159 lines
3.4 KiB
C
159 lines
3.4 KiB
C
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//
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// CH.H
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// Cache Handler
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//
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// Copyright (c) Microsoft 1997-
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//
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#ifndef _H_CH
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#define _H_CH
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//
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//
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// DEFINES
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//
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//
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#define CH_NUM_EVICTION_CATEGORIES 3
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//
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// NOTES:
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// 64K limit on cache
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// CHCACHE includes one entry, so only subtract out header part
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//
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#define CH_MAX_CACHE_ENTRIES \
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( (65535 - (sizeof(CHCACHE) - sizeof(CHENTRY))) / sizeof(CHENTRY) )
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//
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//
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// TYPEDEFS
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//
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//
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typedef struct tagCHCHAIN
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{
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WORD next;
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WORD prev;
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} CHCHAIN;
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typedef CHCHAIN * PCHCHAIN;
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//
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// There are going to be thousands of cache entries so we need to keep
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// the header as compact as possible. We could drop the eviction
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// category, but it is useful info and does round the entry to 16 bytes
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// which makes indexing efficient.
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//
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// Note that the 16 bit code is restricted to 4096 entries unless we take
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// steps to allow huge addressing of the entry array.
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//
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//
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// CHENTRY
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// Cache entry in a Cache tree
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//
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typedef struct tagCHENTRY
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{
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struct tagCHENTRY * pParent;
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struct tagCHENTRY * pLeft;
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struct tagCHENTRY * pRight;
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WORD lHeight;
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WORD rHeight;
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UINT cbData;
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LPBYTE pData;
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UINT checkSum;
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CHCHAIN chain;
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WORD evictionCategory;
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WORD free;
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} CHENTRY;
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typedef CHENTRY * PCHENTRY;
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//
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// A CACHE
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//
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// FORWARD DECLARATION
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typedef struct tagCHCACHE * PCHCACHE;
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#ifdef __cplusplus
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typedef void (* PFNCACHEDEL)(class ASHost * pHost, PCHCACHE pCache, UINT iEntry, LPBYTE pData);
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//
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// Each cache may have several eviction categories. These allow the caller
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// to define classes of data so that it can control what is evicted from
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// the cache. To be a candidate for eviction the eviction class of a LRU
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// entry must match, unless the number of entries in that category is
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// less than the eviction threshold, in which case any cache entry is
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// up for grabs.
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//
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// The EvictionThreshold() function can be used to tune eviction thresholds
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// which default to cEntries/cNumEvictionCategories
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//
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typedef struct tagCHCACHE
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{
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STRUCTURE_STAMP
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PFNCACHEDEL pfnCacheDel;
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UINT cEntries;
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UINT cNumEvictionCategories;
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UINT cbNotHashed;
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//
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// NOTE: CH_NUM_EVICTION_CATEGORIES is 3, so 3 words + 3 words +
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// 3 words == 9 words, not DWORD aligned. Hence we stick the WORD
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// field free after iMRUTail. If CH_NUM_EVICTION_CATEGORIES ever
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// changes to an even value, reshuffle this structure.
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//
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WORD cEvictThreshold[CH_NUM_EVICTION_CATEGORIES];
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WORD iMRUHead[CH_NUM_EVICTION_CATEGORIES];
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WORD iMRUTail[CH_NUM_EVICTION_CATEGORIES];
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WORD free;
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PCHENTRY pRoot;
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PCHENTRY pFirst;
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PCHENTRY pLast;
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CHENTRY Entry[1];
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}
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CHCACHE;
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typedef CHCACHE * PCHCACHE;
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#endif // __cplusplus
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//
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//
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// MACROS
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//
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//
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//
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// BOGUS LAURABU
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// In future, have debug signatures at front of objects to catch heap corruption
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//
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#define IsValidCache(pCache) \
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(!IsBadWritePtr((pCache), sizeof(CHCACHE)))
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#define IsValidCacheEntry(pEntry) \
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(!IsBadWritePtr((pEntry), sizeof(CHENTRY)))
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#define IsValidCacheIndex(pCache, iEntry) \
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((iEntry >= 0) && (iEntry < (pCache)->cEntries))
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#define IsCacheEntryInTree(pEntry) \
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(((pEntry)->lHeight != 0xFFFF) && ((pEntry)->rHeight != 0xFFFF))
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#endif // _H_CH
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