impl/src/main/java/org/apache/myfaces/util/lang/StringUtils.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.myfaces.util.lang;

import java.util.ArrayList;


/**
 * Implements utility functions for the String class
 *
 * <p>
 * Emphasis on performance and reduced memory allocation/garbage collection
 * in exchange for longer more complex code.
 * </p>
 */
public final class StringUtils
{
    private StringUtils()
    {
        // utility class, no instantiation
    }

    //~ Methods ------------------------------------------------------------------------------------

    public static boolean isEmpty(String value)
    {
        return value == null || value.isEmpty();
    }
    
    public static boolean isBlank(String str)
    {
        if (str == null)
        {
            return true;
        }
        int strLen = str.length();
        if (strLen == 0)
        {
            return true;
        }

        for (int i = 0; i < strLen; i++) 
        {
            if (!Character.isWhitespace(str.charAt(i)))
            {
                return false;
            }
        }
        return true;
    }

    public static boolean isNotEmpty(String value)
    {
        return !isEmpty(value);
    }
    
    public static boolean isNotBlank(String value)
    {
        return !isBlank(value);
    }
    
    /**
     * Checks that the string represents a floating point number that CANNOT be
     * in exponential notation
     *
     * @param str the string to check
     *
     * @return boolean
     */
    public static boolean isFloatNoExponent(String str)
    {
        int len = str.length();
        if (len == 0)
        {
            return false;
        }

        // skip first char if sign char
        char c = str.charAt(0);
        int  i = ((c == '-') || (c == '+')) ? 1 : 0;

        // is it only a sign?
        if (i >= len)
        {
            return false;
        }

        boolean decimalPointFound = false;

        do
        {
            c = str.charAt(i);
            if (c == '.')
            {
                // is this a second dot?
                if (decimalPointFound)
                {
                    return false;
                }

                decimalPointFound = true;
            }
            else if (!Character.isDigit(c))
            {
                return false;
            }

            i++;
        }
        while (i < len);

        return true;
    }

    public static boolean isFloatWithOptionalExponent(String str)
    {
        int len = str.length();
        if (len == 0)
        {
            return false;
        }

        // skip first char if sign char
        char c = str.charAt(0);
        int  i = ((c == '-') || (c == '+')) ? 1 : 0;

        // is it only a sign?
        if (i >= len)
        {
            return false;
        }

        boolean exponentFound     = false;
        boolean decimalPointFound = false;

        do
        {
            c = str.charAt(i);
            switch (c)
            {
                case '.':

                    // is this a second one, are we in the exponent?
                    if (decimalPointFound || exponentFound)
                    {
                        return false;
                    }
                    decimalPointFound = true;

                    break;

                case 'e':
                case 'E':

                    // is this a second one?
                    if (exponentFound)
                    {
                        return false;
                    }
                    exponentFound = true;

                    // check for exponent sign
                    c = str.charAt(i + 1);

                    if ((c == '-') || (c == '+'))
                    {
                        i++;
                    }

                    break;

                default:
                    if (!Character.isDigit(c))
                    {
                        return false;
                    }
            }

            i++;
        }
        while (i < len);

        return true;
    }

    public static boolean isInteger(String str)
    {
        int len = str.length();
        if (len == 0)
        {
            return false;
        }

        // skip first char if sign char
        char c = str.charAt(0);
        int  i = ((c == '-') || (c == '+')) ? 1 : 0;

        // is it only a sign?
        if (i >= len)
        {
            return false;
        }

        do
        {
            if (!Character.isDigit(str.charAt(i)))
            {
                return false;
            }
            i++;
        }
        while (i < len);

        return true;
    }

    public static boolean isUnsignedInteger(String str)
    {
        int len = str.length();
        if (len == 0)
        {
            return false;
        }

        for (int i = 0; i < len; i++)
        {
            if (!Character.isDigit(str.charAt(i)))
            {
                return false;
            }
        }

        return true;
    }

    /**
     * Undoubles the quotes inside the string <br> Example:<br>
     * <pre>
     * hello""world becomes hello"world
     * </pre>
     *
     * @param str input string to dequote
     * @param quote the quoting char
     *
     * @return dequoted string
     */
    public static String dequote(String str, char quote)
    {
        // Is there anything to dequote?
        if (str == null)
        {
            return null;
        }

