diff options
Diffstat (limited to 'deps/v8/src/token.cc')
-rw-r--r-- | deps/v8/src/token.cc | 105 |
1 files changed, 0 insertions, 105 deletions
diff --git a/deps/v8/src/token.cc b/deps/v8/src/token.cc index bb42cead4b..0a4ad4c1ad 100644 --- a/deps/v8/src/token.cc +++ b/deps/v8/src/token.cc @@ -55,109 +55,4 @@ int8_t Token::precedence_[NUM_TOKENS] = { #undef T -// A perfect (0 collision) hash table of keyword token values. - -// larger N will reduce the number of collisions (power of 2 for fast %) -const unsigned int N = 128; -// make this small since we have <= 256 tokens -static uint8_t Hashtable[N]; -static bool IsInitialized = false; - - -static unsigned int Hash(const char* s) { - // The following constants have been found using trial-and-error. If the - // keyword set changes, they may have to be recomputed (make them flags - // and play with the flag values). Increasing N is the simplest way to - // reduce the number of collisions. - - // we must use at least 4 or more chars ('const' and 'continue' share - // 'con') - const unsigned int L = 5; - // smaller S tend to reduce the number of collisions - const unsigned int S = 4; - // make this a prime, or at least an odd number - const unsigned int M = 3; - - unsigned int h = 0; - for (unsigned int i = 0; s[i] != '\0' && i < L; i++) { - h += (h << S) + s[i]; - } - // unsigned int % by a power of 2 (otherwise this will not be a bit mask) - return h * M % N; -} - - -Token::Value Token::Lookup(const char* str) { - ASSERT(IsInitialized); - Value k = static_cast<Value>(Hashtable[Hash(str)]); - const char* s = string_[k]; - ASSERT(s != NULL || k == IDENTIFIER); - if (s == NULL || strcmp(s, str) == 0) { - return k; - } - return IDENTIFIER; -} - - -#ifdef DEBUG -// We need this function because C++ doesn't allow the expression -// NULL == NULL, which is a result of macro expansion below. What -// the hell? -static bool IsNull(const char* s) { - return s == NULL; -} -#endif - - -void Token::Initialize() { - if (IsInitialized) return; - - // A list of all keywords, terminated by ILLEGAL. -#define T(name, string, precedence) name, - static Value keyword[] = { - TOKEN_LIST(IGNORE_TOKEN, T, IGNORE_TOKEN) - ILLEGAL - }; -#undef T - - // Assert that the keyword array contains the 25 keywords, 3 future - // reserved words (const, debugger, and native), and the 3 named literals - // defined by ECMA-262 standard. - ASSERT(ARRAY_SIZE(keyword) == 25 + 3 + 3 + 1); // +1 for ILLEGAL sentinel - - // Initialize Hashtable. - ASSERT(NUM_TOKENS <= 256); // Hashtable contains uint8_t elements - for (unsigned int i = 0; i < N; i++) { - Hashtable[i] = IDENTIFIER; - } - - // Insert all keywords into Hashtable. - int collisions = 0; - for (int i = 0; keyword[i] != ILLEGAL; i++) { - Value k = keyword[i]; - unsigned int h = Hash(string_[k]); - if (Hashtable[h] != IDENTIFIER) collisions++; - Hashtable[h] = k; - } - - if (collisions > 0) { - PrintF("%d collisions in keyword hashtable\n", collisions); - FATAL("Fix keyword lookup!"); - } - - IsInitialized = true; - - // Verify hash table. -#define T(name, string, precedence) \ - ASSERT(IsNull(string) || Lookup(string) == IDENTIFIER); - -#define K(name, string, precedence) \ - ASSERT(Lookup(string) == name); - - TOKEN_LIST(T, K, IGNORE_TOKEN) - -#undef K -#undef T -} - } } // namespace v8::internal |