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// SPDX-FileCopyrightText: Copyright 2026 Eden Emulator Project
// SPDX-License-Identifier: GPL-3.0-or-later
// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
// SPDX-License-Identifier: GPL-3.0-or-later
#pragma once
#include <array>
#include <utility>
#include <vector>
#include "common/alignment.h"
#include "common/common_types.h"
namespace VideoCommon {
class UsageTracker {
// PAGE_SHIFT is a macro on FreeBSD
static constexpr size_t BUFFER_BYTES_PER_BITSHIFT = 6;
static constexpr size_t BUFFER_PAGE_SHIFT = 6 + BUFFER_BYTES_PER_BITSHIFT;
static constexpr size_t BUFFER_PAGE_BYTES = 1 << BUFFER_PAGE_SHIFT;
public:
explicit UsageTracker(size_t size) {
const size_t num_pages = (size >> BUFFER_PAGE_SHIFT) + 1;
pages.resize(num_pages, 0ULL);
}
void Reset() noexcept {
std::ranges::fill(pages, 0ULL);
recent.fill({~u64{0}, 0});
}
void Track(u64 offset, u64 size) noexcept {
// Tracking is idempotent until Reset: skip ranges tracked just before. Draws bind the
// same (often multi-megabyte) storage buffers again and again, and each Track wrote a
// word per 4 KiB of the range.
for (const auto& [recent_offset, recent_size] : recent) {
if (recent_offset == offset && recent_size == size) {
return;
}
}
recent[recent_cursor++ % recent.size()] = {offset, size};
const size_t page = offset >> BUFFER_PAGE_SHIFT;
const size_t page_end = (offset + size) >> BUFFER_PAGE_SHIFT;
if (page_end < page || page_end >= pages.size()) {
return;
}
TrackPage(page, offset, size);
if (page == page_end) {
return;
}
for (size_t i = page + 1; i < page_end; i++) {
pages[i] = ~u64{0};
}
const size_t offset_end = offset + size;
const size_t offset_end_page_aligned = Common::AlignDown(offset_end, BUFFER_PAGE_BYTES);
TrackPage(page_end, offset_end_page_aligned, offset_end - offset_end_page_aligned);
}
[[nodiscard]] bool IsUsed(u64 offset, u64 size) const noexcept {
const size_t page = offset >> BUFFER_PAGE_SHIFT;
const size_t page_end = (offset + size) >> BUFFER_PAGE_SHIFT;
if (page_end < page || page_end >= pages.size()) {
return false;
}
if (IsPageUsed(page, offset, size)) {
return true;
}
for (size_t i = page + 1; i < page_end; i++) {
if (pages[i] != 0) {
return true;
}
}
const size_t offset_end = offset + size;
const size_t offset_end_page_aligned = Common::AlignDown(offset_end, BUFFER_PAGE_BYTES);
return IsPageUsed(page_end, offset_end_page_aligned, offset_end - offset_end_page_aligned);
}
private:
void TrackPage(u64 page, u64 offset, u64 size) noexcept {
const size_t offset_in_page = offset % BUFFER_PAGE_BYTES;
const size_t first_bit = offset_in_page >> BUFFER_BYTES_PER_BITSHIFT;
const size_t num_bits = std::min<size_t>(size, BUFFER_PAGE_BYTES) >> BUFFER_BYTES_PER_BITSHIFT;
const size_t mask = ~u64{0} >> (64 - num_bits);
pages[page] |= (~u64{0} & mask) << first_bit;
}
bool IsPageUsed(u64 page, u64 offset, u64 size) const noexcept {
const size_t offset_in_page = offset % BUFFER_PAGE_BYTES;
const size_t first_bit = offset_in_page >> BUFFER_BYTES_PER_BITSHIFT;
const size_t num_bits = std::min<size_t>(size, BUFFER_PAGE_BYTES) >> BUFFER_BYTES_PER_BITSHIFT;
const size_t mask = ~u64{0} >> (64 - num_bits);
const size_t mask2 = (~u64{0} & mask) << first_bit;
return (pages[page] & mask2) != 0;
}
private:
std::vector<u64> pages;
/// Ranges tracked last, (offset, size).
std::array<std::pair<u64, u64>, 4> recent{{{~u64{0}, 0}, {~u64{0}, 0}, {~u64{0}, 0}, {~u64{0}, 0}}};
size_t recent_cursor{};
};
} // namespace VideoCommon
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