[wxWidgets.git] / contrib / src / stc / scintilla / src / RESearch.cxx

// Scintilla source code edit control
/** @file RESearch.cxx
 ** Regular expression search library.
 **/

/*
 * regex - Regular expression pattern matching  and replacement
 *
 * By:  Ozan S. Yigit (oz)
 *      Dept. of Computer Science
 *      York University
 *
 * Original code available from http://www.cs.yorku.ca/~oz/
 * Translation to C++ by Neil Hodgson neilh@scintilla.org
 * Removed all use of register.
 * Converted to modern function prototypes.
 * Put all global/static variables into an object so this code can be
 * used from multiple threads etc.
 *
 * These routines are the PUBLIC DOMAIN equivalents of regex
 * routines as found in 4.nBSD UN*X, with minor extensions.
 *
 * These routines are derived from various implementations found
 * in software tools books, and Conroy's grep. They are NOT derived
 * from licensed/restricted software.
 * For more interesting/academic/complicated implementations,
 * see Henry Spencer's regexp routines, or GNU Emacs pattern
 * matching module.
 *
 * Modification history removed.
 *
 * Interfaces:
 *      RESearch::Compile:        compile a regular expression into a NFA.
 *
 *                      char *RESearch::Compile(s)
 *                      char *s;
 *
 *      RESearch::Execute:        execute the NFA to match a pattern.
 *
 *                      int RESearch::Execute(s)
 *                      char *s;
 *
 *      RESearch::ModifyWord            change RESearch::Execute's understanding of what a "word"
 *                      looks like (for \< and \>) by adding into the
 *                      hidden word-syntax table.
 *
 *                      void RESearch::ModifyWord(s)
 *                      char *s;
 *
 *      RESearch::Substitute:   substitute the matched portions in a new string.
 *
 *                      int RESearch::Substitute(src, dst)
 *                      char *src;
 *                      char *dst;
 *
 *      re_fail:        failure routine for RESearch::Execute.
 *
 *                      void re_fail(msg, op)
 *                      char *msg;
 *                      char op;
 *
 * Regular Expressions:
 *
 *      [1]     char    matches itself, unless it is a special
 *                      character (metachar): . \ [ ] * + ^ $
 *
 *      [2]     .       matches any character.
 *
 *      [3]     \       matches the character following it, except
 *                      when followed by a left or right round bracket,
 *                      a digit 1 to 9 or a left or right angle bracket.
 *                      (see [7], [8] and [9])
 *                      It is used as an escape character for all
 *                      other meta-characters, and itself. When used
 *                      in a set ([4]), it is treated as an ordinary
 *                      character.
 *
 *      [4]     [set]   matches one of the characters in the set.
 *                      If the first character in the set is "^",
 *                      it matches a character NOT in the set, i.e.
 *                      complements the set. A shorthand S-E is
 *                      used to specify a set of characters S upto
 *                      E, inclusive. The special characters "]" and
 *                      "-" have no special meaning if they appear
 *                      as the first chars in the set.
 *                      examples:        match:
 *
 *                              [a-z]    any lowercase alpha
 *
 *                              [^]-]    any char except ] and -
 *
 *                              [^A-Z]   any char except uppercase
 *                                       alpha
 *
 *                              [a-zA-Z] any alpha
 *
 *      [5]     *       any regular expression form [1] to [4], followed by
 *                      closure char (*) matches zero or more matches of
 *                      that form.
 *
 *      [6]     +       same as [5], except it matches one or more.
 *
 *      [7]             a regular expression in the form [1] to [10], enclosed
 *                      as \(form\) matches what form matches. The enclosure
 *                      creates a set of tags, used for [8] and for
 *                      pattern substution. The tagged forms are numbered
 *                      starting from 1.
 *
 *      [8]             a \ followed by a digit 1 to 9 matches whatever a
 *                      previously tagged regular expression ([7]) matched.
 *
 *      [9]     \<      a regular expression starting with a \< construct
 *              \>      and/or ending with a \> construct, restricts the
 *                      pattern matching to the beginning of a word, and/or
 *                      the end of a word. A word is defined to be a character
 *                      string beginning and/or ending with the characters
 *                      A-Z a-z 0-9 and _. It must also be preceded and/or
 *                      followed by any character outside those mentioned.
 *
 *      [10]            a composite regular expression xy where x and y
 *                      are in the form [1] to [10] matches the longest
 *                      match of x followed by a match for y.
 *
 *      [11]    ^       a regular expression starting with a ^ character
 *              $       and/or ending with a $ character, restricts the
 *                      pattern matching to the beginning of the line,
 *                      or the end of line. [anchors] Elsewhere in the
 *                      pattern, ^ and $ are treated as ordinary characters.
 *
 *
 * Acknowledgements:
 *
 *      HCR's Hugh Redelmeier has been most helpful in various
 *      stages of development. He convinced me to include BOW
 *      and EOW constructs, originally invented by Rob Pike at
 *      the University of Toronto.
 *
 * References:
 *              Software tools                  Kernighan & Plauger
 *              Software tools in Pascal        Kernighan & Plauger
 *              Grep [rsx-11 C dist]            David Conroy
 *              ed - text editor                Un*x Programmer's Manual
 *              Advanced editing on Un*x        B. W. Kernighan
 *              RegExp routines                 Henry Spencer
 *
 * Notes:
 *
 *      This implementation uses a bit-set representation for character
 *      classes for speed and compactness. Each character is represented
 *      by one bit in a 128-bit block. Thus, CCL always takes a
 *      constant 16 bytes in the internal nfa, and RESearch::Execute does a single
 *      bit comparison to locate the character in the set.
 *
 * Examples:
 *
 *      pattern:        foo*.*
 *      compile:        CHR f CHR o CLO CHR o END CLO ANY END END
 *      matches:        fo foo fooo foobar fobar foxx ...
 *
 *      pattern:        fo[ob]a[rz]
 *      compile:        CHR f CHR o CCL bitset CHR a CCL bitset END
 *      matches:        fobar fooar fobaz fooaz
 *
 *      pattern:        foo\\+
 *      compile:        CHR f CHR o CHR o CHR \ CLO CHR \ END END
 *      matches:        foo\ foo\\ foo\\\  ...
 *
 *      pattern:        \(foo\)[1-3]\1  (same as foo[1-3]foo)
 *      compile:        BOT 1 CHR f CHR o CHR o EOT 1 CCL bitset REF 1 END
 *      matches:        foo1foo foo2foo foo3foo
 *
 *      pattern:        \(fo.*\)-\1
 *      compile:        BOT 1 CHR f CHR o CLO ANY END EOT 1 CHR - REF 1 END
 *      matches:        foo-foo fo-fo fob-fob foobar-foobar ...
 */