        return dequote(str, 0, str.length(), quote);
    }

    /**
     * Undoubles the quotes inside a substring <br> Example:<br>
     * <pre>
     * hello""world becomes hello"world
     * </pre>
     * WARNING: scan for quote may continue to the end of the string, make sure
     * that either <code>charAt(end + 1) == quote</code> or <code>end =
     * str.lentgth()</code>. If in doubt call
     * <code>dequote(str.substring(begin, end), quote)</code>
     *
     * @param str input string from which to get the substring, must not be
     *        null
     * @param begin begin index for substring
     * @param end end index for substring
     * @param quote the quoting char
     *
     * @return dequoted string
     *
     * @throws IllegalArgumentException if string is incorrectly quoted
     */
    public static String dequote(String str, int begin, int end, char quote)
    {
        // Is there anything to dequote?
        if (begin == end)
        {
            return "";
        }

        int endInt = str.indexOf(quote, begin);

        // If no quotes, return the original string
        // and save StringBuilder allocation/char copying
        if (endInt < 0)
        {
            return str.substring(begin, end);
        }

        StringBuilder sb     = new StringBuilder(end - begin);
        int          beginInt = begin; // need begin later
        do
        {
            if (((endInt + 1) >= end) || (str.charAt(endInt + 1) != quote))
            {
                throw new IllegalArgumentException(
                    "Internal quote not doubled in string '"
                    + str.substring(begin, end) + '\'');
            }

            sb.append(substring(str, beginInt, endInt)).append(quote);
            beginInt = endInt + 2;
            endInt = str.indexOf(quote, beginInt);
        }
        while ((endInt >= 0) && (endInt < end));

        return sb.append(substring(str, beginInt, end)).toString();
    }

    /**
     * Removes the surrounding quote and any double quote inside the string <br>
     * Example:<br>
     * <pre>
     * "hello""world" becomes hello"world
     * </pre>
     *
     * @param str input string to dequote
     * @param quote the quoting char
     *
     * @return dequoted String
     */
    public static String dequoteFull(String str, char quote)
    {
        if (str == null)
        {
            return null;
        }

        return dequoteFull(str, 0, str.length(), quote);
    }

    public static String dequoteFull(String str, int begin, int end, char quote)
    {
        // If empty substring, return empty string
        if (begin == end)
        {
            return "";
        }

        // If not quoted, return string
        if (str.charAt(begin) != quote)
        {
            return str.substring(begin, end);
        }

        int endInt = end - 1;
        if ((str.length() < 2) || (str.charAt(endInt) != quote))
        {
            throw new IllegalArgumentException(
                "Closing quote missing in string '"
                + substring(str, begin, end) + '\'');
        }

        return dequote(str, begin + 1, endInt, quote);
    }

    public static String replace(String str, String repl, String with)
    {
        int lastindex = 0;
        int pos = str.indexOf(repl);

        // If no replacement needed, return the original string
        // and save StringBuilder allocation/char copying
        if (pos < 0)
        {
            return str;
        }

        int          len     = repl.length();
        int          lendiff = with.length() - repl.length();
        StringBuilder out     =
            new StringBuilder((lendiff <= 0) ? str.length()
                : (str.length() + (10 * lendiff)));
        while(pos >= 0)
        {
            out.append(substring(str, lastindex, pos)).append(with);
            lastindex = pos + len;
            pos = str.indexOf(repl, lastindex);
        }

        return out.append(substring(str, lastindex, str.length())).toString();
    }

    public static String replace(String str, char repl, String with)
    {
        int pos = str.indexOf(repl);

