mirror of
https://github.com/Atmosphere-NX/Atmosphere.git
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267 lines
10 KiB
C++
267 lines
10 KiB
C++
/*
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* Copyright (c) 2018-2020 Atmosphère-NX
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms and conditions of the GNU General Public License,
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* version 2, as published by the Free Software Foundation.
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*
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* This program is distributed in the hope it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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* more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#pragma once
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#include <mesosphere/kern_common.hpp>
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#include <mesosphere/kern_select_system_control.hpp>
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namespace ams::kern {
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class KPageBitmap {
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private:
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class RandomBitGenerator {
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private:
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util::TinyMT rng;
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u32 entropy;
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u32 bits_available;
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private:
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void RefreshEntropy() {
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this->entropy = rng.GenerateRandomU32();
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this->bits_available = BITSIZEOF(this->entropy);
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}
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bool GenerateRandomBit() {
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if (this->bits_available == 0) {
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this->RefreshEntropy();
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}
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const bool rnd_bit = (this->entropy & 1) != 0;
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this->entropy >>= 1;
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--this->bits_available;
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return rnd_bit;
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}
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public:
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RandomBitGenerator() : rng(), entropy(), bits_available() {
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this->rng.Initialize(static_cast<u32>(KSystemControl::GenerateRandomU64()));
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}
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size_t SelectRandomBit(u64 bitmap) {
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u64 selected = 0;
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u64 cur_num_bits = BITSIZEOF(bitmap) / 2;
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u64 cur_mask = (1ull << cur_num_bits) - 1;
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while (cur_num_bits) {
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const u64 low = (bitmap >> 0) & cur_mask;
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const u64 high = (bitmap >> cur_num_bits) & cur_mask;
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bool choose_low;
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if (high == 0) {
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/* If only low val is set, choose low. */
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choose_low = true;
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} else if (low == 0) {
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/* If only high val is set, choose high. */
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choose_low = false;
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} else {
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/* If both are set, choose random. */
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choose_low = this->GenerateRandomBit();
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}
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/* If we chose low, proceed with low. */
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if (choose_low) {
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bitmap = low;
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selected += 0;
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} else {
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bitmap = high;
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selected += cur_num_bits;
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}
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/* Proceed. */
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cur_num_bits /= 2;
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cur_mask >>= cur_num_bits;
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}
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return selected;
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}
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};
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public:
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static constexpr size_t MaxDepth = 4;
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private:
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u64 *bit_storages[MaxDepth];
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RandomBitGenerator rng;
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size_t num_bits;
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size_t used_depths;
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public:
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KPageBitmap() : bit_storages(), rng(), num_bits(), used_depths() { /* ... */ }
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constexpr size_t GetNumBits() const { return this->num_bits; }
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constexpr s32 GetHighestDepthIndex() const { return static_cast<s32>(this->used_depths) - 1; }
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u64 *Initialize(u64 *storage, size_t size) {
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/* Initially, everything is un-set. */
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this->num_bits = 0;
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/* Calculate the needed bitmap depth. */
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this->used_depths = static_cast<size_t>(GetRequiredDepth(size));
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MESOSPHERE_ASSERT(this->used_depths <= MaxDepth);
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/* Set the bitmap pointers. */
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for (s32 depth = this->GetHighestDepthIndex(); depth >= 0; depth--) {
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this->bit_storages[depth] = storage;
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size = util::AlignUp(size, BITSIZEOF(u64)) / BITSIZEOF(u64);
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storage += size;
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}
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return storage;
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}
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ssize_t FindFreeBlock(bool random) {
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uintptr_t offset = 0;
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s32 depth = 0;
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if (random) {
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do {
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const u64 v = this->bit_storages[depth][offset];
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if (v == 0) {
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/* If depth is bigger than zero, then a previous level indicated a block was free. */
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MESOSPHERE_ASSERT(depth == 0);
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return -1;
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}
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offset = offset * BITSIZEOF(u64) + this->rng.SelectRandomBit(v);
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++depth;
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} while (depth < static_cast<s32>(this->used_depths));
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} else {
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do {
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const u64 v = this->bit_storages[depth][offset];
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if (v == 0) {
