FileOutputBuffer.h   [plain text]

//=== FileOutputBuffer.h - File Output Buffer -------------------*- C++ -*-===//
//                     The LLVM Compiler Infrastructure
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
// Utility for creating a in-memory buffer that will be written to a file.


#include "llvm/ADT/OwningPtr.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/Support/DataTypes.h"
#include "llvm/Support/FileSystem.h"

namespace llvm {
class error_code;

/// FileOutputBuffer - This interface provides simple way to create an in-memory
/// buffer which will be written to a file. During the lifetime of these
/// objects, the content or existence of the specified file is undefined. That
/// is, creating an OutputBuffer for a file may immediately remove the file.
/// If the FileOutputBuffer is committed, the target file's content will become
/// the buffer content at the time of the commit.  If the FileOutputBuffer is
/// not committed, the file will be deleted in the FileOutputBuffer destructor.
class FileOutputBuffer {

  enum  {
    F_executable = 1  /// set the 'x' bit on the resulting file

  /// Factory method to create an OutputBuffer object which manages a read/write
  /// buffer of the specified size. When committed, the buffer will be written
  /// to the file at the specified path.
  static error_code create(StringRef FilePath, size_t Size,
                           OwningPtr<FileOutputBuffer> &Result,
                           unsigned Flags = 0);

  /// Returns a pointer to the start of the buffer.
  uint8_t *getBufferStart() {
    return (uint8_t*)Region->data();

  /// Returns a pointer to the end of the buffer.
  uint8_t *getBufferEnd() {
    return (uint8_t*)Region->data() + Region->size();

  /// Returns size of the buffer.
  size_t getBufferSize() const {
    return Region->size();

  /// Returns path where file will show up if buffer is committed.
  StringRef getPath() const {
    return FinalPath;

  /// Flushes the content of the buffer to its file and deallocates the
  /// buffer.  If commit() is not called before this object's destructor
  /// is called, the file is deleted in the destructor. The optional parameter
  /// is used if it turns out you want the file size to be smaller than
  /// initially requested.
  error_code commit(int64_t NewSmallerSize = -1);

  /// If this object was previously committed, the destructor just deletes
  /// this object.  If this object was not committed, the destructor
  /// deallocates the buffer and the target file is never written.

  FileOutputBuffer(const FileOutputBuffer &) LLVM_DELETED_FUNCTION;
  FileOutputBuffer &operator=(const FileOutputBuffer &) LLVM_DELETED_FUNCTION;

  FileOutputBuffer(llvm::sys::fs::mapped_file_region *R,
                   StringRef Path, StringRef TempPath);

  OwningPtr<llvm::sys::fs::mapped_file_region> Region;
  SmallString<128>    FinalPath;
  SmallString<128>    TempPath;
} // end namespace llvm