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vfs_concat: fix time complexity of read

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This commit is contained in:
Liam 2023-05-26 15:41:17 -04:00
parent 83b502c08c
commit 0596a4afb1
4 changed files with 129 additions and 74 deletions
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3
src/core/core.cpp
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@ -117,8 +117,7 @@ FileSys::VirtualFile GetGameFileFromPath(const FileSys::VirtualFilesystem& vfs,
return nullptr;
}
return FileSys::ConcatenatedVfsFile::MakeConcatenatedFile(std::move(concat),
dir->GetName());
return FileSys::ConcatenatedVfsFile::MakeConcatenatedFile(concat, dir->GetName());
}
if (Common::FS::IsDir(path)) {

3
src/core/file_sys/romfs.cpp
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@ -140,7 +140,8 @@ VirtualFile CreateRomFS(VirtualDir dir, VirtualDir ext) {
return nullptr;
RomFSBuildContext ctx{dir, ext};
return ConcatenatedVfsFile::MakeConcatenatedFile(0, ctx.Build(), dir->GetName());
auto file_map = ctx.Build();
return ConcatenatedVfsFile::MakeConcatenatedFile(0, file_map, dir->GetName());
}
} // namespace FileSys

169
src/core/file_sys/vfs_concat.cpp
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@ -10,84 +10,105 @@
namespace FileSys {
static bool VerifyConcatenationMapContinuity(const std::multimap<u64, VirtualFile>& map) {
const auto last_valid = --map.end();
for (auto iter = map.begin(); iter != last_valid;) {
const auto old = iter++;
if (old->first + old->second->GetSize() != iter->first) {
ConcatenatedVfsFile::ConcatenatedVfsFile(ConcatenationMap&& concatenation_map_, std::string&& name_)
: concatenation_map(std::move(concatenation_map_)), name(std::move(name_)) {
DEBUG_ASSERT(this->VerifyContinuity());
}
bool ConcatenatedVfsFile::VerifyContinuity() const {
u64 last_offset = 0;
for (auto& entry : concatenation_map) {
if (entry.offset != last_offset) {
return false;
}
last_offset = entry.offset + entry.file->GetSize();
}
return map.begin()->first == 0;
}
ConcatenatedVfsFile::ConcatenatedVfsFile(std::vector<VirtualFile> files_, std::string name_)
: name(std::move(name_)) {
std::size_t next_offset = 0;
for (const auto& file : files_) {
files.emplace(next_offset, file);
next_offset += file->GetSize();
}
}
ConcatenatedVfsFile::ConcatenatedVfsFile(std::multimap<u64, VirtualFile> files_, std::string name_)
: files(std::move(files_)), name(std::move(name_)) {
ASSERT(VerifyConcatenationMapContinuity(files));
return true;
}
ConcatenatedVfsFile::~ConcatenatedVfsFile() = default;
VirtualFile ConcatenatedVfsFile::MakeConcatenatedFile(std::vector<VirtualFile> files,
std::string name) {
if (files.empty())
VirtualFile ConcatenatedVfsFile::MakeConcatenatedFile(const std::vector<VirtualFile>& files,
std::string&& name) {
// Fold trivial cases.
if (files.empty()) {
return nullptr;
if (files.size() == 1)
return files[0];
}
if (files.size() == 1) {
return files.front();
}
return VirtualFile(new ConcatenatedVfsFile(std::move(files), std::move(name)));
// Make the concatenation map from the input.
std::vector<ConcatenationEntry> concatenation_map;
concatenation_map.reserve(files.size());
u64 last_offset = 0;
for (auto& file : files) {
concatenation_map.emplace_back(ConcatenationEntry{
.offset = last_offset,
.file = file,
});
last_offset += file->GetSize();
}
return VirtualFile(new ConcatenatedVfsFile(std::move(concatenation_map), std::move(name)));
}
VirtualFile ConcatenatedVfsFile::MakeConcatenatedFile(u8 filler_byte,
std::multimap<u64, VirtualFile> files,
std::string name) {
if (files.empty())
const std::multimap<u64, VirtualFile>& files,
std::string&& name) {
// Fold trivial cases.
if (files.empty()) {
return nullptr;
if (files.size() == 1)
}
if (files.size() == 1) {
return files.begin()->second;
const auto last_valid = --files.end();
for (auto iter = files.begin(); iter != last_valid;) {
const auto old = iter++;
if (old->first + old->second->GetSize() != iter->first) {
files.emplace(old->first + old->second->GetSize(),
std::make_shared<StaticVfsFile>(filler_byte, iter->first - old->first -
old->second->GetSize()));
}
}
// Ensure the map starts at offset 0 (start of file), otherwise pad to fill.
if (files.begin()->first != 0)
files.emplace(0, std::make_shared<StaticVfsFile>(filler_byte, files.begin()->first));
// Make the concatenation map from the input.
std::vector<ConcatenationEntry> concatenation_map;
return VirtualFile(new ConcatenatedVfsFile(std::move(files), std::move(name)));
concatenation_map.reserve(files.size());
u64 last_offset = 0;
// Iteration of a multimap is ordered, so offset will be strictly non-decreasing.
for (auto& [offset, file] : files) {
if (offset > last_offset) {
concatenation_map.emplace_back(ConcatenationEntry{
.offset = last_offset,
.file = std::make_shared<StaticVfsFile>(filler_byte, offset - last_offset),
});
}
concatenation_map.emplace_back(ConcatenationEntry{
.offset = offset,
.file = file,
});
last_offset = offset + file->GetSize();
}
return VirtualFile(new ConcatenatedVfsFile(std::move(concatenation_map), std::move(name)));
}
std::string ConcatenatedVfsFile::GetName() const {
if (files.empty()) {
if (concatenation_map.empty()) {
return "";
}
if (!name.empty()) {
return name;
}
return files.begin()->second->GetName();
return concatenation_map.front().file->GetName();
}
std::size_t ConcatenatedVfsFile::GetSize() const {
if (files.empty()) {
if (concatenation_map.empty()) {
return 0;
}
return files.rbegin()->first + files.rbegin()->second->GetSize();
return concatenation_map.back().offset + concatenation_map.back().file->GetSize();
}
bool ConcatenatedVfsFile::Resize(std::size_t new_size) {
@ -95,10 +116,10 @@ bool ConcatenatedVfsFile::Resize(std::size_t new_size) {
}
VirtualDir ConcatenatedVfsFile::GetContainingDirectory() const {
if (files.empty()) {
if (concatenation_map.empty()) {
return nullptr;
}
return files.begin()->second->GetContainingDirectory();
return concatenation_map.front().file->GetContainingDirectory();
}
bool ConcatenatedVfsFile::IsWritable() const {
@ -110,25 +131,45 @@ bool ConcatenatedVfsFile::IsReadable() const {
}
std::size_t ConcatenatedVfsFile::Read(u8* data, std::size_t length, std::size_t offset) const {
auto entry = --files.end();
for (auto iter = files.begin(); iter != files.end(); ++iter) {
if (iter->first > offset) {
entry = --iter;
const ConcatenationEntry key{
.offset = offset,
.file = nullptr,
};
// Read nothing if the map is empty.
if (concatenation_map.empty()) {
return 0;
}
// Binary search to find the iterator to the first position we can check.
// It must exist, since we are not empty and are comparing unsigned integers.
auto it = std::prev(std::upper_bound(concatenation_map.begin(), concatenation_map.end(), key));
u64 cur_length = length;
u64 cur_offset = offset;
while (cur_length > 0 && it != concatenation_map.end()) {
// Check if we can read the file at this position.
const auto& file = it->file;
const u64 file_offset = it->offset;
const u64 file_size = file->GetSize();
if (cur_offset >= file_offset + file_size) {
// Entirely out of bounds read.
break;
}
// Read the file at this position.
const u64 intended_read_size = std::min<u64>(cur_length, file_size);
const u64 actual_read_size =
file->Read(data + (cur_offset - offset), intended_read_size, cur_offset - file_offset);
// Update tracking.
cur_offset += actual_read_size;
cur_length -= actual_read_size;
it++;
}
if (entry->first + entry->second->GetSize() <= offset)
return 0;
const auto read_in =
std::min<u64>(entry->first + entry->second->GetSize() - offset, entry->second->GetSize());
if (length > read_in) {
return entry->second->Read(data, read_in, offset - entry->first) +
Read(data + read_in, length - read_in, offset + read_in);
}
return entry->second->Read(data, std::min<u64>(read_in, length), offset - entry->first);
return cur_offset - offset;
}
std::size_t ConcatenatedVfsFile::Write(const u8* data, std::size_t length, std::size_t offset) {