#include "RESearch.h"

#define OKP     1
#define NOP     0

#define CHR     1
#define ANY     2
#define CCL     3
#define BOL     4
#define EOL     5
#define BOT     6
#define EOT     7
#define BOW     8
#define EOW     9
#define REF     10
#define CLO     11

#define END     0

/*
 * The following defines are not meant to be changeable.
 * They are for readability only.
 */
#define BLKIND  0370
#define BITIND  07

#define ASCIIB  0177

const char bitarr[] = {1,2,4,8,16,32,64,'\200'};

#define badpat(x)       (*nfa = END, x)

RESearch::RESearch() {
        Init();
}

RESearch::~RESearch() {
        Clear();
}

void RESearch::Init() {
        sta = NOP;                      /* status of lastpat */
        bol = 0;
        for (int i=0; i<MAXTAG; i++)
                pat[i] = 0;
        for (int j=0; j<BITBLK; j++)
                bittab[j] = 0;
}

void RESearch::Clear() {
        for (int i=0; i<MAXTAG; i++) {
                delete []pat[i];
                pat[i] = 0;
                bopat[i] = NOTFOUND;
                eopat[i] = NOTFOUND;
        }
}

bool RESearch::GrabMatches(CharacterIndexer &ci) {
        bool success = true;
        for (unsigned int i=0; i<MAXTAG; i++) {
                if ((bopat[i] != NOTFOUND) && (eopat[i] != NOTFOUND)) {
                        unsigned int len = eopat[i] - bopat[i];
                        pat[i] = new char[len + 1];
                        if (pat[i]) {
                                for (unsigned int j=0; j<len; j++)
                                        pat[i][j] = ci.CharAt(bopat[i] + j);
                                pat[i][len] = '\0';
                        } else {
                                success = false;
                        }
                }
        }
        return success;
}

