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 *
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 *   Corporation and others.  All Rights Reserved.
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package sun.font;


ScriptRun is used to find runs of characters in the same script, as defined in the Script class. It implements a simple iterator over an array of characters. The iterator will assign COMMON and INHERITED characters to the same script as the preceding characters. If the COMMON and INHERITED characters are first, they will be assigned to the same script as the following characters. The iterator will try to match paired punctuation. If it sees an opening punctuation character, it will remember the script that was assigned to that character, and assign the same script to the matching closing punctuation. No attempt is made to combine related scripts into a single run. In particular, Hiragana, Katakana, and Han characters will appear in seperate runs. Here is an example of how to iterate over script runs: 
void printScriptRuns(char[] text)
{
    ScriptRun scriptRun = new ScriptRun(text, 0, text.length);
    while (scriptRun.next()) {
        int start  = scriptRun.getScriptStart();
        int limit  = scriptRun.getScriptLimit();
        int script = scriptRun.getScriptCode();
        System.out.println("Script \"" + Script.getName(script) + "\" from " +
                           start + " to " + limit + ".");
    }
 }



/**
 * {@code ScriptRun} is used to find runs of characters in
 * the same script, as defined in the {@code Script} class.
 * It implements a simple iterator over an array of characters.
 * The iterator will assign {@code COMMON} and {@code INHERITED}
 * characters to the same script as the preceding characters. If the
 * COMMON and INHERITED characters are first, they will be assigned to
 * the same script as the following characters.
 *
 * The iterator will try to match paired punctuation. If it sees an
 * opening punctuation character, it will remember the script that
 * was assigned to that character, and assign the same script to the
 * matching closing punctuation.
 *
 * No attempt is made to combine related scripts into a single run. In
 * particular, Hiragana, Katakana, and Han characters will appear in seperate
 * runs.

 * Here is an example of how to iterate over script runs:
 * <pre>
 * void printScriptRuns(char[] text)
 * {
 *     ScriptRun scriptRun = new ScriptRun(text, 0, text.length);
 *
 *     while (scriptRun.next()) {
 *         int start  = scriptRun.getScriptStart();
 *         int limit  = scriptRun.getScriptLimit();
 *         int script = scriptRun.getScriptCode();
 *
 *         System.out.println("Script \"" + Script.getName(script) + "\" from " +
 *                            start + " to " + limit + ".");
 *     }
 *  }
 * </pre>
 *
 */
public final class ScriptRun
{
    private char[] text;   // fixed once set by constructor
    private int textStart;
    private int textLimit;

    private int scriptStart;     // change during iteration
    private int scriptLimit;
    private int scriptCode;

    private int[] stack;         // stack used to handle paired punctuation if encountered
    private int parenSP;

    public ScriptRun() {
        // must call init later or we die.
    }

    
Construct a ScriptRun object which iterates over a subrange of the given characetrs. 
Params:
  • chars – the array of characters over which to iterate.
  • start – the index of the first character over which to iterate
  • count – the number of characters over which to iterate
/**
     * Construct a {@code ScriptRun} object which iterates over a subrange
     * of the given characetrs.
     *
     * @param chars the array of characters over which to iterate.
     * @param start the index of the first character over which to iterate
     * @param count the number of characters over which to iterate
     */
    public ScriptRun(char[] chars, int start, int count)
    {
        init(chars, start, count);
    }

    public void init(char[] chars, int start, int count)
    {
        if (chars == null || start < 0 || count < 0 || count > chars.length - start) {
            throw new IllegalArgumentException();
        }

        text = chars;
        textStart = start;
        textLimit = start + count;

        scriptStart = textStart;
        scriptLimit = textStart;
        scriptCode = Script.INVALID_CODE;
        parenSP = 0;
    }

    
Get the starting index of the current script run.

Returns:the index of the first character in the current script run.
/**
     * Get the starting index of the current script run.
     *
     * @return the index of the first character in the current script run.
     */
    public int getScriptStart() {
        return scriptStart;
    }

    
Get the index of the first character after the current script run.

