tools/llvm-objcopy/Buffer.cpp

   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
  16 namespace llvm {
  17 namespace objcopy {
  18
  19 Buffer::~Buffer() {}
  20
  21 static 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
  29 Error 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
  48 Error 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
  59 uint8_t *FileBuffer::getBufferStart() {
  60   return reinterpret_cast<uint8_t *>(Buf->getBufferStart());
  61 }
  62
  63 Error MemBuffer::allocate(size_t Size) {
  64   Buf = WritableMemoryBuffer::getNewMemBuffer(Size, getName());
  65   return Error::success();
  66 }
  67
  68 Error MemBuffer::commit() { return Error::success(); }
  69
  70 uint8_t *MemBuffer::getBufferStart() {
  71   return reinterpret_cast<uint8_t *>(Buf->getBufferStart());
  72 }
  73
  74 std::unique_ptr<WritableMemoryBuffer> MemBuffer::releaseMemoryBuffer() {
  75   return std::move(Buf);
  76 }
  77
  78 } // end namespace objcopy
  79 } // end namespace llvm