1 files changed, 196 insertions, 0 deletions

diff --git a/contrib/llvm-project/llvm/lib/Support/FileOutputBuffer.cpp b/contrib/llvm-project/llvm/lib/Support/FileOutputBuffer.cpp
new file mode 100644
index 000000000000..3d6b569f2993
--- /dev/null
+++ b/contrib/llvm-project/llvm/lib/Support/FileOutputBuffer.cpp
@@ -0,0 +1,196 @@
+//===- FileOutputBuffer.cpp - File Output Buffer ----------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// Utility for creating a in-memory buffer that will be written to a file.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Support/FileOutputBuffer.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/SmallString.h"
+#include "llvm/Support/Errc.h"
+#include "llvm/Support/Memory.h"
+#include "llvm/Support/Path.h"
+#include <system_error>
+
+#if !defined(_MSC_VER) && !defined(__MINGW32__)
+#include <unistd.h>
+#else
+#include <io.h>
+#endif
+
+using namespace llvm;
+using namespace llvm::sys;
+
+namespace {
+// A FileOutputBuffer which creates a temporary file in the same directory
+// as the final output file. The final output file is atomically replaced
+// with the temporary file on commit().
+class OnDiskBuffer : public FileOutputBuffer {
+public:
+  OnDiskBuffer(StringRef Path, fs::TempFile Temp,
+               std::unique_ptr<fs::mapped_file_region> Buf)
+      : FileOutputBuffer(Path), Buffer(std::move(Buf)), Temp(std::move(Temp)) {}
+
+  uint8_t *getBufferStart() const override { return (uint8_t *)Buffer->data(); }
+
+  uint8_t *getBufferEnd() const override {
+    return (uint8_t *)Buffer->data() + Buffer->size();
+  }
+
+  size_t getBufferSize() const override { return Buffer->size(); }
+
+  Error commit() override {
+    // Unmap buffer, letting OS flush dirty pages to file on disk.
+    Buffer.reset();
+
+    // Atomically replace the existing file with the new one.
+    return Temp.keep(FinalPath);
+  }
+
+  ~OnDiskBuffer() override {
+    // Close the mapping before deleting the temp file, so that the removal
+    // succeeds.
+    Buffer.reset();
+    consumeError(Temp.discard());
+  }
+
+  void discard() override {
+    // Delete the temp file if it still was open, but keeping the mapping
+    // active.
+    consumeError(Temp.discard());
+  }
+
+private:
+  std::unique_ptr<fs::mapped_file_region> Buffer;
+  fs::TempFile Temp;
+};
+
+// A FileOutputBuffer which keeps data in memory and writes to the final
+// output file on commit(). This is used only when we cannot use OnDiskBuffer.
+class InMemoryBuffer : public FileOutputBuffer {
+public:
+  InMemoryBuffer(StringRef Path, MemoryBlock Buf, std::size_t BufSize,
+                 unsigned Mode)
+      : FileOutputBuffer(Path), Buffer(Buf), BufferSize(BufSize),
+        Mode(Mode) {}
+
+  uint8_t *getBufferStart() const override { return (uint8_t *)Buffer.base(); }
+
+  uint8_t *getBufferEnd() const override {
+    return (uint8_t *)Buffer.base() + BufferSize;
+  }
+
+  size_t getBufferSize() const override { return BufferSize; }
+
+  Error commit() override {
+    if (FinalPath == "-") {
+      llvm::outs() << StringRef((const char *)Buffer.base(), BufferSize);
+      llvm::outs().flush();
+      return Error::success();
+    }
+
+    using namespace sys::fs;
+    int FD;
+    std::error_code EC;
+    if (auto EC =
+            openFileForWrite(FinalPath, FD, CD_CreateAlways, OF_None, Mode))
+      return errorCodeToError(EC);
+    raw_fd_ostream OS(FD, /*shouldClose=*/true, /*unbuffered=*/true);
+    OS << StringRef((const char *)Buffer.base(), BufferSize);
+    return Error::success();
+  }
+
+private:
+  // Buffer may actually contain a larger memory block than BufferSize
+  OwningMemoryBlock Buffer;
+  size_t BufferSize;
+  unsigned Mode;
+};
+} // namespace
+
+static Expected<std::unique_ptr<InMemoryBuffer>>
+createInMemoryBuffer(StringRef Path, size_t Size, unsigned Mode) {
+  std::error_code EC;
+  MemoryBlock MB = Memory::allocateMappedMemory(
+      Size, nullptr, sys::Memory::MF_READ | sys::Memory::MF_WRITE, EC);
+  if (EC)
+    return errorCodeToError(EC);
+  return llvm::make_unique<InMemoryBuffer>(Path, MB, Size, Mode);
+}
+
+static Expected<std::unique_ptr<FileOutputBuffer>>
+createOnDiskBuffer(StringRef Path, size_t Size, unsigned Mode) {
+  Expected<fs::TempFile> FileOrErr =
+      fs::TempFile::create(Path + ".tmp%%%%%%%", Mode);
+  if (!FileOrErr)
+    return FileOrErr.takeError();
+  fs::TempFile File = std::move(*FileOrErr);
+
+#ifndef _WIN32
+  // On Windows, CreateFileMapping (the mmap function on Windows)
+  // automatically extends the underlying file. We don't need to
+  // extend the file beforehand. _chsize (ftruncate on Windows) is
+  // pretty slow just like it writes specified amount of bytes,
+  // so we should avoid calling that function.
+  if (auto EC = fs::resize_file(File.FD, Size)) {
+    consumeError(File.discard());
+    return errorCodeToError(EC);
+  }
+#endif
+
+  // Mmap it.
+  std::error_code EC;
+  auto MappedFile = llvm::make_unique<fs::mapped_file_region>(
+      fs::convertFDToNativeFile(File.FD), fs::mapped_file_region::readwrite,
+      Size, 0, EC);
+
+  // mmap(2) can fail if the underlying filesystem does not support it.
+  // If that happens, we fall back to in-memory buffer as the last resort.
+  if (EC) {
+    consumeError(File.discard());
+    return createInMemoryBuffer(Path, Size, Mode);
+  }
+
+  return llvm::make_unique<OnDiskBuffer>(Path, std::move(File),
+                                         std::move(MappedFile));
+}
+
+// Create an instance of FileOutputBuffer.
+Expected<std::unique_ptr<FileOutputBuffer>>
+FileOutputBuffer::create(StringRef Path, size_t Size, unsigned Flags) {
+  // Handle "-" as stdout just like llvm::raw_ostream does.
+  if (Path == "-")
+    return createInMemoryBuffer("-", Size, /*Mode=*/0);
+
+  unsigned Mode = fs::all_read | fs::all_write;
+  if (Flags & F_executable)
+    Mode |= fs::all_exe;
+
+  fs::file_status Stat;
+  fs::status(Path, Stat);
+
+  // Usually, we want to create OnDiskBuffer to create a temporary file in
+  // the same directory as the destination file and atomically replaces it
+  // by rename(2).
+  //
+  // However, if the destination file is a special file, we don't want to
+  // use rename (e.g. we don't want to replace /dev/null with a regular
+  // file.) If that's the case, we create an in-memory buffer, open the
+  // destination file and write to it on commit().
+  switch (Stat.type()) {
+  case fs::file_type::directory_file:
+    return errorCodeToError(errc::is_a_directory);
+  case fs::file_type::regular_file:
+  case fs::file_type::file_not_found:
+  case fs::file_type::status_error:
+    return createOnDiskBuffer(Path, Size, Mode);
+  default:
+    return createInMemoryBuffer(Path, Size, Mode);
+  }
+}