/*
* JBoss, Home of Professional Open Source.
*
* See the LEGAL.txt file distributed with this work for information regarding copyright ownership and licensing.
*
* See the AUTHORS.txt file distributed with this work for a full listing of individual contributors.
*/
package org.teiid.designer.core.util;
import java.util.Enumeration;
import java.util.NoSuchElementException;
/**
* The string tokenizer class allows an application to break a
* string into tokens AND (unlike the JDK tokenizer) access the delimiters
* separating the tokens.
* The tokenization method is much simpler than
* the one used by the <code>StreamTokenizer</code> class. The
* <code>StringTokenizer</code> methods do not distinguish among
* identifiers, numbers, and quoted strings, nor do they recognize
* and skip comments.
* <p>
* The set of delimiters (the characters that separate tokens) may
* be specified either at creation time or on a per-token basis.
* <p>
* An instance of <code>StringTokenizer</code> behaves in one of two
* ways, depending on whether it was created with the
* <code>returnDelims</code> flag having the value <code>true</code>
* or <code>false</code>:
* <ul>
* <li>If the flag is <code>false</code>, delimiter characters serve to
* separate tokens. A token is a maximal sequence of consecutive
* characters that are not delimiters.
* <li>If the flag is <code>true</code>, delimiter characters are themselves
* considered to be tokens. A token is thus either one delimiter
* character, or a maximal sequence of consecutive characters that are
* not delimiters.
* </ul><p>
* A <tt>StringTokenizer</tt> object internally maintains a current
* position within the string to be tokenized. Some operations advance this
* current position past the characters processed.<p>
* A token is returned by taking a substring of the string that was used to
* create the <tt>StringTokenizer</tt> object.
* <p>
* The following is one example of the use of the tokenizer. The code:
* <blockquote><pre>
* StringTokenizer st = new StringTokenizer("this is a test");
* while (st.hasMoreTokens()) {
* println(st.nextToken());
* }
* </pre></blockquote>
* <p>
* prints the following output:
* <blockquote><pre>
* this
* is
* a
* test
* </pre></blockquote>
*
*
* @since 8.0
*/
public class EnhancedStringTokenizer implements Enumeration {
private int currentPosition;
private int newPosition;
private int maxPosition;
private String str;
private String delimiters;
private int lastCurrentPosition;
private boolean retDelims;
private boolean delimsChanged;
/**
* maxDelimChar stores the value of the delimiter character with the
* highest value. It is used to optimize the detection of delimiter
* characters.
*/
private char maxDelimChar;
/**
* Set maxDelimChar to the highest char in the delimiter set.
*/
private void setMaxDelimChar() {
if (delimiters == null) {
maxDelimChar = 0;
return;
}
char m = 0;
for (int i = 0; i < delimiters.length(); i++) {
char c = delimiters.charAt(i);
if (m < c)
m = c;
}
maxDelimChar = m;
}
/**
* Constructs a string tokenizer for the specified string. All
* characters in the <code>delim</code> argument are the delimiters
* for separating tokens.
* <p>
* If the <code>returnDelims</code> flag is <code>true</code>, then
* the delimiter characters are also returned as tokens. Each
* delimiter is returned as a string of length one. If the flag is
* <code>false</code>, the delimiter characters are skipped and only
* serve as separators between tokens.
*
* @param str a string to be parsed.
* @param delim the delimiters.
* @param returnDelims flag indicating whether to return the delimiters
* as tokens.
*/
public EnhancedStringTokenizer(String str, String delim, boolean returnDelims) {
currentPosition = 0;
lastCurrentPosition = -1;
newPosition = -1;
delimsChanged = false;
this.str = str;
maxPosition = str.length();
delimiters = delim;
retDelims = returnDelims;
setMaxDelimChar();
}
/**
* Constructs a string tokenizer for the specified string. The
* characters in the <code>delim</code> argument are the delimiters
* for separating tokens. Delimiter characters themselves will not
* be treated as tokens.
*
* @param str a string to be parsed.
* @param delim the delimiters.
*/
public EnhancedStringTokenizer(String str, String delim) {
this(str, delim, false);
}
/**
* Constructs a string tokenizer for the specified string. The
* tokenizer uses the default delimiter set, which is
* <code>" \t\n\r\f"</code>: the space character,
* the tab character, the newline character, the carriage-return character,
* and the form-feed character. Delimiter characters themselves will
* not be treated as tokens.
*
* @param str a string to be parsed.
*/
public EnhancedStringTokenizer(String str) {
this(str, " \t\n\r\f", false); //$NON-NLS-1$
}
/**
* Skips delimiters starting from the specified position. If retDelims
* is false, returns the index of the first non-delimiter character at or
* after startPos. If retDelims is true, startPos is returned.
