RASCSI/cpp/devices/disk_cache.cpp

199 lines
4.2 KiB
C++
Raw Normal View History

//---------------------------------------------------------------------------
//
// X68000 EMULATOR "XM6"
//
// Copyright (C) 2001-2006 (ytanaka@ipc-tokai.or.jp)
// Copyright (C) 2014-2020 GIMONS
//
// XM6i
// Copyright (C) 2010-2015 isaki@NetBSD.org
// Copyright (C) 2010 Y.Sugahara
//
// Imported sava's Anex86/T98Next image and MO format support patch.
// Comments translated to english by akuker.
//
//---------------------------------------------------------------------------
#include "os.h"
#include "disk_track.h"
#include "disk_cache.h"
#include <cstdlib>
#include <cassert>
DiskCache::DiskCache(const string& path, int size, uint32_t blocks, off_t imgoff)
: sec_path(path), sec_size(size), sec_blocks(blocks), imgoffset(imgoff)
{
assert(blocks > 0);
assert(imgoff >= 0);
}
bool DiskCache::Save() const
{
// Save track
for (const cache_t& c : cache) {
// Save if this is a valid track
if (c.disktrk && !c.disktrk->Save(sec_path)) {
return false;
}
}
return true;
}
shared_ptr<DiskTrack> DiskCache::GetTrack(uint32_t block)
{
// Update first
UpdateSerialNumber();
// Calculate track (fixed to 256 sectors/track)
int track = block >> 8;
// Get track data
return Assign(track);
}
bool DiskCache::ReadSector(vector<BYTE>& buf, uint32_t block)
{
shared_ptr<DiskTrack> disktrk = GetTrack(block);
if (disktrk == nullptr) {
return false;
}
// Read the track data to the cache
return disktrk->ReadSector(buf, block & 0xff);
}
bool DiskCache::WriteSector(const vector<BYTE>& buf, uint32_t block)
{
shared_ptr<DiskTrack> disktrk = GetTrack(block);
if (disktrk == nullptr) {
return false;
}
// Write the data to the cache
return disktrk->WriteSector(buf, block & 0xff);
}
//---------------------------------------------------------------------------
//
// Track Assignment
//
//---------------------------------------------------------------------------
shared_ptr<DiskTrack> DiskCache::Assign(int track)
{
assert(sec_size != 0);
assert(track >= 0);
// First, check if it is already assigned
for (cache_t& c : cache) {
if (c.disktrk && c.disktrk->GetTrack() == track) {
// Track match
c.serial = serial;
return c.disktrk;
}
}
// Next, check for empty
for (size_t i = 0; i < cache.size(); i++) {
if (cache[i].disktrk == nullptr) {
// Try loading
if (Load((int)i, track, nullptr)) {
// Success loading
cache[i].serial = serial;
return cache[i].disktrk;
}
// Load failed
return nullptr;
}
}
// Finally, find the youngest serial number and delete it
// Set index 0 as candidate c
uint32_t s = cache[0].serial;
size_t c = 0;
// Compare candidate with serial and update to smaller one
for (size_t i = 0; i < cache.size(); i++) {
assert(cache[i].disktrk);
// Compare and update the existing serial
if (cache[i].serial < s) {
s = cache[i].serial;
c = i;
}
}
// Save this track
if (!cache[c].disktrk->Save(sec_path)) {
return nullptr;
}
// Delete this track
shared_ptr<DiskTrack> disktrk = cache[c].disktrk;
cache[c].disktrk.reset();
if (Load((int)c, track, disktrk)) {
// Successful loading
cache[c].serial = serial;
return cache[c].disktrk;
}
// Load failed
return nullptr;
}
//---------------------------------------------------------------------------
//
// Load cache
//
//---------------------------------------------------------------------------
bool DiskCache::Load(int index, int track, shared_ptr<DiskTrack> disktrk)
{
assert(index >= 0 && index < (int)cache.size());
assert(track >= 0);
assert(cache[index].disktrk == nullptr);
// Get the number of sectors on this track
int sectors = sec_blocks - (track << 8);
assert(sectors > 0);
if (sectors > 0x100) {
sectors = 0x100;
}
// Create a disk track
if (disktrk == nullptr) {
disktrk = make_shared<DiskTrack>();
}
// Initialize disk track
disktrk->Init(track, sec_size, sectors, cd_raw, imgoffset);
// Try loading
if (!disktrk->Load(sec_path)) {
// Failure
return false;
}
// Allocation successful, work set
cache[index].disktrk = disktrk;
return true;
}
void DiskCache::UpdateSerialNumber()
{
// Update and do nothing except 0
serial++;
if (serial != 0) {
return;
}
// Clear serial of all caches
for (cache_t& c : cache) {
c.serial = 0;
}
}