys::fs::file_t FD, const Twine &Filename, uint64_t FileSize,
                uint64_t MapSize, int64_t Offset, bool RequiresNullTerminator,
                bool IsVolatile) {
  llvm_unreachable("getOpenFileImpl");
}

ErrorOr<std::unique_ptr<MemoryBuffer>>
MemoryBuffer::getOpenFile(sys::fs::file_t FD, const Twine &Filename, uint64_t FileSize,
                          bool RequiresNullTerminator, bool IsVolatile) {
  return getOpenFileImpl<MemoryBuffer>(FD, Filename, FileSize, FileSize, 0,
                         RequiresNullTerminator, IsVolatile);
}

ErrorOr<std::unique_ptr<MemoryBuffer>>
MemoryBuffer::getOpenFileSlice(sys::fs::file_t FD, const Twine &Filename, uint64_t MapSize,
                               int64_t Offset, bool IsVolatile) {
  assert(MapSize != uint64_t(-1));
  return getOpenFileImpl<MemoryBuffer>(FD, Filename, -1, MapSize, Offset, false,
                                       IsVolatile);
}

ErrorOr<std::unique_ptr<MemoryBuffer>> MemoryBuffer::getSTDIN() {
  llvm_unreachable("getSTDIN");
}

ErrorOr<std::unique_ptr<MemoryBuffer>>
MemoryBuffer::getFileAsStream(const Twine &Filename) {
  llvm_unreachable("getFileAsStream");
}

MemoryBufferRef MemoryBuffer::getMemBufferRef() const {
  StringRef Data = getBuffer();
  StringRef Identifier = getBufferIdentifier();
  return MemoryBufferRef(Data, Identifier);
}

SmallVectorMemoryBuffer::~SmallVectorMemoryBuffer() {}