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163 lines
4.9 KiB
163 lines
4.9 KiB
16 years ago
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// Copyright 2006-2008 the V8 project authors. All rights reserved.
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// Redistribution and use in source and binary forms, with or without
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// modification, are permitted provided that the following conditions are
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// met:
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//
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// * Redistributions of source code must retain the above copyright
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// notice, this list of conditions and the following disclaimer.
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// * Redistributions in binary form must reproduce the above
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// copyright notice, this list of conditions and the following
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// disclaimer in the documentation and/or other materials provided
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// with the distribution.
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// * Neither the name of Google Inc. nor the names of its
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// contributors may be used to endorse or promote products derived
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// from this software without specific prior written permission.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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#include "v8.h"
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#include "token.h"
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namespace v8 { namespace internal {
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#ifdef DEBUG
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#define T(name, string, precedence) #name,
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const char* Token::name_[NUM_TOKENS] = {
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TOKEN_LIST(T, T, IGNORE_TOKEN)
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};
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#undef T
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#endif
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#define T(name, string, precedence) string,
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const char* Token::string_[NUM_TOKENS] = {
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TOKEN_LIST(T, T, IGNORE_TOKEN)
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};
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#undef T
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#define T(name, string, precedence) precedence,
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int8_t Token::precedence_[NUM_TOKENS] = {
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TOKEN_LIST(T, T, IGNORE_TOKEN)
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};
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#undef T
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// A perfect (0 collision) hash table of keyword token values.
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// larger N will reduce the number of collisions (power of 2 for fast %)
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const unsigned int N = 128;
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// make this small since we have <= 256 tokens
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static uint8_t Hashtable[N];
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static bool IsInitialized = false;
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static unsigned int Hash(const char* s) {
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// The following constants have been found using trial-and-error. If the
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// keyword set changes, they may have to be recomputed (make them flags
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// and play with the flag values). Increasing N is the simplest way to
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// reduce the number of collisions.
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// we must use at least 4 or more chars ('const' and 'continue' share
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// 'con')
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const unsigned int L = 5;
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// smaller S tend to reduce the number of collisions
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const unsigned int S = 4;
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// make this a prime, or at least an odd number
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const unsigned int M = 3;
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unsigned int h = 0;
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for (unsigned int i = 0; s[i] != '\0' && i < L; i++) {
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h += (h << S) + s[i];
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}
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// unsigned int % by a power of 2 (otherwise this will not be a bit mask)
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return h * M % N;
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}
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Token::Value Token::Lookup(const char* str) {
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ASSERT(IsInitialized);
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Value k = static_cast<Value>(Hashtable[Hash(str)]);
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const char* s = string_[k];
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ASSERT(s != NULL || k == IDENTIFIER);
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if (s == NULL || strcmp(s, str) == 0) {
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return k;
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}
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return IDENTIFIER;
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}
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#ifdef DEBUG
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// We need this function because C++ doesn't allow the expression
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// NULL == NULL, which is a result of macro expansion below. What
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// the hell?
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static bool IsNull(const char* s) {
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return s == NULL;
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}
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#endif
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void Token::Initialize() {
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if (IsInitialized) return;
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// A list of all keywords, terminated by ILLEGAL.
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#define T(name, string, precedence) name,
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static Value keyword[] = {
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TOKEN_LIST(IGNORE_TOKEN, T, IGNORE_TOKEN)
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ILLEGAL
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};
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#undef T
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// Assert that the keyword array contains the 25 keywords, 3 future
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// reserved words (const, debugger, and native), and the 3 named literals
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// defined by ECMA-262 standard.
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ASSERT(ARRAY_SIZE(keyword) == 25 + 3 + 3 + 1); // +1 for ILLEGAL sentinel
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// Initialize Hashtable.
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ASSERT(NUM_TOKENS <= 256); // Hashtable contains uint8_t elements
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for (unsigned int i = 0; i < N; i++) {
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Hashtable[i] = IDENTIFIER;
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}
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// Insert all keywords into Hashtable.
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int collisions = 0;
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for (int i = 0; keyword[i] != ILLEGAL; i++) {
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Value k = keyword[i];
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unsigned int h = Hash(string_[k]);
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if (Hashtable[h] != IDENTIFIER) collisions++;
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Hashtable[h] = k;
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}
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if (collisions > 0) {
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PrintF("%d collisions in keyword hashtable\n", collisions);
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FATAL("Fix keyword lookup!");
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}
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IsInitialized = true;
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// Verify hash table.
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#define T(name, string, precedence) \
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ASSERT(IsNull(string) || Lookup(string) == IDENTIFIER);
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#define K(name, string, precedence) \
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ASSERT(Lookup(string) == name);
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TOKEN_LIST(T, K, IGNORE_TOKEN)
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#undef K
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#undef T
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}
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} } // namespace v8::internal
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