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package jdk.nashorn.internal.parser;

import static jdk.nashorn.internal.parser.TokenKind.SPECIAL;
import static jdk.nashorn.internal.parser.TokenType.IDENT;

Fast lookup of operators and keywords.
/** * Fast lookup of operators and keywords. * */
public final class TokenLookup {
Lookup table for tokens.
/** * Lookup table for tokens. */
private static final TokenType[] table;
Table base character.
/** * Table base character. */
private static final int tableBase = ' ';
Table base character.
/** * Table base character. */
private static final int tableLimit = '~';
Table size.
/** * Table size. */
private static final int tableLength = tableLimit - tableBase + 1; static { // Construct the table. table = new TokenType[tableLength]; // For each token type. for (final TokenType tokenType : TokenType.getValues()) { // Get the name. final String name = tokenType.getName(); // Filter tokens. if (name == null) { continue; } // Ignore null and special. if (tokenType.getKind() != SPECIAL) { // Get the first character of the name. final char first = name.charAt(0); // Translate that character into a table index. final int index = first - tableBase; assert index < tableLength : "Token name does not fit lookup table"; // Get the length of the token so that the longest come first. final int length = tokenType.getLength(); // Prepare for table insert. TokenType prev = null; TokenType next = table[index]; // Find the right spot in the table. while(next != null && next.getLength() > length) { prev = next; next = next.getNext(); } // Insert in table. tokenType.setNext(next); if (prev == null) { table[index] = tokenType; } else { prev.setNext(tokenType); } } } } private TokenLookup() { }
Lookup keyword.
Params:
  • content – parse content char array
  • position – index of position to start looking
  • length – max length to scan
Returns:token type for keyword
/** * Lookup keyword. * * @param content parse content char array * @param position index of position to start looking * @param length max length to scan * * @return token type for keyword */
public static TokenType lookupKeyword(final char[] content, final int position, final int length) { assert table != null : "Token lookup table is not initialized"; // First character of keyword. final char first = content[position]; // Must be lower case character. if ('a' <= first && first <= 'z') { // Convert to table index. final int index = first - tableBase; // Get first bucket entry. TokenType tokenType = table[index]; // Search bucket list. while (tokenType != null) { final int tokenLength = tokenType.getLength(); // if we have a length match maybe a keyword. if (tokenLength == length) { // Do an exact compare of string. final String name = tokenType.getName(); int i; for (i = 0; i < length; i++) { if (content[position + i] != name.charAt(i)) { break; } } if (i == length) { // Found a match. return tokenType; } } else if (tokenLength < length) { // Rest of tokens are shorter. break; } // Try next token. tokenType = tokenType.getNext(); } } // Not found. return IDENT; }
Lookup operator.
Params:
  • ch0 – 0th char in stream
  • ch1 – 1st char in stream
  • ch2 – 2nd char in stream
  • ch3 – 3rd char in stream
Returns:the token type for the operator
/** * Lookup operator. * * @param ch0 0th char in stream * @param ch1 1st char in stream * @param ch2 2nd char in stream * @param ch3 3rd char in stream * * @return the token type for the operator */
public static TokenType lookupOperator(final char ch0, final char ch1, final char ch2, final char ch3) { assert table != null : "Token lookup table is not initialized"; // Ignore keyword entries. if (tableBase < ch0 && ch0 <= tableLimit && !('a' <= ch0 && ch0 <= 'z')) { // Convert to index. final int index = ch0 - tableBase; // Get first bucket entry. TokenType tokenType = table[index]; // Search bucket list. while (tokenType != null) { final String name = tokenType.getName(); switch (name.length()) { case 1: // One character entry. return tokenType; case 2: // Two character entry. if (name.charAt(1) == ch1) { return tokenType; } break; case 3: // Three character entry. if (name.charAt(1) == ch1 && name.charAt(2) == ch2) { return tokenType; } break; case 4: // Four character entry. if (name.charAt(1) == ch1 && name.charAt(2) == ch2 && name.charAt(3) == ch3) { return tokenType; } break; default: break; } // Try next token. tokenType = tokenType.getNext(); } } // Not found. return null; } }