void RESearch::ChSet(char c) {
        bittab[((c) & BLKIND) >> 3] |= bitarr[(c) & BITIND];
}

void RESearch::ChSetWithCase(char c, bool caseSensitive) {
        if (caseSensitive) {
                ChSet(c);
        } else {
                if ((c >= 'a') && (c <= 'z')) {
                        ChSet(c);
                        ChSet(static_cast<char>(c - 'a' + 'A'));
                } else if ((c >= 'A') && (c <= 'Z')) {
                        ChSet(c);
                        ChSet(static_cast<char>(c - 'A' + 'a'));
                } else {
                        ChSet(c);
                }
        }
}

const char escapeValue(char ch) {
        switch (ch) {
        case 'a':       return '\a';
        case 'b':       return '\b';
        case 'f':       return '\f';
        case 'n':       return '\n';
        case 'r':       return '\r';
        case 't':       return '\t';
        case 'v':       return '\v';
        }
        return 0;
}

const char *RESearch::Compile(const char *pat, int length, bool caseSensitive, bool posix) {
        char *mp=nfa;          /* nfa pointer       */
        char *lp;              /* saved pointer..   */
        char *sp=nfa;          /* another one..     */
    char *mpMax = mp + MAXNFA - BITBLK - 10;

        int tagi = 0;          /* tag stack index   */
        int tagc = 1;          /* actual tag count  */

        int n;
        char mask;              /* xor mask -CCL/NCL */
        int c1, c2;

        if (!pat || !length)
                if (sta)
                        return 0;
                else
                        return badpat("No previous regular expression");
        sta = NOP;

        const char *p=pat;               /* pattern pointer   */
        for (int i=0; i<length; i++, p++) {
                if (mp > mpMax)
                        return badpat("Pattern too long");
                lp = mp;
                switch(*p) {

                case '.':               /* match any char..  */
                        *mp++ = ANY;
                        break;

                case '^':               /* match beginning.. */
                        if (p == pat)
                                *mp++ = BOL;
                        else {
                                *mp++ = CHR;
                                *mp++ = *p;
                        }
                        break;

                case '$':               /* match endofline.. */
                        if (!*(p+1))
                                *mp++ = EOL;
                        else {
                                *mp++ = CHR;
                                *mp++ = *p;
                        }
                        break;

                case '[':               /* match char class..*/
                        *mp++ = CCL;

                        i++;
                        if (*++p == '^') {
                                mask = '\377';
                                i++;
                                p++;
                        } else
                                mask = 0;

                        if (*p == '-') {                /* real dash */
                                i++;
                                ChSet(*p++);
                        }
                        if (*p == ']') {        /* real brace */
                                i++;
                                ChSet(*p++);
                        }
                        while (*p && *p != ']') {
                                if (*p == '-' && *(p+1) && *(p+1) != ']') {
                                        i++;
                                        p++;
                                        c1 = *(p-2) + 1;
                                        i++;
                                        c2 = *p++;
                                        while (c1 <= c2) {
                                                ChSetWithCase(static_cast<char>(c1++), caseSensitive);
                                        }
                                } else if (*p == '\\' && *(p+1)) {
                                        i++;
                                        p++;
                                        char escape = escapeValue(*p);
                                        if (escape)
                                                ChSetWithCase(escape, caseSensitive);
                                        else
                                                ChSetWithCase(*p, caseSensitive);
                                        i++;
                                        p++;
                                } else {
                                        i++;
                                        ChSetWithCase(*p++, caseSensitive);
                                }
                        }
                        if (!*p)
                                return badpat("Missing ]");

                        for (n = 0; n < BITBLK; bittab[n++] = (char) 0)
                                *mp++ = static_cast<char>(mask ^ bittab[n]);

                        break;

                case '*':               /* match 0 or more.. */
                case '+':               /* match 1 or more.. */
                        if (p == pat)
                                return badpat("Empty closure");
                        lp = sp;                /* previous opcode */
                        if (*lp == CLO)         /* equivalence..   */
                                break;
                        switch(*lp) {

