src/utils/io/tmpfile_posix.cc

// Copyright 2021 The Tint Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#include "src/utils/io/tmpfile.h"

#include <unistd.h>
#include <limits>

#include "src/debug.h"

namespace tint {
namespace utils {

namespace {

std::string TmpFilePath(std::string ext) {
  char const* dir = getenv("TMPDIR");
  if (dir == nullptr) {
    dir = "/tmp";
  }

  // mkstemps requires an `int` for the file extension name but STL represents
  // size_t. Pre-C++20 there the behavior for unsigned-to-signed conversion
  // (when the source value exceeds the representable range) is implementation
  // defined. While such a large file extension is unlikely in practice, we
  // enforce this here at runtime.
  TINT_ASSERT(Utils, ext.length() <=
                         static_cast<size_t>(std::numeric_limits<int>::max()));
  std::string name = std::string(dir) + "/tint_XXXXXX" + ext;
  int file = mkstemps(&name[0], static_cast<int>(ext.length()));
  if (file != -1) {
    close(file);
    return name;
  }
  return "";
}

}  // namespace

TmpFile::TmpFile(std::string extension)
    : path_(TmpFilePath(std::move(extension))) {}

TmpFile::~TmpFile() {
  if (!path_.empty()) {
    remove(path_.c_str());
  }
}

bool TmpFile::Append(const void* data, size_t size) const {
  if (auto* file = fopen(path_.c_str(), "ab")) {
    fwrite(data, size, 1, file);
    fclose(file);
    return true;
  }
  return false;
}

}  // namespace utils
}  // namespace tint