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/* If depth is bigger than zero, then a previous level indicated a block was free. */
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MESOSPHERE_ASSERT(depth == 0);
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return -1;
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}
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offset = offset * BITSIZEOF(u64) + __builtin_ctzll(v);
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++depth;
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} while (depth < static_cast<s32>(this->used_depths));
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}
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return static_cast<ssize_t>(offset);
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}
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void SetBit(size_t offset) {
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this->SetBit(this->GetHighestDepthIndex(), offset);
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this->num_bits++;
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}
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void ClearBit(size_t offset) {
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this->ClearBit(this->GetHighestDepthIndex(), offset);
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this->num_bits--;
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}
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bool ClearRange(size_t offset, size_t count) {
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s32 depth = this->GetHighestDepthIndex();
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u64 *bits = this->bit_storages[depth];
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size_t bit_ind = offset / BITSIZEOF(u64);
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if (AMS_LIKELY(count < BITSIZEOF(u64))) {
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const size_t shift = offset % BITSIZEOF(u64);
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MESOSPHERE_ASSERT(shift + count <= BITSIZEOF(u64));
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/* Check that all the bits are set. */
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const u64 mask = ((u64(1) << count) - 1) << shift;
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u64 v = bits[bit_ind];
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if ((v & mask) != mask) {
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return false;
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}
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/* Clear the bits. */
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v &= ~mask;
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bits[bit_ind] = v;
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if (v == 0) {
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this->ClearBit(depth - 1, bit_ind);
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}
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} else {
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MESOSPHERE_ASSERT(offset % BITSIZEOF(u64) == 0);
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MESOSPHERE_ASSERT(count % BITSIZEOF(u64) == 0);
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/* Check that all the bits are set. */
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size_t remaining = count;
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size_t i = 0;
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do {
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if (bits[bit_ind + i++] != ~u64(0)) {
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return false;
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}
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remaining -= BITSIZEOF(u64);
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} while (remaining > 0);
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/* Clear the bits. */
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remaining = count;
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i = 0;
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do {
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bits[bit_ind + i] = 0;
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this->ClearBit(depth - 1, bit_ind + i);
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i++;
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remaining -= BITSIZEOF(u64);
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} while (remaining > 0);
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}
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this->num_bits -= count;
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return true;
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}
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private:
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void SetBit(s32 depth, size_t offset) {
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while (depth >= 0) {
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size_t ind = offset / BITSIZEOF(u64);
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size_t which = offset % BITSIZEOF(u64);
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const u64 mask = u64(1) << which;
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u64 *bit = std::addressof(this->bit_storages[depth][ind]);
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u64 v = *bit;
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MESOSPHERE_ASSERT((v & mask) == 0);
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*bit = v | mask;
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if (v) {
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break;
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}
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offset = ind;
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depth--;
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}
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}
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void ClearBit(s32 depth, size_t offset) {
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while (depth >= 0) {
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size_t ind = offset / BITSIZEOF(u64);
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size_t which = offset % BITSIZEOF(u64);
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const u64 mask = u64(1) << which;
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u64 *bit = std::addressof(this->bit_storages[depth][ind]);
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u64 v = *bit;
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MESOSPHERE_ASSERT((v & mask) != 0);
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v &= ~mask;
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*bit = v;
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if (v) {
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break;
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}
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offset = ind;
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depth--;
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}
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}
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private:
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static constexpr s32 GetRequiredDepth(size_t region_size) {
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s32 depth = 0;
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while (true) {
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region_size /= BITSIZEOF(u64);
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depth++;
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if (region_size == 0) {
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return depth;
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}
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}
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}
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public:
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static constexpr size_t CalculateMetadataOverheadSize(size_t region_size) {
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size_t overhead_bits = 0;
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for (s32 depth = GetRequiredDepth(region_size) - 1; depth >= 0; depth--) {
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region_size = util::AlignUp(region_size, BITSIZEOF(u64)) / BITSIZEOF(u64);
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overhead_bits += region_size;
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}
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return overhead_bits * sizeof(u64);
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}
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};
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}
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