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