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package bjc.utils.parserutils;
import java.util.LinkedList;
import java.util.List;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import org.apache.commons.lang3.StringUtils;
/**
* Utilities useful for operating on PL tokens.
*
* @author EVE
*
*/
public class TokenUtils {
/**
* Checks if the given expression contains the specified operator in a
* situation that indicates its use as an infix operator.
*
* @param expression
* The expression to check
* @param operator
* The operator to see if it is contained
* @return Whether or not the given expression contains the specified
* operator as a infix operator
*/
public static boolean containsInfixOperator(String expression, String operator) {
return StringUtils.countMatches(expression, operator) == 1 && !expression.equalsIgnoreCase(operator)
&& !expression.startsWith(operator);
}
/*
* This regex matches java-style string escapes
*/
private static String escapeString = "\\\\([btnfr\"'\\\\]" // Match shortform escape sequences like \t or \"
+ "|[0-3]?[0-7]{1,2}" // Match octal escape sequences
+ "|u[0-9a-fA-F]{4})"; // Match unicode escape sequences
private static Pattern escapePatt = Pattern.compile(escapeString);
/*
* This regular expression matches java style double quoted strings
*/
private static Pattern doubleQuotePatt = Pattern.compile("(\"(" + "[^\\\\\"]+" // Match one or more characters that aren't quotes or slashes
+ "|" + escapeString + ")" // Match escape sequences
+ "*\")"); // Match all of those things zero or more times, followed by a closing quote
/**
* Remove double quoted strings from a string.
*
* Splits a string around instances of java-style double-quoted strings.
*
* @param inp
* The string to split.
*
* @return An list containing alternating bits of the string and the
* embedded double-quoted strings that separated them.
*/
public static List<String> removeDQuotedStrings(String inp) {
StringBuffer work = new StringBuffer();
List<String> res = new LinkedList<>();
Matcher mt = doubleQuotePatt.matcher(inp);
while(mt.find()) {
mt.appendReplacement(work, "");
res.add(work.toString());
res.add(mt.group(1));
work = new StringBuffer();
}
mt.appendTail(work);
res.add(work.toString());
return res;
}
/**
* Replace escape characters with their actual equivalents.
*
* @param inp
* The string to replace escape sequences in.
*
* @return The string with escape sequences replaced by their equivalent
* characters.
*/
public static String descapeString(String inp) {
StringBuffer work = new StringBuffer();
Matcher escapeFinder = escapePatt.matcher(inp);
while(escapeFinder.find()) {
String escapeSeq = escapeFinder.group();
String escapeRep = "";
switch(escapeSeq) {
case "\\b":
escapeRep = "\b";
break;
case "\\t":
escapeRep = "\t";
break;
case "\\n":
escapeRep = "\n";
break;
case "\\f":
escapeRep = "\f";
break;
case "\\r":
escapeRep = "\r";
break;
case "\\\"":
escapeRep = "\"";
break;
case "\\'":
escapeRep = "'";
break;
case "\\\\":
escapeRep = "\\";
break;
default:
if(escapeSeq.startsWith("u")) {
escapeRep = handleUnicodeEscape(escapeSeq.substring(1));
} else {
escapeRep = handleOctalEscape(escapeSeq);
}
}
escapeFinder.appendReplacement(work, escapeRep);
}
escapeFinder.appendTail(work);
return work.toString();
}
private static String handleUnicodeEscape(String seq) {
int codepoint = Integer.parseInt(seq, 16);
return new String(Character.toChars(codepoint));
}
private static String handleOctalEscape(String seq) {
int codepoint = Integer.parseInt(seq, 8);
return new String(Character.toChars(codepoint));
}
/**
* Check if a given string would be successfully converted to a double
* by {@link Double#parseDouble(String)}.
*
* @param inp
* The string to check.
* @return Whether the string is a valid double or not.
*/
public static boolean isDouble(String inp) {
return DoubleMatcher.floatingLiteral.matcher(inp).matches();
}
private static Pattern intLitPattern = Pattern.compile("\\A[+\\-]?\\d+\\Z");
/**
* Check if a given string would be successfully converted to a integer
* by {@link Integer#parseInt(String)}.
*
* NOTE: This only checks syntax. Using values out of the range of
* integers will still cause errors.
*
* @param inp
* The input to check.
* @return Whether the string is a valid double or not.
*/
public static boolean isInt(String inp) {
return intLitPattern.matcher(inp).matches();
}
}
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