#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