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115 lines
3.5 KiB
C++
115 lines
3.5 KiB
C++
//===- FileOutputBuffer.cpp - File Output Buffer ----------------*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// Utility for creating a in-memory buffer that will be written to a file.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Support/FileOutputBuffer.h"
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#include "llvm/ADT/STLExtras.h"
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#include "llvm/ADT/SmallString.h"
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#include "llvm/Support/Errc.h"
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#include "llvm/Support/Signals.h"
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#include <system_error>
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#if !defined(_MSC_VER) && !defined(__MINGW32__)
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#include <unistd.h>
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#else
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#include <io.h>
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#endif
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using llvm::sys::fs::mapped_file_region;
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namespace llvm {
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FileOutputBuffer::FileOutputBuffer(std::unique_ptr<mapped_file_region> R,
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StringRef Path, StringRef TmpPath)
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: Region(std::move(R)), FinalPath(Path), TempPath(TmpPath) {}
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FileOutputBuffer::~FileOutputBuffer() {
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sys::fs::remove(Twine(TempPath));
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}
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ErrorOr<std::unique_ptr<FileOutputBuffer>>
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FileOutputBuffer::create(StringRef FilePath, size_t Size, unsigned Flags) {
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// If file already exists, it must be a regular file (to be mappable).
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sys::fs::file_status Stat;
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std::error_code EC = sys::fs::status(FilePath, Stat);
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switch (Stat.type()) {
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case sys::fs::file_type::file_not_found:
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// If file does not exist, we'll create one.
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break;
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case sys::fs::file_type::regular_file: {
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// If file is not currently writable, error out.
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// FIXME: There is no sys::fs:: api for checking this.
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// FIXME: In posix, you use the access() call to check this.
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}
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break;
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default:
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if (EC)
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return EC;
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else
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return make_error_code(errc::operation_not_permitted);
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}
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// Delete target file.
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EC = sys::fs::remove(FilePath);
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if (EC)
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return EC;
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unsigned Mode = sys::fs::all_read | sys::fs::all_write;
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// If requested, make the output file executable.
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if (Flags & F_executable)
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Mode |= sys::fs::all_exe;
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// Create new file in same directory but with random name.
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SmallString<128> TempFilePath;
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int FD;
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EC = sys::fs::createUniqueFile(Twine(FilePath) + ".tmp%%%%%%%", FD,
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TempFilePath, Mode);
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if (EC)
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return EC;
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sys::RemoveFileOnSignal(TempFilePath);
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#ifndef LLVM_ON_WIN32
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// On Windows, CreateFileMapping (the mmap function on Windows)
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// automatically extends the underlying file. We don't need to
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// extend the file beforehand. _chsize (ftruncate on Windows) is
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// pretty slow just like it writes specified amount of bytes,
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// so we should avoid calling that.
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EC = sys::fs::resize_file(FD, Size);
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if (EC)
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return EC;
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#endif
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auto MappedFile = llvm::make_unique<mapped_file_region>(
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FD, mapped_file_region::readwrite, Size, 0, EC);
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int Ret = close(FD);
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if (EC)
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return EC;
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if (Ret)
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return std::error_code(errno, std::generic_category());
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std::unique_ptr<FileOutputBuffer> Buf(
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new FileOutputBuffer(std::move(MappedFile), FilePath, TempFilePath));
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return std::move(Buf);
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}
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std::error_code FileOutputBuffer::commit() {
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// Unmap buffer, letting OS flush dirty pages to file on disk.
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Region.reset();
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// Rename file to final name.
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std::error_code EC = sys::fs::rename(Twine(TempPath), Twine(FinalPath));
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sys::DontRemoveFileOnSignal(TempPath);
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return EC;
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}
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} // namespace
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