[llvm-exegesis][NFC] Fix typo
[llvm-complete.git] / lib / Support / FileOutputBuffer.cpp
blobb8223126227df9c0d090afe6918735473a2b1a86
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.
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/Memory.h"
19 #include "llvm/Support/Path.h"
20 #include <system_error>
22 #if !defined(_MSC_VER) && !defined(__MINGW32__)
23 #include <unistd.h>
24 #else
25 #include <io.h>
26 #endif
28 using namespace llvm;
29 using namespace llvm::sys;
31 namespace {
32 // A FileOutputBuffer which creates a temporary file in the same directory
33 // as the final output file. The final output file is atomically replaced
34 // with the temporary file on commit().
35 class OnDiskBuffer : public FileOutputBuffer {
36 public:
37 OnDiskBuffer(StringRef Path, fs::TempFile Temp,
38 std::unique_ptr<fs::mapped_file_region> Buf)
39 : FileOutputBuffer(Path), Buffer(std::move(Buf)), Temp(std::move(Temp)) {}
41 uint8_t *getBufferStart() const override { return (uint8_t *)Buffer->data(); }
43 uint8_t *getBufferEnd() const override {
44 return (uint8_t *)Buffer->data() + Buffer->size();
47 size_t getBufferSize() const override { return Buffer->size(); }
49 Error commit() override {
50 // Unmap buffer, letting OS flush dirty pages to file on disk.
51 Buffer.reset();
53 // Atomically replace the existing file with the new one.
54 return Temp.keep(FinalPath);
57 ~OnDiskBuffer() override {
58 // Close the mapping before deleting the temp file, so that the removal
59 // succeeds.
60 Buffer.reset();
61 consumeError(Temp.discard());
64 void discard() override {
65 // Delete the temp file if it still was open, but keeping the mapping
66 // active.
67 consumeError(Temp.discard());
70 private:
71 std::unique_ptr<fs::mapped_file_region> Buffer;
72 fs::TempFile Temp;
75 // A FileOutputBuffer which keeps data in memory and writes to the final
76 // output file on commit(). This is used only when we cannot use OnDiskBuffer.
77 class InMemoryBuffer : public FileOutputBuffer {
78 public:
79 InMemoryBuffer(StringRef Path, MemoryBlock Buf, unsigned Mode)
80 : FileOutputBuffer(Path), Buffer(Buf), Mode(Mode) {}
82 uint8_t *getBufferStart() const override { return (uint8_t *)Buffer.base(); }
84 uint8_t *getBufferEnd() const override {
85 return (uint8_t *)Buffer.base() + Buffer.size();
88 size_t getBufferSize() const override { return Buffer.size(); }
90 Error commit() override {
91 using namespace sys::fs;
92 int FD;
93 std::error_code EC;
94 if (auto EC =
95 openFileForWrite(FinalPath, FD, CD_CreateAlways, OF_None, Mode))
96 return errorCodeToError(EC);
97 raw_fd_ostream OS(FD, /*shouldClose=*/true, /*unbuffered=*/true);
98 OS << StringRef((const char *)Buffer.base(), Buffer.size());
99 return Error::success();
102 private:
103 OwningMemoryBlock Buffer;
104 unsigned Mode;
106 } // namespace
108 static Expected<std::unique_ptr<InMemoryBuffer>>
109 createInMemoryBuffer(StringRef Path, size_t Size, unsigned Mode) {
110 std::error_code EC;
111 MemoryBlock MB = Memory::allocateMappedMemory(
112 Size, nullptr, sys::Memory::MF_READ | sys::Memory::MF_WRITE, EC);
113 if (EC)
114 return errorCodeToError(EC);
115 return llvm::make_unique<InMemoryBuffer>(Path, MB, Mode);
118 static Expected<std::unique_ptr<OnDiskBuffer>>
119 createOnDiskBuffer(StringRef Path, size_t Size, bool InitExisting,
120 unsigned Mode) {
121 Expected<fs::TempFile> FileOrErr =
122 fs::TempFile::create(Path + ".tmp%%%%%%%", Mode);
123 if (!FileOrErr)
124 return FileOrErr.takeError();
125 fs::TempFile File = std::move(*FileOrErr);
127 if (InitExisting) {
128 if (auto EC = sys::fs::copy_file(Path, File.FD))
129 return errorCodeToError(EC);
130 } else {
131 #ifndef _WIN32
132 // On Windows, CreateFileMapping (the mmap function on Windows)
133 // automatically extends the underlying file. We don't need to
134 // extend the file beforehand. _chsize (ftruncate on Windows) is
135 // pretty slow just like it writes specified amount of bytes,
136 // so we should avoid calling that function.
137 if (auto EC = fs::resize_file(File.FD, Size)) {
138 consumeError(File.discard());
139 return errorCodeToError(EC);
141 #endif
144 // Mmap it.
145 std::error_code EC;
146 auto MappedFile = llvm::make_unique<fs::mapped_file_region>(
147 File.FD, fs::mapped_file_region::readwrite, Size, 0, EC);
148 if (EC) {
149 consumeError(File.discard());
150 return errorCodeToError(EC);
152 return llvm::make_unique<OnDiskBuffer>(Path, std::move(File),
153 std::move(MappedFile));
156 // Create an instance of FileOutputBuffer.
157 Expected<std::unique_ptr<FileOutputBuffer>>
158 FileOutputBuffer::create(StringRef Path, size_t Size, unsigned Flags) {
159 unsigned Mode = fs::all_read | fs::all_write;
160 if (Flags & F_executable)
161 Mode |= fs::all_exe;
163 fs::file_status Stat;
164 fs::status(Path, Stat);
166 if ((Flags & F_modify) && Size == size_t(-1)) {
167 if (Stat.type() == fs::file_type::regular_file)
168 Size = Stat.getSize();
169 else if (Stat.type() == fs::file_type::file_not_found)
170 return errorCodeToError(errc::no_such_file_or_directory);
171 else
172 return errorCodeToError(errc::invalid_argument);
175 // Usually, we want to create OnDiskBuffer to create a temporary file in
176 // the same directory as the destination file and atomically replaces it
177 // by rename(2).
179 // However, if the destination file is a special file, we don't want to
180 // use rename (e.g. we don't want to replace /dev/null with a regular
181 // file.) If that's the case, we create an in-memory buffer, open the
182 // destination file and write to it on commit().
183 switch (Stat.type()) {
184 case fs::file_type::directory_file:
185 return errorCodeToError(errc::is_a_directory);
186 case fs::file_type::regular_file:
187 case fs::file_type::file_not_found:
188 case fs::file_type::status_error:
189 return createOnDiskBuffer(Path, Size, !!(Flags & F_modify), Mode);
190 default:
191 return createInMemoryBuffer(Path, Size, Mode);