Add content/browser/loader/ for resource loading related classes.

content/browser/renderer_host/resource_buffer.cc

-// Copyright (c) 2012 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 "content/browser/renderer_host/resource_buffer.h"
-
-#include <math.h>
-
-#include "base/logging.h"
-
-namespace content {
-
-// A circular buffer allocator.
-//
-// We keep track of the starting offset (alloc_start_) and the ending offset
-// (alloc_end_).  There are two layouts to keep in mind:
-//
-// #1:
-//    ------------[XXXXXXXXXXXXXXXXXXXXXXX]----
-//                ^                        ^
-//                start                    end
-//
-// #2:
-//    XXXXXXXXXX]---------------------[XXXXXXXX
-//               ^                    ^
-//               end                  start
-//
-// If end <= start, then we have the buffer wraparound case (depicted second).
-// If the buffer is empty, then start and end will be set to -1.
-//
-// Allocations are always contiguous.
-
-ResourceBuffer::ResourceBuffer()
-    : buf_size_(0),
-      min_alloc_size_(0),
-      max_alloc_size_(0),
-      alloc_start_(-1),
-      alloc_end_(-1) {
-}
-
-ResourceBuffer::~ResourceBuffer() {
-}
-
-bool ResourceBuffer::Initialize(int buffer_size,
-                                int min_allocation_size,
-                                int max_allocation_size) {
-  DCHECK(!IsInitialized());
-
-  // It would be wasteful if these are not multiples of min_allocation_size.
-  DCHECK_EQ(0, buffer_size % min_allocation_size);
-  DCHECK_EQ(0, max_allocation_size % min_allocation_size);
-
-  buf_size_ = buffer_size;
-  min_alloc_size_ = min_allocation_size;
-  max_alloc_size_ = max_allocation_size;
-
-  return shared_mem_.CreateAndMapAnonymous(buf_size_);
-}
-
-bool ResourceBuffer::IsInitialized() const {
-  return shared_mem_.memory() != NULL;
-}
-
-bool ResourceBuffer::ShareToProcess(
-    base::ProcessHandle process_handle,
-    base::SharedMemoryHandle* shared_memory_handle,
-    int* shared_memory_size) {
-  DCHECK(IsInitialized());
-
-  if (!shared_mem_.ShareToProcess(process_handle, shared_memory_handle))
-    return false;
-
-  *shared_memory_size = buf_size_;
-  return true;
-}
-
-bool ResourceBuffer::CanAllocate() const {
-  DCHECK(IsInitialized());
-
-  if (alloc_start_ == -1)
-    return true;
-
-  int diff = alloc_end_ - alloc_start_;
-  if (diff > 0)
-    return (buf_size_ - diff) >= min_alloc_size_;
-
-  return -diff >= min_alloc_size_;
-}
-
-char* ResourceBuffer::Allocate(int* size) {
-  DCHECK(CanAllocate());
-
-  int alloc_offset = 0;
-  int alloc_size;
-
-  if (alloc_start_ == -1) {
-    // This is the first allocation.
-    alloc_start_ = 0;
-    alloc_end_ = buf_size_;
-    alloc_size = buf_size_;
-  } else if (alloc_start_ < alloc_end_) {
-    // Append the next allocation if it fits.  Otherwise, wraparound.
-    //
-    // NOTE: We could look to see if a larger allocation is possible by
-    // wrapping around sooner, but instead we just look to fill the space at
-    // the end of the buffer provided that meets the min_alloc_size_
-    // requirement.
-    //
-    if ((buf_size_ - alloc_end_) >= min_alloc_size_) {
-      alloc_offset = alloc_end_;
-      alloc_size = buf_size_ - alloc_end_;
-      alloc_end_ = buf_size_;
-    } else {
-      // It must be possible to allocate a least min_alloc_size_.
-      DCHECK(alloc_start_ >= min_alloc_size_);
-      alloc_size = alloc_start_;
-      alloc_end_ = alloc_start_;
-    }
-  } else {
-    // This is the wraparound case.
-    DCHECK(alloc_end_ < alloc_start_);
-    alloc_offset = alloc_end_;
-    alloc_size = alloc_start_ - alloc_end_;
-    alloc_end_ = alloc_start_;
-  }
-
-  // Make sure alloc_size does not exceed max_alloc_size_.  We store the
-  // current value of alloc_size, so that we can use ShrinkLastAllocation to
-  // trim it back.  This allows us to reuse the alloc_end_ adjustment logic.
-
-  alloc_sizes_.push(alloc_size);
-
-  if (alloc_size > max_alloc_size_) {
-    alloc_size = max_alloc_size_;
-    ShrinkLastAllocation(alloc_size);
-  }
-
-  *size = alloc_size;
-  return static_cast<char*>(shared_mem_.memory()) + alloc_offset;
-}
-
-int ResourceBuffer::GetLastAllocationOffset() const {
-  DCHECK(!alloc_sizes_.empty());
-  DCHECK(alloc_end_ >= alloc_sizes_.back());
-  return alloc_end_ - alloc_sizes_.back();
-}
-
-void ResourceBuffer::ShrinkLastAllocation(int new_size) {
-  DCHECK(!alloc_sizes_.empty());
-
-  int aligned_size = (new_size / min_alloc_size_) * min_alloc_size_;
-  if (aligned_size < new_size)
-    aligned_size += min_alloc_size_;
-
-  DCHECK_LE(new_size, aligned_size);
-  DCHECK_GE(alloc_sizes_.back(), aligned_size);
-
-  int* last_allocation_size = &alloc_sizes_.back();
-  alloc_end_ -= (*last_allocation_size - aligned_size);
-  *last_allocation_size = aligned_size;
-}
-
-void ResourceBuffer::RecycleLeastRecentlyAllocated() {
-  DCHECK(!alloc_sizes_.empty());
-  int allocation_size = alloc_sizes_.front();
-  alloc_sizes_.pop();
-
-  alloc_start_ += allocation_size;
-  DCHECK(alloc_start_ <= buf_size_);
-
-  if (alloc_start_ == alloc_end_) {
-    DCHECK(alloc_sizes_.empty());
-    alloc_start_ = -1;
-    alloc_end_ = -1;
-  } else if (alloc_start_ == buf_size_) {
-    DCHECK(!alloc_sizes_.empty());
-    alloc_start_ = 0;
-  }
-}
-
-}  // namespace content