system/ulib/inspect/include/lib/inspect/limits.h

// Copyright 2018 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#pragma once

#include <zircon/types.h>

namespace inspect {

// The size for order 0.
constexpr size_t kMinOrderShift = 4;
constexpr size_t kMinOrderSize = 1 << kMinOrderShift; // 16 bytes

// The total number of orders in the buddy allocator.
constexpr size_t kNumOrders = 8;

// The size of the maximum order.
constexpr size_t kMaxOrderShift = kMinOrderShift + kNumOrders - 1;
constexpr size_t kMaxOrderSize = 1 << kMaxOrderShift;

// The minimum size for the inspection VMO.
constexpr size_t kMinVmoSize = 4096;
static_assert(kMinVmoSize >= kMaxOrderSize,
              "Maximum order size must fit in the smallest VMO");

// The magic number for verifying the VMO format.
constexpr char kMagicNumber[5] = "INSP";

template <typename T>
constexpr size_t OrderToSize(T order) {
    return kMinOrderSize << order;
}

constexpr size_t IndexForOffset(size_t offset) {
    return offset / kMinOrderSize;
}

} // namespace inspect