FileOutputBuffer.cpp revision 36b56886974eae4f9c5ebc96befd3e7bfe5de338 
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/FileOutputBuffer.h"
15#include "llvm/ADT/OwningPtr.h"
16#include "llvm/ADT/SmallVector.h"
17#include "llvm/Support/raw_ostream.h"
18#include "llvm/Support/system_error.h"
19
20using llvm::sys::fs::mapped_file_region;
21
22namespace llvm {
23FileOutputBuffer::FileOutputBuffer(mapped_file_region * R,
24                                   StringRef Path, StringRef TmpPath)
25  : Region(R)
26  , FinalPath(Path)
27  , TempPath(TmpPath) {
28}
29
30FileOutputBuffer::~FileOutputBuffer() {
31  sys::fs::remove(Twine(TempPath));
32}
33
34error_code FileOutputBuffer::create(StringRef FilePath,
35                                    size_t Size,
36                                    std::unique_ptr<FileOutputBuffer> &Result,
37                                    unsigned Flags) {
38  // If file already exists, it must be a regular file (to be mappable).
39  sys::fs::file_status Stat;
40  error_code EC = sys::fs::status(FilePath, Stat);
41  switch (Stat.type()) {
42    case sys::fs::file_type::file_not_found:
43      // If file does not exist, we'll create one.
44      break;
45    case sys::fs::file_type::regular_file: {
46        // If file is not currently writable, error out.
47        // FIXME: There is no sys::fs:: api for checking this.
48        // FIXME: In posix, you use the access() call to check this.
49      }
50      break;
51    default:
52      if (EC)
53        return EC;
54      else
55        return make_error_code(errc::operation_not_permitted);
56  }
57
58  // Delete target file.
59  EC = sys::fs::remove(FilePath);
60  if (EC)
61    return EC;
62
63  unsigned Mode = sys::fs::all_read | sys::fs::all_write;
64  // If requested, make the output file executable.
65  if (Flags & F_executable)
66    Mode |= sys::fs::all_exe;
67
68  // Create new file in same directory but with random name.
69  SmallString<128> TempFilePath;
70  int FD;
71  EC = sys::fs::createUniqueFile(Twine(FilePath) + ".tmp%%%%%%%", FD,
72                                 TempFilePath, Mode);
73  if (EC)
74    return EC;
75
76  std::unique_ptr<mapped_file_region> MappedFile(new mapped_file_region(
77      FD, true, mapped_file_region::readwrite, Size, 0, EC));
78  if (EC)
79    return EC;
80
81  Result.reset(new FileOutputBuffer(MappedFile.get(), FilePath, TempFilePath));
82  if (Result)
83    MappedFile.release();
84
85  return error_code::success();
86}
87
88error_code FileOutputBuffer::create(StringRef FilePath,
89                                    size_t Size,
90                                    OwningPtr<FileOutputBuffer> &Result,
91                                    unsigned Flags) {
92  std::unique_ptr<FileOutputBuffer> FOB;
93  error_code ec = create(FilePath, Size, FOB, Flags);
94  Result = std::move(FOB);
95  return ec;
96}
97
98error_code FileOutputBuffer::commit(int64_t NewSmallerSize) {
99  // Unmap buffer, letting OS flush dirty pages to file on disk.
100  Region.reset(0);
101
102  // If requested, resize file as part of commit.
103  if ( NewSmallerSize != -1 ) {
104    error_code EC = sys::fs::resize_file(Twine(TempPath), NewSmallerSize);
105    if (EC)
106      return EC;
107  }
108
109  // Rename file to final name.
110  return sys::fs::rename(Twine(TempPath), Twine(FinalPath));
111}
112} // namespace
113