// 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.
// This file contains the definition of the FencedAllocator class.
#ifndef GPU_COMMAND_BUFFER_CLIENT_FENCED_ALLOCATOR_H_
#define GPU_COMMAND_BUFFER_CLIENT_FENCED_ALLOCATOR_H_
#include <vector>
#include "base/bind.h"
#include "base/logging.h"
#include "gpu/command_buffer/common/types.h"
#include "gpu/gpu_export.h"
namespace gpu {
class CommandBufferHelper;
// FencedAllocator provides a mechanism to manage allocations within a fixed
// block of memory (storing the book-keeping externally). Furthermore this
// class allows to free data "pending" the passage of a command buffer token,
// that is, the memory won't be reused until the command buffer has processed
// that token.
//
// NOTE: Although this class is intended to be used in the command buffer
// environment which is multi-process, this class isn't "thread safe", because
// it isn't meant to be shared across modules. It is thread-compatible though
// (see http://www.corp.google.com/eng/doc/cpp_primer.html#thread_safety).
class GPU_EXPORT FencedAllocator {
public:
typedef unsigned int Offset;
// Invalid offset, returned by Alloc in case of failure.
static const Offset kInvalidOffset = 0xffffffffU;
// Creates a FencedAllocator. Note that the size of the buffer is passed, but
// not its base address: everything is handled as offsets into the buffer.
FencedAllocator(unsigned int size,
CommandBufferHelper *helper,
const base::Closure& poll_callback);
~FencedAllocator();
// Allocates a block of memory. If the buffer is out of directly available
// memory, this function may wait until memory that was freed "pending a
// token" can be re-used.
//
// Parameters:
// size: the size of the memory block to allocate.
//
// Returns:
// the offset of the allocated memory block, or kInvalidOffset if out of
// memory.
Offset Alloc(unsigned int size);
// Frees a block of memory.
//
// Parameters:
// offset: the offset of the memory block to free.
void Free(Offset offset);
// Frees a block of memory, pending the passage of a token. That memory won't
// be re-allocated until the token has passed through the command stream.
//
// Parameters:
// offset: the offset of the memory block to free.
// token: the token value to wait for before re-using the memory.
void FreePendingToken(Offset offset, int32 token);
// Frees any blocks pending a token for which the token has been read.
void FreeUnused();
// Gets the size of the largest free block that is available without waiting.
unsigned int GetLargestFreeSize();
// Gets the size of the largest free block that can be allocated if the
// caller can wait. Allocating a block of this size will succeed, but may
// block.
unsigned int GetLargestFreeOrPendingSize();
// Checks for consistency inside the book-keeping structures. Used for
// testing.
bool CheckConsistency();
// True if any memory is allocated.
bool InUse();
// Return bytes of memory that is IN_USE
size_t bytes_in_use() const { return bytes_in_use_; }
private:
// Status of a block of memory, for book-keeping.
enum State {
IN_USE,
FREE,
FREE_PENDING_TOKEN
};
// Book-keeping sturcture that describes a block of memory.
struct Block {
State state;
Offset offset;
unsigned int size;
int32 token; // token to wait for in the FREE_PENDING_TOKEN case.
};
// Comparison functor for memory block sorting.
class OffsetCmp {
public:
bool operator() (const Block &left, const Block &right) {
return left.offset < right.offset;
}
};
typedef std::vector<Block> Container;
typedef unsigned int BlockIndex;
static const int32 kUnusedToken = 0;
// Gets the index of a memory block, given its offset.
BlockIndex GetBlockByOffset(Offset offset);
// Collapse a free block with its neighbours if they are free. Returns the
// index of the collapsed block.
// NOTE: this will invalidate block indices.
BlockIndex CollapseFreeBlock(BlockIndex index);
// Waits for a FREE_PENDING_TOKEN block to be usable, and free it. Returns
// the new index of that block (since it may have been collapsed).
// NOTE: this will invalidate block indices.
BlockIndex WaitForTokenAndFreeBlock(BlockIndex index);
// Allocates a block of memory inside a given block, splitting it in two
// (unless that block is of the exact requested size).
