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// 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 = 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) {
if (overflow_)
result = AllocateInSegment(overflow_, delta);
if (!result) {
AddOverflowSegment(delta);
result = AllocateInSegment(overflow_, delta);
}
}
if (func) {
PendingDestructor dtor;
dtor.func = func;
dtor.address = result;
pending_dtors_.push_back(dtor);
}
return result;
}
void* ScratchBuffer::AllocateInSegment(Segment* segment, size_t delta) {
void* result;
if (static_cast<size_t>(segment->end - segment->cursor) >= delta) {
result = segment->cursor;
memset(result, 0, delta);
segment->cursor += delta;
} else {
result = NULL;
}
return result;
}
void ScratchBuffer::AddOverflowSegment(size_t delta) {
if (delta < kMinSegmentSize)
delta = kMinSegmentSize;
// Ensure segment buffer is aligned.
size_t segment_size = internal::Align(sizeof(Segment)) + delta;
Segment* segment = static_cast<Segment*>(malloc(segment_size));
segment->next = overflow_;
segment->cursor = reinterpret_cast<char*>(segment + 1);
segment->end = segment->cursor + delta;
overflow_ = segment;
}
} // namespace internal
} // namespace mojo
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