//===--- MemoryBuffer.cpp - Memory Buffer implementation ------------------===//

//

//                     The LLVM Compiler Infrastructure

//

// This file is distributed under the University of Illinois Open Source

// License. See LICENSE.TXT for details.

//

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

//

//  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 <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_ks;

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

// 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.

class MemoryBufferMem : public MemoryBuffer {

public:

  MemoryBufferMem(StringRef InputData, bool RequiresNullTerminator) {

    init(InputData.begin(), InputData.end(), RequiresNullTerminator);

  }

  const char *getBufferIdentifier() const override {

     // The name is stored after the class itself.

    return reinterpret_cast<const char*>(this + 1);

  }

  BufferKind getBufferKind() const override {

    return MemoryBuffer_Malloc;

  }

};

}

static ErrorOr<std::unique_ptr<MemoryBuffer>>

getFileAux(const Twine &Filename, int64_t FileSize, uint64_t MapSize, 

           uint64_t Offset, bool RequiresNullTerminator, bool IsVolatileSize);

std::unique_ptr<MemoryBuffer>

MemoryBuffer::getMemBuffer(StringRef InputData, StringRef BufferName,

                           bool RequiresNullTerminator) {

  auto *Ret = new (NamedBufferAlloc(BufferName))

      MemoryBufferMem(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));

}

std::unique_ptr<MemoryBuffer>

MemoryBuffer::getMemBufferCopy(StringRef InputData, const Twine &BufferName) {

  std::unique_ptr<MemoryBuffer> Buf =

      getNewUninitMemBuffer(InputData.size(), BufferName);

  if (!Buf)

    return nullptr;

  memcpy(const_cast<char*>(Buf->getBufferStart()), InputData.data(),

         InputData.size());

  return Buf;

}

std::unique_ptr<MemoryBuffer>

MemoryBuffer::getNewUninitMemBuffer(size_t Size, const Twine &BufferName) {

  // 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(MemoryBufferMem) + 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(MemoryBufferMem), 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) MemoryBufferMem(StringRef(Buf, Size), true);

  return std::unique_ptr<MemoryBuffer>(Ret);

}

std::unique_ptr<MemoryBuffer>

MemoryBuffer::getNewMemBuffer(size_t Size, StringRef BufferName) {

  std::unique_ptr<MemoryBuffer> SB = getNewUninitMemBuffer(Size, BufferName);

  if (!SB)

    return nullptr;

  memset(const_cast<char*>(SB->getBufferStart()), 0, Size);

  return SB;

}

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) {

  return getFileAux(FilePath, -1, MapSize, Offset, false, false);

}

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

// MemoryBuffer::getFile implementation.

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

namespace {

/// \brief Memory maps a file descriptor using sys::fs::mapped_file_region.

///

/// This handles converting the offset into a legal offset on the platform.

class MemoryBufferMMapFile : public MemoryBuffer {

  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, int FD, uint64_t Len,

                       uint64_t Offset, std::error_code &EC)

      : MFR(FD, sys::fs::mapped_file_region::readonly,

            getLegalMapSize(Len, Offset), getLegalMapOffset(Offset), EC) {

    if (!EC) {

      const char *Start = getStart(Len, Offset);

      init(Start, Start + Len, RequiresNullTerminator);

    }

  }

  const char *getBufferIdentifier() const override {

    // The name is stored after the class itself.

    return reinterpret_cast<const char *>(this + 1);

  }

  BufferKind getBufferKind() const override {

    return MemoryBuffer_MMap;

  }

};

}

static ErrorOr<std::unique_ptr<MemoryBuffer>>

getMemoryBufferForStream(int FD, const Twine &BufferName) {

  const ssize_t ChunkSize = 4096*4;

  SmallString<ChunkSize> Buffer;

  ssize_t ReadBytes;

  // Read into Buffer until we hit EOF.

  do {

    Buffer.reserve(Buffer.size() + ChunkSize);

    ReadBytes = read(FD, Buffer.end(), ChunkSize);

    if (ReadBytes == -1) {

      if (errno == EINTR) continue;

      return std::error_code(errno, std::generic_category());

    }

    Buffer.set_size(Buffer.size() + ReadBytes);

  } while (ReadBytes != 0);

  return MemoryBuffer::getMemBufferCopy(Buffer, BufferName);

}

ErrorOr<std::unique_ptr<MemoryBuffer>>

MemoryBuffer::getFile(const Twine &Filename, int64_t FileSize,

                      bool RequiresNullTerminator, bool IsVolatileSize) {

  return getFileAux(Filename, FileSize, FileSize, 0,

                    RequiresNullTerminator, IsVolatileSize);

}

static ErrorOr<std::unique_ptr<MemoryBuffer>>

getOpenFileImpl(int FD, const Twine &Filename, uint64_t FileSize,

                uint64_t MapSize, int64_t Offset, bool RequiresNullTerminator,

                bool IsVolatileSize);

static ErrorOr<std::unique_ptr<MemoryBuffer>>

getFileAux(const Twine &Filename, int64_t FileSize, uint64_t MapSize,

           uint64_t Offset, bool RequiresNullTerminator, bool IsVolatileSize) {

  int FD;

  std::error_code EC = sys::fs::openFileForRead(Filename, FD);

  if (EC)

    return EC;

  ErrorOr<std::unique_ptr<MemoryBuffer>> Ret =

      getOpenFileImpl(FD, Filename, FileSize, MapSize, Offset,

                      RequiresNullTerminator, IsVolatileSize);

  close(FD);

  return Ret;

}

static bool shouldUseMmap(int FD,

                          size_t FileSize,

                          size_t MapSize,

                          off_t Offset,

                          bool RequiresNullTerminator,

                          int PageSize,

                          bool IsVolatileSize) {

  // mmap may leave the buffer without null terminator if the file size changed

  // by the time the last page is mapped in, so avoid it if the file size is

  // likely to change.

  if (IsVolatileSize)

    return false;

  // We don't use mmap for small files because this can severely fragment our

  // address space.

  if (MapSize < 4 * 4096 || MapSize < (unsigned)PageSize)

    return false;

  if (!RequiresNullTerminator)

    return true;

  // If we don't know the file size, use fstat to find out.  fstat on an open

  // file descriptor is cheaper than stat on a random path.