                        case BOL:
                        case BOT:
                        case EOT:
                        case BOW:
                        case EOW:
                        case REF:
                                return badpat("Illegal closure");
                        default:
                                break;
                        }

                        if (*p == '+')
                                for (sp = mp; lp < sp; lp++)
                                        *mp++ = *lp;

                        *mp++ = END;
                        *mp++ = END;
                        sp = mp;
                        while (--mp > lp)
                                *mp = mp[-1];
                        *mp = CLO;
                        mp = sp;
                        break;

                case '\\':              /* tags, backrefs .. */
                        i++;
                        switch(*++p) {

                        case '<':
                                *mp++ = BOW;
                                break;
                        case '>':
                                if (*sp == BOW)
                                        return badpat("Null pattern inside \\<\\>");
                                *mp++ = EOW;
                                break;
                        case '1':
                        case '2':
                        case '3':
                        case '4':
                        case '5':
                        case '6':
                        case '7':
                        case '8':
                        case '9':
                                n = *p-'0';
                                if (tagi > 0 && tagstk[tagi] == n)
                                        return badpat("Cyclical reference");
                                if (tagc > n) {
                                        *mp++ = static_cast<char>(REF);
                                        *mp++ = static_cast<char>(n);
                                }
                                else
                                        return badpat("Undetermined reference");
                                break;
                        case 'a':
                        case 'b':
                        case 'n':
                        case 'f':
                        case 'r':
                        case 't':
                        case 'v':
                                *mp++ = CHR;
                                *mp++ = escapeValue(*p);
                                break;
                        default:
                                if (!posix && *p == '(') {
                                        if (tagc < MAXTAG) {
                                                tagstk[++tagi] = tagc;
                                                *mp++ = BOT;
                                                *mp++ = static_cast<char>(tagc++);
                                        }
                                        else
                                                return badpat("Too many \\(\\) pairs");
                                } else if (!posix && *p == ')') {
                                        if (*sp == BOT)
                                                return badpat("Null pattern inside \\(\\)");
                                        if (tagi > 0) {
                                                *mp++ = static_cast<char>(EOT);
                                                *mp++ = static_cast<char>(tagstk[tagi--]);
                                        }
                                        else
                                                return badpat("Unmatched \\)");
                                } else {
                                        *mp++ = CHR;
                                        *mp++ = *p;
                                }
                        }
                        break;

                default :               /* an ordinary char  */
                        if (posix && *p == '(') {
                                if (tagc < MAXTAG) {
                                        tagstk[++tagi] = tagc;
                                        *mp++ = BOT;
                                        *mp++ = static_cast<char>(tagc++);
                                }
                                else
                                        return badpat("Too many () pairs");
                        } else if (posix && *p == ')') {
                                if (*sp == BOT)
                                        return badpat("Null pattern inside ()");
                                if (tagi > 0) {
                                        *mp++ = static_cast<char>(EOT);
                                        *mp++ = static_cast<char>(tagstk[tagi--]);
                                }
                                else
                                        return badpat("Unmatched )");
                        } else if (caseSensitive) {
                                *mp++ = CHR;
                                *mp++ = *p;
                        } else {
                                *mp++ = CCL;
                                mask = 0;
                                ChSetWithCase(*p, false);
                                for (n = 0; n < BITBLK; bittab[n++] = (char) 0)
                                        *mp++ = static_cast<char>(mask ^ bittab[n]);
                        }
                        break;
                }
                sp = lp;
        }
        if (tagi > 0)
                return badpat((posix ? "Unmatched (" : "Unmatched \\("));
        *mp = END;
        sta = OKP;
        return 0;
}

/*
 * RESearch::Execute:
 *      execute nfa to find a match.
 *
 *      special cases: (nfa[0])
 *              BOL
 *                      Match only once, starting from the
 *                      beginning.
 *              CHR
 *                      First locate the character without
 *                      calling PMatch, and if found, call
 *                      PMatch for the remaining string.
 *              END
 *                      RESearch::Compile failed, poor luser did not
 *                      check for it. Fail fast.
 *
 *      If a match is found, bopat[0] and eopat[0] are set
 *      to the beginning and the end of the matched fragment,
 *      respectively.
 *
 */

int RESearch::Execute(CharacterIndexer &ci, int lp, int endp) {
        char c;
        int ep = NOTFOUND;
        char *ap = nfa;

        bol = lp;
        failure = 0;

