// 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.
 * Some extensions by Philippe Lhoste PhiLho(a)GMX.net
 * '?' extensions by Michael Mullin masmullin@gmail.com
 *
 * 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.
 *
 *          const char *RESearch::Compile(const char *pattern, int length,
 *                                        bool caseSensitive, bool posix)
 *
 * Returns a short error string if they fail.
 *
 *  RESearch::Execute:      execute the NFA to match a pattern.
 *
 *          int RESearch::Execute(characterIndexer &ci, int lp, int endp)
 *
 *  RESearch::Substitute:   substitute the matched portions in a new string.
 *
 *          int RESearch::Substitute(CharacterIndexer &ci, char *src, char *dst)
 *
 *  re_fail:                failure routine for RESearch::Execute. (no longer used)
 *
 *          void re_fail(char *msg, char op)
 *
 * Regular Expressions:
 *
 *      [1]     char    matches itself, unless it is a special
 *                      character (metachar): . \ [ ] * + ? ^ $
 *                      and ( ) if posix option.
 *
 *      [2]     .       matches any character.
 *
 *      [3]     \       matches the character following it, except:
 *                      - \a, \b, \f, \n, \r, \t, \v match the corresponding C
 *                      escape char, respectively BEL, BS, FF, LF, CR, TAB and VT;
 *                      Note that \r and \n are never matched because Scintilla
 *                      regex searches are made line per line
 *                      (stripped of end-of-line chars).
 *                      - if not in posix mode, when followed by a
 *                      left or right round bracket (see [8]);
 *                      - when followed by a digit 1 to 9 (see [9]);
 *                      - when followed by a left or right angle bracket
 *                      (see [10]);
 *                      - when followed by d, D, s, S, w or W (see [11]);
 *                      - when followed by x and two hexa digits (see [12].
 *                      Backslash is used as an escape character for all
 *                      other meta-characters, and itself.
 *
 *      [4]     [set]   matches one of the characters in the set.
 *                      If the first character in the set is "^",
 *                      it matches the characters NOT in the set, i.e.
 *                      complements the set. A shorthand S-E (start dash end)
 *                      is used to specify a set of characters S up to
 *                      E, inclusive. S and E must be characters, otherwise
 *                      the dash is taken literally (eg. in expression [\d-a]).
 *                      The special characters "]" and "-" have no special
 *                      meaning if they appear as the first chars in the set.
 *                      To include both, put - first: [-]A-Z]
 *                      (or just backslash them).
 *                      examples:        match:
 *
 *                              [-]|]    matches these 3 chars,
 *
 *                              []-|]    matches from ] to | chars
 *
 *                              [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]
 *                      (except [8], [9] and [10] forms of [3]),
 *                      followed by closure char (*)
 *                      matches zero or more matches of that form.
 *
 *      [6]     +       same as [5], except it matches one or more.
 *
 *      [5-6]           Both [5] and [6] are greedy (they match as much as possible).
 *                      Unless they are followed by the 'lazy' quantifier (?)
 *                      In which case both [5] and [6] try to match as little as possible
 *
 *      [7]     ?       same as [5] except it matches zero or one.
 *
 *      [8]             a regular expression in the form [1] to [13], enclosed
 *                      as \(form\) (or (form) with posix flag) matches what
 *                      form matches. The enclosure creates a set of tags,
 *                      used for [9] and for pattern substitution.
 *                      The tagged forms are numbered starting from 1.
 *
 *      [9]             a \ followed by a digit 1 to 9 matches whatever a
 *                      previously tagged regular expression ([8]) matched.
 *
 *      [10]    \<      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 _. Scintilla extends this definition
 *                      by user setting. The word must also be preceded and/or
 *                      followed by any character outside those mentioned.
 *
 *      [11]    \l      a backslash followed by d, D, s, S, w or W,
 *                      becomes a character class (both inside and
 *                      outside sets []).
 *                        d: decimal digits
 *                        D: any char except decimal digits
 *                        s: whitespace (space, \t \n \r \f \v)
 *                        S: any char except whitespace (see above)
 *                        w: alphanumeric & underscore (changed by user setting)
 *                        W: any char except alphanumeric & underscore (see above)
 *
 *      [12]    \xHH    a backslash followed by x and two hexa digits,
 *                      becomes the character whose Ascii code is equal
 *                      to these digits. If not followed by two digits,
 *                      it is 'x' char itself.
 *
 *      [13]            a composite regular expression xy where x and y
 *                      are in the form [1] to [12] matches the longest
 *                      match of x followed by a match for y.
 *
 *      [14]    ^       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 256-bit block. Thus, CCL always takes a
 *  constant 32 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 <stdlib.h>