28
src/core/file_sys/vfs_concat.h
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@ -3,6 +3,7 @@
#pragma once
#include <compare>
#include <map>
#include <memory>
#include "core/file_sys/vfs.h"
@ -12,19 +13,33 @@ namespace FileSys {
// Class that wraps multiple vfs files and concatenates them, making reads seamless. Currently
// read-only.
class ConcatenatedVfsFile : public VfsFile {
explicit ConcatenatedVfsFile(std::vector<VirtualFile> files, std::string name_);
explicit ConcatenatedVfsFile(std::multimap<u64, VirtualFile> files, std::string name_);
private:
struct ConcatenationEntry {
u64 offset;
VirtualFile file;
auto operator<=>(const ConcatenationEntry& other) const {
return this->offset <=> other.offset;
}
};
using ConcatenationMap = std::vector<ConcatenationEntry>;
explicit ConcatenatedVfsFile(std::vector<ConcatenationEntry>&& concatenation_map,
std::string&& name);
bool VerifyContinuity() const;
public:
~ConcatenatedVfsFile() override;
/// Wrapper function to allow for more efficient handling of files.size() == 0, 1 cases.
static VirtualFile MakeConcatenatedFile(std::vector<VirtualFile> files, std::string name);
static VirtualFile MakeConcatenatedFile(const std::vector<VirtualFile>& files,
std::string&& name);
/// Convenience function that turns a map of offsets to files into a concatenated file, filling
/// gaps with a given filler byte.
static VirtualFile MakeConcatenatedFile(u8 filler_byte, std::multimap<u64, VirtualFile> files,
std::string name);
static VirtualFile MakeConcatenatedFile(u8 filler_byte,
const std::multimap<u64, VirtualFile>& files,
std::string&& name);
std::string GetName() const override;
std::size_t GetSize() const override;
@ -37,8 +52,7 @@ public:
bool Rename(std::string_view new_name) override;
private:
// Maps starting offset to file -- more efficient.
std::multimap<u64, VirtualFile> files;
ConcatenationMap concatenation_map;
std::string name;
};