        Clear();

        switch(*ap) {

        case BOL:                       /* anchored: match from BOL only */
                ep = PMatch(ci, lp, endp, ap);
                break;
        case EOL:                       /* just searching for end of line normal path doesn't work */
                if (*(ap+1) == END) {
                        lp = endp;
                        ep = lp;
                        break;
                } else {
                        return 0;
                }
        case CHR:                       /* ordinary char: locate it fast */
                c = *(ap+1);
                while ((lp < endp) && (ci.CharAt(lp) != c))
                        lp++;
                if (lp >= endp)         /* if EOS, fail, else fall thru. */
                        return 0;
        default:                        /* regular matching all the way. */
                while (lp < endp) {
                        ep = PMatch(ci, lp, endp, ap);
                        if (ep != NOTFOUND)
                                break;
                        lp++;
                }
                break;
        case END:                       /* munged automaton. fail always */
                return 0;
        }
        if (ep == NOTFOUND)
                return 0;

        bopat[0] = lp;
        eopat[0] = ep;
        return 1;
}

/*
 * PMatch: internal routine for the hard part
 *
 *      This code is partly snarfed from an early grep written by
 *      David Conroy. The backref and tag stuff, and various other
 *      innovations are by oz.
 *
 *      special case optimizations: (nfa[n], nfa[n+1])
 *              CLO ANY
 *                      We KNOW .* will match everything upto the
 *                      end of line. Thus, directly go to the end of
 *                      line, without recursive PMatch calls. As in
 *                      the other closure cases, the remaining pattern
 *                      must be matched by moving backwards on the
 *                      string recursively, to find a match for xy
 *                      (x is ".*" and y is the remaining pattern)
 *                      where the match satisfies the LONGEST match for
 *                      x followed by a match for y.
 *              CLO CHR
 *                      We can again scan the string forward for the
 *                      single char and at the point of failure, we
 *                      execute the remaining nfa recursively, same as
 *                      above.
 *
 *      At the end of a successful match, bopat[n] and eopat[n]
 *      are set to the beginning and end of subpatterns matched
 *      by tagged expressions (n = 1 to 9).
 *
 */

extern void re_fail(char *,char);

/*
 * character classification table for word boundary operators BOW
 * and EOW. the reason for not using ctype macros is that we can
 * let the user add into our own table. see RESearch::ModifyWord. This table
 * is not in the bitset form, since we may wish to extend it in the
 * future for other character classifications.
 *
 *      TRUE for 0-9 A-Z a-z _
 */
static char chrtyp[MAXCHR] = {
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 1, 1,
        1, 1, 1, 1, 1, 1, 1, 1, 0, 0,
        0, 0, 0, 0, 0, 1, 1, 1, 1, 1,
        1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
        1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
        1, 0, 0, 0, 0, 1, 0, 1, 1, 1,
        1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
        1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
        1, 1, 1, 0, 0, 0, 0, 0
        };

#define inascii(x)      (0177&(x))
#define iswordc(x)      chrtyp[inascii(x)]
#define isinset(x,y)    ((x)[((y)&BLKIND)>>3] & bitarr[(y)&BITIND])

/*
 * skip values for CLO XXX to skip past the closure
 */

#define ANYSKIP 2       /* [CLO] ANY END ...         */
#define CHRSKIP 3       /* [CLO] CHR chr END ...     */
#define CCLSKIP 34      /* [CLO] CCL 32bytes END ... */

int RESearch::PMatch(CharacterIndexer &ci, int lp, int endp, char *ap) {
        int op, c, n;
        int e;          /* extra pointer for CLO */
        int bp;         /* beginning of subpat.. */
        int ep;         /* ending of subpat..    */
        int are;                        /* to save the line ptr. */