Returns:the index of the first character after the current script run.
/**
     * Get the index of the first character after the current script run.
     *
     * @return the index of the first character after the current script run.
     */
    public int getScriptLimit() {
        return scriptLimit;
    }

    
Get the script code for the script of the current script run.

See Also:
Returns:the script code for the script of the current script run.
/**
     * Get the script code for the script of the current script run.
     *
     * @return the script code for the script of the current script run.
     * @see Script
     */
    public int getScriptCode() {
        return scriptCode;
    }

    
Find the next script run. Returns false if there isn't another run, returns true if there is. 
Returns:false if there isn't another run, true if there is.
/**
     * Find the next script run. Returns {@code false} if there
     * isn't another run, returns {@code true} if there is.
     *
     * @return {@code false} if there isn't another run, {@code true} if there is.
     */
    public boolean next() {
        int startSP  = parenSP;  // used to find the first new open character

        // if we've fallen off the end of the text, we're done
        if (scriptLimit >= textLimit) {
            return false;
        }

        scriptCode  = Script.COMMON;
        scriptStart = scriptLimit;

        int ch;

        while ((ch = nextCodePoint()) != DONE) {
            int sc = ScriptRunData.getScript(ch);
            int pairIndex = sc == Script.COMMON ? getPairIndex(ch) : -1;

            // Paired character handling:
            //
            // if it's an open character, push it onto the stack.
            // if it's a close character, find the matching open on the
            // stack, and use that script code. Any non-matching open
            // characters above it on the stack will be popped.
            if (pairIndex >= 0) {
                if ((pairIndex & 1) == 0) {
                    if (stack == null) {
                        stack = new int[32];
                    } else if (parenSP == stack.length) {
                        int[] newstack = new int[stack.length + 32];
                        System.arraycopy(stack, 0, newstack, 0, stack.length);
                        stack = newstack;
                    }

                    stack[parenSP++] = pairIndex;
                    stack[parenSP++] = scriptCode;
                } else if (parenSP > 0) {
                    int pi = pairIndex & ~1;

                    while ((parenSP -= 2) >= 0 && stack[parenSP] != pi);

                    if (parenSP >= 0) {
                        sc = stack[parenSP+1];
                    } else {
                      parenSP = 0;
                    }
                    if (parenSP < startSP) {
                        startSP = parenSP;
                    }
               }
            }

            if (sameScript(scriptCode, sc)) {
                if (scriptCode <= Script.INHERITED && sc > Script.INHERITED) {
                    scriptCode = sc;

                    // now that we have a final script code, fix any open
                    // characters we pushed before we knew the script code.
                    while (startSP < parenSP) {
                        stack[startSP+1] = scriptCode;
                        startSP += 2;
                    }
                }

                // if this character is a close paired character,
                // pop it from the stack
                if (pairIndex > 0 && (pairIndex & 1) != 0 && parenSP > 0) {
                    parenSP -= 2;
                }
            } else {
                // We've just seen the first character of
                // the next run. Back over it so we'll see
                // it again the next time.
                pushback(ch);

                // we're outta here
                break;
            }
        }

        return true;
    }

    static final int SURROGATE_START = 0x10000;
    static final int LEAD_START = 0xd800;
    static final int LEAD_LIMIT = 0xdc00;
    static final int TAIL_START = 0xdc00;
    static final int TAIL_LIMIT = 0xe000;
    static final int LEAD_SURROGATE_SHIFT = 10;
    static final int SURROGATE_OFFSET = SURROGATE_START - (LEAD_START << LEAD_SURROGATE_SHIFT) - TAIL_START;

    static final int DONE = -1;

    private int nextCodePoint() {
        if (scriptLimit >= textLimit) {
            return DONE;
        }
        int ch = text[scriptLimit++];
        if (ch >= LEAD_START && ch < LEAD_LIMIT && scriptLimit < textLimit) {
            int nch = text[scriptLimit];
            if (nch >= TAIL_START && nch < TAIL_LIMIT) {
                ++scriptLimit;
                ch = (ch << LEAD_SURROGATE_SHIFT) + nch + SURROGATE_OFFSET;
            }
        }
        return ch;
    }

    private void pushback(int ch) {
        if (ch >= 0) {
            if (ch >= 0x10000) {
                scriptLimit -= 2;
            } else {
                scriptLimit -= 1;
            }
        }
    }