// NOTE: this will invalidate block indices.
// Returns the offset of the allocated block (NOTE: this is different from
// the other functions that return a block index).
Offset AllocInBlock(BlockIndex index, unsigned int size);
CommandBufferHelper *helper_;
base::Closure poll_callback_;
Container blocks_;
size_t bytes_in_use_;
DISALLOW_IMPLICIT_CONSTRUCTORS(FencedAllocator);
};
// This class functions just like FencedAllocator, but its API uses pointers
// instead of offsets.
class FencedAllocatorWrapper {
public:
FencedAllocatorWrapper(unsigned int size,
CommandBufferHelper* helper,
const base::Closure& poll_callback,
void* base)
: allocator_(size, helper, poll_callback),
base_(base) { }
// Allocates a block of memory. If the buffer is out of directly available
// memory, this function may wait until memory that was freed "pending a
// token" can be re-used.
//
// Parameters:
// size: the size of the memory block to allocate.
//
// Returns:
// the pointer to the allocated memory block, or NULL if out of
// memory.
void *Alloc(unsigned int size) {
FencedAllocator::Offset offset = allocator_.Alloc(size);
return GetPointer(offset);
}
// Allocates a block of memory. If the buffer is out of directly available
// memory, this function may wait until memory that was freed "pending a
// token" can be re-used.
// This is a type-safe version of Alloc, returning a typed pointer.
//
// Parameters:
// count: the number of elements to allocate.
//
// Returns:
// the pointer to the allocated memory block, or NULL if out of
// memory.
template <typename T> T *AllocTyped(unsigned int count) {
return static_cast<T *>(Alloc(count * sizeof(T)));
}
// Frees a block of memory.
//
// Parameters:
// pointer: the pointer to the memory block to free.
void Free(void *pointer) {
DCHECK(pointer);
allocator_.Free(GetOffset(pointer));
}
// Frees a block of memory, pending the passage of a token. That memory won't
// be re-allocated until the token has passed through the command stream.
//
// Parameters:
// pointer: the pointer to the memory block to free.
// token: the token value to wait for before re-using the memory.
void FreePendingToken(void *pointer, int32 token) {
DCHECK(pointer);
allocator_.FreePendingToken(GetOffset(pointer), token);
}
// Frees any blocks pending a token for which the token has been read.
void FreeUnused() {
allocator_.FreeUnused();
}
// Gets a pointer to a memory block given the base memory and the offset.
// It translates FencedAllocator::kInvalidOffset to NULL.
void *GetPointer(FencedAllocator::Offset offset) {
return (offset == FencedAllocator::kInvalidOffset) ?
NULL : static_cast<char *>(base_) + offset;
}
// Gets the offset to a memory block given the base memory and the address.
// It translates NULL to FencedAllocator::kInvalidOffset.
FencedAllocator::Offset GetOffset(void *pointer) {
return pointer ?
static_cast<FencedAllocator::Offset>(
static_cast<char*>(pointer) - static_cast<char*>(base_)) :
FencedAllocator::kInvalidOffset;
}
// Gets the size of the largest free block that is available without waiting.
unsigned int GetLargestFreeSize() {
return allocator_.GetLargestFreeSize();
}
// Gets the size of the largest free block that can be allocated if the
// caller can wait.
unsigned int GetLargestFreeOrPendingSize() {
return allocator_.GetLargestFreeOrPendingSize();
}
// Checks for consistency inside the book-keeping structures. Used for
// testing.
bool CheckConsistency() {
return allocator_.CheckConsistency();
}
// True if any memory is allocated.
bool InUse() {
return allocator_.InUse();
}
FencedAllocator &allocator() { return allocator_; }
size_t bytes_in_use() const { return allocator_.bytes_in_use(); }
private:
FencedAllocator allocator_;
void* base_;
DISALLOW_IMPLICIT_CONSTRUCTORS(FencedAllocatorWrapper);
};
} // namespace gpu
#endif // GPU_COMMAND_BUFFER_CLIENT_FENCED_ALLOCATOR_H_