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// Copyright (c) 2011 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 GPU_COMMAND_BUFFER_COMMON_COMMAND_BUFFER_H_
#define GPU_COMMAND_BUFFER_COMMON_COMMAND_BUFFER_H_
#include "../common/buffer.h"
#include "../common/constants.h"
namespace base {
class SharedMemory;
}
namespace gpu {
// Common interface for CommandBuffer implementations.
class CommandBuffer {
public:
enum {
kMaxCommandBufferSize = 4 * 1024 * 1024
};
struct State {
State()
: num_entries(0),
get_offset(0),
put_offset(0),
token(-1),
error(error::kNoError),
generation(0) {
}
// Size of the command buffer in command buffer entries.
int32 num_entries;
// The offset (in entries) from which the reader is reading.
int32 get_offset;
// The offset (in entries) at which the writer is writing.
int32 put_offset;
// The current token value. This is used by the writer to defer
// changes to shared memory objects until the reader has reached a certain
// point in the command buffer. The reader is responsible for updating the
// token value, for example in response to an asynchronous set token command
// embedded in the command buffer. The default token value is zero.
int32 token;
// Error status.
error::Error error;
// Generation index of this state. The generation index is incremented every
// time a new state is retrieved from the command processor, so that
// consistency can be kept even if IPC messages are processed out-of-order.
uint32 generation;
};
CommandBuffer() {
}
virtual ~CommandBuffer() {
}
// Initialize the command buffer with the given size.
virtual bool Initialize(int32 size) = 0;
// Initialize the command buffer using the given preallocated buffer.
virtual bool Initialize(base::SharedMemory* buffer, int32 size) = 0;
// Gets the ring buffer for the command buffer.
virtual Buffer GetRingBuffer() = 0;
// Returns the current status.
virtual State GetState() = 0;
// The writer calls this to update its put offset. This ensures the reader
// sees the latest added commands, and will eventually process them.
virtual void Flush(int32 put_offset) = 0;
// The writer calls this to update its put offset. This function returns the
// reader's most recent get offset. Does not return until after the put offset
// change callback has been invoked. Returns -1 if the put offset is invalid.
// If last_known_get is different from the reader's current get pointer, this
// function will return immediately, otherwise it guarantees that the reader
// has processed some commands before returning (assuming the command buffer
// isn't empty and there is no error).
virtual State FlushSync(int32 put_offset, int32 last_known_get) = 0;
// Sets the current get offset. This can be called from any thread.
virtual void SetGetOffset(int32 get_offset) = 0;
// Create a transfer buffer and return a handle that uniquely
// identifies it or -1 on error. id_request lets the caller request a
// specific id for the transfer buffer, or -1 if the caller does not care.
// If the requested id can not be fulfilled, a different id will be returned.
// id_request must be either -1 or between 0 and 100.
virtual int32 CreateTransferBuffer(size_t size, int32 id_request) = 0;
// Register an existing shared memory object and get an ID that can be used
// to identify it in the command buffer. Callee dups the handle until
// DestroyTransferBuffer is called. id_request lets the caller request a
// specific id for the transfer buffer, or -1 if the caller does not care.
// If the requested id can not be fulfilled, a different id will be returned.
// id_request must be either -1 or between 0 and 100.
virtual int32 RegisterTransferBuffer(base::SharedMemory* shared_memory,
size_t size,
int32 id_request) = 0;
// Destroy a transfer buffer and recycle the handle.
virtual void DestroyTransferBuffer(int32 id) = 0;
// Get the transfer buffer associated with a handle.
virtual Buffer GetTransferBuffer(int32 handle) = 0;
// Allows the reader to update the current token value.
virtual void SetToken(int32 token) = 0;
// Allows the reader to set the current parse error.
virtual void SetParseError(error::Error) = 0;
private:
DISALLOW_COPY_AND_ASSIGN(CommandBuffer);
};
// Synchronizing other mechanisms (such as IPC) with the CommandBuffer requires
// inserting (writing) a token into the buffer and knowing what the last token
// read at that point was. ReadWriteTokens is a convenience struct for passing
// these pairs around. Expected usage is to compare a current token to
// [last_token_read,last_token_written).
class ReadWriteTokens {
public:
ReadWriteTokens(int32 read, int32 written);
// Required to support pickling. Use by anything else will DCHECK in InRange.
ReadWriteTokens();
// Return true iff |value| is in the range described by |tokens|, accounting
// for (up to) one wrap-around.
bool InRange(int32 token) const;
// These want to be private (and const) but can't in order to support
// pickling.
int32 last_token_read;
int32 last_token_written;
};
} // namespace gpu
#endif // GPU_COMMAND_BUFFER_COMMON_COMMAND_BUFFER_H_
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