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// Copyright 2010 Dolphin Emulator Project
// SPDX-License-Identifier: GPL-2.0-or-later
#pragma once
#include <algorithm>
#include <cstring>
#include <memory>
#include <string>
#include <type_traits>
#include "Common/CommonTypes.h"
#include "Common/IOFile.h"
#include "Common/Version.h"
// On disk format:
// header{
// u32 'DCAC';
// u32 version; // svn_rev
// u16 sizeof(key_type);
// u16 sizeof(value_type);
//}
// key_value_pair{
// u32 value_size;
// key_type key;
// value_type[value_size] value;
//}
template <typename K, typename V>
class LinearDiskCacheReader
{
public:
virtual void Read(const K& key, const V* value, u32 value_size) = 0;
};
// Dead simple unsorted key-value store with append functionality.
// No random read functionality, all reading is done in OpenAndRead.
// Keys and values can contain any characters, including \0.
//
// Suitable for caching generated shader bytecode between executions.
// Not tuned for extreme performance but should be reasonably fast.
// Does not support keys or values larger than 2GB, which should be reasonable.
// Keys must have non-zero length; values can have zero length.
// K and V are some POD type
// K : the key type
// V : value array type
template <typename K, typename V>
class LinearDiskCache
{
public:
// return number of read entries
u32 OpenAndRead(const std::string& filename, LinearDiskCacheReader<K, V>& reader)
{
// Since we're reading/writing directly to the storage of K instances,
// K must be trivially copyable.
static_assert(std::is_trivially_copyable<K>::value, "K must be a trivially copyable type");
// close any currently opened file
Close();
m_num_entries = 0;
// try opening for reading/writing
m_file.Open(filename, "r+b");
const u64 file_size = m_file.GetSize();
m_header.Init();
if (m_file.IsOpen() && ValidateHeader())
{
// good header, read some key/value pairs
K key;
std::unique_ptr<V[]> value = nullptr;
u32 value_size = 0;
u32 entry_number = 0;
u64 last_valid_value_start = m_file.Tell();
while (m_file.ReadArray(&value_size, 1))
{
const u64 next_extent = m_file.Tell() + sizeof(value_size) + value_size;
if (next_extent > file_size)
break;
// TODO: use make_unique_for_overwrite in C++20
value = std::unique_ptr<V[]>(new V[value_size]);
// read key/value and pass to reader
if (m_file.ReadArray(&key, 1) && m_file.ReadArray(value.get(), value_size) &&
m_file.ReadArray(&entry_number, 1) && entry_number == m_num_entries + 1)
{
last_valid_value_start = m_file.Tell();
reader.Read(key, value.get(), value_size);
}
else
{
break;
}
m_num_entries++;
}
m_file.ClearError();
m_file.Seek(last_valid_value_start, File::SeekOrigin::Begin);
return m_num_entries;
}
// failed to open file for reading or bad header
// close and recreate file
Close();
m_file.Open(filename, "wb");
WriteHeader();
return 0;
}
void Sync() { m_file.Flush(); }
void Close()
{
if (m_file.IsOpen())
m_file.Close();
}
// Appends a key-value pair to the store.
void Append(const K& key, const V* value, u32 value_size)
{
// TODO: Should do a check that we don't already have "key"? (I think each caller does that
// already.)
m_file.WriteArray(&value_size, 1);
m_file.WriteArray(&key, 1);
m_file.WriteArray(value, value_size);
m_num_entries++;
m_file.WriteArray(&m_num_entries, 1);
}
private:
void WriteHeader() { m_file.WriteArray(&m_header, 1); }
bool ValidateHeader()
{
char file_header[sizeof(Header)];
return (m_file.ReadArray(file_header, sizeof(Header)) &&
!memcmp((const char*)&m_header, file_header, sizeof(Header)));
}
struct Header
{
void Init()
{
// Null-terminator is intentionally not copied.
std::memcpy(&id, "DCAC", sizeof(u32));
std::memcpy(ver, Common::GetScmRevGitStr().c_str(),
std::min(Common::GetScmRevGitStr().size(), sizeof(ver)));
}
u32 id = 0;
const u16 key_t_size = sizeof(K);
const u16 value_t_size = sizeof(V);
char ver[40] = {};
} m_header;
File::IOFile m_file;
u32 m_num_entries = 0;
};
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