key_value_cache/key_value_cache.go

   1 package key_value_cache
   2
   3 import (
   4         "errors"
   5
   6         "github.com/sjmudd/pstop/lib"
   7 )
   8
   9 // provide a mapping from filename to table.schema etc
  10 type KeyValueCache struct {
  11         cache                                            map[string]string
  12         read_requests, served_from_cache, write_requests int
  13 }
  14
  15 // create a new KeyValueCache entry
  16 func NewKeyValueCache() KeyValueCache {
  17         lib.Logger.Println("KeyValueCache()")
  18         var kvc KeyValueCache
  19
  20         return kvc
  21 }
  22
  23 // return value if found
  24 func (kvc *KeyValueCache) Get(key string) (result string, err error) {
  25         lib.Logger.Println("KeyValueCache.Get(", key, ")")
  26         if kvc.cache == nil {
  27                 lib.Logger.Println("KeyValueCache.Get() kvc.cache is empty so enabling it")
  28                 kvc.cache = make(map[string]string)
  29                 kvc.read_requests = 0
  30                 kvc.served_from_cache = 0
  31                 kvc.write_requests = 0
  32         }
  33
  34         kvc.read_requests++
  35
  36         if result, ok := kvc.cache[key]; ok {
  37                 kvc.served_from_cache++
  38                 lib.Logger.Println("Found: read_requests/servced_from_cache:", kvc.read_requests, kvc.served_from_cache)
  39                 return result, nil
  40         } else {
  41                 lib.Logger.Println("Not found: read_requests/served_from_cache:", kvc.read_requests, kvc.served_from_cache)
  42                 return "", errors.New("Not found")
  43         }
  44 }
  45
  46 // write to cache and return value
  47 func (kvc *KeyValueCache) Put(key, value string) string {
  48         lib.Logger.Println("KeyValueCache.Put(", key, ",", value, ")")
  49         kvc.cache[key] = value
  50         return value
  51 }
  52
  53 func (kvc *KeyValueCache) Statistics() (int, int, int) {
  54         return kvc.read_requests, kvc.served_from_cache, kvc.write_requests
  55 }