        while ((op = *ap++) != END)
                switch(op) {

                case CHR:
                        if (ci.CharAt(lp++) != *ap++)
                                return NOTFOUND;
                        break;
                case ANY:
                        if (lp++ >= endp)
                                return NOTFOUND;
                        break;
                case CCL:
                        c = ci.CharAt(lp++);
                        if (!isinset(ap,c))
                                return NOTFOUND;
                        ap += BITBLK;
                        break;
                case BOL:
                        if (lp != bol)
                                return NOTFOUND;
                        break;
                case EOL:
                        if (lp < endp)
                                return NOTFOUND;
                        break;
                case BOT:
                        bopat[*ap++] = lp;
                        break;
                case EOT:
                        eopat[*ap++] = lp;
                        break;
                case BOW:
                        if (lp!=bol && iswordc(ci.CharAt(lp-1)) || !iswordc(ci.CharAt(lp)))
                                return NOTFOUND;
                        break;
                case EOW:
                        if (lp==bol || !iswordc(ci.CharAt(lp-1)) || iswordc(ci.CharAt(lp)))
                                return NOTFOUND;
                        break;
                case REF:
                        n = *ap++;
                        bp = bopat[n];
                        ep = eopat[n];
                        while (bp < ep)
                                if (ci.CharAt(bp++) != ci.CharAt(lp++))
                                        return NOTFOUND;
                        break;
                case CLO:
                        are = lp;
                        switch(*ap) {

                        case ANY:
                                while (lp < endp)
                                        lp++;
                                n = ANYSKIP;
                                break;
                        case CHR:
                                c = *(ap+1);
                                while ((lp < endp) && (c == ci.CharAt(lp)))
                                        lp++;
                                n = CHRSKIP;
                                break;
                        case CCL:
                                while ((lp < endp) && isinset(ap+1,ci.CharAt(lp)))
                                        lp++;
                                n = CCLSKIP;
                                break;
                        default:
                                failure = true;
                                //re_fail("closure: bad nfa.", *ap);
                                return NOTFOUND;
                        }

                        ap += n;

                        while (lp >= are) {
                                if ((e = PMatch(ci, lp, endp, ap)) != NOTFOUND)
                                        return e;
                                --lp;
                        }
                        return NOTFOUND;
                default:
                        //re_fail("RESearch::Execute: bad nfa.", static_cast<char>(op));
                        return NOTFOUND;
                }
        return lp;
}

/*
 * RESearch::ModifyWord:
 *      add new characters into the word table to change RESearch::Execute's
 *      understanding of what a word should look like. Note that we
 *      only accept additions into the word definition.
 *
 *      If the string parameter is 0 or null string, the table is
 *      reset back to the default containing A-Z a-z 0-9 _. [We use
 *      the compact bitset representation for the default table]
 */

static char deftab[16] = {
        0, 0, 0, 0, 0, 0, '\377', 003, '\376', '\377', '\377', '\207',
        '\376', '\377', '\377', 007
};

void RESearch::ModifyWord(char *s) {
        int i;

        if (!s || !*s) {
                for (i = 0; i < MAXCHR; i++)
                        if (!isinset(deftab,i))
                                iswordc(i) = 0;
        }
        else
                while(*s)
                        iswordc(*s++) = 1;
}

/*
 * RESearch::Substitute:
 *      substitute the matched portions of the src in dst.
 *
 *      &       substitute the entire matched pattern.
 *
 *      \digit  substitute a subpattern, with the given tag number.
 *              Tags are numbered from 1 to 9. If the particular
 *              tagged subpattern does not exist, null is substituted.
 */
int RESearch::Substitute(CharacterIndexer &ci, char *src, char *dst) {
        char c;
        int  pin;
        int bp;
        int ep;

        if (!*src || !bopat[0])
                return 0;

        while ((c = *src++) != 0) {
                switch(c) {

                case '&':
                        pin = 0;
                        break;

                case '\\':
                        c = *src++;
                        if (c >= '0' && c <= '9') {
                                pin = c - '0';
                                break;
                        }

                default:
                        *dst++ = c;
                        continue;
                }

                if ((bp = bopat[pin]) != 0 && (ep = eopat[pin]) != 0) {
                        while (ci.CharAt(bp) && bp < ep)
                                *dst++ = ci.CharAt(bp++);
                        if (bp < ep)
                                return 0;
                }
        }
        *dst = (char) 0;
        return 1;
}