include/llvm/Support/FileUtilities.h

//===- llvm/Support/FileUtilities.h - File System Utilities -----*- C++ -*-===//
//
// 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 defines a family of utility functions which are useful for doing
// various things with files.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_SUPPORT_FILEUTILITIES_H
#define LLVM_SUPPORT_FILEUTILITIES_H

#include "llvm/ADT/StringRef.h"
#include "llvm/Support/Error.h"
#include "llvm/Support/FileSystem.h"

#include <system_error>

namespace llvm {

  /// DiffFilesWithTolerance - Compare the two files specified, returning 0 if
  /// the files match, 1 if they are different, and 2 if there is a file error.
  /// This function allows you to specify an absolute and relative FP error that
  /// is allowed to exist.  If you specify a string to fill in for the error
  /// option, it will set the string to an error message if an error occurs, or
  /// if the files are different.
  ///
  int DiffFilesWithTolerance(StringRef FileA,
                             StringRef FileB,
                             double AbsTol, double RelTol,
                             std::string *Error = nullptr);


  /// FileRemover - This class is a simple object meant to be stack allocated.
  /// If an exception is thrown from a region, the object removes the filename
  /// specified (if deleteIt is true).
  ///
  class FileRemover {
    SmallString<128> Filename;
    bool DeleteIt;
  public:
    FileRemover() : DeleteIt(false) {}

    explicit FileRemover(const Twine& filename, bool deleteIt = true)
      : DeleteIt(deleteIt) {
      filename.toVector(Filename);
    }

    ~FileRemover() {
      if (DeleteIt) {
        // Ignore problems deleting the file.
        sys::fs::remove(Filename);
      }
    }

    /// setFile - Give ownership of the file to the FileRemover so it will
    /// be removed when the object is destroyed.  If the FileRemover already
    /// had ownership of a file, remove it first.
    void setFile(const Twine& filename, bool deleteIt = true) {
      if (DeleteIt) {
        // Ignore problems deleting the file.
        sys::fs::remove(Filename);
      }

      Filename.clear();
      filename.toVector(Filename);
      DeleteIt = deleteIt;
    }

    /// releaseFile - Take ownership of the file away from the FileRemover so it
    /// will not be removed when the object is destroyed.
    void releaseFile() { DeleteIt = false; }
  };

  /// FilePermssionsApplier helps to copy permissions from an input file to
  /// an output one. It memorizes the status of the input file and can apply
  /// permissions and dates to the output file.
  class FilePermissionsApplier {
  public:
    static Expected<FilePermissionsApplier> create(StringRef InputFilename);

    /// Apply stored permissions to the \p OutputFilename.
    /// Copy LastAccess and ModificationTime if \p CopyDates is true.
    /// Overwrite stored permissions if \p OverwritePermissions is specified.
    Error
    apply(StringRef OutputFilename, bool CopyDates = false,
          std::optional<sys::fs::perms> OverwritePermissions = std::nullopt);

  private:
    FilePermissionsApplier(StringRef InputFilename, sys::fs::file_status Status)
        : InputFilename(InputFilename), InputStatus(Status) {}

    StringRef InputFilename;
    sys::fs::file_status InputStatus;
  };
} // End llvm namespace

#endif