Collect unclean shutdown debug information

components/browser_watcher/postmortem_minidump_writer.h

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef COMPONENTS_BROWSER_WATCHER_POSTMORTEM_MINIDUMP_WRITER_H_
+#define COMPONENTS_BROWSER_WATCHER_POSTMORTEM_MINIDUMP_WRITER_H_
+
+#include <stdint.h>
+
+#include "base/files/file_path.h"
+#include "base/files/scoped_file.h"
+#include "base/macros.h"
+#include "base/strings/string_piece.h"
+#include "components/browser_watcher/stability_report.pb.h"
+
+namespace browser_watcher {
+
+// A class with functionality for writing minimal minidump containers to wrap
+// postmortem stability reports.
+// TODO(manzagop): remove this class once CrashPad takes over writing postmortem
+//     minidumps.
+class PostmortemMinidumpWriter {
+ public:
+  using Position = uint32_t;
+
+  PostmortemMinidumpWriter();
+  ~PostmortemMinidumpWriter() = default;
+
+  // Write to |minidump| a minimal minidump that wraps |report|. Returns true on
+  // success, false otherwise.
+  bool WriteDump(const base::FilePath& minidump, const StabilityReport& report);
+
+ private:
+  // The minidump header is always located at the head.
+  static const Position kHeaderPos = 0U;
+
+  // Allocate |size_bytes| within the minidump. On succress, |pos| contains the

[scottmg, 2016/08/03 22:47:06]

success

[manzagop (departed), 2016/08/10 15:59:51]

Done.

+  // location of the allocation. Returns true on success, false otherwise.
+  bool Allocate(size_t size_bytes, Position* pos);
+
+  // Write to pre-allocated space.
+  template <class DataType>
+  bool Write(Position pos, const DataType& data);
+  bool WriteBytes(Position pos, size_t size_bytes, const void* data);
+
+  // Allocate space for and write the contents of |data|. On success, |pos|
+  // contains the location of the write. Returns true on success, false
+  // otherwise.
+  template <class DataType>
+  bool Append(const DataType& data, Position* pos);
+  bool AppendBytes(base::StringPiece data, Position* pos);
+
+  // Safely increment |cursor_| by |size_bytes|.
+  bool IncrementCursor(size_t size_bytes);
+
+  // The next allocatable position.
+  Position cursor_;
+
+  // The file to write to.
+  base::ScopedFILE minidump_;
+
+  DISALLOW_COPY_AND_ASSIGN(PostmortemMinidumpWriter);
+};
+
+template <class DataType>
+bool PostmortemMinidumpWriter::Write(Position pos, const DataType& data) {
+  return WriteBytes(pos, sizeof(data), &data);
+}
+
+template <class DataType>
+bool PostmortemMinidumpWriter::Append(const DataType& data, Position* pos) {
+  DCHECK(pos);
+  if (!Allocate(sizeof(data), pos))
+    return false;
+  return Write(*pos, data);
+}
+
+}  // namespace browser_watcher
+
+#endif  // COMPONENTS_BROWSER_WATCHER_POSTMORTEM_MINIDUMP_WRITER_H_