1//===- Buffer.cpp ---------------------------------------------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8
9#include "Buffer.h"
10#include "llvm/Support/FileOutputBuffer.h"
11#include "llvm/Support/FileSystem.h"
12#include "llvm/Support/MemoryBuffer.h"
13#include "llvm/Support/Process.h"
14#include <memory>
15
16namespace llvm {
17namespace objcopy {
18
19Buffer::~Buffer() {}
20
21static Error createEmptyFile(StringRef FileName) {
22  // Create an empty tempfile and atomically swap it in place with the desired
23  // output file.
24  Expected<sys::fs::TempFile> Temp =
25      sys::fs::TempFile::create(FileName + ".temp-empty-%%%%%%%");
26  return Temp ? Temp->keep(FileName) : Temp.takeError();
27}
28
29Error FileBuffer::allocate(size_t Size) {
30  // When a 0-sized file is requested, skip allocation but defer file
31  // creation/truncation until commit() to avoid side effects if something
32  // happens between allocate() and commit().
33  if (Size == 0) {
34    EmptyFile = true;
35    return Error::success();
36  }
37
38  Expected<std::unique_ptr<FileOutputBuffer>> BufferOrErr =
39      FileOutputBuffer::create(getName(), Size, FileOutputBuffer::F_executable);
40  // FileOutputBuffer::create() returns an Error that is just a wrapper around
41  // std::error_code. Wrap it in FileError to include the actual filename.
42  if (!BufferOrErr)
43    return createFileError(getName(), BufferOrErr.takeError());
44  Buf = std::move(*BufferOrErr);
45  return Error::success();
46}
47
48Error FileBuffer::commit() {
49  if (EmptyFile)
50    return createEmptyFile(getName());
51
52  assert(Buf && "allocate() not called before commit()!");
53  Error Err = Buf->commit();
54  // FileOutputBuffer::commit() returns an Error that is just a wrapper around
55  // std::error_code. Wrap it in FileError to include the actual filename.
56  return Err ? createFileError(getName(), std::move(Err)) : std::move(Err);
57}
58
59uint8_t *FileBuffer::getBufferStart() {
60  return reinterpret_cast<uint8_t *>(Buf->getBufferStart());
61}
62
63Error MemBuffer::allocate(size_t Size) {
64  Buf = WritableMemoryBuffer::getNewMemBuffer(Size, getName());
65  return Error::success();
66}
67
68Error MemBuffer::commit() { return Error::success(); }
69
70uint8_t *MemBuffer::getBufferStart() {
71  return reinterpret_cast<uint8_t *>(Buf->getBufferStart());
72}
73
74std::unique_ptr<WritableMemoryBuffer> MemBuffer::releaseMemoryBuffer() {
75  return std::move(Buf);
76}
77
78} // end namespace objcopy
79} // end namespace llvm
80