  // FIXME: this chunk of code is duplicated, but it avoids a fstat when

  // RequiresNullTerminator = false and MapSize != -1.

  if (FileSize == size_t(-1)) {

    sys::fs::file_status Status;

    if (sys::fs::status(FD, Status))

      return false;

    FileSize = Status.getSize();

  }

  // If we need a null terminator and the end of the map is inside the file,

  // we cannot use mmap.

  size_t End = Offset + MapSize;

  assert(End <= FileSize);

  if (End != FileSize)

    return false;

  // Don't try to map files that are exactly a multiple of the system page size

  // if we need a null terminator.

  if ((FileSize & (PageSize -1)) == 0)

    return false;

#if defined(__CYGWIN__)

  // Don't try to map files that are exactly a multiple of the physical page size

  // if we need a null terminator.

  // FIXME: We should reorganize again getPageSize() on Win32.

  if ((FileSize & (4096 - 1)) == 0)

    return false;

#endif

  return true;

}

static ErrorOr<std::unique_ptr<MemoryBuffer>>

getOpenFileImpl(int FD, const Twine &Filename, uint64_t FileSize,

                uint64_t MapSize, int64_t Offset, bool RequiresNullTerminator,

                bool IsVolatileSize) {

  static int PageSize = 4096;

  // Default is to map the full file.

  if (MapSize == uint64_t(-1)) {

    // If we don't know the file size, use fstat to find out.  fstat on an open

    // file descriptor is cheaper than stat on a random path.

    if (FileSize == uint64_t(-1)) {

      sys::fs::file_status Status;

      std::error_code EC = sys::fs::status(FD, Status);

      if (EC)

        return EC;

      // If this not a file or a block device (e.g. it's a named pipe

      // or character device), we can't trust the size. Create the memory

      // buffer by copying off the stream.

      sys::fs::file_type Type = Status.type();

      if (Type != sys::fs::file_type::regular_file &&

          Type != sys::fs::file_type::block_file)

        return getMemoryBufferForStream(FD, Filename);

      FileSize = Status.getSize();

    }

    MapSize = FileSize;

  }

  if (shouldUseMmap(FD, FileSize, MapSize, Offset, RequiresNullTerminator,

                    PageSize, IsVolatileSize)) {

    std::error_code EC;

    std::unique_ptr<MemoryBuffer> Result(

        new (NamedBufferAlloc(Filename))

        MemoryBufferMMapFile(RequiresNullTerminator, FD, MapSize, Offset, EC));

    if (!EC)

      return std::move(Result);

  }

  std::unique_ptr<MemoryBuffer> Buf =

      MemoryBuffer::getNewUninitMemBuffer(MapSize, Filename);

  if (!Buf) {

    // Failed to create a buffer. The only way it can fail is if

    // new(std::nothrow) returns 0.

    return make_error_code(errc::not_enough_memory);

  }

  char *BufPtr = const_cast<char *>(Buf->getBufferStart());

  size_t BytesLeft = MapSize;

#ifndef HAVE_PREAD

  if (lseek(FD, Offset, SEEK_SET) == -1)

    return std::error_code(errno, std::generic_category());

#endif

  while (BytesLeft) {

#ifdef HAVE_PREAD

    ssize_t NumRead = ::pread(FD, BufPtr, BytesLeft, MapSize-BytesLeft+Offset);

#else

    ssize_t NumRead = ::read(FD, BufPtr, BytesLeft);

#endif

    if (NumRead == -1) {

      if (errno == EINTR)

        continue;

      // Error while reading.

      return std::error_code(errno, std::generic_category());

    }

    if (NumRead == 0) {

      memset(BufPtr, 0, BytesLeft); // zero-initialize rest of the buffer.

      break;

    }

    BytesLeft -= NumRead;

    BufPtr += NumRead;

  }

  return std::move(Buf);

}

ErrorOr<std::unique_ptr<MemoryBuffer>>

MemoryBuffer::getOpenFile(int FD, const Twine &Filename, uint64_t FileSize,

                          bool RequiresNullTerminator, bool IsVolatileSize) {

  return getOpenFileImpl(FD, Filename, FileSize, FileSize, 0,

                         RequiresNullTerminator, IsVolatileSize);

}

ErrorOr<std::unique_ptr<MemoryBuffer>>

MemoryBuffer::getOpenFileSlice(int FD, const Twine &Filename, uint64_t MapSize,

                               int64_t Offset) {

  assert(MapSize != uint64_t(-1));

  return getOpenFileImpl(FD, Filename, -1, MapSize, Offset, false,

                         /*IsVolatileSize*/ false);

}

ErrorOr<std::unique_ptr<MemoryBuffer>> MemoryBuffer::getSTDIN() {

  // Read in all of the data from stdin, we cannot mmap stdin.

  //

  // FIXME: That isn't necessarily true, we should try to mmap stdin and

  // fallback if it fails.

  return getMemoryBufferForStream(0, "<stdin>");

}

MemoryBufferRef MemoryBuffer::getMemBufferRef() const {

  StringRef Data = getBuffer();

  StringRef Identifier = getBufferIdentifier();

  return MemoryBufferRef(Data, Identifier);

}