*/
private int skipDelimiters(int startPos) {
if (delimiters == null)
throw new NullPointerException();
int position = startPos;
while (!retDelims && position < maxPosition) {
char c = str.charAt(position);
if ((c > maxDelimChar) || (delimiters.indexOf(c) < 0))
break;
position++;
}
return position;
}
/**
* Skips ahead from startPos and returns the index of the next delimiter
* character encountered, or maxPosition if no such delimiter is found.
*/
private int scanToken(int startPos) {
int position = startPos;
while (position < maxPosition) {
char c = str.charAt(position);
if ((c <= maxDelimChar) && (delimiters.indexOf(c) >= 0))
break;
position++;
}
if (retDelims && (startPos == position)) {
char c = str.charAt(position);
if ((c <= maxDelimChar) && (delimiters.indexOf(c) >= 0))
position++;
}
return position;
}
/**
* Tests if there are more tokens available from this tokenizer's string.
* If this method returns <tt>true</tt>, then a subsequent call to
* <tt>nextToken</tt> with no argument will successfully return a token.
*
* @return <code>true</code> if and only if there is at least one token
* in the string after the current position; <code>false</code>
* otherwise.
*/
public boolean hasMoreTokens() {
/*
* Temporary store this position and use it in the following
* nextToken() method only if the delimiters have'nt been changed in
* that nextToken() invocation.
*/
newPosition = skipDelimiters(currentPosition);
return (newPosition < maxPosition);
}
/**
* Return the next delimiter character(s) that appear in the String.
* Typically, this method is called immediately after or immediate
* before the {@link #nextToken()} method.
* @return the dlimiter character(s), or null if there is no delimiter
* @since 4.2
*/
public String nextDelimiters() {
if ( currentPosition == 0 && lastCurrentPosition == -1 ) {
lastCurrentPosition = 0;
return null;
}
final int nextPosition = (newPosition >= 0 && !delimsChanged ) ? newPosition : skipDelimiters(currentPosition);
if ( nextPosition == lastCurrentPosition ) {
// There are no more ..
return null;
}
final String result = str.substring(lastCurrentPosition,nextPosition);
lastCurrentPosition = maxPosition;
return result;
}
/**
* Returns the next token from this string tokenizer.
*
* @return the next token from this string tokenizer.
* @exception NoSuchElementException if there are no more tokens in this
* tokenizer's string.
*/
public String nextToken() {
/*
* If next position already computed in hasMoreElements() and
* delimiters have changed between the computation and this invocation,
* then use the computed value.
*/
currentPosition = (newPosition >= 0 && !delimsChanged) ?
newPosition : skipDelimiters(currentPosition);
/* Reset these anyway */
delimsChanged = false;
newPosition = -1;
if (currentPosition >= maxPosition)
throw new NoSuchElementException();
int start = currentPosition;
currentPosition = scanToken(currentPosition);
String result = str.substring(start, currentPosition);
lastCurrentPosition = currentPosition;
return result;
}
/**
* Returns the next token in this string tokenizer's string. First,
* the set of characters considered to be delimiters by this
* <tt>StringTokenizer</tt> object is changed to be the characters in
* the string <tt>delim</tt>. Then the next token in the string
* after the current position is returned. The current position is
* advanced beyond the recognized token. The new delimiter set
* remains the default after this call.
*
* @param delim the new delimiters.
* @return the next token, after switching to the new delimiter set.
* @exception NoSuchElementException if there are no more tokens in this
* tokenizer's string.
*/
public String nextToken(String delim) {
delimiters = delim;
/* delimiter string specified, so set the appropriate flag. */
delimsChanged = true;
setMaxDelimChar();
return nextToken();
}
/**
* Returns the same value as the <code>hasMoreTokens</code>
* method. It exists so that this class can implement the
* <code>Enumeration</code> interface.
*
* @return <code>true</code> if there are more tokens;
* <code>false</code> otherwise.
* @see java.util.Enumeration
* @see java.util.StringTokenizer#hasMoreTokens()
*/
@Override
public boolean hasMoreElements() {
return hasMoreTokens();
}
/**
* Returns the same value as the <code>nextToken</code> method,
* except that its declared return value is <code>Object</code> rather than
* <code>String</code>. It exists so that this class can implement the
* <code>Enumeration</code> interface.
*
* @return the next token in the string.
* @exception NoSuchElementException if there are no more tokens in this
* tokenizer's string.
* @see java.util.Enumeration
* @see java.util.StringTokenizer#nextToken()
*/
@Override
public Object nextElement() {
return nextToken();
}
/**
* Calculates the number of times that this tokenizer's
* <code>nextToken</code> method can be called before it generates an
* exception. The current position is not advanced.
*
* @return the number of tokens remaining in the string using the current
* delimiter set.
* @see java.util.StringTokenizer#nextToken()
*/
public int countTokens() {
int count = 0;
int currpos = currentPosition;
while (currpos < maxPosition) {
currpos = skipDelimiters(currpos);
if (currpos >= maxPosition)
break;
currpos = scanToken(currpos);
count++;
}
return count;
}
}