| 1 | package geo |
| 2 | |
| 3 | import ( |
| 4 | "net" |
| 5 | "sync" |
| 6 | "time" |
| 7 | ) |
| 8 | |
| 9 | // Snapshot is one answer from one reader: the result, that reader's source, |
| 10 | // and whether any reader was loaded at all (geoip spec §5.4, codex R2-4). |
| 11 | // Headers, analytics and attribution all come from one Snapshot, so a swap |
| 12 | // between the lookup and the response can never relabel the data. |
| 13 | type Snapshot struct { |
| 14 | Result Result |
| 15 | Found bool |
| 16 | Source string // empty only when Loaded is false |
| 17 | Loaded bool |
| 18 | } |
| 19 | |
| 20 | // Swappable is a reader that can be replaced while lookups run. The old |
| 21 | // mapping is closed only after the write lock has been taken and released, |
| 22 | // so no lookup is ever in flight on an unmapped file. There is deliberately |
| 23 | // no Source() method: a source read apart from its lookup is the race this |
| 24 | // type exists to prevent. |
| 25 | type Swappable struct { |
| 26 | mu sync.RWMutex |
| 27 | cur *MMDB |
| 28 | } |
| 29 | |
| 30 | func NewSwappable() *Swappable { return &Swappable{} } |
| 31 | |
| 32 | // Lookup answers under one read lock. |
| 33 | func (s *Swappable) Lookup(ip net.IP) Snapshot { |
| 34 | s.mu.RLock() |
| 35 | defer s.mu.RUnlock() |
| 36 | if s.cur == nil { |
| 37 | return Snapshot{} |
| 38 | } |
| 39 | r, ok := s.cur.Lookup(ip) |
| 40 | return Snapshot{Result: r, Found: ok, Source: s.cur.Source(), Loaded: true} |
| 41 | } |
| 42 | |
| 43 | // Locate makes Swappable a Locator, so the console's region guess can hold |
| 44 | // it without ever seeing the *MMDB underneath (codex R3-2). |
| 45 | func (s *Swappable) Locate(ip net.IP) (Point, bool) { |
| 46 | s.mu.RLock() |
| 47 | defer s.mu.RUnlock() |
| 48 | if s.cur == nil { |
| 49 | return Point{}, false |
| 50 | } |
| 51 | return s.cur.Locate(ip) |
| 52 | } |
| 53 | |
| 54 | // Loaded reports the current reader's source and build time. |
| 55 | func (s *Swappable) Loaded() (source string, build time.Time, ok bool) { |
| 56 | s.mu.RLock() |
| 57 | defer s.mu.RUnlock() |
| 58 | if s.cur == nil { |
| 59 | return "", time.Time{}, false |
| 60 | } |
| 61 | return s.cur.Source(), s.cur.BuildEpoch(), true |
| 62 | } |
| 63 | |
| 64 | // Swap installs next (nil = none) and closes the previous reader after |
| 65 | // every lookup that could see it has finished. Go's RWMutex blocks new |
| 66 | // readers while a writer waits, so lookups cannot starve a swap. |
| 67 | func (s *Swappable) Swap(next *MMDB) { |
| 68 | s.mu.Lock() |
| 69 | old := s.cur |
| 70 | s.cur = next |
| 71 | s.mu.Unlock() |
| 72 | if old != nil && old != next { |
| 73 | old.Close() |
| 74 | } |
| 75 | } |
| 76 | |
| 77 | // LocateFrom is Locate plus the answering reader's source, under one read |
| 78 | // lock, so a credit shown beside a guess always names the database that |
| 79 | // made it. |
| 80 | func (s *Swappable) LocateFrom(ip net.IP) (Point, bool, string) { |
| 81 | s.mu.RLock() |
| 82 | defer s.mu.RUnlock() |
| 83 | if s.cur == nil { |
| 84 | return Point{}, false, "" |
| 85 | } |
| 86 | p, ok := s.cur.Locate(ip) |
| 87 | return p, ok, s.cur.Source() |
| 88 | } |
| 89 | |
amadan