feat: add LayoutMeasure and measureLayout
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dualfroz committed
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1 file changed
+159
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#include "vf/RegionCompact.h"
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#include <algorithm>
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namespace vf {
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namespace {
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std::size_t divideUp(std::size_t value, std::size_t unit) {
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return unit == 0 ? 0 : (value + unit - 1) / unit;
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}
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struct LayoutMeasure {
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bool ok = false;
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SaveHeader header;
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std::vector<SaveTableEntry> entries;
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uint32_t totalSectors = 0;
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uint32_t headerSectors = 0;
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uint32_t referencedSectors = 0;
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uint32_t holeSectors = 0;
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uint32_t excessSectors = 0;
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uint32_t slackBytes = 0;
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};
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LayoutMeasure measureLayout(const uint8_t* data, std::size_t size) {
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LayoutMeasure measure;
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if (!readSaveHeader(data, size, measure.header)) return measure;
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if (measure.header.magic != saveMagic) return measure;
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if (!isKnownSaveVersion(measure.header.version)) return measure;
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if (measure.header.sectorBytes == 0) return measure;
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if (!readSaveTable(data, size, measure.header, measure.entries)) return measure;
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uint32_t sectorBytes = measure.header.sectorBytes;
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measure.totalSectors = static_cast<uint32_t>(divideUp(size, sectorBytes));
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measure.headerSectors = static_cast<uint32_t>(saveHeaderSectors(measure.header));
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for (const SaveTableEntry& entry : measure.entries) {
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measure.referencedSectors += entry.sectorCount;
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uint32_t needed =
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static_cast<uint32_t>(divideUp(entry.payloadBytes, sectorBytes));
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if (entry.sectorCount > needed) measure.excessSectors += entry.sectorCount - needed;
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uint32_t runBytes = entry.sectorCount * sectorBytes;
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if (runBytes > entry.payloadBytes) measure.slackBytes += runBytes - entry.payloadBytes;
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}
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uint32_t accounted = measure.headerSectors + measure.referencedSectors;
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measure.holeSectors = measure.totalSectors > accounted ? measure.totalSectors - accounted : 0;
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measure.ok = true;
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return measure;
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}
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void rewriteTableChecksum(ByteBuffer& buffer, const SaveHeader& header) {
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if (!versionHasChecksum(static_cast<SaveVersion>(header.version))) return;
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std::size_t tableBytes = saveTableBytes(header);
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uint32_t checksum = fnv1a32(buffer.data() + saveHeaderBytes, tableBytes);
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saveWriteU32At(buffer.data(), buffer.size(), 24, checksum);
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}
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} // namespace
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bool updateChunkInPlace(ByteBuffer& buffer, const SaveChunkRecord& record, bool compressBody) {
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SaveHeader header;
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if (!readSaveHeader(buffer.data(), buffer.size(), header)) return false;
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if (header.magic != saveMagic || !isKnownSaveVersion(header.version)) return false;
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if (header.sectorBytes == 0) return false;
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std::vector<SaveTableEntry> entries;
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if (!readSaveTable(buffer.data(), buffer.size(), header, entries)) return false;
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std::size_t slot = entries.size();
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for (std::size_t i = 0; i < entries.size(); ++i)
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if (entries[i].coord == record.coord) slot = i;
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if (slot == entries.size()) return false;
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SaveVersion version = static_cast<SaveVersion>(header.version);
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ByteBuffer payload = encodeChunkPayload(version, record, compressBody);
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uint32_t sectorBytes = header.sectorBytes;
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uint32_t needed = static_cast<uint32_t>(divideUp(payload.size(), sectorBytes));
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std::size_t entryAt = saveHeaderBytes + slot * saveEntryBytes;
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if (needed <= entries[slot].sectorCount) {
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std::size_t at = static_cast<std::size_t>(entries[slot].sectorOffset) * sectorBytes;
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std::size_t runBytes = static_cast<std::size_t>(entries[slot].sectorCount) * sectorBytes;
