funfs/wvdiskcache.h

   1 /*
   2  * Worldvisions Weaver Software:
   3  *   Copyright (C) 1997-2003 Net Integration Technologies, Inc.
   4  *
   5  * WvDiskCache uses GDBM hash to help keep track of the least recently used
   6  * files in an on-disk cache of file with an enforced maximum size.
   7  */
   8
   9 #ifndef __WVDISKCACHE_H
  10 #define __WVDISKCACHE_H
  11
  12 #include <wvautoconf.h>
  13
  14 #ifdef WITH_GDBM
  15
  16 #include <wvcallback.h>
  17 #include <wvstring.h>
  18 #include <wvgdbmhash.h>
  19 #include <wvbuf.h>
  20
  21 struct DCFileInfo
  22 {
  23     DCFileInfo() {};
  24     DCFileInfo(size_t _size, WvStringParm _next, WvStringParm _prev)
  25         : size(_size), next(_next), prev(_prev) {};
  26     DCFileInfo(const DCFileInfo &other)
  27     {
  28         size = other.size;
  29         next = other.next;
  30         prev = other.prev;
  31     }
  32     size_t size;
  33     WvString next;
  34     WvString prev;
  35 };
  36
  37
  38 template <>
  39 class DatumAdapter<DCFileInfo> : public DatumAdapterBase
  40 {
  41 public:
  42     typedef DCFileInfo ReturnType;
  43     operator DCFileInfo ()
  44         { return convert(mydatum); }
  45     static ReturnType convert(datum convertme)
  46     {
  47         WvInPlaceBuf buf(convertme.dptr, convertme.dsize, convertme.dsize);
  48         DCFileInfo fileinfo;
  49         fileinfo.size = atoi(buf.getstr(buf.strchr('\0')));
  50         fileinfo.next = buf.getstr(buf.strchr('\0'));
  51         fileinfo.prev = buf.getstr(buf.strchr('\0'));
  52         return fileinfo;
  53     }
  54     DatumAdapter(DCFileInfo fileinfo)
  55     {
  56         dynbuf.zap();
  57         dynbuf.putstr(fileinfo.size); dynbuf.putch('\0');
  58         dynbuf.putstr(fileinfo.next); dynbuf.putch('\0');
  59         dynbuf.putstr(fileinfo.prev); dynbuf.putch('\0');
  60         mydatum.dsize = dynbuf.used();
  61         mydatum.dptr = (char *)dynbuf.get(dynbuf.used());
  62     }
  63     DatumAdapter(const DatumAdapter<DCFileInfo> &other)
  64     {
  65         // I don't know what's going on here....
  66         // My theory is that gcc 3.x is crazy.
  67         // Where is my implicit conversion to a base class?
  68         dynbuf.merge(*((WvDynBufBase<unsigned char> *)&other.dynbuf),
  69                 other.dynbuf.used());
  70     }
  71 private:
  72     WvDynBuf dynbuf;
  73 };
  74
  75
  76 typedef WvCallback<void, WvStringParm> DiskCacheCallback;
  77
  78 class WvDiskCache
  79 {
  80 public:
  81     WvDiskCache(WvStringParm hashpath, int megabytes);
  82     void add(WvStringParm path, size_t size);
  83     void remove(WvString path);
  84     void set_remove_callback(const DiskCacheCallback &_callback)
  85         { callback = _callback; }
  86     void set_max(int megabytes);
  87     int current_size() { return cur_size / 1024; };
  88     int count() { return xcount; };
  89 protected:
  90     void purge();
  91     size_t max_size, cur_size;
  92     int xcount;
  93     WvString head, tail;
  94     DiskCacheCallback callback;
  95     WvGdbmHash<WvString, DCFileInfo> backend;
  96 };
  97
  98 #endif
  99
 100 #endif