Mojo: more idiomatic C++ bindings

mojo/public/cpp/bindings/lib/scratch_buffer.cc

-// Copyright 2014 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.
-
-#include "mojo/public/cpp/bindings/lib/scratch_buffer.h"
-
-#include <assert.h>
-#include <stdlib.h>
-#include <string.h>
-
-#include <algorithm>
-
-#include "mojo/public/cpp/bindings/lib/bindings_serialization.h"
-
-// Scrub memory in debug builds to help catch use-after-free bugs.
-#ifdef NDEBUG
-#define DEBUG_SCRUB(address, size) (void) (address), (void) (size)
-#else
-#define DEBUG_SCRUB(address, size) memset(address, 0xCD, size)
-#endif
-
-namespace mojo {
-namespace internal {
-
-ScratchBuffer::ScratchBuffer()
-    : overflow_(NULL) {
-  fixed_.next = NULL;
-  fixed_.cursor = internal::AlignPointer(fixed_data_);
-  fixed_.end = fixed_data_ + kMinSegmentSize;
-}
-
-ScratchBuffer::~ScratchBuffer() {
-  // Invoke destructors in reverse order to mirror allocation order.
-  std::deque<PendingDestructor>::reverse_iterator it;
-  for (it = pending_dtors_.rbegin(); it != pending_dtors_.rend(); ++it)
-    it->func(it->address);
-
-  while (overflow_) {
-    Segment* doomed = overflow_;
-    overflow_ = overflow_->next;
-    DEBUG_SCRUB(doomed, doomed->end - reinterpret_cast<char*>(doomed));
-    free(doomed);
-  }
-  DEBUG_SCRUB(fixed_data_, sizeof(fixed_data_));
-}
-
-void* ScratchBuffer::Allocate(size_t delta, Destructor func) {
-  delta = internal::Align(delta);
-  void* result = AllocateInSegment(&fixed_, delta);
-  if (!result && overflow_)
-    result = AllocateInSegment(overflow_, delta);
-
-  if (!result && AddOverflowSegment(delta))
-    result = AllocateInSegment(overflow_, delta);
-
-  if (func && result) {
-    PendingDestructor dtor;
-    dtor.func = func;
-    dtor.address = result;
-    pending_dtors_.push_back(dtor);
-  }
-  return result;
-}
-
-void* ScratchBuffer::AllocateInSegment(Segment* segment, size_t delta) {
-  if (static_cast<size_t>(segment->end - segment->cursor) >= delta) {
-    void* result = segment->cursor;
-    memset(result, 0, delta);  // Required to avoid info leaks.
-    segment->cursor += delta;
-    return result;
-  }
-  return NULL;
-}
-
-bool ScratchBuffer::AddOverflowSegment(size_t delta) {
-  if (delta < kMinSegmentSize)
-    delta = kMinSegmentSize;
-
-  if (delta > kMaxSegmentSize)
-    return false;
-
-  // Ensure segment buffer is aligned.
-  size_t padded_segment_size = internal::Align(sizeof(Segment));
-  Segment* segment = static_cast<Segment*>(
-      malloc(padded_segment_size + delta));
-  if (segment) {
-    segment->next = overflow_;
-    segment->cursor = reinterpret_cast<char*>(segment) + padded_segment_size;
-    segment->end = segment->cursor + delta;
-    overflow_ = segment;
-    return true;
-  }
-
-  return false;
-}
-
-}  // namespace internal
-}  // namespace mojo