        // If no replacement needed, return the original string
        // and save StringBuilder allocation/char copying
        if (pos < 0)
        {
            return str;
        }

        int          len       = str.length();
        int          lendiff   = with.length() - 1;
        StringBuilder out       =
            new StringBuilder((lendiff <= 0) ? str.length()
                : (str.length() + (10 * lendiff)));
        int          lastindex = 0;
        while( pos >= 0)
        {
            out.append(substring(str, lastindex, pos)).append(with);
            lastindex = pos + 1;
            pos = str.indexOf(repl, lastindex);
        }

        return out.append(substring(str, lastindex, len)).toString();
    }
    
    public static StringBuffer replace(
        StringBuffer out, String s, String repl, String with)
    {
        int lastindex = 0;
        int len = repl.length();
        int index = s.indexOf(repl);
        while (index >= 0)
        {
            // we have search string at position index
            out.append(substring(s, lastindex, index)).append(with);
            lastindex = index + len;
            index = s.indexOf(repl, lastindex);
        }

        return out.append(substring(s, lastindex, len));
    }

    public static StringBuilder replace(
        StringBuilder out, String s, String repl, String with)
    {
        int lastindex = 0;
        int len = repl.length();
        int index = s.indexOf(repl);
        while (index >= 0)
        {
            // we have search string at position index
            out.append(substring(s, lastindex, index)).append(with);
            lastindex = index + len;
            index = s.indexOf(repl, lastindex);
        }

        return out.append(substring(s, lastindex, len));
    }

    /**
     * Split a string into an array of strings arround a character separator.
     * This  function will be efficient for longer strings
     *
     * @param str the string to be split
     * @param separator the separator character
     *
     * @return array of string subparts
     */
    public static String[] splitLongString(String str, char separator)
    {
        int len = (str == null) ? 0 : str.length();
        if (str == null || len == 0)
        {
            return ArrayUtils.EMPTY_STRING_ARRAY;
        }

        int       oldPos = 0;
        ArrayList list = new ArrayList();
        int pos = str.indexOf(separator);
        while(pos >= 0)
        {
            list.add(substring(str, oldPos, pos));
            oldPos = (pos + 1);
            pos = str.indexOf(separator, oldPos);
        }


        list.add(substring(str, oldPos, len));

        return (String[]) list.toArray(ArrayUtils.EMPTY_STRING_ARRAY);
    }

    /**
     * Split a string into an array of strings arround a character separator.
     * Each element can be optionally quoted by the quote character.<br>
     * This function will be efficient for long strings
     *
     * @param str the string to be split
     * @param separator the separator character
     * @param quote the quote character
     *
     * @return array of string subparts
     *
     * @throws IllegalArgumentException DOCUMENT ME!
     */
    public static String[] splitLongString(
        String str, char separator, char quote)
    {
        int len = (str == null) ? 0 : str.length();
        if (str == null || len == 0)
        {
            return ArrayUtils.EMPTY_STRING_ARRAY;
        }

        int       oldPos = 0;
        ArrayList list = new ArrayList();
        for (int pos = 0; pos < len; oldPos = ++pos)
        {
            // Skip quoted text, if any
            while ((pos < len) && (str.charAt(pos) == quote))
            {
                pos = str.indexOf(quote, pos + 1) + 1;

                if (pos == 0)
                {
                    throw new IllegalArgumentException(
                        "Closing quote missing in string '" + str + '\'');
                }
            }

            boolean quoted;

            if (pos != oldPos)
            {
                quoted = true;

                if ((pos < len) && (str.charAt(pos) != separator))
                {
                    throw new IllegalArgumentException(
                        "Separator must follow closing quote in string '"
                        + str + '\'');
                }
            }
            else
            {
                quoted     = false;
                pos        = str.indexOf(separator, pos);
                if (pos < 0)
                {
                    pos = len;
                }
            }

            list.add(
                quoted ? dequote(str, oldPos + 1, pos - 1, quote)
                    : substring(str, oldPos, pos));
        }

        return (String[]) list.toArray(ArrayUtils.EMPTY_STRING_ARRAY);
    }

    /**
     * Split a string into an array of strings arround a character separator.
     * This  function will be efficient for short strings, for longer strings,
     * another approach may be better
     *
     * @param str the string to be split
     * @param separator the separator character
     *
     * @return array of string subparts
     */
    public static String[] splitShortString(String str, char separator)
    {
        int len = (str == null) ? 0 : str.length();
        if (str == null || len == 0)
        {
            return org.apache.myfaces.util.lang.ArrayUtils.EMPTY_STRING_ARRAY;
        }

        int lastTokenIndex = 0;

        // Step 1: how many substrings?
        //      We exchange double scan time for less memory allocation
        for (int pos = str.indexOf(separator);
            pos >= 0; pos = str.indexOf(separator, pos + 1))
        {
            lastTokenIndex++;
        }

