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

content/browser/renderer_host/resource_buffer.h

-// 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.
-
-#ifndef CONTENT_BROWSER_RENDERER_HOST_RESOURCE_BUFFER_H_
-#define CONTENT_BROWSER_RENDERER_HOST_RESOURCE_BUFFER_H_
-
-#include <queue>
-
-#include "base/basictypes.h"
-#include "base/memory/ref_counted.h"
-#include "base/shared_memory.h"
-#include "content/common/content_export.h"
-
-namespace content {
-
-// ResourceBuffer implements a simple "circular buffer" allocation strategy.
-// Allocations are recycled in FIFO order.
-//
-// You can think of the ResourceBuffer as a FIFO.  The Allocate method reserves
-// space in the buffer.  Allocate may be called multiple times until the buffer
-// is fully reserved (at which point CanAllocate returns false).  Allocations
-// are freed in FIFO order via a call to RecycleLeastRecentlyAllocated.
-//
-// ResourceBuffer is reference-counted for the benefit of consumers, who need
-// to ensure that ResourceBuffer stays alive while they are using its memory.
-//
-// EXAMPLE USAGE:
-//
-//   // Writes data into the ResourceBuffer, and returns the location (byte
-//   // offset and count) of the bytes written into the ResourceBuffer's shared
-//   // memory buffer.
-//   void WriteToBuffer(ResourceBuffer* buf, int* offset, int* count) {
-//     DCHECK(buf->CanAllocate());
-//
-//     *offset = -1;
-//     *count = 0;
-//
-//     int size;
-//     char* ptr = buf->Allocate(&size);
-//     if (!ptr) { /* handle error */ }
-//
-//     int bytes_read = static_cast<int>(fread(ptr, 1, size, file_pointer_));
-//     if (!bytes_read) { /* handle error */ }
-//
-//     if (bytes_read < size)
-//       buf->ShrinkLastAllocation(bytes_read);
-//
-//     *offset = buf->GetLastAllocationOffset();
-//     *count = bytes_read;
-//   }
-//
-// NOTE: As the above example illustrates, the ResourceBuffer keeps track of
-// the last allocation made.  Calling ShrinkLastAllocation is optional, as it
-// just helps the ResourceBuffer optimize storage and be more aggressive about
-// returning larger allocations from the Allocate method.
-//
-class CONTENT_EXPORT ResourceBuffer
-    : public base::RefCountedThreadSafe<ResourceBuffer> {
- public:
-  ResourceBuffer();
-
-  // Initialize the shared memory buffer.  It will be buffer_size bytes in
-  // length.  The min/max_allocation_size parameters control the behavior of
-  // the Allocate method.  It will prefer to return segments that are
-  // max_allocation_size in length, but will return segments less than that if
-  // space is limited.  It will not return allocations smaller than
-  // min_allocation_size.
-  bool Initialize(int buffer_size,
-                  int min_allocation_size,
-                  int max_allocation_size);
-  bool IsInitialized() const;
-
-  // Returns a shared memory handle that can be passed to the given process.
-  // The shared memory handle is only intended to be interpretted by code
-  // running in the specified process.  NOTE: The caller should ensure that
-  // this memory eventually be returned to the operating system.
-  bool ShareToProcess(base::ProcessHandle process_handle,
-                      base::SharedMemoryHandle* shared_memory_handle,
-                      int* shared_memory_size);
-
-  // Returns true if Allocate will succeed.
-  bool CanAllocate() const;
-
-  // Returns a pointer into the shared memory buffer or NULL if the buffer is
-  // already fully allocated.  The returned size will be max_allocation_size
-  // unless the buffer is close to being full.
-  char* Allocate(int* size);
-
-  // Returns the offset into the shared memory buffer where the last allocation
-  // returned by Allocate can be found.
-  int GetLastAllocationOffset() const;
-
-  // Called to reduce the size of the last allocation returned by Allocate.  It
-  // is OK for new_size to match the current size of the last allocation.
-  void ShrinkLastAllocation(int new_size);
-
-  // Called to allow reuse of memory that was previously allocated.  See notes
-  // above the class for more details about this method.
-  void RecycleLeastRecentlyAllocated();
-
- private:
-  friend class base::RefCountedThreadSafe<ResourceBuffer>;
-  ~ResourceBuffer();
-
-  base::SharedMemory shared_mem_;
-
-  int buf_size_;
-  int min_alloc_size_;
-  int max_alloc_size_;
-
-  // These point to the range of the shared memory that is currently allocated.
-  // If alloc_start_ is -1, then the range is empty and nothing is allocated.
-  // Otherwise, alloc_start_ points to the start of the allocated range, and
-  // alloc_end_ points just beyond the end of the previous allocation.  In the
-  // wraparound case, alloc_end_ <= alloc_start_.  See resource_buffer.cc for
-  // more details about these members.
-  int alloc_start_;
-  int alloc_end_;
-
-  std::queue<int> alloc_sizes_;
-
-  DISALLOW_COPY_AND_ASSIGN(ResourceBuffer);
-};
-
-}  // namespace content
-
-#endif  // CONTENT_BROWSER_RENDERER_HOST_RESOURCE_BUFFER_H_