--------------------------------------------------------------------------- Track Assignment ---------------------------------------------------------------------------
| 74 | // |
| 75 | //--------------------------------------------------------------------------- |
| 76 | shared_ptr<DiskTrack> DiskCache::Assign(int64_t track) |
| 77 | { |
| 78 | assert(sec_size != 0); |
| 79 | assert(track >= 0); |
| 80 | |
| 81 | // First, check if it is already assigned |
| 82 | for (cache_t& c : cache) { |
| 83 | if (c.disktrk && c.disktrk->GetTrack() == track) { |
| 84 | // Track match |
| 85 | c.serial = serial; |
| 86 | return c.disktrk; |
| 87 | } |
| 88 | } |
| 89 | |
| 90 | // Next, check for empty |
| 91 | for (size_t i = 0; i < cache.size(); i++) { |
| 92 | if (cache[i].disktrk == nullptr) { |
| 93 | // Try loading |
| 94 | if (Load(static_cast<int>(i), track, nullptr)) { |
| 95 | // Success loading |
| 96 | cache[i].serial = serial; |
| 97 | return cache[i].disktrk; |
| 98 | } |
| 99 | |
| 100 | // Load failed |
| 101 | return nullptr; |
| 102 | } |
| 103 | } |
| 104 | |
| 105 | // Finally, find the youngest serial number and delete it |
| 106 | |
| 107 | // Set index 0 as candidate c |
| 108 | uint32_t s = cache[0].serial; |
| 109 | size_t c = 0; |
| 110 | |
| 111 | // Compare candidate with serial and update to smaller one |
| 112 | for (size_t i = 0; i < cache.size(); i++) { |
| 113 | assert(cache[i].disktrk); |
| 114 | |
| 115 | // Compare and update the existing serial |
| 116 | if (cache[i].serial < s) { |
| 117 | s = cache[i].serial; |
| 118 | c = i; |
| 119 | } |
| 120 | } |
| 121 | |
| 122 | // Save this track |
| 123 | if (!cache[c].disktrk->Save(sec_path, cache_miss_write_count)) { |
| 124 | return nullptr; |
| 125 | } |
| 126 | |
| 127 | // Delete this track |
| 128 | shared_ptr<DiskTrack> disktrk = cache[c].disktrk; |
| 129 | cache[c].disktrk.reset(); |
| 130 | |
| 131 | if (Load(static_cast<int>(c), track, disktrk)) { |
| 132 | // Successful loading |
| 133 | cache[c].serial = serial; |