chromium/third_party/dawn/src/dawn/native/CommandAllocator.h

// Copyright 2017 The Dawn & Tint Authors
//
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// modification, are permitted provided that the following conditions are met:
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//    this list of conditions and the following disclaimer in the documentation
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#ifndef SRC_DAWN_NATIVE_COMMANDALLOCATOR_H_
#define SRC_DAWN_NATIVE_COMMANDALLOCATOR_H_

#include <cstddef>
#include <cstdint>
#include <limits>
#include <memory>
#include <string_view>
#include <vector>

#include "dawn/common/Assert.h"
#include "dawn/common/Math.h"
#include "dawn/common/NonCopyable.h"
#include "partition_alloc/pointers/raw_ptr_exclusion.h"

namespace dawn::native {

// Allocation for command buffers should be fast. To avoid doing an allocation per command
// or to avoid copying commands when reallocing, we use a linear allocator in a growing set
// of large memory blocks. We also use this to have the format to be (u32 commandId, command),
// so that iteration over the commands is easy.

// Usage of the allocator and iterator:
//     CommandAllocator allocator;
//     DrawCommand* cmd = allocator.Allocate<DrawCommand>(CommandType::Draw);
//     // Fill command
//     // Repeat allocation and filling commands
//
//     CommandIterator commands(allocator);
//     CommandType type;
//     while(commands.NextCommandId(&type)) {
//         switch(type) {
//              case CommandType::Draw:
//                  DrawCommand* draw = commands.NextCommand<DrawCommand>();
//                  // Do the draw
//                  break;
//              // other cases
//         }
//     }

// Note that you need to extract the commands from the CommandAllocator before destroying it
// and must tell the CommandIterator when the allocated commands have been processed for
// deletion.

// These are the lists of blocks, should not be used directly, only through CommandAllocator
// and CommandIterator
struct BlockDef { … };
CommandBlocks;

namespace detail {
constexpr uint32_t kEndOfBlock = …;
constexpr uint32_t kAdditionalData = …;
}  // namespace detail

class CommandAllocator;

class CommandIterator : public NonCopyable { … };

class CommandAllocator : public NonCopyable { … };

}  // namespace dawn::native

#endif  // SRC_DAWN_NATIVE_COMMANDALLOCATOR_H_