        // Step 2: allocate exact size array
        String[] list   = new String[lastTokenIndex + 1];

        int      oldPos = 0;

        // Step 3: retrieve substrings
        int pos = str.indexOf(separator);
        int i = 0;
        
        while (pos >= 0)
        {
            list[i++] = substring(str, oldPos, pos);
            oldPos = (pos + 1);
            pos = str.indexOf(separator, oldPos);
        }

        list[lastTokenIndex] = substring(str, oldPos, len);

        return list;
    }

    /**
     * Split a string into an array of strings arround a character separator.
     * Each element can be optionally quoted by the quote character.<br>
     * This function will be efficient for short strings, for longer strings,
     * another approach may be better
     *
     * @param str the string to be split
     * @param separator the separator character
     * @param quote the quote character
     *
     * @return array of string subparts
     *
     * @throws IllegalArgumentException DOCUMENT ME!
     */
    public static String[] splitShortString(
        String str, char separator, char quote)
    {
        int len = (str == null) ? 0 : str.length();
        if (str == null || len == 0)
        {
            return ArrayUtils.EMPTY_STRING_ARRAY;
        }

        // Step 1: how many substrings?
        //      We exchange double scan time for less memory allocation
        int tokenCount = 0;
        for (int pos = 0; pos < len; pos++)
        {
            tokenCount++;

            int oldPos = pos;

            // Skip quoted text, if any
            while ((pos < len) && (str.charAt(pos) == quote))
            {
                pos = str.indexOf(quote, pos + 1) + 1;

                // pos == 0 is not found (-1 returned by indexOf + 1)
                if (pos == 0)
                {
                    throw new IllegalArgumentException(
                        "Closing quote missing in string '" + str + '\'');
                }
            }

            if (pos != oldPos)
            {
                if ((pos < len) && (str.charAt(pos) != separator))
                {
                    throw new IllegalArgumentException(
                        "Separator must follow closing quote in strng '"
                        + str + '\'');
                }
            }
            else
            {
                pos = str.indexOf(separator, pos);
                if (pos < 0)
                {
                    break;
                }
            }
        }

        // Main loop will finish one substring short when last char is separator
        if (str.charAt(len - 1) == separator)
        {
            tokenCount++;
        }

        // Step 2: allocate exact size array
        String[] list = new String[tokenCount];

        // Step 3: retrieve substrings
        // Note: on this pass we do not check for correctness,
        //       since we have already done so
        tokenCount--; // we want to stop one token short

        int oldPos = 0;
        for (int pos = 0, i = 0; i < tokenCount; i++, oldPos = ++pos)
        {
            boolean quoted;

            // Skip quoted text, if any
            while (str.charAt(pos) == quote)
            {
                pos = str.indexOf(quote, pos + 1) + 1;
            }

            if (pos != oldPos)
            {
                quoted = true;

                if (str.charAt(pos) != separator)
                {
                    throw new IllegalArgumentException(
                        "Separator must follow closing quote in strng '"
                        + str + '\'');
                }
            }
            else
            {
                quoted     = false;
                pos        = str.indexOf(separator, pos);
            }

            list[i] =
                quoted ? dequote(str, oldPos + 1, pos - 1, quote)
                    : substring(str, oldPos, pos);
        }

        list[tokenCount] = dequoteFull(str, oldPos, len, quote);

        return list;
    }

    public static String substring(String str, int begin, int end)
    {
        if (begin == end)
        {
            return "";
        }

        return str.substring(begin, end);
    }

    public static String[] trim(String[] strings)
    {
        if (strings == null)
        {
            return null;
        }

        for (int i = 0, len = strings.length; i < len; i++)
        {
            strings[i] = strings[i].trim();
        }

        return strings;
    }

    /**
     * Returns the minimum index &gt;= 0, if any
     *
     * <p>
     * Use to find the first of two characters in a string:<br>
     * <code>minIndex(s.indexOf('/'), indexOf('\'))</code>
     * </p>
     *
     * @param a
     * @param b
     * @return 
     */
    public static int minIndex(int a, int b)
    {
        return (a < 0) ? b
            : (b < 0) ? a
                : (a < b) ? a : b;
    }
}