Subversion Repositories mkgmap

/*
 * Copyright (C) 2008,2014 Steve Ratcliffe
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License version 2 as
 *  published by the Free Software Foundation.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *
 * Author: Steve Ratcliffe
 * Create date: May 10, 2008
 */
package uk.me.parabola.mkgmap.scan;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.Reader;
import java.util.LinkedList;

/**
 * Read a file in terms of word and symbol tokens.
 *
 * @author Steve Ratcliffe
 */
public class TokenScanner {
        private static final int NO_PUSHBACK = 0;

        // Reading state
        private final Reader reader;
        private int pushback = NO_PUSHBACK;
        private boolean isEOF;

        private final String fileName;
        private int linenumber;

        private final LinkedList<Token> tokens = new LinkedList<>();

        private boolean bol = true;

        // Extra word characters.
        private String extraWordChars = "";
        private String commentChar = "#";

        public TokenScanner(String filename, Reader reader) {
                if (reader instanceof BufferedReader)
                        this.reader = reader;
                else
                        this.reader = new BufferedReader(reader);
                fileName = filename;
        }

        /**
         * Peek and return the first token.  It is not consumed.
         */
        public Token peekToken() {
                ensureTok();
                return tokens.peek();
        }

        /**
         * Get and remove the next token. May return space or newline. This is the
         * only place that a token is removed from the tokens queue.
         */
        public Token nextRawToken() {
                ensureTok();

                if (bol) {
                        bol = false;
                        linenumber++;
                }

                Token token = tokens.removeFirst();
                if (token.getType() == TokType.EOL)
                        bol = true;

                return token;
        }

        /**
         * Get the next token tht is not a space or newline.
         * @return The first valid text or symbol token.
         */
        public Token nextToken() {
                skipSpace();
                return nextRawToken();
        }

        /**
         * Push a token back to the beginning of the token queue.
         * @param tok The token to add to the beginning of the queue.
         */
        public void pushToken(Token tok) {
                tokens.push(tok);
        }

        /**
         * Get the value of the next non-space token and consume the token.  You'd
         * probably only call this after having peeked the type earlier.
         * Any initial space is skipped.
         */
        public String nextValue() {
                skipSpace();
                return nextRawToken().getValue();
        }

        public boolean isEndOfFile() {
                ensureTok();
                if (tokens.isEmpty()) {
                        return isEOF;
                } else {
                        return tokens.peek().getType() == TokType.EOF;
                }
        }

        /**
         * Skip any white space.  After calling this the next token
         * will be end of file or something other than SPACE or EOL.
         */
        public void skipSpace() {
                while (!isEndOfFile()) {
                        if (tokens.peek().isValue(commentChar)) {
                                skipLine();
                                continue;
                        }
                        if (!tokens.peek().isWhiteSpace())
                                break;
                        nextRawToken();
                }
        }

        /**
         * Skip everything up to a new line token.  The new line
         * token will be consumed, so the next token will the the first
         * on a new line (or at EOF).
         */
        public void skipLine() {
                while (!isEndOfFile()) {
                        Token t = nextRawToken();
                        if (t.getType() == TokType.EOL)
                                break;
                }
        }

        private void ensureTok() {
                if (tokens.isEmpty())
                        fillTok();
        }

        private void fillTok() {
                Token t = readTok();
                tokens.add(t);
        }

        /**
         * Read a token from the input stream.  There are only a few
         * kinds of token that are recognised on input.  Other token
         * types are recognised or constructed later on.
         * @return A token.  Never returns null or throws an exception.
         * Once end of file or an error occurs the routine will always return
         * EOF.
         */
        private Token readTok() {
                if (isEOF)
                        return new Token(TokType.EOF);

                int c = readChar();

                if (c == -1) {
                        isEOF = true;
                        return new Token(TokType.EOF);
                }

                StringBuilder val = new StringBuilder();
                val.append((char) c);

                TokType tt;
                if (c == '\r') {
                        c = readChar();
                        if (c != '\n')
                                pushback = c;
                        tt = TokType.EOL;
                } else if (c == '\n') {
                        tt = TokType.EOL;
                } else if (isSpace(c)) {
                        while (isSpace(c = readChar()) && c != '\n')
                                val.append((char) c);

                        pushback = c;
                        tt = TokType.SPACE;
                } else if (isWordChar(c)) {
                        while (isWordChar(c = readChar()))
                                val.append((char) c);
                        pushback = c;
                        tt = TokType.TEXT;
                } else {
                        // A symbol.  The value has already been set.  Some symbols
                        // combine from multiple characters.
                        if (c == '!' || c == '<' || c == '>') {
                                c = readChar();
                                if (c == '=')
                                        val.append('=');
                                else
                                        pushback = c;
                        } else if (c == '&' || c == '|') {
                                // Allow && and || as single symbols
                                int c2 = readChar();
                                if (c2 == c)
                                        val.append((char) c2);
                                else
                                        pushback = c2;
                        }
                        tt = TokType.SYMBOL;
                }

                Token t = new Token(tt);
                t.setValue(val.toString());
                return t;
        }

