vfs_concat: fix time complexity of read

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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@ -117,8 +117,7 @@ FileSys::VirtualFile GetGameFileFromPath(const FileSys::VirtualFilesystem& vfs,
return nullptr; return nullptr;
} }
return FileSys::ConcatenatedVfsFile::MakeConcatenatedFile(std::move(concat), return FileSys::ConcatenatedVfsFile::MakeConcatenatedFile(concat, dir->GetName());
dir->GetName());
} }
if (Common::FS::IsDir(path)) { if (Common::FS::IsDir(path)) {

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@ -140,7 +140,8 @@ VirtualFile CreateRomFS(VirtualDir dir, VirtualDir ext) {
return nullptr; return nullptr;
RomFSBuildContext ctx{dir, ext}; 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 } // namespace FileSys

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@ -10,84 +10,105 @@
namespace FileSys { namespace FileSys {
static bool VerifyConcatenationMapContinuity(const std::multimap<u64, VirtualFile>& map) { ConcatenatedVfsFile::ConcatenatedVfsFile(ConcatenationMap&& concatenation_map_, std::string&& name_)
const auto last_valid = --map.end(); : concatenation_map(std::move(concatenation_map_)), name(std::move(name_)) {
for (auto iter = map.begin(); iter != last_valid;) { DEBUG_ASSERT(this->VerifyContinuity());
const auto old = iter++; }
if (old->first + old->second->GetSize() != iter->first) {
bool ConcatenatedVfsFile::VerifyContinuity() const {
u64 last_offset = 0;
for (auto& entry : concatenation_map) {
if (entry.offset != last_offset) {
return false; return false;
} }
last_offset = entry.offset + entry.file->GetSize();
} }
return map.begin()->first == 0; return true;
}
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));
} }
ConcatenatedVfsFile::~ConcatenatedVfsFile() = default; ConcatenatedVfsFile::~ConcatenatedVfsFile() = default;
VirtualFile ConcatenatedVfsFile::MakeConcatenatedFile(std::vector<VirtualFile> files, VirtualFile ConcatenatedVfsFile::MakeConcatenatedFile(const std::vector<VirtualFile>& files,
std::string name) { std::string&& name) {
if (files.empty()) // Fold trivial cases.
if (files.empty()) {
return nullptr; 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, VirtualFile ConcatenatedVfsFile::MakeConcatenatedFile(u8 filler_byte,
std::multimap<u64, VirtualFile> files, const std::multimap<u64, VirtualFile>& files,
std::string name) { std::string&& name) {
if (files.empty()) // Fold trivial cases.
if (files.empty()) {
return nullptr; return nullptr;
if (files.size() == 1) }
if (files.size() == 1) {
return files.begin()->second; 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. // Make the concatenation map from the input.
if (files.begin()->first != 0) std::vector<ConcatenationEntry> concatenation_map;
files.emplace(0, std::make_shared<StaticVfsFile>(filler_byte, files.begin()->first));
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 { std::string ConcatenatedVfsFile::GetName() const {
if (files.empty()) { if (concatenation_map.empty()) {
return ""; return "";
} }
if (!name.empty()) { if (!name.empty()) {
return name; return name;
} }
return files.begin()->second->GetName(); return concatenation_map.front().file->GetName();
} }
std::size_t ConcatenatedVfsFile::GetSize() const { std::size_t ConcatenatedVfsFile::GetSize() const {
if (files.empty()) { if (concatenation_map.empty()) {
return 0; 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) { bool ConcatenatedVfsFile::Resize(std::size_t new_size) {
@ -95,10 +116,10 @@ bool ConcatenatedVfsFile::Resize(std::size_t new_size) {
} }
VirtualDir ConcatenatedVfsFile::GetContainingDirectory() const { VirtualDir ConcatenatedVfsFile::GetContainingDirectory() const {
if (files.empty()) { if (concatenation_map.empty()) {
return nullptr; return nullptr;
} }
return files.begin()->second->GetContainingDirectory(); return concatenation_map.front().file->GetContainingDirectory();
} }
bool ConcatenatedVfsFile::IsWritable() const { 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 { std::size_t ConcatenatedVfsFile::Read(u8* data, std::size_t length, std::size_t offset) const {
auto entry = --files.end(); const ConcatenationEntry key{
for (auto iter = files.begin(); iter != files.end(); ++iter) { .offset = offset,
if (iter->first > offset) { .file = nullptr,
entry = --iter; };
// 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; 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 cur_offset - 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);
} }
std::size_t ConcatenatedVfsFile::Write(const u8* data, std::size_t length, std::size_t offset) { std::size_t ConcatenatedVfsFile::Write(const u8* data, std::size_t length, std::size_t offset) {

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