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if (at + runBytes > buffer.size()) return false;
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std::fill(buffer.begin() + static_cast<std::ptrdiff_t>(at),
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buffer.begin() + static_cast<std::ptrdiff_t>(at + runBytes), uint8_t{0});
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std::copy(payload.begin(), payload.end(),
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buffer.begin() + static_cast<std::ptrdiff_t>(at));
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saveWriteU32At(buffer.data(), buffer.size(), entryAt + 20,
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static_cast<uint32_t>(payload.size()));
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rewriteTableChecksum(buffer, header);
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return true;
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}
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if (buffer.size() % sectorBytes != 0)
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buffer.resize(divideUp(buffer.size(), sectorBytes) * sectorBytes, 0);
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uint32_t newOffset = static_cast<uint32_t>(buffer.size() / sectorBytes);
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buffer.resize(buffer.size() + static_cast<std::size_t>(needed) * sectorBytes, 0);
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std::copy(payload.begin(), payload.end(),
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buffer.begin() + static_cast<std::ptrdiff_t>(
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static_cast<std::size_t>(newOffset) * sectorBytes));
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saveWriteU32At(buffer.data(), buffer.size(), entryAt + 12, newOffset);
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saveWriteU32At(buffer.data(), buffer.size(), entryAt + 16, needed);
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saveWriteU32At(buffer.data(), buffer.size(), entryAt + 20,
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static_cast<uint32_t>(payload.size()));
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rewriteTableChecksum(buffer, header);
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return true;
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}
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std::vector<ChunkFragment> RegionCompactor::survey(const ByteBuffer& buffer) const {
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return survey(buffer.data(), buffer.size());
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}
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std::vector<ChunkFragment> RegionCompactor::survey(const uint8_t* data, std::size_t size) const {
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std::vector<ChunkFragment> fragments;
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LayoutMeasure measure = measureLayout(data, size);
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if (!measure.ok) return fragments;
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uint32_t sectorBytes = measure.header.sectorBytes;
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SaveVersion version = static_cast<SaveVersion>(measure.header.version);
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for (std::size_t i = 0; i < measure.entries.size(); ++i) {
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const SaveTableEntry& entry = measure.entries[i];
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ChunkFragment fragment;
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fragment.coord = entry.coord;
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fragment.entryIndex = static_cast<int>(i);
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fragment.sectorOffset = entry.sectorOffset;
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fragment.sectorCount = entry.sectorCount;
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fragment.payloadBytes = entry.payloadBytes;
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fragment.neededSectors = static_cast<uint32_t>(divideUp(entry.payloadBytes, sectorBytes));
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fragment.excessSectors = entry.sectorCount > fragment.neededSectors
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? entry.sectorCount - fragment.neededSectors
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: 0;
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uint32_t runBytes = entry.sectorCount * sectorBytes;
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fragment.slackBytes = runBytes > entry.payloadBytes ? runBytes - entry.payloadBytes : 0;
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std::size_t at = static_cast<std::size_t>(entry.sectorOffset) * sectorBytes;
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fragment.reachable =
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entry.sectorCount != 0 && at + entry.payloadBytes <= size && at < size;
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if (fragment.reachable && versionHasMetadata(version)) {
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uint32_t flags = 0;
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if (saveReadU32At(data, size, at, flags))
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fragment.empty = (flags & saveRecordEmpty) != 0;
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}
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fragments.push_back(fragment);
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}
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return fragments;
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}
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int RegionCompactor::fragmentationPercent(const ByteBuffer& buffer) const {
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return fragmentationPercent(buffer.data(), buffer.size());
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}
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int RegionCompactor::fragmentationPercent(const uint8_t* data, std::size_t size) const {
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LayoutMeasure measure = measureLayout(data, size);
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if (!measure.ok || measure.totalSectors == 0) return -1;
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uint32_t reclaimable = measure.holeSectors + measure.excessSectors;
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return static_cast<int>((reclaimable * 100u) / measure.totalSectors);
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}
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