#include "CharClassify.h"
#include "RESearch.h"

// Shut up annoying Visual C++ warnings:
#ifdef _MSC_VER
#pragma warning(disable: 4514)
#endif

#ifdef SCI_NAMESPACE
using namespace Scintilla;
#endif

#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 CLQ     12 /* 0 to 1 closure */
#define LCLO    13 /* lazy closure */

#define END     0

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

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

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

/*
 * Character classification table for word boundary operators BOW
 * and EOW is passed in by the creator of this object (Scintilla
 * Document). The Document default state is that word chars are:
 * 0-9, a-z, A-Z and _
 */

RESearch::RESearch(CharClassify *charClassTable) {
    failure = 0;
    charClass = charClassTable;
    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(unsigned char c) {
    bittab[((c) & BLKIND) >> 3] |= bitarr[(c) & BITIND];
}

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

unsigned char escapeValue(unsigned 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;
}

static int GetHexaChar(unsigned char hd1, unsigned char hd2) {
    int hexValue = 0;
    if (hd1 >= '0' && hd1 <= '9') {
        hexValue += 16 * (hd1 - '0');
    } else if (hd1 >= 'A' && hd1 <= 'F') {
        hexValue += 16 * (hd1 - 'A' + 10);
    } else if (hd1 >= 'a' && hd1 <= 'f') {
        hexValue += 16 * (hd1 - 'a' + 10);
    } else
        return -1;
    if (hd2 >= '0' && hd2 <= '9') {
        hexValue += hd2 - '0';
    } else if (hd2 >= 'A' && hd2 <= 'F') {
        hexValue += hd2 - 'A' + 10;
    } else if (hd2 >= 'a' && hd2 <= 'f') {
        hexValue += hd2 - 'a' + 10;
    } else
        return -1;
    return hexValue;
}

/**
 * Called when the parser finds a backslash not followed
 * by a valid expression (like \( in non-Posix mode).
 * @param pattern: pointer on the char after the backslash.
 * @param incr: (out) number of chars to skip after expression evaluation.
 * @return the char if it resolves to a simple char,
 * or -1 for a char class. In this case, bittab is changed.
 */
int RESearch::GetBackslashExpression(
    const char *pattern,
    int &incr) {
    // Since error reporting is primitive and messages are not used anyway,
    // I choose to interpret unexpected syntax in a logical way instead
    // of reporting errors. Otherwise, we can stick on, eg., PCRE behavior.
    incr = 0;   // Most of the time, will skip the char "naturally".
    int c;
    int result = -1;
    unsigned char bsc = *pattern;
    if (!bsc) {
        // Avoid overrun
        result = '\\';  // \ at end of pattern, take it literally
        return result;
    }

    switch (bsc) {
    case 'a':
    case 'b':
    case 'n':
    case 'f':
    case 'r':
    case 't':
    case 'v':
        result = escapeValue(bsc);
        break;
    case 'x': {
            unsigned char hd1 = *(pattern + 1);
            unsigned char hd2 = *(pattern + 2);
            int hexValue = GetHexaChar(hd1, hd2);
            if (hexValue >= 0) {
                result = hexValue;
                incr = 2;   // Must skip the digits
            } else {
                result = 'x';   // \x without 2 digits: see it as 'x'
            }
        }
        break;
    case 'd':
        for (c = '0'; c <= '9'; c++) {
            ChSet(static_cast<unsigned char>(c));
        }
        break;
    case 'D':
        for (c = 0; c < MAXCHR; c++) {
            if (c < '0' || c > '9') {
                ChSet(static_cast<unsigned char>(c));
            }
        }
        break;
    case 's':
        ChSet(' ');
        ChSet('\t');
        ChSet('\n');
        ChSet('\r');
        ChSet('\f');
        ChSet('\v');
        break;
    case 'S':
        for (c = 0; c < MAXCHR; c++) {
            if (c != ' ' && !(c >= 0x09 && c <= 0x0D)) {
                ChSet(static_cast<unsigned char>(c));
            }
        }
        break;
    case 'w':
        for (c = 0; c < MAXCHR; c++) {
            if (iswordc(static_cast<unsigned char>(c))) {
                ChSet(static_cast<unsigned char>(c));
            }
        }
        break;
    case 'W':
        for (c = 0; c < MAXCHR; c++) {
            if (!iswordc(static_cast<unsigned char>(c))) {
                ChSet(static_cast<unsigned char>(c));
            }
        }
        break;
    default:
        result = bsc;
    }
    return result;
}

const char *RESearch::Compile(const char *pattern, 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, prevChar;

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

    const char *p=pattern;     /* 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 == pattern)
                *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;
            prevChar = 0;

