src/llvm/lib/Support/FileOutputBuffer.cpp

   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