Introduce MinidumpWritable, its dependencies, and their tests

util/file/file_writer.cc

+// Copyright 2014 The Crashpad Authors. All rights reserved.
+//
+// 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 "util/file/file_writer.h"
+
+#include <algorithm>
+
+#include "base/logging.h"
+#include "base/posix/eintr_wrapper.h"
+#include "util/file/fd_io.h"
+
+namespace crashpad {
+
+// Ensure type compatibility between WritableIoVec and iovec.
+COMPILE_ASSERT(sizeof(WritableIoVec) == sizeof(iovec), WritableIoVec_size);
+COMPILE_ASSERT(offsetof(WritableIoVec, iov_base) == offsetof(iovec, iov_base),
+               WritableIoVec_base_offset);
+COMPILE_ASSERT(offsetof(WritableIoVec, iov_len) == offsetof(iovec, iov_len),
+               WritableIoVec_len_offset);
+
+FileWriter::FileWriter() : fd_() {
+}
+
+FileWriter::~FileWriter() {
+}
+
+bool FileWriter::Open(const base::FilePath& path, int oflag, mode_t mode) {
+  CHECK(!fd_.is_valid());
+
+  DCHECK((oflag & O_WRONLY) || (oflag & O_RDWR));
+
+  fd_.reset(HANDLE_EINTR(open(path.value().c_str(), oflag, mode)));
+  if (!fd_.is_valid()) {
+    PLOG(ERROR) << "open " << path.value();
+    return false;
+  }
+
+  return true;
+}
+
+void FileWriter::Close() {
+  CHECK(fd_.is_valid());
+
+  fd_.reset();
+}
+
+bool FileWriter::Write(const void* data, size_t size) {
+  DCHECK(fd_.is_valid());
+
+  // TODO(mark): Write no more than SSIZE_MAX bytes in a single call.
+  ssize_t written = WriteFD(fd_.get(), data, size);
+  if (written < 0) {
+    PLOG(ERROR) << "write";
+    return false;
+  } else if (written == 0) {
+    LOG(ERROR) << "write: returned 0";
+    return false;
+  }
+
+  return true;
+}
+
+bool FileWriter::WriteIoVec(std::vector<WritableIoVec>* iovecs) {
+  DCHECK(fd_.is_valid());
+
+  ssize_t size = 0;
+  for (const WritableIoVec& iov : *iovecs) {
+    // TODO(mark): Check to avoid overflow of ssize_t, and fail with EINVAL.
+    size += iov.iov_len;
+  }
+
+  // Get an iovec*, because that’s what writev wants. The only difference
+  // between WritableIoVec and iovec is that WritableIoVec’s iov_base is a
+  // pointer to a const buffer, where iovec’s iov_base isn’t. writev doesn’t
+  // actually write to the data, so this cast is safe here. iovec’s iov_base is
+  // non-const because the same structure is used for readv and writev, and
+  // readv needs to write to the buffer that iov_base points to.
+  iovec* iov = reinterpret_cast<iovec*>(&(*iovecs)[0]);
+  size_t remaining_iovecs = iovecs->size();
+
+  while (size > 0) {
+    size_t writev_iovec_count =
+        std::min(remaining_iovecs, static_cast<size_t>(IOV_MAX));
+    ssize_t written = HANDLE_EINTR(writev(fd_.get(), iov, writev_iovec_count));
+    if (written < 0) {
+      PLOG(ERROR) << "writev";
+      return false;
+    } else if (written == 0) {
+      LOG(ERROR) << "writev: returned 0";
+      return false;
+    }
+
+    size -= written;
+    DCHECK_GE(size, 0);
+
+    if (size == 0) {
+      remaining_iovecs = 0;
+      break;
+    }
+
+    while (written > 0) {
+      size_t wrote_this_iovec =
+          std::min(static_cast<size_t>(written), iov->iov_len);
+      written -= wrote_this_iovec;
+      if (wrote_this_iovec < iov->iov_len) {
+        iov->iov_base =
+            reinterpret_cast<char*>(iov->iov_base) + wrote_this_iovec;
+        iov->iov_len -= wrote_this_iovec;
+      } else {
+        ++iov;
+        --remaining_iovecs;
+      }
+    }
+  }
+
+  DCHECK_EQ(remaining_iovecs, 0u);
+
+#ifndef NDEBUG
+  // The interface says that |iovecs| is not sacred, so scramble it to make sure
+  // that nobody depends on it.
+  memset(&(*iovecs)[0], 0xa5, sizeof((*iovecs)[0]) * iovecs->size());
+#endif
+
+  return true;
+}
+
+off_t FileWriter::Seek(off_t offset, int whence) {
+  DCHECK(fd_.is_valid());
+
+  off_t rv = lseek(fd_.get(), offset, whence);
+  if (rv < 0) {
+    PLOG(ERROR) << "lseek";
+  }
+
+  return rv;
+}
+
+}  // namespace crashpad