1 //===- FileOutputBuffer.cpp - File Output Buffer ----------------*- C++ -*-===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // Utility for creating a in-memory buffer that will be written to a file.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "llvm/Support/Errc.h"
15 #include "llvm/ADT/STLExtras.h"
16 #include "llvm/ADT/SmallVector.h"
17 #include "llvm/Support/FileOutputBuffer.h"
18 #include "llvm/Support/raw_ostream.h"
19 #include <system_error>
20 
21 #if !defined(_MSC_VER) && !defined(__MINGW32__)
22 #include <unistd.h>
23 #else
24 #include <io.h>
25 #endif
26 
27 using llvm::sys::fs::mapped_file_region;
28 
29 namespace llvm {
30 FileOutputBuffer::FileOutputBuffer(std::unique_ptr<mapped_file_region> R,
31                                    StringRef Path, StringRef TmpPath)
32     : Region(std::move(R)), FinalPath(Path), TempPath(TmpPath) {}
33 
34 FileOutputBuffer::~FileOutputBuffer() {
35   sys::fs::remove(Twine(TempPath));
36 }
37 
38 std::error_code
39 FileOutputBuffer::create(StringRef FilePath, size_t Size,
40                          std::unique_ptr<FileOutputBuffer> &Result,
41                          unsigned Flags) {
42   // If file already exists, it must be a regular file (to be mappable).
43   sys::fs::file_status Stat;
44   std::error_code EC = sys::fs::status(FilePath, Stat);
45   switch (Stat.type()) {
46     case sys::fs::file_type::file_not_found:
47       // If file does not exist, we'll create one.
48       break;
49     case sys::fs::file_type::regular_file: {
50         // If file is not currently writable, error out.
51         // FIXME: There is no sys::fs:: api for checking this.
52         // FIXME: In posix, you use the access() call to check this.
53       }
54       break;
55     default:
56       if (EC)
57         return EC;
58       else
59         return make_error_code(errc::operation_not_permitted);
60   }
61 
62   // Delete target file.
63   EC = sys::fs::remove(FilePath);
64   if (EC)
65     return EC;
66 
67   unsigned Mode = sys::fs::all_read | sys::fs::all_write;
68   // If requested, make the output file executable.
69   if (Flags & F_executable)
70     Mode |= sys::fs::all_exe;
71 
72   // Create new file in same directory but with random name.
73   SmallString<128> TempFilePath;
74   int FD;
75   EC = sys::fs::createUniqueFile(Twine(FilePath) + ".tmp%%%%%%%", FD,
76                                  TempFilePath, Mode);
77   if (EC)
78     return EC;
79 
80   EC = sys::fs::resize_file(FD, Size);
81   if (EC)
82     return EC;
83 
84   auto MappedFile = llvm::make_unique<mapped_file_region>(
85       FD, mapped_file_region::readwrite, Size, 0, EC);
86   int Ret = close(FD);
87   if (EC)
88     return EC;
89   if (Ret)
90     return std::error_code(errno, std::generic_category());
91 
92   Result.reset(
93       new FileOutputBuffer(std::move(MappedFile), FilePath, TempFilePath));
94 
95   return std::error_code();
96 }
97 
98 std::error_code FileOutputBuffer::commit() {
99   // Unmap buffer, letting OS flush dirty pages to file on disk.
100   Region.reset();
101 
102 
103   // Rename file to final name.
104   return sys::fs::rename(Twine(TempPath), Twine(FinalPath));
105 }
106 } // namespace
107