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/Support/FileOutputBuffer.h"
16 #include "llvm/ADT/SmallVector.h"
17 #include "llvm/Support/raw_ostream.h"
18 #include <system_error>
19
20 using llvm::sys::fs::mapped_file_region;
21
22 namespace llvm {
FileOutputBuffer(mapped_file_region * R,StringRef Path,StringRef TmpPath)23 FileOutputBuffer::FileOutputBuffer(mapped_file_region * R,
24 StringRef Path, StringRef TmpPath)
25 : Region(R)
26 , FinalPath(Path)
27 , TempPath(TmpPath) {
28 }
29
~FileOutputBuffer()30 FileOutputBuffer::~FileOutputBuffer() {
31 sys::fs::remove(Twine(TempPath));
32 }
33
34 std::error_code
create(StringRef FilePath,size_t Size,std::unique_ptr<FileOutputBuffer> & Result,unsigned Flags)35 FileOutputBuffer::create(StringRef FilePath, 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 std::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 std::error_code();
86 }
87
commit(int64_t NewSmallerSize)88 std::error_code FileOutputBuffer::commit(int64_t NewSmallerSize) {
89 // Unmap buffer, letting OS flush dirty pages to file on disk.
90 Region.reset(nullptr);
91
92 // If requested, resize file as part of commit.
93 if ( NewSmallerSize != -1 ) {
94 std::error_code EC = sys::fs::resize_file(Twine(TempPath), NewSmallerSize);
95 if (EC)
96 return EC;
97 }
98
99 // Rename file to final name.
100 return sys::fs::rename(Twine(TempPath), Twine(FinalPath));
101 }
102 } // namespace
103