1 //===- FileOutputBuffer.cpp - File Output Buffer ----------------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // Utility for creating a in-memory buffer that will be written to a file.
12 //===----------------------------------------------------------------------===//
14 #include "llvm/Support/FileOutputBuffer.h"
15 #include "llvm/ADT/STLExtras.h"
16 #include "llvm/ADT/SmallString.h"
17 #include "llvm/Support/Errc.h"
18 #include "llvm/Support/Path.h"
19 #include "llvm/Support/Signals.h"
20 #include <system_error>
22 #if !defined(_MSC_VER) && !defined(__MINGW32__)
28 using llvm::sys::fs::mapped_file_region;
31 FileOutputBuffer::FileOutputBuffer(std::unique_ptr<mapped_file_region> R,
32 StringRef Path, StringRef TmpPath,
34 : Region(std::move(R)), FinalPath(Path), TempPath(TmpPath),
35 IsRegular(IsRegular) {}
37 FileOutputBuffer::~FileOutputBuffer() {
38 // Close the mapping before deleting the temp file, so that the removal
41 sys::fs::remove(Twine(TempPath));
44 ErrorOr<std::unique_ptr<FileOutputBuffer>>
45 FileOutputBuffer::create(StringRef FilePath, size_t Size, unsigned Flags) {
46 // Check file is not a regular file, in which case we cannot remove it.
47 sys::fs::file_status Stat;
48 std::error_code EC = sys::fs::status(FilePath, Stat);
49 bool IsRegular = true;
50 switch (Stat.type()) {
51 case sys::fs::file_type::file_not_found:
52 // If file does not exist, we'll create one.
54 case sys::fs::file_type::regular_file: {
55 // If file is not currently writable, error out.
56 // FIXME: There is no sys::fs:: api for checking this.
57 // FIXME: In posix, you use the access() call to check this.
60 case sys::fs::file_type::directory_file:
61 return errc::is_a_directory;
69 // Delete target file.
70 EC = sys::fs::remove(FilePath);
75 SmallString<128> TempFilePath;
78 unsigned Mode = sys::fs::all_read | sys::fs::all_write;
79 // If requested, make the output file executable.
80 if (Flags & F_executable)
81 Mode |= sys::fs::all_exe;
82 // Create new file in same directory but with random name.
83 EC = sys::fs::createUniqueFile(Twine(FilePath) + ".tmp%%%%%%%", FD,
86 // Create a temporary file. Since this is a special file, we will not move
87 // it and the new file can be in another filesystem. This avoids trying to
88 // create a temporary file in /dev when outputting to /dev/null for example.
89 EC = sys::fs::createTemporaryFile(sys::path::filename(FilePath), "", FD,
96 sys::RemoveFileOnSignal(TempFilePath);
99 // On Windows, CreateFileMapping (the mmap function on Windows)
100 // automatically extends the underlying file. We don't need to
101 // extend the file beforehand. _chsize (ftruncate on Windows) is
102 // pretty slow just like it writes specified amount of bytes,
103 // so we should avoid calling that.
104 EC = sys::fs::resize_file(FD, Size);
109 auto MappedFile = llvm::make_unique<mapped_file_region>(
110 FD, mapped_file_region::readwrite, Size, 0, EC);
115 return std::error_code(errno, std::generic_category());
117 std::unique_ptr<FileOutputBuffer> Buf(new FileOutputBuffer(
118 std::move(MappedFile), FilePath, TempFilePath, IsRegular));
119 return std::move(Buf);
122 std::error_code FileOutputBuffer::commit() {
123 // Unmap buffer, letting OS flush dirty pages to file on disk.
128 // Rename file to final name.
129 EC = sys::fs::rename(Twine(TempPath), Twine(FinalPath));
130 sys::DontRemoveFileOnSignal(TempPath);
132 EC = sys::fs::copy_file(TempPath, FinalPath);
133 std::error_code RMEC = sys::fs::remove(TempPath);
134 sys::DontRemoveFileOnSignal(TempPath);