        /**
         * Read a single character.
         * @return The next character, or -1 if at EOF. The isEOF field will also be set to true at end of file.
         */
        private int readChar() {
                int c;
                if (pushback != NO_PUSHBACK) {
                        c = pushback;
                        pushback = NO_PUSHBACK;
                        return c;
                }

                try {
                        c = reader.read();
                } catch (IOException e) {
                        isEOF = true;
                        c = -1;
                }

                return c;
        }

        private boolean isSpace(int nextch) {
                return Character.isWhitespace(nextch) || nextch == '\uFEFF';
        }

        private boolean isWordChar(int ch) {
                return Character.isLetterOrDigit(ch)
                                || ch == '_'
                                || extraWordChars.indexOf(ch) >= 0;
        }

        /**
         * Read the tokens up until the end of the line and combine then
         * into one string.
         *
         * @return A single string, not including the newline terminator.  Never
         * returns null, returns an empty string if there is nothing there.  The
         * end of line is consumed.
         */
        public String readLine() {
                String res = readUntil(TokType.EOL, null);
                nextRawToken();  // use up new line
                return res;
        }

        /**
         * Read tokens until one of the given type and value is found and return the result as a single string.
         * The searched token is not consumed from the input.
         *
         * @param type The token type to search for.
         * @param value The string value of the token to search for.
         * @return A single string of all the tokens preceding the searched token.
         */
        public String readUntil(TokType type, String value) {
                StringBuilder sb = new StringBuilder();
                while (!isEndOfFile()) {
                        Token t = peekToken();
                        if (t.getType() == type && (value == null || value.equals(t.getValue())))
                                break;
                        sb.append(nextRawToken().getValue());
                }
                return sb.toString().trim();
        }

        /**
         * Convenience routine to get an integer.  Skips space and reads a
         * token.  This token is converted to an integer if possible.
         * @return An integer as read from the next non space token.
         * @throws NumberFormatException When the next symbol isn't
         * a valid integer.
         */
        public int nextInt() throws NumberFormatException {
                skipSpace();
                Token t = nextRawToken();
                if (t == null)
                        throw new NumberFormatException("no number");

                return Integer.parseInt(t.getValue());
        }

        /**
         * As {@link #nextWordWithInfo()} but just the string is returned.
         * @return The next word as a string.  A quoted entity is regarded as a
         * word for the purposes of this scanner.
         */
        public String nextWord() {
                WordInfo info = nextWordWithInfo();
                return info.getText();
        }

        /**
         * Read a string that can be quoted.  If it is quoted, then everything
         * until the closing quotes is part of the string.  Both single
         * and double quotes can be used.
         *
         * If there are no quotes then it behaves like nextToken apart from
         * skipping space.
         *
         * Initial and final space is skipped.
         *
         * The word string is returned along with a flag to indicate whether it
         * was quoted or not.
         */
        public WordInfo nextWordWithInfo() {
                skipSpace();
                Token tok = peekToken();
                char quotec = 0;
                if (tok.getType() == TokType.SYMBOL) {
                        String s = tok.getValue();
                        if ("'".equals(s) || "\"".equals(s)) {
                                quotec = s.charAt(0);
                                nextRawToken();
                        }
                }

                StringBuilder sb = new StringBuilder();
                while (!isEndOfFile()) {
                        tok = nextRawToken();
                        if (quotec == 0) {
                                sb.append(tok.getValue());
                                break;
                        } else {
                                if (tok.isValue(String.valueOf(quotec)))
                                        break;
                                sb.append(tok.getValue());
                        }
                }
                skipSpace();
                return new WordInfo(sb.toString(), quotec != 0);
        }

        /**
         * Check the value of the next token without consuming it.
         *
         * @param val String value to compare against.
         * @return True if the next token has the same value as the argument.
         */
        public boolean checkToken(String val) {
                skipSpace();
                Token tok = peekToken();
                if (val == null || tok.getValue() == null)
                        return false;
                return val.equals(tok.getValue());
        }

        /**
         * Validate the next word is the given value.  Space is skipped before
         * checking, the checked value is consumed.  Use when you want to
         * ensure that a required syntax element is present.
         *
         * The input will either be positioned after the required word or an
         * exception will have been thrown.
         *
         * @param val The string value to look for.
         * @throws SyntaxException If the required string is not found.
         */
        public void validateNext(String val) {
                skipSpace();
                Token tok = nextToken();
                if (val == null || !val.equals(tok.getValue()))
                        throw new SyntaxException(this, "Expecting " + val + ", instead saw " + tok.getValue());
        }

        public int getLinenumber() {
                return linenumber;
        }

        public String getFileName() {
                return fileName;
        }

        /**
         * Extra word characters are characters that should be considered as part of a word in addition
         * to alphanumerics and underscore.
         * @param extraWordChars A string containing all the characters to be considered part of a word.
         */
        public void setExtraWordChars(String extraWordChars) {
                this.extraWordChars = extraWordChars;
        }

        /**
         * The skip space routine, will skip all characters after a '#' until the end of the
         * line as part of its skip white space functionality.
         *
         * This is a mis-feature if your comment character is not '#' or that character is
         * sometimes important. Therefore you can turn this off by passing in an empty string here.
         */
        public void setCommentChar(String commentChar) {
                if (commentChar == null)
                        this.commentChar = "";
                else
                        this.commentChar = commentChar;
        }
}