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

            if (*p == '-') {    /* real dash */
                i++;
                prevChar = *p;
                ChSet(*p++);
            }
            if (*p == ']') {    /* real brace */
                i++;
                prevChar = *p;
                ChSet(*p++);
            }
            while (*p && *p != ']') {
                if (*p == '-') {
                    if (prevChar < 0) {
                        // Previous def. was a char class like \d, take dash literally
                        prevChar = *p;
                        ChSet(*p);
                    } else if (*(p+1)) {
                        if (*(p+1) != ']') {
                            c1 = prevChar + 1;
                            i++;
                            c2 = static_cast<unsigned char>(*++p);
                            if (c2 == '\\') {
                                if (!*(p+1))    // End of RE
                                    return badpat("Missing ]");
                                else {
                                    i++;
                                    p++;
                                    int incr;
                                    c2 = GetBackslashExpression(p, incr);
                                    i += incr;
                                    p += incr;
                                    if (c2 >= 0) {
                                        // Convention: \c (c is any char) is case sensitive, whatever the option
                                        ChSet(static_cast<unsigned char>(c2));
                                        prevChar = c2;
                                    } else {
                                        // bittab is already changed
                                        prevChar = -1;
                                    }
                                }
                            }
                            if (prevChar < 0) {
                                // Char after dash is char class like \d, take dash literally
                                prevChar = '-';
                                ChSet('-');
                            } else {
                                // Put all chars between c1 and c2 included in the char set
                                while (c1 <= c2) {
                                    ChSetWithCase(static_cast<unsigned char>(c1++), caseSensitive);
                                }
                            }
                        } else {
                            // Dash before the ], take it literally
                            prevChar = *p;
                            ChSet(*p);
                        }
                    } else {
                        return badpat("Missing ]");
                    }
                } else if (*p == '\\' && *(p+1)) {
                    i++;
                    p++;
                    int incr;
                    int c = GetBackslashExpression(p, incr);
                    i += incr;
                    p += incr;
                    if (c >= 0) {
                        // Convention: \c (c is any char) is case sensitive, whatever the option
                        ChSet(static_cast<unsigned char>(c));
                        prevChar = c;
                    } else {
                        // bittab is already changed
                        prevChar = -1;
                    }
                } else {
                    prevChar = static_cast<unsigned char>(*p);
                    ChSetWithCase(*p, caseSensitive);
                }
                i++;
                p++;
            }
            if (!*p)
                return badpat("Missing ]");

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

            break;

        case '*':               /* match 0 or more... */
        case '+':               /* match 1 or more... */
        case '?':
            if (p == pattern)
                return badpat("Empty closure");
            lp = sp;        /* previous opcode */
            if (*lp == CLO || *lp == LCLO)      /* 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];
            if (*p == '?')          *mp = CLQ;
            else if (*(p+1) == '?') *mp = LCLO;
            else                    *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;
            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 {
                    int incr;
                    int c = GetBackslashExpression(p, incr);
                    i += incr;
                    p += incr;
                    if (c >= 0) {
                        *mp++ = CHR;
                        *mp++ = static_cast<unsigned char>(c);
                    } else {
                        *mp++ = CCL;
                        mask = 0;
                        for (n = 0; n < BITBLK; bittab[n++] = 0)
                            *mp++ = static_cast<char>(mask ^ bittab[n]);
                    }
                }
            }
            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 {
                unsigned char c = *p;
                if (!c) // End of RE
                    c = '\\';   // We take it as raw backslash
                if (caseSensitive || !iswordc(c)) {
                    *mp++ = CHR;
                    *mp++ = c;
                } else {
                    *mp++ = CCL;
                    mask = 0;
                    ChSetWithCase(c, false);
                    for (n = 0; n < BITBLK; bittab[n++] = 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) {
    unsigned 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);

#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 32 bytes 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.  */
    int llp;    /* lazy lp for LCLO       */

    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:
            if (lp >= endp)
                return NOTFOUND;
            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[static_cast<int>(*ap++)] = lp;
            break;
        case EOT:
            eopat[static_cast<int>(*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 LCLO:
        case CLQ:
        case CLO:
            are = lp;
            switch (*ap) {

            case ANY:
                if (op == CLO || op == LCLO)
                    while (lp < endp)
                        lp++;
                else if (lp < endp)
                    lp++;

                n = ANYSKIP;
                break;
            case CHR:
                c = *(ap+1);
                if (op == CLO || op == LCLO)
                    while ((lp < endp) && (c == ci.CharAt(lp)))
                        lp++;
                else if ((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;

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

/*
 * 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) {
    unsigned 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 = '\0';
    return 1;
}

