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26 #ifndef CachedTranscendentalFunction_h
27 #define CachedTranscendentalFunction_h
33 typedef double (*TranscendentalFunctionPtr)(double);
35 // CachedTranscendentalFunction provides a generic mechanism to cache results
36 // for pure functions with the signature "double func(double)", and where NaN
38 template<TranscendentalFunctionPtr orignalFunction>
39 class CachedTranscendentalFunction {
46 CachedTranscendentalFunction()
51 ~CachedTranscendentalFunction()
57 JSValue operator() (double operand)
59 if (UNLIKELY(!m_cache))
61 CacheEntry* entry = &m_cache[hash(operand)];
63 if (entry->operand == operand)
64 return jsDoubleNumber(entry->result);
65 double result = orignalFunction(operand);
66 entry->operand = operand;
67 entry->result = result;
68 return jsDoubleNumber(result);
74 // Lazily allocate the table, populate with NaN->NaN mapping.
75 m_cache = static_cast<CacheEntry*>(fastMalloc(s_cacheSize * sizeof(CacheEntry)));
76 for (unsigned x = 0; x < s_cacheSize; ++x) {
77 m_cache[x].operand = std::numeric_limits<double>::quiet_NaN();
78 m_cache[x].result = std::numeric_limits<double>::quiet_NaN();
82 static unsigned hash(double d)
84 union doubleAndUInt64 {
90 unsigned x = u.is[0] ^ u.is[1];
91 x = (x >> 20) ^ (x >> 8);
92 return x & (s_cacheSize - 1);
95 static const unsigned s_cacheSize = 0x1000;
101 #endif // CachedTranscendentalFunction_h