    
Compare two script codes to see if they are in the same script. If one script is
a strong script, and the other is INHERITED or COMMON, it will compare equal.

Params:
  • scriptOne – one of the script codes.
  • scriptTwo – the other script code.
See Also:
Returns:true if the two scripts are the same.
/**
     * Compare two script codes to see if they are in the same script. If one script is
     * a strong script, and the other is INHERITED or COMMON, it will compare equal.
     *
     * @param scriptOne one of the script codes.
     * @param scriptTwo the other script code.
     * @return {@code true} if the two scripts are the same.
     * @see Script
     */
    private static boolean sameScript(int scriptOne, int scriptTwo) {
        return scriptOne == scriptTwo || scriptOne <= Script.INHERITED || scriptTwo <= Script.INHERITED;
    }

    
Find the highest bit that's set in a word. Uses a binary search through
the bits.

Params:
  • n – the word in which to find the highest bit that's set.
Returns:the bit number (counting from the low order bit) of the highest bit.
/**
     * Find the highest bit that's set in a word. Uses a binary search through
     * the bits.
     *
     * @param n the word in which to find the highest bit that's set.
     * @return the bit number (counting from the low order bit) of the highest bit.
     */
    private static byte highBit(int n)
    {
        if (n <= 0) {
            return -32;
        }

        byte bit = 0;

        if (n >= 1 << 16) {
            n >>= 16;
            bit += 16;
        }

        if (n >= 1 << 8) {
            n >>= 8;
            bit += 8;
        }

        if (n >= 1 << 4) {
            n >>= 4;
            bit += 4;
        }

        if (n >= 1 << 2) {
            n >>= 2;
            bit += 2;
        }

        if (n >= 1 << 1) {
            n >>= 1;
            bit += 1;
        }

        return bit;
    }

    
Search the pairedChars array for the given character.

Params:
  • ch – the character for which to search.
Returns:the index of the character in the table, or -1 if it's not there.
/**
     * Search the pairedChars array for the given character.
     *
     * @param ch the character for which to search.
     * @return the index of the character in the table, or -1 if it's not there.
     */
    private static int getPairIndex(int ch)
    {
        int probe = pairedCharPower;
        int index = 0;

        if (ch >= pairedChars[pairedCharExtra]) {
            index = pairedCharExtra;
        }

        while (probe > (1 << 0)) {
            probe >>= 1;

            if (ch >= pairedChars[index + probe]) {
                index += probe;
            }
        }

        if (pairedChars[index] != ch) {
            index = -1;
        }

        return index;
    }

    // all common
    private static int[] pairedChars = {
        0x0028, 0x0029, // ascii paired punctuation  // common
        0x003c, 0x003e, // common
        0x005b, 0x005d, // common
        0x007b, 0x007d, // common
        0x00ab, 0x00bb, // guillemets // common
        0x2018, 0x2019, // general punctuation // common
        0x201c, 0x201d, // common
        0x2039, 0x203a, // common
        0x3008, 0x3009, // chinese paired punctuation // common
        0x300a, 0x300b,
        0x300c, 0x300d,
        0x300e, 0x300f,
        0x3010, 0x3011,
        0x3014, 0x3015,
        0x3016, 0x3017,
        0x3018, 0x3019,
        0x301a, 0x301b
    };

    private static final int pairedCharPower = 1 << highBit(pairedChars.length);
    private static final int pairedCharExtra = pairedChars.length - pairedCharPower;

}